inositol-3-4-5-trisphosphate and inositol-4-5-bisphosphate

Phosphatase and tensin homologue (PTEN) is a dual lipid-protein phosphatase that catalyzes the conversion of phosphoinositol 3,4,5-triphosphate to phosphoinositol 4,5-bisphosphate and thereby inhibits PI3K-Akt-dependent cell proliferation, migration, and tumor vascularization. We have uncovered a previously unrecognized role for PTEN in regulating Ca(2+) entry through transient receptor potential canonical channel 6 (TRPC6) that does not require PTEN phosphatase activity. We show that PTEN tail-domain residues 394-403 permit PTEN to associate with TRPC6. The inflammatory mediator thrombin promotes this association. Deletion of PTEN residues 394-403 prevents TRPC6 cell surface expression and Ca(2+) entry. However, PTEN mutant, C124S, which lacks phosphatase activity, did not alter TRPC6 activity. Thrombin failed to increase endothelial monolayer permeability in the endothelial cells, transducing the Δ394-403 PTEN mutant. Paradoxically, we also show that thrombin failed to induce endothelial cell migration and tube formation in cells transducing the Δ394-403 PTEN mutant. Our results demonstrate that PTEN, through residues 394-403, serves as a scaffold for TRPC6, enabling cell surface expression of the channel. Ca(2+) entry through TRPC6 induces an increase in endothelial permeability and directly promotes angiogenesis. Thus, PTEN is indicated to play a role beyond suppressing PI3K signaling.

Topics: Amino Acid Sequence; Calcium; Capillary Permeability; Cell Movement; Cell Proliferation; Cells, Cultured; Endothelial Cells; Gene Expression Regulation; Hemostatics; Humans; Inflammation Mediators; Inositol Phosphates; Mutation, Missense; Neovascularization, Physiologic; Phosphatidylinositol 3-Kinases; Protein Structure, Tertiary; Proto-Oncogene Proteins c-akt; PTEN Phosphohydrolase; Sequence Deletion; Signal Transduction; Thrombin; TRPC Cation Channels; TRPC6 Cation Channel