Myristoylated alanine‐rich C kinase substrate coordinates native TRPC1 channel activation by phosphatidylinositol 4,5‐bisphosphate and protein kinase C in vascular smooth muscle

Canonical transient receptor potential 1 (TRPC1) Ca 2+ ‐permeable cation channels contribute to vascular tone and blood vessel remodeling and represent potential therapeutic targets for cardiovascular disease. Protein kinase C (PKC) and phosphatidylinositol 4,5‐bisphosphate [PI(4,5)P 2 ] are obligatory for native TRPC1 channel activation in vascular smooth muscle cells (VSMCs) but how PKC and PI(4,5)P 2 act together to induce channel gating remains unresolved. The present study reveals that myristoylated alanine‐rich C kinase substrate (MARCKS) protein coordinates activation of TRPC1 channels by PKC and PI(4,5)P 2 . TRPC1 channels and MARCKS form signaling complexes with PI(4,5)P 2 bound to MARCKS; in this configuration TRPC1 channels are closed. Activators of TRPC1 channels induce PKC phosphorylation of TRPC1 proteins, which causes dissociation of TRPC1 subunits from MARCKS and release of PI(4,5)P 2 from MARCKS; PI(4,5)P 2 subsequently binds to TRPC1 subunits to induce channel opening. Calmodulin acting at, or upstream of, MARCKS is also required for TRPC1 channel opening through a similar gating mechanism involving PKC and PI(4,5)P 2 . These novel findings show that MARCKS coordinates native TRPC1 channel activation in VSMCs by acting as a reversible PI(4,5)P 2 buffer, which is regulated by PKC‐mediated TRPC1 phosphorylation. Moreover, our data provide evidence that PI(4,5)P 2 is a gating ligand of TRPC1 channels.—Shi, J., Birnbaumer, L., Large, W. A., and Albert, A. P. Myristoylated alanine‐rich C kinase substrate coordinates native TRPC1 channel activation by phosphatidylinositol 4,5‐bisphosphate and protein kinase C in vascular smooth muscle. FASEB J . 28, 244–255 (2014). www.fasebj.org