Regulation of T-type calcium channels by Rho-associated kinase

We investigated the regulation of T-type channels by Rho-associated kinase (ROCK). Activation of ROCK via the endogenous ligand lysophosphatidic acid (LPA) reversibly inhibited the peak current amplitudes of rat Ca v 3.1 and Ca v 3.3 channels without affecting the voltage dependence of activation or inactivation, whereas Ca v 3.2 currents showed depolarizing shifts in these parameters. LPA-induced inhibition of Ca v 3.1 was dependent on intracellular GTP, and was antagonized by treatment with ROCK and RhoA inhibitors, LPA receptor antagonists or GDPßS. Site-directed mutagenesis of the Ca v 3.1 α 1 subunit revealed that the ROCK-mediated effects involve two distinct phosphorylation consensus sites in the domain II-III linker. ROCK activation by LPA reduced native T-type currents in Y79 retinoblastoma and in lateral habenular neurons, and upregulated native Ca v 3.2 current in dorsal root ganglion neurons. Our data suggest that ROCK is an important regulator of T-type calcium channels, with potentially far-reaching implications for multiple cell functions modulated by LPA.