Shedding of kidney injury molecule-1, a putative adhesion protein involved in renal regeneration.
KIM-1 (kidney injury molecule-1) is a type I transmembrane glycoprotein expressed on dedifferentiated renal proximal tubule epithelial cells undergoing regeneration after toxic or ischemic injury. The extracellular domain of KIM-1 is composed of an immunoglobulin-like domain topping a long mucin-like domain, a structure that points to a possible role in cell adhesion by homology to several known adhesion proteins. Two splice variants (a and b), of the human KIM-1 having identical extracellular domains, differ in their cytoplasmic domains and tissue distributions. In this study, we report that the KIM-1b transcript is expressed predominantly in adult human kidney. We describe the generation of 10 monoclonal antibodies against the extracellular domain of human KIM-1, the mapping of their binding sites, and their use in identifying various forms of the protein. We show that human KIM-1b is expressed in adult kidney cell lines, and we demonstrate that a soluble form of KIM-1 is shed constitutively into the culture medium of the cell lines expressing endogenous or recombinant KIM-1b by membrane-proximal cleavage. A monoclonal antibody that binds at or close to the proteolytic site can partially block the shedding of KIM-1. Release of soluble KIM-1 is enhanced by activating the cells with phorbol 12-myristate 13-acetate and can be inhibited with two metalloproteinase inhibitors, BB-94 (Batimastat) and GM6001 (Ilomastat), suggesting that the cleavage is mediated by a metalloproteinase. We propose that the shedding of KIM-1 in the kidney undergoing regeneration constitutes an active mechanism allowing dedifferentiated regenerating cells to scatter on denuded patches of the basement membrane and reconstitute a continuous epithelial layer.
Bailly
Veronique
V
BIOGEN Inc., Cambridge, Massachusetts 02142, USA. Veronique_Bailly@biogen.com
Zhang
Zhiwei
Z
Meier
Werner
W
Cate
Richard
R
Sanicola
Michele
M
Bonventre
Joseph V
JV
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D001665:Binding Sites; D019921:Biotinylation; D015153:Blotting, Western; D019556:COS Cells; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000737:chemistry* / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004151:Dipeptides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D007668:Kidney / Q000378:metabolism / Q000502:physiology*; D008565:Membrane Proteins; D008666:Metalloendopeptidases / Q000037:antagonists & inhibitors; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000494:pharmacology; D011233:Precipitin Tests; D011480:Protease Inhibitors / Q000494:pharmacology; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D013876:Thiophenes / Q000494:pharmacology; D013997:Time Factors; D014018:Tissue Distribution
D000970:Antineoplastic Agents; D015815:Cell Adhesion Molecules; D004151:Dipeptides; D008565:Membrane Proteins; D008666:Metalloendopeptidases; D010649:Phenylalanine; D011480:Protease Inhibitors; D012333:RNA, Messenger; D011994:Recombinant Proteins; D013876:Thiophenes; C110936:Havcr1 protein, rat; C078131:N-(2(R)-2-(hydroxamidocarbonylmethyl)-4-methylpentanoyl)-L-tryptophan methylamide; C080985:batimastat