Model of Cavin4 involvement in T-tubule formation and maturation. In WT muscle, initial T-tubule formation involves Bin1-mediated membrane deformation. Bin1b recruits Cavin4b through an interaction between the Bin1b SH3-binding domain and the Cavin4b PRD, which enhances T-tubule formation and stabilization. As the T-tubule matures, Cav3 is recycled back to the sarcolemma through a Cavin4-dependent mechanism, either by diffusion within the plane of the membrane (1) or via budding of carriers (2). In the absence of Cavin4, Cav3 accumulates within the T-tubules, generating caveola-like structures, and fragmentation occurs. These aberrant T-tubules can be stabilized by high expression of Bin1, which also promotes redistribution of Cav3/caveolae back to the sarcolemma.