title: Ultrastructural and immunohistochemical localization of plasma membrane Ca2+-ATPase 4 in Ca2+-transporting epithelia.
abstract: Plasma membrane Ca(2+)-ATPases (PMCAs) participate in epithelial Ca(2+) transport and intracellular Ca(2+) signaling. The Pmca4 isoform is enriched in distal nephron isolates and decreased in mice lacking the epithelial transient receptor potential vanilloid 5 Ca(2+) channel. We therefore hypothesized that Pmca4 plays a significant role in transcellular Ca(2+) flux and investigated the localization and regulation of Pmca4 in Ca(2+)-transporting epithelia. Using antibodies directed specifically against Pmca4, we found it expressed only in the smooth muscle layer of mouse and human intestines, whereas pan-specific Pmca antibodies detected Pmca1 in lateral membranes of enterocytes. In the kidney, Pmca4 showed broad localization to the distal nephron. In the mouse, expression was most abundant in segments coexpressing the epithelial ransient receptor potential vanilloid 5 Ca(2+) channel. Significant, albeit lower, expression was also evident in the region encompassing the cortical thick ascending limbs, macula densa, and early distal tubules as well as smooth muscle layers surrounding renal vessels. In the human kidney, a similar pattern of distribution was observed, with the highest PMCA4 expression in Na(+)-Cl(-) cotransporter-positive tubules. Electron microscopy demonstrated Pmca4 localization in distal nephron cells at both the basolateral membrane and intracellular perinuclear compartments but not submembranous vesicles, suggesting rapid trafficking to the plasma membrane is unlikely to occur in vivo. Pmca4 expression was not altered by perturbations in Ca(2+) balance, pointing to a housekeeping function of the pump in Ca(2+)-transporting epithelia. In conclusion, Pmca4 shows a divergent expression pattern in Ca(2+)-transporting epithelia, inferring diverse roles for this isoform not limited to transepithelial Ca(2+) transport.
authors.affiliation: Department of Pediatrics, The University of Alberta, Edmonton, Alberta, Canada; Membrane Protein Disease Research Group, The University of Alberta, Edmonton, Alberta, Canada;
authors.forename: R Todd
authors.initials: RT
authors.lastname: Alexander
authors.affiliation: Membrane Protein Disease Research Group, The University of Alberta, Edmonton, Alberta, Canada;
authors.forename: Megan R
authors.initials: MR
authors.lastname: Beggs
authors.affiliation: Department of Urology, Odense University Hospital, Odense, Denmark;
authors.forename: Reza
authors.initials: R
authors.lastname: Zamani
authors.affiliation: Department of Clinical Pathology, Odense University Hospital, Odense, Denmark;
authors.forename: Niels
authors.initials: N
authors.lastname: Marcussen
authors.affiliation: Department of Biomedicine, University of Aarhus, Aarhus, Denmark; and.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Frische
authors.affiliation: Department of Cardiovascular and Renal Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Demark hdimke@health.sdu.dk.
authors.forename: Henrik
authors.initials: H
authors.lastname: Dimke
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D002136:Calcium, Dietary / Q000494:pharmacology; D002462:Cell Membrane / Q000201:enzymology* / Q000648:ultrastructure*; D004847:Epithelial Cells / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure; D005260:Female; D015870:Gene Expression; D006801:Humans; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000378:metabolism; D007685:Kidney Tubules, Collecting / Q000378:metabolism; D008297:Male; D051379:Mice; D009399:Nephrons / Q000378:metabolism; D015388:Organelles / Q000201:enzymology / Q000378:metabolism; D053499:Plasma Membrane Calcium-Transporting ATPases / Q000378:metabolism*; D044169:Receptors, Calcium-Sensing / Q000378:metabolism; D050916:TRPV Cation Channels / Q000378:metabolism
chemical_list: D015220:Calcium Channels; D002136:Calcium, Dietary; D044169:Receptors, Calcium-Sensing; D050916:TRPV Cation Channels; C492240:Trpv5 protein, mouse; D053499:Plasma Membrane Calcium-Transporting ATPases; D002118:Calcium
keywords: ATP2B4; kidney; transcellular calcium transport