Kidney injury molecule–1 is a phosphatidylserine receptor that confers a phagocytic phenotype on epithelial cells
J. Clin. Invest. Takaharu Ichimura, et al. 118:1657 doi:10.1172/JCI34487 [Go to this article.]

Figure 3
KIM-1–expressing kidney epithelial cell lines avidly bind and phagocytose apoptotic and necrotic material. (A) KIM-1 (red) in a KIM1-PK1 cell (left panel) is expressed at high levels (arrows) at the point of binding of multiple apoptotic thymocytes (green and blue) and is part of the initial phagocytic cup (arrowhead). Scale bar: 5 μm. At later time points (right panel), KIM-1 remains associated with the internalized apoptotic cell, resulting in ring enhancement (arrow) of the apoptotic body. The cell border is highlighted by broken lines. Scale bar: 10 μm. (B) Multiple apoptotic thymocytes labeled with CMFDA (green) were localized intracellularly in KIM-1–expressing cells after coculture. Internalized apoptotic thymocytes are visualized in the confocal plane of cortical actin filaments (red) in this confocal image confirming internalization. Cell nuclei (N) are highlighted. Scale bar: 10 μm. (C) DIC with fluorescence (green) microscopic images of KIM1-PK1 cells confirm ingestion of CMFDA-labeled (green) apoptotic LLC-PK1 cells (left panel) or sonicated LLC-PK1 cell debris (middle panel). pCDNA-PK1 cells in the same experiment showing no phagocytosis of apoptotic cells (right panel). These microscopic studies confirm internalization of fluorescent apoptotic or necrotic cell debris (arrowheads). Original magnification, ×60.