Ubiquitylation of phosphatidylinositol 4-phosphate 5-kinase type I γ by HECTD1 regulates focal adhesion dynamics and cell migration

Phosphatidylinositol 4-phosphate 5-kinase type I_γ (PIPKI_γ90) binds talin and localizes at focal adhesions (FAs). Phosphatidylinositol (4,5)-bisphosphate (PIP_γ) generated by PIPKIc90 is essential for FA formation and cell migration. On the other hand, PIPKI_γ90 and the b-integrin tail compete for overlapping binding sites on talin. Enhanced PIPKI_γ90-talin interaction suppresses talin binding to the bintegrin. It is unknown how PIPKI_γ90 is removed from the PIPKI_γ90-talin complex after on-site PIP₂ production during cell migration. Here we show that PIPKI_γ90 is a substrate for HECTD1, an E3 ubiquitin ligase regulating cell migration. HECTD1 ubiquitinated PIPKI_γ90 at lysine 97 and resulted in PIPKI_γ90 degradation. Expression of the mutant PIPKIc90K97R enhanced PIP₂ and PIP₃ production, inhibited FA assembly and disassembly and inhibited cancer cell migration, invasion and metastasis. Interestingly, mutation at tryptophan 647 abolished the inhibition of PIPKI_γ90^K97R on FA dynamics and partially rescued cancer cell migration and invasion. Thus, cycling PIPKI_γ90 ubiquitylation by HECTD1 and consequent degradation remove PIPKI_γ90 from talin after on-site PIP₂ production, providing an essential regulatory mechanism for FA dynamics and cell migration.