Mitsugumin 29 (or MG29) is a synaptophysin-family member protein localized specifically in the triad junction of skeletal muscle, where the transverse tubular (T-tubule) invagination of plasma membrane touches the terminal cistemae of sarcoplasmic reticulum (SR). The triad junction provides the structural framework for interaction between the dihydropyridine receptor/voltage sensor and the ryanodine receptor (RyR)/Ca release channel, and is essential for the operation of excitation-contraction (E-C) coupling. MG29 appears to be indispensable for triad formation, since swollen T-tubules and vacuolated SR networks are observed in skeletal muscle isolated from the mg29(-/-) mice. The long term goal of this project is to understand the cellular and molecular function of MG29 in E-C coupling of muscle cells, specifically to test the hypothesis that MG29 is a key protein involved in the biogenesis of the T-tubule system, and the proper organization of the T-tubule structure is essential for both short-term E-C coupling and long term cellular Ca homeostasis. A distinct phenotype of mg29(-/-) mice is their increased susceptibility to muscle fatigue, which may be linked to an altered Ca signaling in the mutant muscle.
Aim 1 of this project is to correlate the MG29-mediated changes in membrane structure with short-term changes in voltage-induced Ca release (VICR) and Ca-induced Ca release (CICR) in skeletal muscle. The defective membrane structure associated with deletion of MG29 could alter the retrograde interaction between RyR and store-operated Ca channel (SOC) in the plasma membrane, and affect long-term Ca homeostasis in muscle cells.
Aim 2 of this project will investigate the mechanism of SOC regulation in skeletal muscle by MG29, by exploring the potential interaction of MG29 with RyR, caveolin-3 and other associated proteins.
Aim 3 is designed to further test the role of T-tubule structure in the differential mechanism of Ca signaling in cardiac and skeletal muscles. A transgenic mouse has been generated that switched the mg29 gene from skeletal to cardiac muscle (mhc. mg29). The changes in efficacy of E-C coupling in cardiac myocytes and skeletal myotubes isolated from the mhc-mg29 and mg29(-/-) mice will be compared with the wild type controls, in order to understand the contribution of T-tubules to Ca signaling in heart and skeletal muscle and the molecular basis of muscle fatigue. ? ? Overall, fulfillment of experiments proposed in this project shall lead us to better understanding of the molecular mechanism of E-C coupling, in particular with respect to the roles of MG29 and RyR in the activation of CICR, VICR, and SOC in cardiac and skeletal muscles. In addition, our studies with the mutant mice will provide new insights into the cellular mechanism of muscle exercise physiology and cardiovascular diseases.

Agency
National Institute of Health (NIH)
Institute
National Institute on Aging (NIA)
Type
Research Project (R01)
Project #
5R01AG015556-10
Application #
7097918
Study Section
Cardiovascular and Pulmonary Research A Study Section (CVA)
Program Officer
Williams, John
Project Start
1997-09-01
Project End
2008-08-31
Budget Start
2006-09-01
Budget End
2008-08-31
Support Year
10
Fiscal Year
2006
Total Cost
$341,654
Indirect Cost
Name
University of Medicine & Dentistry of NJ
Department
Physiology
Type
Schools of Medicine
DUNS #
617022384
City
Piscataway
State
NJ
Country
United States
Zip Code
08854
Weisleder, Noah; Takizawa, Norio; Lin, Peihui et al. (2012) Recombinant MG53 protein modulates therapeutic cell membrane repair in treatment of muscular dystrophy. Sci Transl Med 4:139ra85
Zhao, Xiaoli; Yamazaki, Daiju; Kakizawa, Sho et al. (2011) Molecular architecture of Ca2+ signaling control in muscle and heart cells. Channels (Austin) 5:391-6
Weisleder, Noah; Ma, Jianjie (2008) Altered Ca2+ sparks in aging skeletal and cardiac muscle. Ageing Res Rev 7:177-88
Weisleder, Noah; Ferrante, Christopher; Hirata, Yutaka et al. (2007) Systemic ablation of RyR3 alters Ca2+ spark signaling in adult skeletal muscle. Cell Calcium 42:548-55
Ko, Jae-Kyun; Choi, Kyoung-Han; Pan, Zui et al. (2007) The tail-anchoring domain of Bfl1 and HCCS1 targets mitochondrial membrane permeability to induce apoptosis. J Cell Sci 120:2912-23
Landstrom, Andrew P; Weisleder, Noah; Batalden, Karin B et al. (2007) Mutations in JPH2-encoded junctophilin-2 associated with hypertrophic cardiomyopathy in humans. J Mol Cell Cardiol 42:1026-35
Weisleder, Noah; Brotto, Marco; Komazaki, Shinji et al. (2006) Muscle aging is associated with compromised Ca2+ spark signaling and segregated intracellular Ca2+ release. J Cell Biol 174:639-45
Zhao, Xiaoli; Weisleder, Noah; Han, Xuehai et al. (2006) Azumolene inhibits a component of store-operated calcium entry coupled to the skeletal muscle ryanodine receptor. J Biol Chem 281:33477-86
Hirata, Yutaka; Brotto, Marco; Weisleder, Noah et al. (2006) Uncoupling store-operated Ca2+ entry and altered Ca2+ release from sarcoplasmic reticulum through silencing of junctophilin genes. Biophys J 90:4418-27
Ko, Jae-Kyun; Ma, Jianjie (2005) A rapid and efficient PCR-based mutagenesis method applicable to cell physiology study. Am J Physiol Cell Physiol 288:C1273-8

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