title: New isoforms of rat Aquaporin-4.
abstract: Aquaporin-4 (AQP4) is a brain aquaporin implicated in the pathophysiology of numerous clinical conditions including brain edema. Here we show that rat AQP4 has six cDNA isoforms, formed by alternative splicing. These are named AQP4a-f, where AQP4a and AQP4c correspond to the two classical M1 and M23 isoforms, respectively. The various isoforms are differentially expressed in kidney and brain, and their prevalence does not correspond to the level of the respective mRNAs, pointing to posttranscriptional regulation. The three isoforms lacking exon 2, AQP4b, AQP4d, and AQP4f, have an intracellular localization when expressed in cell lines and do not transport water when expressed in Xenopus oocytes. In contrast, the largest of the new isoforms, AQP4e, which contains a novel N-terminal domain, is localized at the plasma membrane in cell lines and functions as a water transporter in Xenopus oocytes.
authors.affiliation: Center for Molecular Biology and Neuroscience, University of Oslo, Oslo, Norway.
authors.forename: Svein Erik
authors.initials: SE
authors.lastname: Moe
authors.forename: Jan Gunnar
authors.initials: JG
authors.lastname: Sorbo
authors.forename: Rikke
authors.initials: R
authors.lastname: Sogaard
authors.forename: Thomas
authors.initials: T
authors.lastname: Zeuthen
authors.forename: Ole
authors.initials: O
authors.lastname: Petter Ottersen
authors.forename: Torgeir
authors.initials: T
authors.lastname: Holen
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D051401:Aquaporin 4 / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers; D018076:DNA, Complementary; D006367:HeLa Cells; D006801:Humans; D020033:Protein Isoforms / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: C496032:Aqp4 protein, rat; D051401:Aquaporin 4; D017931:DNA Primers; D018076:DNA, Complementary; D020033:Protein Isoforms; D012333:RNA, Messenger