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Rab10 regulates macropinocytosis and degradation pathways in macrophages
Author(s) -
Xiao Zhijian,
Koh Yvette,
Lucas Richard,
Hung Yu,
Stow Jennifer
Publication year - 2021
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2021.35.s1.04978
Subject(s) - pinocytosis , microbiology and biotechnology , endosome , rab , endocytic cycle , lysosome , phosphorylation , biology , signal transduction , endocytosis , chemistry , biochemistry , cell , gtpase , intracellular , enzyme
The endocytic‐lysosomal degradation pathway is a dynamic and interconnected vesicular network comprising macropinosomes, endosomes, and lysosomes that support trafficking, sorting, signaling and catabolism of receptors and other cargo. Extracellular proteins ingested by macropinocytosis are delivered to lysosomes for degradation and recycling to support cell growth. Rab GTPases mediate many stages of trafficking and other functions in this pathway. Members of the Rab8 subfamily have key roles in trafficking and signaling in macropinosomes. Here, we examined the role of Rab10, another member of the Rab8 subfamily, in macropinosome maturation as a portal for intersection with lysosomes. GFP‐Rab10 is recruited to early macropinosomes but not normally to lysosomes in macrophages activated with LPS or CSF‐1. GFP‐Rab10 is retained on sorting tubules emerging from early macropinosomes. CRISPR or siRNA depletion of Rab10 reduces macropinocytic uptake and trafficking of dextran and tubulation of macropinosomes suggesting roles for Rab10 in macropinosome maturation. The lysomotropic agent chloroquine (CQ) classically disrupts endo‐lysosome pathways and we show it disrupts macropinocytic maturation, inducing lysosomal stress through accumulation of cargo. CQ also results in stress‐induced Rab10 phosphorylation accompanied by its enrichment on macropinosomes and on stressed lysosomes. The results of trafficking studies and use of additional inhibitors reveals that phospho‐Rab10 appearing on the stressed lysosomes originates from macropinosomes, suggesting a CQ‐induced fusion of macropinosomes and lysosomes. From our results we conclude that phosphorylated Rab10 is actually delivered to macropinosomes, and not directly to lysosomes, as previously reported. Rab10 is thus a key regulator of macropinosome trafficking and maturation in macrophages.