Similar to skeletal muscle myofibers, cardiomyocytes in the heart appear to be particularly susceptible to membrane instability and rupture with the slightest perturbation, in part because of their contractile status that produces ongoing mechanical deformation. Mutations in genes that disrupt or weaken the membrane anchoring proteins of the dystrophin-glycoprotein complex (DGC) or the integrin adhesion network causes a wide range of muscular dystrophies that also cause cardiomyopathy. We have recently shown that the thromobospondin gene family (Thbs1- 5) plays a critical role in membrane stability through both effects on the ER stress response and secretory pathways, as well as controlling the integrin complexes present on the sarcolemma. In our previous cycle of funding we showed that overexpression of select Thbs proteins in the heart or skeletal muscle can have remarkable effects on sarcolemma stability in heart and skeletal muscle cells, while KO mice for the same Thbs genes have reciprocal effects that complement exactly the overexpression effect. Thus, in this renewal application we will attempt to uncover the molecular mechanisms whereby the Thbs proteins serve to regulate sarcolemmal stability during ER stress and healing, in part, through coding for select integrin heterodimers on the cell surface of cardiomyocytes. We propose the unifying hypothesis that the Thbs proteins are stress-induced ER resident factors that facilitate healing after injury or with stress by serving as intra-vesicular chaperones for sarcolemmal delivery of integrins through the secretory pathway. To address this hypothesis we propose 3 specific aims.
Aim #1 will compare Thbs3 versus Thbs4 in regulating cardiac sarcolemma stability and disease with doxorubicin induced cardiomyopathy and muscular dystrophy (models of membrane instability).
Aim #2 we will attempt to rescue the enhanced cardiac disease phenotype and sarcolemmal instability of Thbs3 TG and Thbs4-/- mice by integrin overexpression in vivo.
Aim #3 we will examine the molecular mechanisms whereby Thbs3 reduces membrane stability and Thbs4 increases it through integrin processing within the cell. Defining the molecular mechanisms in play and how selective integrin sorting is achieved by the Thbs proteins during stress stimulation and healing will suggest novel treatment approaches for MI injury and post-ischemic heart failure.

Public Health Relevance

The endoplasmic reticulum (ER) stress response appears to be a universal feature of all cardiomyopathies as well as healing after infarction injury to the heart. Here we have identified a novel function for the thrombospondin (Thbs) gene family as intracellular regulators of the ER stress response and healing, whereby these factors alter the plasma membrane content of integrins in a selective manner to ultimately impact membrane stability. Understanding how and why thrombospondins have this role is of great medical relevance as loss of membrane stability underlies many forms of heart disease.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Myocardial Ischemia and Metabolism Study Section (MIM)
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Adhikari, Bishow B
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Cincinnati Children's Hospital Medical Center
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Brody, Matthew J; Vanhoutte, Davy; Schips, Tobias G et al. (2018) Defective Flux of Thrombospondin-4 through the Secretory Pathway Impairs Cardiomyocyte Membrane Stability and Causes Cardiomyopathy. Mol Cell Biol :
Schwanekamp, Jennifer A; Lorts, Angela; Sargent, Michelle A et al. (2017) TGFBI functions similar to periostin but is uniquely dispensable during cardiac injury. PLoS One 12:e0181945
Cai, Chen-Leng; Molkentin, Jeffery D (2017) The Elusive Progenitor Cell in Cardiac Regeneration: Slip Slidin' Away. Circ Res 120:400-406
Khalil, Hadi; Kanisicak, Onur; Prasad, Vikram et al. (2017) Fibroblast-specific TGF-?-Smad2/3 signaling underlies cardiac fibrosis. J Clin Invest 127:3770-3783
Molkentin, Jeffery D; Bugg, Darrian; Ghearing, Natasha et al. (2017) Fibroblast-Specific Genetic Manipulation of p38 Mitogen-Activated Protein Kinase In Vivo Reveals Its Central Regulatory Role in Fibrosis. Circulation 136:549-561
Liu, Ruijie; van Berlo, Jop H; York, Allen J et al. (2016) DUSP8 Regulates Cardiac Ventricular Remodeling by Altering ERK1/2 Signaling. Circ Res 119:249-60
Gupta, Manish K; McLendon, Patrick M; Gulick, James et al. (2016) UBC9-Mediated Sumoylation Favorably Impacts Cardiac Function in Compromised Hearts. Circ Res 118:1894-905
James, Jeanne; Robbins, Jeffrey (2016) Healing a Heart Through Genetic Intervention. Circ Res 118:920-2
Vanhoutte, Davy; Schips, Tobias G; Kwong, Jennifer Q et al. (2016) Thrombospondin expression in myofibers stabilizes muscle membranes. Elife 5:
Brody, Matthew J; Schips, Tobias G; Vanhoutte, Davy et al. (2016) Dissection of Thrombospondin-4 Domains Involved in Intracellular Adaptive Endoplasmic Reticulum Stress-Responsive Signaling. Mol Cell Biol 36:2-12

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