Expression of the tail‐anchored protein SLMAP in developing myocardium and during remodelling after myocardial infarction

Abstract

The Organization of Excitation-Contraction (E-C) coupling mechanism is temporally regulated during heart remodelling. The molecular components involved in organizing membranes junctions with respect to the contractile apparatus remain elusive. SLMAP (Sarcolemmal Membrane Associated Protein) is a unique molecule shown to localize in cardiac membranes as well as the contractile apparatus and may serve to organizing the E-C coupling mechanism. The aim of this study was to investigate SLMAP expression and localization in developing myocardium and after Myocardial Infarction (MI) to correlate changes with any reorganization of the E-C coupling mechanism. SLMAP was located at the Z-disc, T-tubules and Sarcolemmal Membranes of rat myocardium as assessed by Immunostaining and Western blot analysis. SLMAP expression was significantly increased (p<0.005) from embryonic (E) day 16 to postnatal (P1) and gradually decreased (p<0.01) to low levels at 13 weeks. In a rat heart MI model induced by coronary ligation, SLMAP1 levels significantly increased (4 weeks post-surgery) in Infarct tissue vs. remote left ventricle (LV) (p<0.05) and SHAM (p<0.005). The location of SLMAP and temporal changes in its expression in normal and defective myocardium suggest that SLMAP may serve a role in organizing the E-C coupling apparatus during normal cardiac growth and in remodelling post MI. This work was supported by a grant from HSFO.