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bioRxiv · 10.64898/2025.12.16.694573

LRRK2 is activated by phosphatidylinositol 3-phosphate in conjunction with CASM

Kuwahara, T.·Yoshii, G.·Sakurai, M.·Suenaga, S.·Nakanishi, H.·Jefferson, M.·Wileman, T.·Tomii, K.·Iwatsubo, T.
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Abstract

LRRK2 is a Parkinsons 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 LRRK2 was potently activated upon treatment with PIKfyve inhibitors that increase cellular phosphatidylinositol 3-phosphate (PI3P) levels, and that additional treatment with the class III phosphoinositide 3-kinase (PI3K) inhibitors blocking PI3P generation suppressed LRRK2 activation. Cellular PI3P levels were indeed correlated with the LRRK2 kinase activity. CASM-induced LRRK2 activation, 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 activation that requires CASM, Rab and PI3P-rich membranes.

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Kuwahara, T., Yoshii, G., Sakurai, M., Suenaga, S., Nakanishi, H., Jefferson, M., Wileman, T., Tomii, K., Iwatsubo, T.. 2025-12-18. LRRK2 is activated by phosphatidylinositol 3-phosphate in conjunction with CASM. https://doi.org/10.64898/2025.12.16.694573

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