@article{,

title = {Multilayered regulation of cardiac ion channels},

author = {Zhang SS and Shaw RM},

year  = {2013},

date = {2013-03-03},

journal = {Biochim Biophys Acta},

volume = {1833},

number = {876-85},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Performance of the REVEAL model in WHO Group 2 to 5 pulmonary hypertension: application beyond pulmonary arterial hypertension.},

author = {Cogswell R and McGlothlin D and Kobashigawa E and Shaw R and De Marco T. },

year  = {2013},

date = {2013-03-03},

journal = {J Heart Lung Transplant},

volume = {32},

number = {293-8},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid23266405,

title = {Reduced sodium channels in human ARVC},

author = {Shaw RM},

year  = {2013},

date = {2013-03-01},

journal = {Heart Rhythm},

volume = {10},

number = {3},

pages = {420--421},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid23596510,

title = {Dynasore protects mitochondria and improves cardiac lusitropy in Langendorff perfused mouse heart},

author = {Gao D, Zhang L, Dhillon R, Hong TT, Shaw RM, Zhu J},

year  = {2013},

date = {2013-01-01},

journal = {PLoS ONE},

volume = {8},

number = {4},

pages = {e60967},

abstract = {Heart failure due to diastolic dysfunction exacts a major economic, morbidity and mortality burden in the United States. Therapeutic agents to improve diastolic dysfunction are limited. It was recently found that Dynamin related protein 1 (Drp1) mediates mitochondrial fission during ischemia/reperfusion (I/R) injury, whereas inhibition of Drp1 decreases myocardial infarct size. We hypothesized that Dynasore, a small noncompetitive dynamin GTPase inhibitor, could have beneficial effects on cardiac physiology during I/R injury. In Langendorff perfused mouse hearts subjected to I/R (30 minutes of global ischemia followed by 1 hour of reperfusion), pretreatment with 1 µM Dynasore prevented I/R induced elevation of left ventricular end diastolic pressure (LVEDP), indicating a significant and specific lusitropic effect. Dynasore also decreased cardiac troponin I efflux during reperfusion and reduced infarct size. In cultured adult mouse cardiomyocytes subjected to oxidative stress, Dynasore increased cardiomyocyte survival and viability identified by trypan blue exclusion assay and reduced cellular Adenosine triphosphate(ATP) depletion. Moreover, in cultured cells, Dynasore pretreatment protected mitochondrial fragmentation induced by oxidative stress. Dynasore protects cardiac lusitropy and limits cell damage through a mechanism that maintains mitochondrial morphology and intracellular ATP in stressed cells. Mitochondrial protection through an agent such as Dynasore can have clinical benefit by positively influencing the energetics of diastolic dysfunction.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid22300662,

title = {Plasma BIN1 correlates with heart failure and predicts arrhythmia in patients with arrhythmogenic right ventricular cardiomyopathy},

author = {Hong TT, Cogswell R, James CA, Kang G, Pullinger CR, Malloy MJ, Kane JP, Wojciak J, Calkins H, Scheinman MM, Tseng ZH, Ganz P, DeMarco T, Judge DP, and Shaw RM},

year  = {2012},

date = {2012-06-01},

journal = {Heart Rhythm},

volume = {9},

number = {6},

pages = {961--967},

abstract = {Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a disorder involving diseased cardiac muscle. Bridging integrator 1 (BIN1) is a membrane-associated protein important to cardiomyocyte homeostasis and is downregulated in cardiomyopathy. We hypothesized that BIN1 could be released into the circulation and that blood-available BIN1 can provide useful data on the cardiac status of patients whose hearts are failing secondary to ARVC. To determine whether plasma BIN1 levels can be used to measure disease severity in patients with ARVC. We performed a retrospective cohort study of 24 patients with ARVC. Plasma BIN1 levels were assessed for their ability to correlate with cardiac functional status and predict ventricular arrhythmias. Mean plasma BIN1 levels were decreased in patients with ARVC with heart failure (15 ± 7 vs 60 ± 17 in patients without heart failure, P <.05; the plasma BIN1 level was 60 ± 10 in non-ARVC normal controls). BIN1 levels correlated inversely with number of previous ventricular arrhythmia (R = -.47; P <.05), and low BIN1 levels correctly classified patients with advanced heart failure or ventricular arrhythmia (receiver operator curve area under the curve of 0.88 ± 0.07). Low BIN1 levels also predicted future ventricular arrhythmias (receiver operator curve area under the curve of 0.89 ± 0.09). In a stratified analysis, BIN1 levels could predict future arrhythmias in patients without severe heart failure (n = 20) with an accuracy of 82%. In the 7 patients with ARVC with serial blood samples, all of whom had evidence of disease progression during follow-up, plasma BIN1 levels decreased significantly (a decrease of 63%; P <.05). Plasma BIN1 level seems to correlate with cardiac functional status and the presence or absence of sustained ventricular arrhythmias in a small cohort of patients with ARVC and can predict future ventricular arrhythmias.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid22138472,

title = {BIN1 is reduced and Cav1.2 trafficking is impaired in human failing cardiomyocytes},

author = {Hong TT, Smyth JW, Chu K, Vogan J, Fong TS, Jensen BC, Fang K, Halushka MK, Russell SD, Colecraft H, Hoopes CW, Ocorr K, Chi NC, and Shaw RM},

