Bin1 Regulates CaV1.2 Channel Clustering in Ventricular Myocytes

L-type Cav1.2 channels are expressed in the plasma membranes of excitable cells including cardiac myocytes where they play a key role in excitation-contraction coupling. Recently, we reported that Cav1.2 channels form clusters that undergo dynamic, reciprocal, allosteric interactions. This ‘functional coupling’ facilitates Ca2+ influx by increasing activity (NPo) of adjoined channels and occurs through C-terminal-to-C-terminal interactions. Physical proximity of Cav1.2 channels on the plasma membrane is an essential requirement for functional interactions of the channels. In the present study, we investigated the role of two scaffolding proteins, A-Kinase Anchoring Protein 150 (AKAP150) and Bridging Integrator 1 (BIN1), in the clustering of Cav1.2 channels in ventricular myocytes. Both of these proteins are known to directly interact with Cav1.2 channels. AKAP150 is important for local membrane targeting of PKA, PKCα and calcineurin, while Bin1 has established roles in cardiac t-tubule folding and in the trafficking and localization of Cav1.2 channels to t-tubules. Using GSD super-resolution imaging, we found that clustering of Cav1.2 channels in these cells is unaltered by genetic ablation of AKAP79/150 such that the area of CaV1.2 clusters was similar in WT (2379 ± 43 nm) and AKAP150-/- myocytes (2379 ± 43 nm). However, heterozygous deletion of Bin1 significantly reduced Cav1.2 channel cluster size. The area of CaV1.2 channel clusters was approximately 42% smaller in BIN1+/- (1379 ± 43 nm) than in WT (2349 ± 76 nm2) ventricular myocytes (pu003c 0.0001). This data suggests that Bin1 is a key regulator of Cav1.2 channel clustering in heart.