title: Unique localization of mRNA encoding plasma membrane Ca2+ pump isoform 3 in rat thin descending loop of Henle.
abstract: In our previous study of plasma membrane Ca2+ pump (PMCA) isozymes in the rat kidney, we found that the mRNA coding isoform PMCA3 was detected primarily in the outer medullary zone of rat kidney tissue. We now investigated the location of the mRNAs coding for isoforms PMCA3 and PMCA4 of Ca2+ pump in the nephron segments that are present in outer medullary parenchyma using the method of reverse transcription and polymerase chain reaction. In mRNA extracted from whole dissected outer medulla we detected mRNA encoding three splice variants (a, b, and c) of isoform PMCA3; isoform PMCA4 was found in the outer medulla almost exclusively as variant b. Analysis of mRNA from microdissected tubule segments show that proximal straight tubules (PST), medullary thick ascending limbs, outer medullary collecting ducts, and descending thin limb of Henle's loop (DTL) all contained mRNA for isoform 4b. In contrast, the mRNA encoding isoform 3 was detected exclusively in DTL and not in other nephron segments. The unique presence of isoform 3 in DTL is rather surprising, since the specific role of this nephron segment in vectorial Ca2+ transport or in intracellular Ca2+ signaling is not known. The data suggest that isoform 3 in cells of the DTL may have a hitherto unrecognized specific role in Ca2+ signaling or transport of Ca2+, which is distinct from the role of the isoforms of the PMCA in all other nephron segments.
authors.affiliation: Department of Biochemistry and Molecular Biology, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA.
authors.forename: A J
authors.initials: AJ
authors.lastname: Caride
authors.forename: E N
authors.initials: EN
authors.lastname: Chini
authors.forename: M
authors.initials: M
authors.lastname: Yamaki
authors.forename: T P
authors.initials: TP
authors.lastname: Dousa
authors.forename: J T
authors.initials: JT
authors.lastname: Penniston
mesh_terms: D000818:Animals; D001483:Base Sequence; D000252:Calcium-Transporting ATPases / Q000737:chemistry / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D007536:Isomerism; D007679:Kidney Medulla / Q000378:metabolism; D008138:Loop of Henle / Q000378:metabolism*; D008297:Male; D015335:Molecular Probes / Q000235:genetics; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D015335:Molecular Probes; D012333:RNA, Messenger; D000252:Calcium-Transporting ATPases