Molecular identification of Na⁺–H⁺ exchanger isoforms (NHE2) in the gills of the euryhaline teleost Fundulus heteroclitus

Abstract

In the current study, reverse-transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE) PCR were used to clone full-length putative Na(+)-H(+) exchanger isoforms (NHE2a) cDNA from the gills of Fundulus heteroclitus. The 2480 bp cDNA includes a coding region for a protein that shows a 57% amino acid homology to rabbit NHE2. These sequences allowed data mining of available fish genome data, which revealed at least three NHE2 subtypes in some teleost species.

Ion uptake pathways in European sea bass Dicentrarchus labrax

“…No nhe1 expression difference between SW and FW has been shown in the rainbow trout in different tissues including gills, kidney and anterior intestine (Genz et al, 2011). Few studies have quantified the expression of different nhe2 paralogs, notably nhe2c (Edwards et al, 2010). We have identified three nhe2…”

“…are not expressed in the posterior kidney and intestine and nhe2a was not clearly detected in any osmoregulatory tissue. This is not the case in killifish, where NHE2a has been identified in cuboidal cells, the cell type expressing basolateral VHA and being involved in Na + uptake (Edwards et al, 2010;Laurent et al, 2006).…”

“…Several paralogs have been identified in teleosts for nhe (1, 2, 3) probably due to putative genome duplication events (Glasauer and Neuhauss, 2014;Meyer and Van de Peer, 2005). Two or three nhe2 paralogous genes have been identified in F. heteroclitus, Takifugu rubripes, Gasterosteus aculeatus, and the longhorn sculpin Myoxocephalus octodecemspinosus but functional differences remain to be analyzed (Edwards et al, 2010). Contrary to NHE2 and 3, NHE1 has been shown to be expressed in basolateral membranes and is mainly involved in pH homeostasis and cell volume regulation of epithelial and non-epithelial cells (Tse et al, 1993).…”

“…NHE (2/3) has also been identified in PNA+ ionocytes of rainbow trout (for a review, see Dymowska et al, 2012). NHE2a has been shown in cuboidal cells of killifish Fundulus heteroclitus, the cell type responsible for Na + uptake (Edwards et al, 2010;Laurent et al, 2006). As VHA is expressed in basolateral membranes of…”

A brief history of fish osmoregulation: the central role of the Mt. Desert Island Biological Laboratory

“…B. Claiborne and colleagues, working at the MDIBL, who demonstrated that recovery from induced acidosis in the longhorn sculpin was inhibited by low external Na + concentrations (20–30 mM) or by external amiloride [or the more Na/H-specific 5- N , N -hexamethylene-amiloride (HMA)] (Claiborne and Evans, 1988). These physiological data were corroborated by subsequent molecular data showing immunolocalization of Na + /H + exchanger isoforms (NHEs), and V-H + -ATPase, in the gill epithelium of the sculpin in seawater (Claiborne et al, 1999; Catches et al, 2006), and this gill localization of NHEs has now been extended to the little skate (Choe et al, 2002), spiny dogfish (Tresguerres et al, 2005; Choe et al, 2007), and killifish (Claiborne et al, 1999; Choe et al, 2002; Edwards et al, 2010) at the MDIBL. V-H + -ATPase and a Cl − /${\text{HCO}}_3^{-}$ exchanger (pendrin) have also been immunolocalized in the gill epithelium of the Atlantic stingray in seawater (Piermarini and Evans, 2001; Piermarini et al, 2002).…”