STAC (SH3 and cysteine rich domain) is a calcium channel modulator protein consisting of conserved cysteine-rich and SH3 domains 1. The protein functions primarily as an adaptor that regulates voltage-gated calcium channel trafficking and activity. In skeletal muscle, STAC3 is essential for excitation-contraction coupling, mediating mechanical coupling between the L-type calcium channel CaV1.1 and the ryanodine receptor RyR1 23. STAC proteins associate with the IQ domain in the C-terminus of CaV1 channels through conserved C1 and SH3 domains 4. Mechanistically, STAC proteins suppress calcium-dependent inactivation (CDI) of L-type calcium channels by interfering with calcium-calmodulin feedback regulation 54. In neurons, STAC2 expression increases substantially postnatally in forebrain and cerebellum, suggesting developmental regulation of L-type channel calcium signaling 5. Mutations in STAC3 cause congenital myopathy and severe muscle disease by disrupting the mechanical coupling essential for muscle contraction 2. While STAC3's role in skeletal muscle is well-characterized, neuronal STAC isoforms (STAC1 and STAC2) appear to function as tuning regulators of neuronal L-type calcium channels, though their complete functional significance in brain remains incompletely understood.