year  = {2012},

date = {2012-05-01},

journal = {Heart Rhythm},

volume = {9},

number = {5},

pages = {812--820},

abstract = {Heart failure is a growing epidemic, and a typical aspect of heart failure pathophysiology is altered calcium transients. Normal cardiac calcium transients are initiated by Cav1.2 channels at cardiac T tubules. Bridging integrator 1 (BIN1) is a membrane scaffolding protein that causes Cav1.2 to traffic to T tubules in healthy hearts. The mechanisms of Cav1.2 trafficking in heart failure are not known. To study BIN1 expression and its effect on Cav1.2 trafficking in failing hearts. Intact myocardium and freshly isolated cardiomyocytes from nonfailing and end-stage failing human hearts were used to study BIN1 expression and Cav1.2 localization. To confirm Cav1.2 surface expression dependence on BIN1, patch-clamp recordings were performed of Cav1.2 current in cell lines with and without trafficking-competent BIN1. Also, in adult mouse cardiomyocytes, surface Cav1.2 and calcium transients were studied after small hairpin RNA-mediated knockdown of BIN1. For a functional readout in intact heart, calcium transients and cardiac contractility were analyzed in a zebrafish model with morpholino-mediated knockdown of BIN1. BIN1 expression is significantly decreased in failing cardiomyocytes at both mRNA (30% down) and protein (36% down) levels. Peripheral Cav1.2 is reduced to 42% by imaging, and a biochemical T-tubule fraction of Cav1.2 is reduced to 68%. The total calcium current is reduced to 41% in a cell line expressing a nontrafficking BIN1 mutant. In mouse cardiomyocytes, BIN1 knockdown decreases surface Cav1.2 and impairs calcium transients. In zebrafish hearts, BIN1 knockdown causes a 75% reduction in calcium transients and severe ventricular contractile dysfunction. The data indicate that BIN1 is significantly reduced in human heart failure, and this reduction impairs Cav1.2 trafficking, calcium transients, and contractility.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Validation of the Registry to Evaluate Early and Long-Term Pulmonary Arterial Hypertension Disease Management (REVEAL) pulmonary hypertension prediction model in a unique population and utility in the prediction of long-term survival..},

author = {Cogswell R and Kobashigawa E and McGlothlin D and Shaw R and De Marco T.},

year  = {2012},

date = {2012-03-03},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Redox-sensitive sulfenic acid modification regulates surface expression of the cardiovascular voltage-gated potassium channel Kv1.5.},

author = {Svoboda LK and Reddie KG and Zhang L and Vesely ED and Williams ES and Schumacher SM and O'Connell RP and Shaw R and Day SM and Anumonwo JM and Carroll KS and Martens JR.},

year  = {2012},

date = {2012-03-03},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid22328533,

title = {Actin cytoskeleton rest stops regulate anterograde traffic of connexin 43 vesicles to the plasma membrane},

author = {Smyth JW, Vogan J, Buch P, Zhang SS, Fong T, Hong TT, Shaw RM},

year  = {2012},

date = {2012-03-01},

journal = {Circ. Res.},

volume = {110},

number = {7},

pages = {978--989},

abstract = {The intracellular trafficking of connexin 43 (Cx43) hemichannels presents opportunities to regulate cardiomyocyte gap junction coupling. Although it is known that Cx43 hemichannels are transported along microtubules to the plasma membrane, the role of actin in Cx43 forward trafficking is unknown. We explored whether the actin cytoskeleton is involved in Cx43 forward trafficking. High-resolution imaging reveals that Cx43 vesicles colocalize with nonsarcomeric actin in adult cardiomyocytes. Live-cell fluorescence imaging reveals Cx43 vesicles as stationary or traveling slowly (average speed 0.09 μm/s) when associated with actin. At any time, the majority (81.7%) of vesicles travel at subkinesin rates, suggesting that actin is important for Cx43 transport. Using Cx43 containing a hemagglutinin tag in the second extracellular loop, we developed an assay to detect transport of de novo Cx43 hemichannels to the plasma membrane after release from Brefeldin A-induced endoplasmic reticulum/Golgi vesicular transport block. Latrunculin A (for specific interference of actin) was used as an intervention after reinitiation of vesicular transport. Disruption of actin inhibits delivery of Cx43 to the cell surface. Moreover, using the assay in primary cardiomyocytes, actin inhibition causes an 82% decrease (P<0.01) in de novo endogenous Cx43 delivery to cell-cell borders. In Langendorff-perfused mouse heart preparations, Cx43/β-actin complexing is disrupted during acute ischemia, and inhibition of actin polymerization is sufficient to reduce levels of Cx43 gap junctions at intercalated discs. Actin is a necessary component of the cytoskeleton-based forward trafficking apparatus for Cx43. In cardiomyocytes, Cx43 vesicles spend a majority of their time pausing at nonsarcomeric actin rest stops when not undergoing microtubule-based transport to the plasma membrane. Deleterious effects on this interaction between Cx43 and the actin cytoskeleton during acute ischemia contribute to losses in Cx43 localization at intercalated discs.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid21798227,

title = {The gap junction life cycle},

author = {Smyth JW and Shaw RM },

year  = {2012},

date = {2012-01-01},

journal = {Heart Rhythm},

volume = {9},

number = {1},

pages = {151--153},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid22289454,

