KIDNEY INJURY MOLECULE-1 (KIM-1), A PUTATIVE EPITHELIAL-CELL ADHESIONMOLECULE CONTAINING A NOVEL IMMUNOGLOBULIN DOMAIN, IS UP-REGULATED INRENAL-CELLS AFTER INJURY

We report the identification of rat and human cDNAs for a type 1 membr ane protein that contains a novel six-cysteine immunoglobulin-like dom ain and a mucin domain; it is named kidney injury molecule-1 (KIM-1). Structurally, KIM-1 is a member of the immunoglobulin gene superfamily most reminiscent of mucosal addressin cell adhesion molecule 1 (MAdCA M-1). Human KIM-1 exhibits homology to a monkey gene, hepatitis A viru s cell receptor 1 (HAVcr-1), which was identified recently as a recept or for the hepatitis A virus, KIM-1 mRNA and protein are expressed at a low level in normal kidney but are increased dramatically in postisc hemic kidney, In situ hybridization and immunohistochemistry revealed that KIM-1 is expressed in proliferating bromodeoxyuridine-positive an d dedifferentiated vimentin-positive epithelial cells in regenerating proximal tubules, Structure and expression data suggest that KIM-1 is an epithelial cell adhesion molecule up-regulated in the cells, which are dedifferentiated and undergoing replication, KIM-1 may play an imp ortant role in the restoration of the morphological integrity and func tion to postischemic kidney.