Phospholipase C δ1 affects integrin-mediated cell adhesion and migration by altering available phosphatidylinositol 4,5-bisphosphate levels

Integrins are primary extracellular matrix receptors that play essential roles in homeostasis and development. Integrin activity is tightly regulated and is associated with conformational states. Although phosphatidylinositol 4,5-bisphosphate (PIP₂), produced by phosphatidylinositol 4-phosphate 5-kinases, is involved in integrin activation, it is unclear whether PIP₂-reducing enzymes affect integrin conformation and integrin-mediated cell behavior by altering PIP₂ levels. Herein, we showed that phospholipase C (PLC) δ1, a PIP₂-hydrolyzing enzyme, affected integrin-mediated cell adhesion and migration. In PLCδ1 null murine fibroblasts and PLCδ1 knockdown-human melanoma cells, integrin-mediated cell behavior and basal PIP₂ levels in the plasma membrane increased compared with those in control cells. PLCδ1 reduction led to increases in the extended conformation of integrin β1 ectodomain and the interaction between integrin and its activator/stabilizer talin in the absence of ligands. Overexpression of full-length-PLCδ1 or its pleckstrin homology domain but not their PIP₂-binding incompetent mutants inhibited the integrin-mediated cell behavior. To understand how altering plasma membrane PIP₂ levels affects integrin-mediated cell behavior, the catalytic domain of PIP₂ phosphatase was used. It reduced the basal levels of plasma membrane PIP₂, inhibited integrin-mediated cell migration, increased the closed conformation of the integrin β1 headpiece, and decreased integrin-talin interaction. These data suggested that the effects of PLCδ1 reduction were due to a PIP₂ increase and that the plasma membrane PIP₂ levels affected integrin conformation in the absence of ligands. Our results revealed that PLCδ1 finely tunes integrin-mediated cell adhesion and migration and integrin conformation by altering available PIP₂ levels in the plasma membrane.