title = {Visualizing cardiac ion channel trafficking pathways},

author = {Smyth JW and Shaw RM },

year  = {2012},

date = {2012-01-01},

journal = {Meth. Enzymol.},

volume = {505},

pages = {187--202},

abstract = {Understanding cardiac electrical and mechanical function requires knowledge of cardiac muscle at the subcellular level. Traditional biochemical and electrophysiological techniques have provided invaluable information in the description of ion channels and their occurrence in various tissues. This knowledge is the basis for our current ability to understand how subcellular ion channel localization occurs and is regulated. We are now in an era whereby individual ion channels can be followed from the moment of their synthesis to placement on the plasma membrane, movements within the membrane, internalization back into the cytoplasm, and degradation. Such insight opens many possibilities for the dissection of regulatory elements governing ion channel expression and function, which will in turn be translated to future therapies for cardiac disease. In this chapter, we discuss the structure of cardiomyocytes and their submembrane domains, the ion channels that we study, and the techniques that can be employed to visualize cardiac ion channel trafficking in real time.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid21825130,

title = {Iroquois homeobox gene 3 establishes fast conduction in the cardiac His-Purkinje network},

author = {Zhang SS*, Kim KH*, Rosen A*, Smyth JW*, Sakuma R*, Delgado-Olguín P, Davis M, Chi NC, Puviindran V, Gaborit N, Sukonnik T, Wylie JN, Brand-Arzamendi K, Farman G, Kim J, Rose RA, Marsden PA, Zhu Y, Zhou YQ, Miquerol L, Henkelman RM, Stainier DY, Shaw RM, Hui CC, Bruneau BG, Backx PH},

year  = {2011},

date = {2011-06-01},

journal = {Proc. Natl. Acad. Sci. U.S.A.},

volume = {108},

number = {33},

pages = {13576--13581},

abstract = {Rapid electrical conduction in the His-Purkinje system tightly controls spatiotemporal activation of the ventricles. Although recent work has shed much light on the regulation of early specification and morphogenesis of the His-Purkinje system, less is known about how transcriptional regulation establishes impulse conduction properties of the constituent cells. Here we show that Iroquois homeobox gene 3 (Irx3) is critical for efficient conduction in this specialized tissue by antithetically regulating two gap junction-forming connexins (Cxs). Loss of Irx3 resulted in disruption of the rapid coordinated spread of ventricular excitation, reduced levels of Cx40, and ectopic Cx43 expression in the proximal bundle branches. Irx3 directly represses Cx43 transcription and indirectly activates Cx40 transcription. Our results reveal a critical role for Irx3 in the precise regulation of intercellular gap junction coupling and impulse propagation in the heart.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid20550924,

title = {Cardiac muscle is not a uniform syncytium},

author = {Shaw RM and Rudy Y},

year  = {2010},

date = {2010-06-01},

journal = {Biophys. J.},

volume = {98},

number = {12},

pages = {3102--3103},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid20621620,

title = {Forward trafficking of ion channels: what the clinician needs to know},

author = {Smyth JW and Shaw RM},

year  = {2010},

date = {2010-06-01},

journal = {Heart Rhythm},

volume = {7},

number = {8},

pages = {1135--1140},

abstract = {Each heartbeat requires precisely orchestrated action potential propagation through the myocardium, achieved by coordination of about a million ion channels on the surface of each cardiomyocyte. Specific ion channels must occur within discrete subdomains of the sarcolemma to exert their electrophysiological effects with highest efficiency (e.g., voltage-gated Ca(2+) channels at T-tubules and gap junctions at intercalated discs). Regulation of ion channel movement to their appropriate membrane subdomain is an exciting research frontier with opportunity for novel therapeutic manipulation of ion channels in the treatment of heart disease. Although much research has generally focused on internalization and subsequent degradation of ion channels, the field of forward trafficking of de novo ion channels from the cell interior to the sarcolemma has now emerged as a key regulatory step in cardiac electrophysiological function. In this brief review, we provide an overview of the current understanding of the cellular biology governing the forward trafficking of ion channels.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid20675583,

title = {Cardiac conduction is required to preserve cardiac chamber morphology},

author = {Chi NC, Bussen M, Brand-Arzamendi K, Ding C, Olgin JE, Shaw RM, Martin GR, and Stainier DY},

year  = {2010},

date = {2010-06-01},

journal = {Proc. Natl. Acad. Sci. U.S.A.},

volume = {107},

number = {33},

pages = {14662--14667},

abstract = {Electrical cardiac forces have been previously hypothesized to play a significant role in cardiac morphogenesis and remodeling. In response to electrical forces, cultured cardiomyocytes rearrange their cytoskeletal structure and modify their gene expression profile. To translate such in vitro data to the intact heart, we used a collection of zebrafish cardiac mutants and transgenics to investigate whether cardiac conduction could influence in vivo cardiac morphogenesis independent of contractile forces. We show that the cardiac mutant dco(s226) develops heart failure and interrupted cardiac morphogenesis following uncoordinated ventricular contraction. Using in vivo optical mapping/calcium imaging, we determined that the dco cardiac phenotype was primarily due to aberrant ventricular conduction. Because cardiac contraction and intracardiac hemodynamic forces can also influence cardiac development, we further analyzed the dco phenotype in noncontractile hearts and observed that disorganized ventricular conduction could affect cardiomyocyte morphology and subsequent heart morphogenesis in the absence of contraction or flow. By positional cloning, we found that dco encodes Gja3/Cx46, a gap junction protein not previously implicated in heart formation or function. Detailed analysis of the mouse Cx46 mutant revealed the presence of cardiac conduction defects frequently associated with human heart failure. Overall, these in vivo studies indicate that cardiac electrical forces are required to preserve cardiac chamber morphology and may act as a key epigenetic factor in cardiac remodeling.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid20169111,

