Rapid, voltage-dependent potentiation of skeletal muscle L-type calcium channels requires phosphorylation by cAMP-dependent protein kinase (PKA) anchored via an A kinase anchoring protein (AKAP). Here we report the isolation, primary sequence determination, and functional characterization of AKAP15, a lipid-anchored protein of 81 amino acid residues with a single amphipathic helix that binds PKA. AKAP15 colocalizes with L-type calcium channels in transverse tubules and is associated with L-type calcium channels in transfected cells. A peptide fragment of AKAP15 encompassing the RII- binding domain blocks voltage-dependent potentiation. These results indicate that AKAP15 targets PKA to the calcium channel and plays a critical role in voltage-dependent potentiation and regulation of skeletal muscle contraction. The expression of AKAP15 in the brain and heart suggests that it may mediate rapid PKA regulation of L-type calcium channels in neurons and cardiac myocytes.
Gray, P. C., Johnson, B. D., Westenbroek, R. E., Hays, L. G., Yates, J. R., Scheuer, T., … Murphy, B. J. (1998). Primary structure and function of an A kinase anchoring protein associated with calcium channels. Neuron, 20(5), 1017–1026. https://doi.org/10.1016/S0896-6273(00)80482-1