PIKfyve inhibition induces LRRK2 activation through phosphatidylinositol 3-phosphate and CASM

LRRK2 is a Parkinson's disease (PD)-associated kinase that phosphorylates Rab GTPases. Hyperactivation of LRRK2, which is thought to cause PD, occurs on stressed endolysosomal membranes via CASM (conjugation of ATG8 to single membranes) and Rab, whereas the involvement of specific membrane lipids remained unclear. Here, we found that the inhibition of PIKfyve that metabolizes phosphatidylinositol 3-phosphate (PI3P) induces hyperactivation of LRRK2, and that additional inhibition of the class III phosphoinositide 3-kinase (PI3K) that generates PI3P suppressed LRRK2 hyperactivation. Cellular PI3P levels were indeed elevated when LRRK2 was activated. CASM-induced activation of LRRK2, but not CASM itself, was suppressed by PI3K inhibitors, whereas inhibition of CASM or Rab12/Rab29 suppressed LRRK2 activation induced by PIKfyve inhibitors. LRRK2 and phospho-Rab10 were co-localized with PI3P on LAMP1-positive enlarged vacuoles, and LRRK2 directly bound PI3P in vitro via its N-terminal positively charged amino acids. Together, we propose an updated mechanism of LRRK2 hyperactivation that simultaneously requires CASM, Rab and PI3P-rich membranes.