Molecular Identification of a Kidney Specific Murine Organic Cation Transporter Like-1 (Moctl1).

초록

Recently discovered organic ion transporters are expressed in various tissues, which are all epithelial tissues that transport endogenous and exogenous compounds and their metabolites. There are organic anion transporter (OAT), organic cation transporter (OCT), organic anion transporter like protein (OATLP) and organic cation tansporter like (OCTL). When considering the variety of charged organic ionic compounds, the existence of other isoforms of organic ion transporters can be assumed. In this connection, we have searched for a new isoform in the expressed sequence tag (EST) database using hOAT4 amino acid sequence as a “query.” We found a candidate clone (BC021449) from the mouse kidney cDNA library. This clone was identified ortholog of ORCTL3 or OCTL-1. The mOCTL1 cDNA consisted of 2016 base pairs that encoded a 551 amino acid residue protein with 12 putative transmembrane domains. The deduced amino acid sequence of mOCTL1 showed 35 to 40% identity to those of the other members of the OATs and OCTs. According to the tissue distribution with performing Northern blot analysis, about a 2.4 kb transcript of mOCTL1 was observed in the kidney. About a 90-kDa band was detected when Western blot analysis in the mouse kidney was done with using synthesized oligopeptide-induced mOCTL1 antibody. The immunohistochemical result showed mOCTL1 was stained at the glomerulus (the parietal epithelial cells and podocytes), pars recta of proximal tubule, distal convoluted tubules, connecting tubules and collecting tubules. From these results, mOCTL1 may be a candidate for an organic ion transporter isoform that was identified in the kidney.