Protein kinase C-mediated phosphorylation of the CaT-L calmodulin binding site counteracts calcium-dependent calmodulin binding, thereby preventing channel inactivation.
The study identifies a biochemical mechanism where CaT-L calcium channel activity is competitively regulated by calmodulin binding and protein kinase C-dependent phosphorylation.
A finely tuned Ca(2+) signaling system is essential for cells to transduce extracellular stimuli, to regulate growth, and to differentiate. We have recently cloned CaT-like (CaT-L), a highly selective Ca(2+) channel closely related to the epithelial calcium channels (ECaC) and the calcium transport protein CaT1. CaT-L is expressed in selected exocrine tissues, and its expression also strikingly correlates with the malignancy of prostate cancer. The expression pattern and selective Ca(2+) permeation properties suggest an important function in Ca(2+) uptake and a role in tumor progression, but not much is known about the regulation of this subfamily of ion channels. We now demonstrate a biochemical and functional mechanism by which cells can control CaT-L activity. CaT-L is regulated by means of a unique calmodulin binding site, which, at the same time, is a target for protein kinase C-dependent phosphorylation. We show that Ca(2+)-dependent calmodulin binding to CaT-L, which facilitates channel inactivation, can be counteracted by protein kinase C-mediated phosphorylation of the calmodulin binding site.
Niemeyer et al. (2001) studied this question. Protein kinase C and calmodulin was evaluated on CaT-L channel inactivation. Protein kinase C-mediated phosphorylation of the CaT-L calmodulin binding site counteracts calcium-dependent calmodulin binding, thereby preventing channel inactivation.