title: G protein α12(Gα12) is a negative regulator of kidney injury molecule-1-mediated efferocytosis.
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 G12protein (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 Pathol185: 1207-1215, 2015). Here, we investigated the role that Gα12plays in KIM-1-mediated efferocytosis by TECs. We showed that KIM-1 remains bound to Gα12and suppresses its activity during phagocytosis. When we silenced Gα12expression using small interefering RNA, KIM-1-mediated engulfment of apoptotic cells was increased significantly; in contrast overexpression of constitutively active Gα12(QLGα12) 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 Gα12on efferocytosis. Consistent with this, silencing Gα12suppressed 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 Gα12enhanced efferocytosis by primary TECs. Our data reveal a previously unknown role for Gα12in 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 Gα12in acute kidney injury.
authors.affiliation: Department of Microbiology and Immunology, Western University, London, Ontario, Canada.|Matthew Mailing Centre for Translational Transplant Studies, Lawson Health Research Institute, London, Ontario, Canada.
authors.forename: Ola Z
authors.initials: OZ
authors.lastname: Ismail
authors.affiliation: Matthew Mailing Centre for Translational Transplant Studies, Lawson Health Research Institute, London, Ontario, Canada.
authors.forename: Xizhong
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Renal Division and Biomedical Engineering Division, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts; and.
authors.forename: Joseph V
authors.initials: JV
authors.lastname: Bonventre
authors.affiliation: Department of Microbiology and Immunology, Western University, London, Ontario, Canada; Lakshman.Gunaratnam@lhsc.on.ca.|Matthew Mailing Centre for Translational Transplant Studies, Lawson Health Research Institute, London, Ontario, Canada.|Division of Nephrology, Department of Medicine, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada.
authors.forename: Lakshman
authors.initials: L
authors.lastname: Gunaratnam
mesh_terms: D000818:Animals; D002470:Cell Survival / Q000502:physiology; D004847:Epithelial Cells / Q000378:metabolism; D044365:GTP-Binding Protein alpha Subunits, G12-G13 / Q000378:metabolism*; D057809:HEK293 Cells; D000072596:Hepatitis A Virus Cellular Receptor 1 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007668:Kidney / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D010587:Phagocytosis / Q000502:physiology*; D013552:Swine
chemical_list: D000072596:Hepatitis A Virus Cellular Receptor 1; D044365:GTP-Binding Protein alpha Subunits, G12-G13
keywords: G protein; Gα12; kidney; kidney injury molecule-1 (KIM-1); phagocytosis