The rapid and precise clearance of apoptotic cells (efferocytosis) involves a series of phagocytic processes through which apoptotic cells are recognized, engulfed, and degraded within phagocytes. The Rho-family GTPases critically rearrange the cytoskeleton for these phagocytic processes, but we know little about the mechanisms by which regulatory proteins control the spatiotemporal activities of the Rho-family GTPases. Here, we identify ArhGAP12 as a functional GTPase-activating protein (GAP) of Rac1 during Stabilin-2 mediated efferocytosis. ArhGAP12 constitutively forms a complex with the phosphatidylserine receptor, Stabilin-2, via direct interaction with the downstream protein, GULP, but is released from the complex when Stabilin-2 interacts with apoptotic cells. When the phagocytic cup is closed and the apoptotic cell is surrounded by the phagosomal membrane, ArhGAP12 localizes to the phagocytic cup via a specific interaction with phosphatidylinositol-4,5-bisphosphate, which is transiently biosynthesized in the phagocytic cup. Down-regulation of ArhGAP12 results in sustained Rac1 activity, arrangement of F-actin, and delayed phagosome-lysosome fusion. Our results collectively suggest that ArhGAP12 carries dual roles in Stabilin-2 mediated efferocytosis: it binds to GULP/Stabilin-2 and switches off Rac1 basal activity and switches on the Rac1 by releasing itself from the complex. In addition, the spatiotemporal membrane targeting of ArhGAP12 inactivates Rac1 in a time-specific and spatially coordinated manner to orchestrate phagosome maturation. This may shed light on how other RhoGAPs spatiotemporally inactivate Rac or Cdc42 during phagocytosis by various cells, in different circumstances.
|Number of pages||13|
|Journal||Biochimica et Biophysica Acta - Molecular Cell Research|
|Publication status||Published - 2019 Oct|
Bibliographical noteFunding Information:
This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education ( NRF-2018R1D1A3A03001116 ); the National Research Foundation of Korea (NRF) grant funded by the Korea government ( 2014R1A5A2009242 ); the National Research Foundation of Korea (NRF) funded by the Korea government ( 2017R1A3B1023418 ); Asan Institute for Life Sciences, Asan Medical Center ( 2016-585 ), Republic of Korea. The work was also supported by a grant ( R35GM122530 ) from National Institutes of Health , USA.
© 2019 Elsevier B.V.
- Phagosome maturation
- Rac1 activity
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology