Critical role of cAMP-dependent protein kinase anchoring to the L-type calcium channel Ca_v1.2 via A-kinase anchor protein 150 in neurons

The cAMP-dependent protein kinase (PKA) regulates a wide array of cellular functions. In brain and heart PKA increases the activity of the L-type Ca ²⁺ channel Ca_v1.2 in response to β-adrenergic stimulation. Ca_v1.2 forms a complex with the β₂- adrenergic receptor, the trimeric G_S protein, adenylyl cyclase, and PKA wherein highly localized signaling occurs [Davare, M. A., Avdonin, V., Hall, D. D., Peden, E. M., Burette, A., Weinberg, R. J., Horne, M. C., Hoshi, T., and Hell, J. W. (2001) Science 293, 98-101]. PKA primarily phosphorylates Ca _v1.2 on serine 1928 of the central, pore-forming α ₁1.2 subunit. Here we demonstrate that the A-kinase anchor protein 150 (AKAP150) is critical for PKA-mediated regulation of Ca_v1.2 in the brain. AKAP150 and MAP2B specifically co-immunoprecipitate with Ca _v1.2 from rat brain. Recombinant AKAP75, the bovine homologue to rat AKAP150, binds directly to three different sites of α₁1.2. MAP2B from rat brain also interacts with these same sites in pull-down assays. Gene disruption of AKAP150 in mice dramatically reduces co-immunoprecipitation of PKA with Ca_v1.2 and prevents phosphorylation of serine 1928 upon β-adrenergic stimulation in vivo. These results demonstrate the physiological relevance of PKA anchoring by AKAPs in general and AKAP150 specifically in the regulation of Ca_v1.2 in vivo.