Abstract 400: Regulated Levels of Sarcolemmal Membrane Protein Isoform 3 Impact Cardiac Function in Mice
The sarcolemmal membrane-associated proteins (SLMAPs) are a family of tail-anchored membrane proteins generated by alternative splicing of the SLMAP gene. A ubiquitously expressed SLMAP isoform 3 encompasses an N-terminal FHA domain with extended coiled-coil structure and has been implicated in cell cycle control. Heart function in transgenic mice with cardiac-specific overexpression of SLMAP3 cDNA driven by α myosin heavy chain promoter was evaluated by echocardiography. qPCR and western blot were used to analyze gene and protein expression respectively. Structure and fibrosis was analyzed by H&E and Masson’s Trichrome staining. Function analysis showed a 15% (p<0.05) decrease in ejection fraction and 19% (p<0.05) decrease in fractional shortening in transgenic mice as early as 5 weeks and persisted into old age at 44 weeks. Transgenic mice presented a mild systolic dysfunction and a trend towards dilated cardiomyopathy without any premature death. Natriuretic peptide ANP and BNP levels were not changed and there was no difference in left ventricular mass or activation of the hypertrophic factor Akt1 in SLMAP3 expressing myocardium. However, significant changes in calcium handling proteins with a significant decrease in phosphorylation of phospholamban ser16 (p<0.05) along with a down-regulation of sarco-endoplasmic reticulum Ca2+ ATPase protein and increased ryanodine receptor 2 phosphorylation ser2808 (p<0.05) were noted at 5 weeks of age in transgenic hearts. These data indicate that increased SLMAP3 levels did not influence cardiac remodeling or hypertrophic growth but did impact membrane biology of calcium transport systems in myocardium leading to depressed contractility. Thus regulated levels of SLMAP3 are important to support normal heart function.
Author Disclosures: J. Mlynarova: None. M. Trentin-Sonoda: None. M. Salih: None. F. Gaisler da Silva: None. J.L. Major: None. M. Sorelli Carneiro-Ramos: None. B.S. Tuana: None.
- © 2015 by American Heart Association, Inc.