NH2-terminal heterogeneity in the KCC3 K+-Cl− cotransporter

• DOI: 10.1152/ajprenal.00464.2004
• Publication Date: 2005-07-27T20:13:08Z
• Authors: Adriana Mercado; Norma Vázquez; Luyan Song; Rosa Cortés; Alissa H. Enck; Rick Welch; Eric Delpire; Gerardo Gamba; David B. Mount
• Keywords: Northern blot

The SLC12A6 gene encoding the K + -Cl − cotransporter KCC3 is expressed in multiple tissues, including kidney. Here, we report molecular characterization of several NH 2 -terminal isoforms human and mouse KCC3, along with intrarenal localization functional Xenopus laevis oocytes. Two major isoforms, KCC3a KCC3b, are generated by transcriptional initiation 5′ two distinct first coding exons. Northern blot analysis tissues indicates that KCC3b expression particularly robust kidney, which also expresses KCC3a. Western blotting tissue using an exon 3-specific antibody reveals kidney unique expressing immunoreactive protein a lower mass, suggestive evidence shorter predominates Immunofluorescence basolateral entire length proximal tubule, both rat. Removal 15-residue alternative splicing generates KCC3a-x2M KCC3b-x2M isoforms; other events at acceptor site within 1a generate KCC3a-S isoform, 60 residues than This variation sequence cytoplasmic domains occurs to stretch highly conserved affects content putative phosphorylation sites. Kinetic X. oocytes apparent m s for Rb Cl 10.7 ± 2.5 7.3 1.2 mM, respectively, anion selectivity Br > PO 4 = I SCN gluconate. All five activated cell swelling (hypotonic conditions), no activity under isotonic conditions. Although do not differ osmotic set point activation, this activation more rapid proteins. In summary, there significant heterogeneity Basolateral swelling-activated cotransport mediated likely functions volume regulation during transepithelial transport salt solutes tubule.