title: Molecular characterization of the α-subunit of Na⁺/K⁺ ATPase from the euryhaline barnacle Balanus improvisus reveals multiple genes and differential expression of alternative splice variants.
abstract: The euryhaline bay barnacle Balanus improvisus has one of the broadest salinity tolerances of any barnacle species. It is able to complete its life cycle in salinities close to freshwater (3 PSU) up to fully marine conditions (35 PSU) and is regarded as one of few truly brackish-water species. Na⁺/K⁺ ATPase (NAK) has been shown to be important for osmoregulation when marine organisms are challenged by changing salinities, and we therefore cloned and examined the expression of different NAKs from B. improvisus. We found two main gene variants, NAK1 and NAK2, which were approximately 70% identical at the protein level. The NAK1 mRNA existed in a long and short variant with the encoded proteins differing only by 27 N-terminal amino acids. This N-terminal stretch was coded for by a separate exon, and the two variants of NAK1 mRNAs appeared to be created by alternative splicing. We furthermore showed that the two NAK1 isoforms were differentially expressed in different life stages and in various tissues of adult barnacle, i.e the long isoform was predominant in cyprids and in adult cirri. In barnacle cyprid larvae that were exposed to a combination of different salinities and pCO2 levels, the expression of the long NAK1 mRNA increased relative to the short in low salinities. We suggest that the alternatively spliced long variant of the Nak1 protein might be of importance for osmoregulation in B. improvisus in low salinity conditions.
authors.affiliation: Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Ulrika
authors.initials: U
authors.lastname: Lind
authors.forename: Magnus
authors.initials: M
authors.lastname: Alm Rosenblad
authors.forename: Anna-Lisa
authors.initials: AL
authors.lastname: Wrange
authors.forename: Kristina S
authors.initials: KS
authors.lastname: Sundell
authors.forename: Per R
authors.initials: PR
authors.lastname: Jonsson
authors.forename: Carl
authors.initials: C
authors.lastname: André
authors.forename: Jonathan
authors.initials: J
authors.lastname: Havenhand
authors.forename: Anders
authors.initials: A
authors.lastname: Blomberg
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D005091:Exons / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D059014:High-Throughput Nucleotide Sequencing; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D010802:Phylogeny; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D021122:Protein Subunits / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D054712:Salinity; D012623:Seawater / Q000737:chemistry; D016415:Sequence Alignment; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001468:Thoracica / Q000201:enzymology* / Q000254:growth & development / Q000502:physiology
chemical_list: D020033:Protein Isoforms; D021122:Protein Subunits; D012333:RNA, Messenger; D000254:Sodium-Potassium-Exchanging ATPase