P.5.1 Sarcolemmal repair and reorganization of microtubule

Dysferlin is a sarcolemmal protein that is defective in Miyoshi myopathy and LGMD2B, and is involved in sarcolemmal repair. Proteomics analyses have identified multiple dysferlin-binding partners including cytoskeletal proteins. Affixin, a binding partner of dysferlin, regulates cytoskeletal actin. We reported that affixin, β- and γ-actin accumulated at the sarcolemmal injury site of wild-type mice in response to membrane rapture. α-tubulin and microtubule-associated proteins have been reported as dysferlin binding partners, however, their involvement in sarcolemmal repair remains unclear. The purpose of this study is to examine involvement of microtubule in sarcolemmal repair. To clarify molecular behavior of α-tubulin in sarcolemmal repair, GFP2-tagged human α-tubulin was expressed in mouse FDB muscle (C57BL/6J and dysferlin-deficient SJL) by electroporation. Membrane wound-repair assay of single myofiber was performed using confocal microscope equipped two-photon laser. GFP2-α-tubulin expressed in wild-type mice was localized at sarcolemma and T-tubule, and observed as a striated pattern. This striation pattern of GFP2-α-tubulin was slightly disorganized in SJL mice. After sarcolemmal injury, GFP2-α-tubulin in wild-type mice was disassembled and accumulates slower compared to GFP-β- and γ -actin. In SJL mice, GFP2-α-tubulin around the injury site was depolymerized, however, accumulation of GFP2-α-tubulin was not observed. α-Tubulin may also have a role in sarcolemmal repair.