title = {BIN1 localizes the L-type calcium channel to cardiac T-tubules},

author = {Hong TT, Smyth JW, Gao D, Chu K, Vogan J, Fong TS, Jensen BC, Colecraft, H, and Shaw RM},

year  = {2010},

date = {2010-02-01},

journal = {PLoS Biol.},

volume = {8},

number = {2},

pages = {e1000312},

abstract = {The BAR domain protein superfamily is involved in membrane invagination and endocytosis, but its role in organizing membrane proteins has not been explored. In particular, the membrane scaffolding protein BIN1 functions to initiate T-tubule genesis in skeletal muscle cells. Constitutive knockdown of BIN1 in mice is perinatal lethal, which is associated with an induced dilated hypertrophic cardiomyopathy. However, the functional role of BIN1 in cardiomyocytes is not known. An important function of cardiac T-tubules is to allow L-type calcium channels (Cav1.2) to be in close proximity to sarcoplasmic reticulum-based ryanodine receptors to initiate the intracellular calcium transient. Efficient excitation-contraction (EC) coupling and normal cardiac contractility depend upon Cav1.2 localization to T-tubules. We hypothesized that BIN1 not only exists at cardiac T-tubules, but it also localizes Cav1.2 to these membrane structures. We report that BIN1 localizes to cardiac T-tubules and clusters there with Cav1.2. Studies involve freshly acquired human and mouse adult cardiomyocytes using complementary immunocytochemistry, electron microscopy with dual immunogold labeling, and co-immunoprecipitation. Furthermore, we use surface biotinylation and live cell confocal and total internal fluorescence microscopy imaging in cardiomyocytes and cell lines to explore delivery of Cav1.2 to BIN1 structures. We find visually and quantitatively that dynamic microtubules are tethered to membrane scaffolded by BIN1, allowing targeted delivery of Cav1.2 from the microtubules to the associated membrane. Since Cav1.2 delivery to BIN1 occurs in reductionist non-myocyte cell lines, we find that other myocyte-specific structures are not essential and there is an intrinsic relationship between microtubule-based Cav1.2 delivery and its BIN1 scaffold. In differentiated mouse cardiomyocytes, knockdown of BIN1 reduces surface Cav1.2 and delays development of the calcium transient, indicating that Cav1.2 targeting to BIN1 is functionally important to cardiac calcium signaling. We have identified that membrane-associated BIN1 not only induces membrane curvature but can direct specific antegrade delivery of microtubule-transported membrane proteins. Furthermore, this paradigm provides a microtubule and BIN1-dependent mechanism of Cav1.2 delivery to T-tubules. This novel Cav1.2 trafficking pathway should serve as an important regulatory aspect of EC coupling, affecting cardiac contractility in mammalian hearts.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid20038810,

title = {Limited forward trafficking of connexin 43 reduces cell-cell coupling in stressed human and mouse myocardium},

author = {Smyth JW, Hong TT, Gao D, Vogan J, Jensen BC, Fong TS, Simpson PC, Stainier DY, Chi NC, Shaw RM},

year  = {2010},

date = {2010-01-01},

journal = {J. Clin. Invest.},

volume = {120},

number = {1},

pages = {266--279},

abstract = {Gap junctions form electrical conduits between adjacent myocardial cells, permitting rapid spatial passage of the excitation current essential to each heartbeat. Arrhythmogenic decreases in gap junction coupling are a characteristic of stressed, failing, and aging myocardium, but the mechanisms of decreased coupling are poorly understood. We previously found that microtubules bearing gap junction hemichannels (connexons) can deliver their cargo directly to adherens junctions. The specificity of this delivery requires the microtubule plus-end tracking protein EB1. We performed this study to investigate the hypothesis that the oxidative stress that accompanies acute and chronic ischemic disease perturbs connexon forward trafficking. We found that EB1 was displaced in ischemic human hearts, stressed mouse hearts, and isolated cells subjected to oxidative stress. As a result, we observed limited microtubule interaction with adherens junctions at intercalated discs and reduced connexon delivery and gap junction coupling. A point mutation within the tubulin-binding domain of EB1 reproduced EB1 displacement and diminished connexon delivery, confirming that EB1 displacement can limit gap junction coupling. In zebrafish hearts, oxidative stress also reduced the membrane localization of connexin and slowed the spatial spread of excitation. We anticipate that protecting the microtubule-based forward delivery apparatus of connexons could improve cell-cell coupling and reduce ischemia-related cardiac arrhythmias.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid19217425,

title = {Cardiac fibroblasts regulate myocardial proliferation through beta1 integrin signaling},

author = {Ieda M, Tsuchihashi T, Ivey KN, Ross RS, Hong TT, Shaw RM, and Srivastava D},

