Expression of syntaxins in rat kidney.
Previously, we demonstrated that a putative vesicle-targeting protein, syntaxin-4, is expressed in renal collecting duct principal cells and is localized to the apical plasma membrane, suggesting a role in targeting aquaporin-2-containing vesicles to the apical plasma membrane. To investigate whether other syntaxin isoforms are present in the renal collecting duct, we determined the intrarenal localization of syntaxin-2 and -3. Reverse transcription-polymerase chain reaction (RT-PCR) experiments using total RNA extracted from kidney and various organs revealed that both syntaxin-2 and -3 are expressed in kidney cortex and medulla. RT-PCR experiments using microdissected tubules and vascular structures from the kidney revealed that syntaxin-3 mRNA, but not syntaxin-2, is expressed in collecting duct cells. Syntaxin-3 mRNA was also relatively abundant in the thick ascending limb of Henle's loop and in vasa recta. Syntaxin-2 mRNA was found chiefly in glomeruli. To investigate the localization of syntaxin-3 protein, a peptide-derived polyclonal antibody was raised in rabbits. In immunoblotting experiments, this antibody labeled a 37-kDa protein in inner medulla that was most abundant in plasma membrane-enriched subcellular fractions. Immunoperoxidase labeling of thin cryosections combined with immunogold electron microscopy showed that, in contrast to the labeling seen for syntaxin-4, syntaxin-3 labeling in medullary collecting duct was predominantly in the basolateral plasma membrane of intercalated cells. These results suggest the possibility that syntaxin-3 may be involved in selective targeting of acid-base transporters and/or in basolateral membrane remodeling in response to systemic acid-base perturbations.
Mandon
B
B
Laboratory of Kidney and Electrolyte Metabolism, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892-0951, USA.
Nielsen
S
S
Kishore
B K
BK
Knepper
M A
MA
D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies; D000954:Antigens, Surface / Q000096:biosynthesis*; D007150:Immunohistochemistry; D007668:Kidney / Q000098:blood supply / Q000166:cytology / Q000378:metabolism*; D007672:Kidney Cortex / Q000378:metabolism; D007679:Kidney Medulla / Q000378:metabolism; D007684:Kidney Tubules / Q000378:metabolism; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000096:biosynthesis*; D009928:Organ Specificity; D010446:Peptide Fragments / Q000737:chemistry / Q000276:immunology; D016133:Polymerase Chain Reaction / Q000379:methods; D012333:RNA, Messenger / Q000096:biosynthesis; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley; D013347:Subcellular Fractions / Q000378:metabolism / Q000648:ultrastructure; D050827:Syntaxin 1; D014158:Transcription, Genetic
D000906:Antibodies; D000954:Antigens, Surface; D009419:Nerve Tissue Proteins; D010446:Peptide Fragments; D012333:RNA, Messenger; D050827:Syntaxin 1