Inhibition of lipid kinase PIKfyve reveals a role for phosphatase Inpp4b in the regulation of PI(3)P-mediated lysosome dynamics through VPS34 activity.

Autor: Saffi GT; Department of Pharmacology & Toxicology, University of Toronto, Toronto, Ontario, Canada., Wang CA; Department of Pharmacology & Toxicology, University of Toronto, Toronto, Ontario, Canada., Mangialardi EM; Department of Pharmacology & Toxicology, University of Toronto, Toronto, Ontario, Canada., Vacher J; Institut de Recherches Cliniques de Montréal (IRCM), Département de Médecine, Université de Montréal, Montréal, Québec, Canada., Botelho RJ; Department of Chemistry and Biology, Ryerson University, Toronto, Ontario, Canada., Salmena L; Department of Pharmacology & Toxicology, University of Toronto, Toronto, Ontario, Canada; Princess Margaret Cancer Centre, University Health Network, Toronto, Ontario, Canada. Electronic address: leonardo.salmena@utoronto.ca.
Jazyk: angličtina
Zdroj: The Journal of biological chemistry [J Biol Chem] 2022 Aug; Vol. 298 (8), pp. 102187. Date of Electronic Publication: 2022 Jun 26.
DOI: 10.1016/j.jbc.2022.102187
Abstrakt: Lysosome membranes contain diverse phosphoinositide (PtdIns) lipids that coordinate lysosome function and dynamics. The PtdIns repertoire on lysosomes is tightly regulated by the actions of diverse PtdIns kinases and phosphatases; however, specific roles for PtdIns in lysosomal functions and dynamics are currently unclear and require further investigation. It was previously shown that PIKfyve, a lipid kinase that synthesizes PtdIns(3,5)P 2 from PtdIns(3)P, controls lysosome "fusion-fission" cycle dynamics, autophagosome turnover, and endocytic cargo delivery. Furthermore, INPP4B, a PtdIns 4-phosphatase that hydrolyzes PtdIns(3,4)P 2 to form PtdIns(3)P, is emerging as a cancer-associated protein with roles in lysosomal biogenesis and other lysosomal functions. Here, we investigated the consequences of disrupting PIKfyve function in Inpp4b-deficient mouse embryonic fibroblasts. Through confocal fluorescence imaging, we observed the formation of massively enlarged lysosomes, accompanied by exacerbated reduction of endocytic trafficking, disrupted lysosome fusion-fission dynamics, and inhibition of autophagy. Finally, HPLC scintillation quantification of 3 H-myo-inositol labeled PtdIns and PtdIns immunofluorescence staining, we observed that lysosomal PtdIns(3)P levels were significantly elevated in Inpp4b-deficient cells due to the hyperactivation of phosphatidylinositol 3-kinase catalytic subunit VPS34 enzymatic activity. In conclusion, our study identifies a novel signaling axis that maintains normal lysosomal homeostasis and dynamics, which includes the catalytic functions of Inpp4b, PIKfyve, and VPS34.
Competing Interests: Conflict of interests The authors declare no competing or financial interests.
(Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)
Databáze: MEDLINE
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