year  = {2009},

date = {2009-02-01},

journal = {Dev. Cell},

volume = {16},

number = {2},

pages = {233--244},

abstract = {Growth and expansion of ventricular chambers is essential during heart development and is achieved by proliferation of cardiac progenitors. Adult cardiomyocytes, by contrast, achieve growth through hypertrophy rather than hyperplasia. Although epicardial-derived signals may contribute to the proliferative process in myocytes, the factors and cell types responsible for development of the ventricular myocardial thickness are unclear. Using a coculture system, we found that embryonic cardiac fibroblasts induced proliferation of cardiomyocytes, in contrast to adult cardiac fibroblasts that promoted myocyte hypertrophy. We identified fibronectin, collagen, and heparin-binding EGF-like growth factor as embryonic cardiac fibroblast-specific signals that collaboratively promoted cardiomyocyte proliferation in a paracrine fashion. Myocardial beta1-integrin was required for this proliferative response, and ventricular cardiomyocyte-specific deletion of beta1-integrin in mice resulted in reduced myocardial proliferation and impaired ventricular compaction. These findings reveal a previously unrecognized paracrine function of embryonic cardiac fibroblasts in regulating cardiomyocyte proliferation.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid18427137,

title = {Stromal cell-derived factor-1alpha is cardioprotective after myocardial infarction},

author = {Saxena A, Fish JE, White MD, Yu S, Smyth JW, Shaw RM, DiMaio JM, Srivastava},

year  = {2008},

date = {2008-06-10},

journal = {Circulation},

volume = {117},

number = {17},

pages = {2224--2231},

abstract = {Heart disease is a leading cause of mortality throughout the world. Tissue damage from vascular occlusive events results in the replacement of contractile myocardium by nonfunctional scar tissue. The potential of new technologies to regenerate damaged myocardium is significant, although cell-based therapies must overcome several technical barriers. One possible cell-independent alternative is the direct administration of small proteins to damaged myocardium. Here we show that the secreted signaling protein stromal cell-derived factor-1alpha (SDF-1alpha), which activates the cell-survival factor protein kinase B (PKB/Akt) via the G protein-coupled receptor CXCR4, protected tissue after an acute ischemic event in mice and activated Akt within endothelial cells and myocytes of the heart. Significantly better cardiac function than in control mice was evident as early as 24 hours after infarction as well as at 3, 14, and 28 days after infarction. Prolonged survival of hypoxic myocardium was followed by an increase in levels of vascular endothelial growth factor protein and neoangiogenesis. Consistent with improved cardiac function, mice exposed to SDF-1alpha demonstrated significantly decreased scar formation than control mice. These findings suggest that SDF-1alpha may serve a tissue-protective and regenerative role for solid organs suffering a hypoxic insult.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid18456207,

title = {Visualizing ion channel dynamics at the plasma membrane},

author = {Smyth JW and Shaw RM},

year  = {2008},

date = {2008-06-01},

journal = {Heart Rhythm},

volume = {5},

number = {6 Suppl},

pages = {7--11},

abstract = {Cardiac ion channels are surprisingly dynamic in nature, and are continuously formed, trafficked to specific subregions of plasma membrane, inserted in the plasma membrane, and removed to be degraded or recycled. Because of these movements, which affect channel availability, ion channel function is dependent on not just channel biophysical properties but channel trafficking as well. The development of molecular techniques to tag proteins of interest with fluorescent and other genetically encoded proteins, and of advanced imaging modalities such as total internal reflection microscopy (TIRF), have created new opportunities to understand the intracellular movement of proteins near the plasma membrane and their dynamics therein. In this article we present approaches for ion channel biologists to the use of fluorescent and nonfluorescent fusion proteins, techniques for cloning and expression of fusion proteins in mammalian cells, and imaging techniques for live-cell high-resolution microscopy. For illustration, original data are presented on creation of a stable cell line capable of inducible expression of connexin 43 tagged to green fluorescent protein and its distribution viewed with both wide-field epifluorescence and TIRF microscopy. With revolutionary advances in fluorescence microscopy, ion channel biologists are now entering a new realm of studying channel function, which is to understand the mechanisms of channel trafficking.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid18479184,

title = {Genetic and physiologic dissection of the vertebrate cardiac conduction system},

author = {Chi NC, Shaw RM, Jungblut B, Huisken J, Ferrer T, Arnaout R, Scott I, Beis D, Xiao T, Baier H, Jan LY, Tristani-Firouzi M and Stainier DY},

year  = {2008},

date = {2008-05-01},

journal = {PLoS Biol.},

volume = {6},

number = {5},

pages = {e109},

abstract = {Vertebrate hearts depend on highly specialized cardiomyocytes that form the cardiac conduction system (CCS) to coordinate chamber contraction and drive blood efficiently and unidirectionally throughout the organism. Defects in this specialized wiring system can lead to syncope and sudden cardiac death. Thus, a greater understanding of cardiac conduction development may help to prevent these devastating clinical outcomes. Utilizing a cardiac-specific fluorescent calcium indicator zebrafish transgenic line, Tg(cmlc2:gCaMP)(s878), that allows for in vivo optical mapping analysis in intact animals, we identified and analyzed four distinct stages of cardiac conduction development that correspond to cellular and anatomical changes of the developing heart. Additionally, we observed that epigenetic factors, such as hemodynamic flow and contraction, regulate the fast conduction network of this specialized electrical system. To identify novel regulators of the CCS, we designed and performed a new, physiology-based, forward genetic screen and identified for the first time, to our knowledge, 17 conduction-specific mutations. Positional cloning of hobgoblin(s634) revealed that tcf2, a homeobox transcription factor gene involved in mature onset diabetes of the young and familial glomerulocystic kidney disease, also regulates conduction between the atrium and the ventricle. The combination of the Tg(cmlc2:gCaMP)(s878) line/in vivo optical mapping technique and characterization of cardiac conduction mutants provides a novel multidisciplinary approach to further understand the molecular determinants of the vertebrate CCS.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Congestive Heart Failure},

author = {Shaw RM},

year  = {2008},

date = {2008-03-03},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid18347092,

title = {Foxn4 directly regulates tbx2b expression and atrioventricular canal formation},

author = {Chi NC, Shaw RM, De Val S, Kang G, Jan LY, Black BL, and Stainier DY},

year  = {2008},

date = {2008-03-01},

journal = {Genes Dev.},

volume = {22},

number = {6},

pages = {734--739},

abstract = {Cardiac chamber formation represents an essential evolutionary milestone that allows for the heart to receive (atrium) and pump (ventricle) blood throughout a closed circulatory system. Here, we reveal a novel transcriptional pathway between foxn4 and tbx genes that facilitates this evolutionary event. We show that the zebrafish gene slipjig, which encodes Foxn4, regulates the formation of the atrioventricular (AV) canal to divide the heart. sli/foxn4 is expressed in the AV canal, and its encoded product binds to a highly conserved tbx2 enhancer domain that contains Foxn4- and T-box-binding sites, both necessary to regulate tbx2b expression in the AV canal.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Acute vincristine pretreatment protects adult mouse cardiac myocytes from oxidative stress.},

author = {Chatterjee K and Zhang and J and Honbo N and Simonis U and Shaw RM and and Karliner J.},

year  = {2007},

date = {2007-03-03},

journal = {JMCC},

volume = {43},

number = {327-36},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid17289573,

title = {Microtubule plus-end-tracking proteins target gap junctions directly from the cell interior to adherens junctions},

author = {Shaw RM*, Fay AJ*, Puthenveedu MA, Von Zastrow M, Jan YN, and Jan LY},

year  = {2007},

date = {2007-02-01},

journal = {Cell},

volume = {128},

number = {3},

pages = {547--560},

abstract = {Gap junctions are intercellular channels that connect the cytoplasms of adjacent cells. For gap junctions to properly control organ formation and electrical synchronization in the heart and the brain, connexin-based hemichannels must be correctly targeted to cell-cell borders. While it is generally accepted that gap junctions form via lateral diffusion of hemichannels following microtubule-mediated delivery to the plasma membrane, we provide evidence for direct targeting of hemichannels to cell-cell junctions through a pathway that is dependent on microtubules; through the adherens-junction proteins N-cadherin and beta-catenin; through the microtubule plus-end-tracking protein (+TIP) EB1; and through its interacting protein p150(Glued). Based on live cell microscopy that includes fluorescence recovery after photobleaching (FRAP), total internal reflection fluorescence (TIRF), deconvolution, and siRNA knockdown, we propose that preferential tethering of microtubule plus ends at the adherens junction promotes delivery of connexin hemichannels directly to the cell-cell border. These findings support an unanticipated mechanism for protein delivery to points of cell-cell contact.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid15967996,

title = {Mammalian electrophysiology on a microfluidic platform},

author = {Ionescu- Zanetti C*, Shaw RM*, Seo J, Jan LY, and Lee LP},

year  = {2005},

date = {2005-06-01},

journal = {Proc. Natl. Acad. Sci. U.S.A.},

volume = {102},

number = {26},

pages = {9112--9117},

abstract = {The recent development of automated patch clamp technology has increased the throughput of electrophysiology but at the expense of visual access to the cells being studied. To improve visualization and the control of cell position, we have developed a simple alternative patch clamp technique based on microfluidic junctions between a main chamber and lateral recording capillaries, all fabricated by micromolding of polydimethylsiloxane (PDMS). PDMS substrates eliminate the need for vibration isolation and allow direct cell visualization and manipulation using standard microscopy. Microfluidic integration allows recording capillaries to be arrayed 20 microm apart, for a total chamber volume of <0.5 nl. The geometry of the recording capillaries permits high-quality, stable, whole-cell seals despite the hydrophobicity of the PDMS surface. Using this device, we are able to demonstrate reliable whole-cell recording of mammalian cells on an inexpensive microfluidic platform. Recordings of activation of the voltage-sensitive potassium channel Kv2.1 in mammalian cells compare well with traditional pipette recordings. The results make possible the integration of whole-cell electrophysiology with easily manufactured microfluidic lab-on-a-chip devices.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Microfluidic application-specific integrated device for monitoring direct cell-cell communication via gap junctions between individual cell pairs},

author = {Lee PJ and Hung PJ and Shaw R and Jan L and Lee and LP},

year  = {2005},

date = {2005-03-03},

journal = {App Phys Lett},

volume = {86},

number = {223902},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {VEGF gene delivery to myocardium: Deleterious effects of unregulated expression.},

author = {Lee RJ and Springer ML and Blanco-Bose WE and Shaw RM and Ursell PC and and Blau HM},

