Defects in the cytoskeletal architecture of the heart are associated with dilated cardiomyopathies. Here, we focus on cytoskeletal elements that stabilize the transverse (t) tubules of cardiac muscle and that link them to the nearby sarcoplasmic/endoplasmic reticulum (SR/ER). Recent results suggest that the interface between the t-tubules and the SR/ER is composed of at least two different protein arrays. One is composed of the classic mediators of excitation-contraction coupling, voltage-gated Ca channels in the t-tubule and Ca release channels (ryanodine receptors) in the SR/ER. The second is composed of other integral membrane proteins of the t-tubule and the SR/ER, linked by a membrane-bound cytoskeletal network of spectrin and ankyrin. Spectrin and its associated proteins are also likely to bind to and stabilize the t-tubular membrane at sites that are not closely apposed to the SR/ER membrane. We propose to test the hypothesis that the cytoskeleton of t-tubules is composed of two distinct spectrin networks, one that helps organize and stabilize the t-tubular membranes, and another that links them to the SR/ER in a complex that is regulated by phosphorylation. We will use a combination of molecular, cell biological, ultrastructural, proteomics and physiological approaches to address this hypothesis. We have five specific aims: (1) to characterize alphaII-cardi+, an alternatively spliced form of spectrin that is selectively expressed in the heart, and the complexes it forms; (2) to characterize other spectrins and the complexes they form at the cardiac t-tubule membrane; (3) to identify the spectrins and ankyrins that link the t-tubule to the SR/ER membrane, and the proteins with which they interact; (4) to study the effects of phosphorylation on the spectrin complexes at t-tubules; (5) to assess the effects of altering the spectrin network at t-tubules on the morphology and physiology of cardiocytes. Each of these aims is supported by our preliminary results, which suggest that t-tubules and their interactions with the SR/ER are coordinated by unique spectrin complexes, regulated by local signaling cascades. Defining these interactions and the mechanisms that control them should provide unique insights into how the heart functions normally, and how changes in cytoskeletal architecture at the t-tubules can result in cardiomyopathy.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL075106-05
Application #
7348395
Study Section
Cardiovascular and Pulmonary Research A Study Section (CVA)
Program Officer
Evans, Frank
Project Start
2003-12-22
Project End
2009-11-30
Budget Start
2007-12-01
Budget End
2009-11-30
Support Year
5
Fiscal Year
2008
Total Cost
$352,012
Indirect Cost
Name
University of Maryland Baltimore
Department
Physiology
Type
Schools of Medicine
DUNS #
188435911
City
Baltimore
State
MD
Country
United States
Zip Code
21201
Nestor, Michael W; Cai, Xiang; Stone, Michele R et al. (2011) The actin binding domain of ýýI-spectrin regulates the morphological and functional dynamics of dendritic spines. PLoS One 6:e16197
Zhang, Yinghua; Resneck, Wendy G; Lee, Pervis C et al. (2010) Characterization and expression of a heart-selective alternatively spliced variant of alpha II-spectrin, cardi+, during development in the rat. J Mol Cell Cardiol 48:1050-9
Kontrogianni-Konstantopoulos, Aikaterini; Ackermann, Maegen A; Bowman, Amber L et al. (2009) Muscle giants: molecular scaffolds in sarcomerogenesis. Physiol Rev 89:1217-67
Ursitti, Jeanine A; Petrich, Brian G; Lee, Pervis C et al. (2007) Role of an alternatively spliced form of alphaII-spectrin in localization of connexin 43 in cardiomyocytes and regulation by stress-activated protein kinase. J Mol Cell Cardiol 42:572-81