Molecular characterization of V-type H(+)-ATPase (B-subunit) in gills of euryhaline crabs and its physiological role in osmoregulatory ion uptake

• Published in: Journal of experimental biology Vol. 204; no. Pt 1; pp. 25 - 37
• Main Authors: Weihrauch, D, Ziegler, A, Siebers, D, Towle, D W
• Format: Journal Article
• Language: English
• Published: England 01.01.2001
• Subjects: 3' Untranslated Regions; Amino Acid Sequence; Animals; Base Sequence; Brachyura - enzymology; DNA, Complementary - chemistry; Gene Expression; Gills - enzymology; Humans; Immunohistochemistry; Molecular Sequence Data; Osmolar Concentration; Polymerase Chain Reaction; Proton-Translocating ATPases - chemistry; Proton-Translocating ATPases - genetics; Proton-Translocating ATPases - physiology; Sequence Alignment; Sodium Chloride; Vacuolar Proton-Translocating ATPases; Water-Electrolyte Balance - physiology
• ISSN: 0022-0949; 1477-9145
• DOI: 10.1242/jeb.204.1.25

The vacuolar-type H(+)-ATPase (V-ATPase) has been implicated in osmoregulatory ion uptake across external epithelia of a growing variety of species adapted to life in fresh water. In the present study, we investigated whether the V-ATPase may also function in a euryhaline species that tolerates brackish water (8 salinity) but not fresh water, the shore crab Carcinus maenas. cDNA coding for the regulatory B-subunit of the V-ATPase was amplified and sequenced from C. maenas gills and partially sequenced from four other crab species. Two isoforms differing in the 3'-untranslated region were found in C. maenas. In this species, the abundance of B-subunit mRNA was greater in the respiratory anterior gills than the ion-transporting posterior gills and was not increased by acclimation to dilute salinity. Immunocytochemical analysis showed that the B-subunit protein is not targeted to the apical membrane but is distributed throughout the cytoplasmic compartment. Physiological studies of isolated perfused gills indicated that the V-ATPase inhibitor bafilomycin had no effect on transepithelial potential difference. Thus, in contrast to the freshwater-tolerant Chinese crab Eriocheir sinensis, in which the V-ATPase appears to play an important osmoregulatory role, the V-ATPase in C. maenas probably functions in acidification of intracellular organelles but not in transbranchial NaCl uptake.