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Am J Physiol Renal Physiol. 2016 Apr 1;310(7):F607-F620. doi: 10.1152/ajprenal.00169.2015. Epub 2015 Dec 23.

G protein α12 (Gα12) is a negative regulator of kidney injury molecule-1-mediated efferocytosis.

Author information

1
Department of Microbiology and Immunology, Western University, London, Ontario, Canada.
2
Matthew Mailing Centre for Translational Transplant Studies, Lawson Health Research Institute, London, Ontario, Canada.
3
Renal Division and Biomedical Engineering Division, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts; and.
4
Department of Microbiology and Immunology, Western University, London, Ontario, Canada; Lakshman.Gunaratnam@lhsc.on.ca.
5
Division of Nephrology, Department of Medicine, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada.

Abstract

Kidney injury molecule-1 (KIM-1) is a receptor for the "eat me" signal, phosphatidylserine, on apoptotic cells. The specific upregulation of KIM-1 by injured tubular epithelial cells (TECs) enables them to clear apoptotic cells (also known as efferocytosis), thereby protecting from acute kidney injury. Recently, we uncovered that KIM-1 binds directly to the α-subunit of heterotrimeric G12 protein (Gα12) and inhibits its activation by reactive oxygen species during renal ischemia-reperfusion injury (Ismail OZ, Zhang X, Wei J, Haig A, Denker BM, Suri RS, Sener A, Gunaratnam L. Am J Pathol 185: 1207-1215, 2015). Here, we investigated the role that Gα12 plays in KIM-1-mediated efferocytosis by TECs. We showed that KIM-1 remains bound to Gα12 and suppresses its activity during phagocytosis. When we silenced Gα12 expression using small interefering RNA, KIM-1-mediated engulfment of apoptotic cells was increased significantly; in contrast overexpression of constitutively active Gα12 (QL12) resulted in inhibition of efferocytosis. Inhibition of RhoA, a key effector of Gα12, using a chemical inhibitor or expression of dominant-negative RhoA, had the same effect as inhibition of Gα12 on efferocytosis. Consistent with this, silencing Gα12 suppressed active RhoA in KIM-1-expressing cells. Finally, using primary TECs from Kim-1+/+ and Kim-1-/- mice, we confirmed that engulfment of apoptotic cells requires KIM-1 expression and that silencing Gα12 enhanced efferocytosis by primary TECs. Our data reveal a previously unknown role for Gα12 in regulating efferocytosis and that renal TECs require KIM-1 to mediate this process. These results may have therapeutic implications given the known harmful role of Gα12 in acute kidney injury.

KEYWORDS:

G protein; Gα12; kidney; kidney injury molecule-1 (KIM-1); phagocytosis

PMID:
26697979
PMCID:
PMC4971893
DOI:
10.1152/ajprenal.00169.2015
[Indexed for MEDLINE]
Free PMC Article

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