title: SNARE expression and localization in renal epithelial cells suggest mechanism for variability of trafficking phenotypes.
abstract: The apical- and basolateral-specific distribution of target soluble N-ethylmaleimide-sensitive factor attachment protein receptors (t-SNAREs) of the syntaxin family appear to be critical for polarity in epithelial cells. To test whether differential SNARE expression and/or subcellular localization may contribute to the known diversity of trafficking phenotypes of epithelial cell types in vivo, we have investigated the distribution of syntaxins 2, 3, and 4 in epithelial cells along the renal tubule. Syntaxins 3 and 4 are restricted to the apical and basolateral domains, respectively, in all cell types, indicating that their mutually exclusive localizations are important for cell polarity. The expression level of syntaxin 3 is highly variable, depending on the cell type, suggesting that it is regulated in concert with the cellular requirement for apical exocytic pathways. While syntaxin 4 localizes all along the basal and lateral plasma membrane domains in vivo, it is restricted to the lateral membrane in Madin-Darby canine kidney (MDCK) cells in two-dimensional monolayer culture. When cultured as cysts in collagen, however, MDCK cells target syntaxin 4 correctly to the basal and lateral membranes. Unexpectedly, the polarity of syntaxin 2 is inverted between different tubule cell types, suggesting a role in establishing plasticity of targeting. The vesicle-associated (v)-SNARE endobrevin is highly expressed in intercalated cells and colocalizes with the H(+)-ATPase in alpha- but not beta-intercalated cells, suggesting its involvement in H(+)-ATPase trafficking in the former cell type. These results suggest that epithelial membrane trafficking phenotypes in vivo are highly variable and that different cell types express or localize SNARE proteins differentially as a mechanism to achieve this variability.
authors.affiliation: Department of Cell Biology, Lerner Research Institute, and Urological Institute, The Cleveland Clinic, Cleveland, Ohio 44195, USA.
authors.forename: Xin
authors.initials: X
authors.lastname: Li
authors.forename: Seng Hui
authors.initials: SH
authors.lastname: Low
authors.forename: Masumi
authors.initials: M
authors.lastname: Miura
authors.forename: Thomas
authors.initials: T
authors.lastname: Weimbs
mesh_terms: D000818:Animals; D000918:Antibody Specificity; D000954:Antigens, Surface / Q000032:analysis / Q000235:genetics; D002460:Cell Line; D016764:Cell Polarity / Q000502:physiology; D004847:Epithelial Cells / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D015870:Gene Expression / Q000502:physiology; D007668:Kidney / Q000166:cytology / Q000378:metabolism*; D008297:Male; D008561:Membrane Fusion / Q000502:physiology; D008565:Membrane Proteins / Q000032:analysis / Q000235:genetics* / Q000276:immunology; D009419:Nerve Tissue Proteins / Q000032:analysis / Q000235:genetics; D010641:Phenotype; D021381:Protein Transport / Q000502:physiology*; D050765:Qa-SNARE Proteins; D050683:R-SNARE Proteins; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley; D050600:SNARE Proteins; D050827:Syntaxin 1; D033921:Vesicular Transport Proteins
chemical_list: D000954:Antigens, Surface; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050765:Qa-SNARE Proteins; D050683:R-SNARE Proteins; D050600:SNARE Proteins; D050827:Syntaxin 1; C491830:Vamp8 protein, rat; D033921:Vesicular Transport Proteins