Serine496 of β2 subunit of L-type Ca2+ channel participates in molecular crosstalk between activation of (Na++K+)-ATPase and the channel.

Activation of (Na++K+)-ATPase (NKA) regulates cardiac L-type Ca2+ channel (LTCC) function through molecular crosstalk. The mechanism underlying NKA-LTCC crosstalk remains poorly understood. We have previously shown that activation of NKA leads to phosphorylation of LTCC α1 Ser1928. Here we investigated whether LTCC β2 subunit is modulated by NKA activation and found that LTCC β2 Ser496 is phosphorylated in response to activation of NKA. Src inhibitor PP1 and Erk1/2 inhibitor PD98059 abolish LTCC β2 Ser496 phosphorylation, suggesting that NKA-mediated β2 Ser496 phosphorylation is dependent of Src/Erk1/2 signaling pathway. Protein kinase G (PKG) inhibitor KT5823 failed to inhibit the phosphorylation of β2 Ser496, indicating that the NKA-LTCC crosstalk is independent of PKG activity. The results of nifedipine sensitive 45Ca influx experiments suggest that phosphorylation of β2 Ser496 may play a key down-regulation role in attenuating the accelerated activity of α1 subunit of the channel. Ouabain does not cause a phosphorylation on β2 Ser496, indicating a fundamental difference between activation and inhibition of NKA-mediated biological processes. This study provides the first evidence to demonstrate that LTCC β2 subunit is coupled with the movement of signals in the mechanism of activation of NKA-mediated crosstalk with LTCC.