year  = {2000},

date = {2000-03-03},

journal = {Circulation},

volume = {102},

number = {898-901},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid10318671,

title = {Effects of IKr and IKs heterogeneity on action potential duration and its rate dependence: a simulation study},

author = {Viswanathan PC, Shaw RM and Rudy Y},

year  = {1999},

date = {1999-05-01},

journal = {Circulation},

volume = {99},

number = {18},

pages = {2466--2474},

abstract = {A growing body of evidence suggests that heterogeneity of ion channel expression and electrophysiological characteristics is an important property of the ventricular myocardium. The 2 components of the delayed rectifier potassium current, IKr (rapid) and IKs (slow), play a dominant role in the repolarization of the action potential and are important determinants of its duration. In this report, the effects of heterogeneities of IKr and IKs on action potential duration (APD) and its rate dependence (adaptation) are studied with the use of the LRd model of a mammalian ventricular cell. Results demonstrate the importance of IKs density variations in heterogeneity of repolarization. Cells with reduced IKs (eg, mid-myocardial M cells) display long APD and steep dependence of APD on rate. Mechanistically, accumulation of IKs activation and increased sodium calcium exchange current, INaCa, secondary to Na+ accumulation at a fast rate underlie the steep APD-rate relation of these cells. When cells are electrotonically coupled in a multicellular fiber through resistive gap junction, APD differences are reduced. The results demonstrate strong dependence of APD heterogeneity on the degree of intercellular coupling even in the normal physiological range. Highly reduced coupling maximizes APD heterogeneity. Heterogeneity of IKs:IKr density strongly influences APD and its rate dependence. However, in the intact myocardium, the degree of gap-junction coupling may be an important factor that determines the manifestation of APD heterogeneity and dispersion of repolarization. The clinical significance of this study is in the context of repolarization abnormalities and associated arrhythmias (eg, long QT syndrome and torsade de pointes).},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {“Gap junctions and the spread of electrical current”. In: “Heart cell communication in health and disease.},

author = {Shaw RM and Rudy Y},

year  = {1998},

date = {1998-03-03},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid9351447,

title = {Ionic mechanisms of propagation in cardiac tissue. Roles of the sodium and L-type calcium currents during reduced excitability and decreased gap junction coupling},

author = {Shaw RM and Rudy Y},

year  = {1997},

date = {1997-11-01},

journal = {Circ. Res.},

volume = {81},

number = {5},

pages = {727--741},

abstract = {In cardiac tissue, reduced membrane excitability and reduced gap junction coupling both slow conduction velocity of the action potential. However, the ionic mechanisms of slow conduction for the two conditions are very different. We explored, using a multicellular theoretical fiber, the ionic mechanisms and functional role of the fast sodium current, INa, and the L-type calcium current, ICa(L), during conduction slowing for the two fiber conditions. A safety factor for conduction (SF) was formulated and computed for each condition. Reduced excitability caused a lower SF as conduction velocity decreased. In contrast, reduced gap junction coupling caused a paradoxical increase in SF as conduction velocity decreased. The opposite effect of the two conditions on SF was reflected in the minimum attainable conduction velocity before failure: decreased excitability could reduce velocity to only one third of control (from 54 to 17 cm/s) before failure occurred, whereas decreased coupling could reduce velocity to as low as 0.26 cm/s before block. Under normal conditions and conditions of reduced excitability, ICa(L) had a minimal effect on SF and on conduction. However, ICa(L) played a major role in sustaining conduction when intercellular coupling was reduced. This phenomenon demonstrates that structural, nonmembrane factors can cause a switch of intrinsic membrane processes that support conduction. High intracellular calcium concentration, [Ca]i, lowered propagation safety and caused earlier block when intercellular coupling was reduced. [Ca]i affected conduction via calcium-dependent inactivation of ICa(L). The increase of safety factor during reduced coupling suggests a major involvement of uncoupling in stable slow conduction in infarcted myocardium, making microreentry possible. Reliance on ICa(L) for this type of conduction suggests ICa(L) as a possible target for antiarrhythmic drug therapy.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid9349389,

title = {Electrophysiologic effects of acute myocardial ischemia: a theoretical study of altered cell excitability and action potential duration},

