p85? regulatory subunit isoform controls PI3-kinase and TRPC6 membrane translocation

Activation of phosphatidylinositol 3-kinase (PI3K) by lipid oxidation products, including lysophosphatidylcho-line (lysoPC), increases the externalization of canonical transient receptor potential 6 (TRPC6) channels leading to a subsequent increase in intracellular calcium that contributes to cytoskeletal changes which inhibit endo-thelial cell (EC) migration in vitro and impair EC healing of arterial injuries in vivo. The PI3K p110 alpha and p110 delta catalytic subunit isoforms regulate lysoPC-induced TRPC6 externalization in vitro, but have many other func-tions. The goal of the current study is to identify the PI3K regulatory subunit isoform involved in TRPC6 externalization to potentially identify a more specific treatment regimen to improve EC migration and arterial healing, while minimizing off-target effects. Decreasing the p85 alpha regulatory subunit isoform protein levels, but not the p85 beta and p55 gamma regulatory subunit isoforms, with small interfering RNA inhibits lysoPC-induced trans -location of the PI3K catalytic subunit to the plasma membrane, dramatically decreased phosphatidylinositol (3,4,5)-trisphosphate (PIP3) production and TRPC6 externalization, and significantly improves EC migration in the presence of lysoPC. These results identify the important and specific role of p85 alpha in controlling translocation of PI3K from the cytosol to the plasma membrane and PI3K-mediated TRPC externalization by oxidized lipids. Current PI3K inhibitors block the catalytic subunit, but our data suggest that the regulatory subunit is a novel therapeutic target to promote EC migration and healing after arterial injuries that occur with angioplasty.

Automated summary

Activation of PI3K by lipid oxidation products leads to TRPC6 channels externalization and enhances intracellular calcium, inhibiting EC migration. Identifying the specific PI3K isoform involved in TRPC6 externalization could lead to a targeted treatment to improve EC migration and arterial healing.