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Gandhi R, Yi J, Ha J, Shi H, Ismail O, Nathoo S, Bonventre JV, Zhang X, Gunaratnam L. Accelerated receptor shedding inhibits kidney injury molecule-1 (KIM-1)-mediated efferocytosis. Am J Physiol Renal Physiol 2014; 307:F205-21. [PMID: 24829508 DOI: 10.1152/ajprenal.00638.2013] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
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.
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Affiliation(s)
- Rushi 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 Yi
- Department of Microbiology and Immunology, Western University, London, Ontario, Canada; Matthew Mailing Centre for Translational Transplant Studies, Lawson Health Research Institute, London, Ontario, Canada
| | - Jihyen Ha
- Department of Microbiology and Immunology, Western University, London, Ontario, Canada
| | - Hang Shi
- Department of Microbiology and Immunology, Western University, London, Ontario, Canada; Centre for Human Immunology, Western University, London, Ontario, Canada; and
| | - Ola Ismail
- Department of Microbiology and Immunology, Western University, London, Ontario, Canada
| | - Sahra Nathoo
- Department of Microbiology and Immunology, Western University, London, Ontario, Canada
| | - Joseph V Bonventre
- Renal Division, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Xizhong Zhang
- 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
| | - Lakshman Gunaratnam
- 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
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