author = {Shaw RM and Rudy Y},

year  = {1997},

date = {1997-06-05},

journal = {Cardiovasc. Res.},

volume = {35},

number = {2},

pages = {256--272},

abstract = {To study the ionic mechanisms of electrophysiologic changes in cell excitability and action potential duration during the acute phase of myocardial ischemia. Using an ionic-based theoretical model of the cardiac ventricular cell, the dynamic LRd model, we have simulated the three major component conditions of acute ischemia (elevated [K]o, acidosis and anoxia) at the level of individual ionic currents and ionic concentrations. The conditions were applied individually and in combination to identify ionic mechanisms responsible for reduced excitability at rest potentials, delayed recovery of excitability, and shortened action potential duration. Increased extracellular potassium ([K]o) had the major effect on cell excitability by depolarizing resting membrane potential (Vrest), causing reduction in sodium channel availability. Acidosis caused a [K]o-independent reduction in maximum upstroke velocity, (dVm/dt)max. A transition from sodium-current dominated to calcium-current dominated upstroke occurred, and calcium current alone was able to sustain the upstroke, but only after sodium channels were almost completely (97%) inactivated. Acidic conditions prevented the transition to calcium dominated upstroke by acidic reduction of both sodium and calcium currents. Anoxia, simulated by lowering [ATP]i and activating the APT-dependent potassium current, IK(ATP), was the only process that could decrease action potential duration by more than 50% and reproduce AP shape changes that are observed experimentally. Acidic or anoxic depression of the L-type calcium current could not reproduce the observed action potential shape changes and APD shortening. Delayed recovery of excitability, known as 'post-repolarization refractoriness', was determined by the voltage-dependent kinetics of sodium channel recovery; Vrest depolarization caused by elevated [K]o increased the time constant of (dVm/dt)max recovery from tau = 10.3 ms at [K]o = 4.5 mM to tau = 81.4 ms at [K]o = 12 mM, reflecting major slowing of sodium-channel recovery. Anoxia and acidosis had little affect on tau. The major conditions of acute ischemia, namely elevated [K]o, acidosis and anoxia, applied at the ionic channel level are sufficient to simulate the major electrical changes associated with ischemia. Depression of membrane excitability and delayed recovery of excitability in the single, unloaded cell are caused by elevated [K]o with additional excitability depression by acidosis. Major changes in action potential duration and shape can only be accounted for by anoxia-dependent opening of IK(ATP).},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid8978331,

title = {Electrophysiologic effects of acute myocardial ischemia. A mechanistic investigation of action potential conduction and conduction failure},

author = {Shaw RM and Rudy Y},

year  = {1997},

date = {1997-01-01},

journal = {Circ. Res.},

volume = {80},

number = {1},

pages = {124--138},

abstract = {A multicellular ventricular fiber model was used to determine mechanisms of slowed conduction and conduction failure during acute ischemia. We simulated the three major pathophysiological component conditions of acute ischemia: elevated [K+]o, acidosis, and anoxia. Elevated [K+]o was the major determinant of conduction, causing supernormal conduction, depressed conduction, and conduction block as [K+]o was gradually increased from 4.5 to 14.4 mmol/L. Only elevated [K+]o caused conduction failure when varied within the range reported for acute ischemia. Before block, depressed upstrokes consisted of two distinct components: the first to the fast Na+ current (INa) and the second to the L-type Ca2+ current (ICa(L)). Even in highly depressed conduction, excitability was maintained by INa, with conduction block occurring at 95% INa inactivation. However, because ICa(L) supported the later phase of the depressed upstroke, ICa(L) enhanced conduction and delayed block by increasing the electrotonic source current. At [K+]o = 18 mmol/L, slow action potentials generated by ICa(L) were obtained with 10% ICa(L) augmentation. However, in the presence of acidosis and anoxia, significantly larger (120%) ICa(L) augmentation was required. The depressant effect was due mostly to anoxic activation of outward ATP-sensitive K+ current, which counteracts inward ICa(L) and, by lowering the action potential amplitude, decreases the electrotonic current available to depolarize downstream cells. The simulations highlight the interactive nature of electrophysiological ischemic changes during propagation and demonstrate that both membrane changes and load factors (by downstream fiber) must be considered.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid9330736,

title = {Cardiac excitation: an interactive process of ion channels and gap junctions},

author = {Rudy Y and Shaw RM},

year  = {1997},

date = {1997-01-01},

volume = {430},

pages = {269--279},

abstract = {Theoretical simulations were performed to study the interplay between membrane ionic currents and gap-junction coupling in determining cardiac conduction. Results demonstrate that a much slower conduction velocity can be achieved with reduced gap-junction coupling than with reduced membrane excitability. Also, uniform reduction in intercellular coupling increases spatial asymmetries of excitability and, consequently, the vulnerability to unidirectional block.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid7780627,

title = {The vulnerable window for unidirectional block in cardiac tissue: characterization and dependence on membrane excitability and intercellular coupling},

author = {Shaw RM and Rudy Y},

year  = {1995},

date = {1995-02-01},

journal = {J. Cardiovasc. Electrophysiol.},

volume = {6},

number = {2},

pages = {115--131},

abstract = {Unidirectional block is a requisite event in the initiation of reentry in cardiac tissue, but its initiation and behavior in the presence of tissue pathologies remain poorly understood. Previous experimental and theoretical reports on vulnerability to unidirectional block under conditions of reduced cellular coupling and reduced membrane excitability have varied due to differences in experimental and simulation protocols. We have addressed the issue of vulnerability to unidirectional block using the recent Luo-Rudy membrane model and computer simulations of propagation in a one-dimensional cardiac fiber. The vulnerable window (VW) of unidirectional block from premature stimulation is expressed in units of time, VWtime, and as a range of membrane potentials at the stimulus site, VWpot. VWpot and VWtime were quantified over a range of membrane excitability and gap junction resistances (intercellular coupling). With normal membrane excitability and intercellular coupling, VWpot and VWtime were small (VWpot = 0.44 mV},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{,

title = {Bremsstrahlung imaging using the gamma camera: Factors affecting attenuation},

author = {Clarke LP and Cullom SJ and Shaw R and Reece C and Penney BC and King MA and Silbiger M.},

year  = {1992},

date = {1992-03-03},

journal = {Factors affecting attenuation},

volume = {33},

number = {161-6},

keywords = {},

pubstate = {published},

tppubtype = {article}

}