Accelerated receptor shedding inhibits kidney injury molecule-1 (KIM-1)-mediated efferocytosis.
Efficient clearance of apoptotic cells (efferocytosis) prevents inflammation and permits repair following tissue injury. Kidney injury molecule-1 (KIM-1) is a receptor for phosphatidylserine, an "eat-me" signal exposed on the surface of apoptotic cells that marks them for phagocytic clearance. KIM-1 is upregulated on proximal tubule epithelial cells (PTECs) during ischemic acute kidney injury (AKI), enabling efferocytosis by surviving PTECs. KIM-1 is spontaneously cleaved at its ectodomain region to generate a soluble fragment that serves a sensitive and specific biomarker for AKI, but the biological relevance of KIM-1 shedding is unknown. Here, we sought to determine how KIM-1 shedding might regulate efferocytosis. Using cells that endogenously and exogenously express KIM-1, we found that hydrogen peroxide-mediated oxidative injury or PMA treatment accelerated KIM-1 shedding in a dose-dependent manner. KIM-1 shedding was also accelerated when apoptotic cells were added. Accelerated shedding or the presence of excess soluble KIM-1 in the extracellular milieu significantly inhibited efferocytosis. We also identified that TNF-α-converting enzyme (TACE or ADAM17) mediates both the spontaneous and PMA-accelerated shedding of KIM-1. While accelerated shedding inhibited efferocytosis, we found that spontaneous KIM-1 cleavage does not affect the phagocytic efficiency of PTECs. Our results suggest that KIM-1 shedding is accelerated by worsening cellular injury, and excess soluble KIM-1 competitively inhibits efferocytosis. These findings may be important in AKI when there is severe cellular injury.
Department of Microbiology and Immunology, Western University, London, Ontario, Canada; Matthew Mailing Centre for Translational Transplant Studies, Lawson Health Research Institute, London, Ontario, Canada;
Rushi
R
Gandhi
Department of Microbiology and Immunology, Western University, London, Ontario, Canada; Matthew Mailing Centre for Translational Transplant Studies, Lawson Health Research Institute, London, Ontario, Canada;
James
J
Yi
Department of Microbiology and Immunology, Western University, London, Ontario, Canada;
Jihyen
J
Ha
Department of Microbiology and Immunology, Western University, London, Ontario, Canada; Centre for Human Immunology, Western University, London, Ontario, Canada; and.
Hang
H
Shi
Department of Microbiology and Immunology, Western University, London, Ontario, Canada;
Ola
O
Ismail
Department of Microbiology and Immunology, Western University, London, Ontario, Canada;
Sahra
S
Nathoo
Renal Division, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts.
Joseph V
JV
Bonventre
Division of Nephrology, Department of Medicine, Schulich School of Medicine and Dentistry, London, Ontario, Canada; Matthew Mailing Centre for Translational Transplant Studies, Lawson Health Research Institute, London, Ontario, Canada;
Xizhong
X
Zhang
Department of Microbiology and Immunology, Western University, London, Ontario, Canada; Division of Nephrology, Department of Medicine, Schulich School of Medicine and Dentistry, London, Ontario, Canada; Matthew Mailing Centre for Translational Transplant Studies, Lawson Health Research Institute, London, Ontario, Canada; Centre for Human Immunology, Western University, London, Ontario, Canada; and Lakshman.Gunaratnam@LHSC.ON.CA.
Lakshman
L
Gunaratnam
D051722:ADAM Proteins / Q000378:metabolism; D000072198:ADAM17 Protein; D058186:Acute Kidney Injury / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D017077:Culture Media, Conditioned / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D000072596:Hepatitis A Virus Cellular Receptor 1; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007668:Kidney / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D018374:LLC-PK1 Cells; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018384:Oxidative Stress; D010587:Phagocytosis / Q000187:drug effects; D011991:Receptors, Virus / Q000378:metabolism*; D013552:Swine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors
D017077:Culture Media, Conditioned; C491143:HAVCR1 protein, human; C442240:Havcr1 protein, mouse; D000072596:Hepatitis A Virus Cellular Receptor 1; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D011991:Receptors, Virus; D006861:Hydrogen Peroxide; D051722:ADAM Proteins; D000072198:ADAM17 Protein; C000606462:ADAM17 protein, human; C000606463:Adam17 protein, mouse; D013755:Tetradecanoylphorbol Acetate
efferocytosis; kidney injury molecule-1 (KIM-1); proximal tubule epithelial cells (PTECs); receptor; shedding