Short- and long-term, salinity-induced modulation of V-ATPase activity in the posterior gills of the true freshwater crab, Dilocarcinus pagei (Brachyura, Trichodactylidae)

Abstract

To better understand the biochemical mechanisms underlying anisosmotic extracellular regulation in the freshwater Brachyura, we kinetically characterized the V-ATPase from the posterior gills of Dilocarcinus pagei, acclimated for 10days to salinities up to 21‰. Specific activity was highest in fresh water (26.5±2.1U mg(-1)), decreasing in 5‰ to 21‰, attaining 3-fold less at 15‰. Apparent affinities for ATP and Mg(2+) respectively increased 3.2- and 2-fold at 10‰, suggesting expression of different isoenzymes. In a 240-h time-course study of exposure to 21‰, maximum specific activity decreased 2.5- to 4-fold within 1 to 24h while apparent affinities for ATP and Mg(2+) respectively increased by 12-fold within 24h and 2.4-fold after 1h, unchanged thereafter. K(I) for bafilomycin A(1) decreased 150-fold after 1h, remaining constant up to 120h. This is the first kinetic analysis of V-ATPase specific activity in crustacean gills during salinity acclimation. Our findings indicate active gill Cl(-) uptake by D. pagei in fresh water, and short- and long-term down-regulation of V-ATPase-driven ion uptake processes during salinity exposure, aiding in comprehension of the biochemical adaptations underpinning the establishment of the Brachyura in fresh water.

A kinetic characterization of the gill V(H+)-ATPase in juvenile and adult Macrobrachium amazonicum, a diadromous palaemonid shrimp

“…Lee et al (2011) have shown that the V(H + )-ATPase exhibits an evolutionary shift to elevated activity in freshwater populations of the copepod Eurytemora affinis. Maximal gill V(H + )-ATPase in M. amazonicum was found at pH 7.5 independently of ontogenetic stage and is in close agreement with data for several crustaceans (Onken and Putzenlechner, 1995;Zare and Greenaway, 1998;Onken et al, 2000;Weihrauch et al, 2004;Pan et al, 2007;Firmino et al, 2011). In contrast, V(H + )-ATPase activity of the mussel Cygnea anadonta decreases considerably near pH 8.0 (Oliveira et al, 2004).…”

“…V(H + )-ATPase activities have been measured in anterior and posterior gills of freshwater crabs, including Eriocheir sinensis (Onken and Putzenlechner, 1995;Morris, 2001) and Dilocarcinus pagei (Weihrauch et al, 2004), and a gill V(H + )-ATPase already has been partially characterized kinetically in microsomal gill preparations of M. amazonicum (Faleiros et al, 2010) and D. pagei (Firmino et al, 2011). In contrast, V(H + )-ATPase activity is very reduced in the euryhaline blue crabs Table 2 Kinetic parameters for the stimulation by ATP and Mg 2+ , and K I values for inhibition by bafilomycin A 1 , of V(H + )-ATPase activity in gill microsomal fractions from juvenile and adult Macrobrachium amazonicum.…”

“…Its apparent affinity for ATP is 3-fold greater than the juvenile, and 5.5-and 20-times greater, respectively, than the microsomal gill enzyme from M. amazonicum (Faleiros et al, 2010) and D. pagei (Firmino et al, 2011). The K 0.5 value for Mg 2+ of the adult gill V(H + )-ATPase is 5-fold less than that for the juvenile, and is 2-and 4-fold less, respectively, than for M. amazonicum (Faleiros et al, 2010) and D. pagei (Firmino et al, 2011).…”

“…Its apparent affinity for ATP is 3-fold greater than the juvenile, and 5.5-and 20-times greater, respectively, than the microsomal gill enzyme from M. amazonicum (Faleiros et al, 2010) and D. pagei (Firmino et al, 2011). The K 0.5 value for Mg 2+ of the adult gill V(H + )-ATPase is 5-fold less than that for the juvenile, and is 2-and 4-fold less, respectively, than for M. amazonicum (Faleiros et al, 2010) and D. pagei (Firmino et al, 2011). The inhibition constant for bafilomycin A 1 of the adult enzyme is 2-fold less than for the juvenile, and is 10-fold higher than previously reported for M. amazonicum (Faleiros et al, 2010), and 2.5-fold less than for D. pagei (Firmino et al, 2011).…”

Effects of salinity acclimation and eyestalk ablation on Na+, K+, 2Cl− cotransporter gene expression in the gill of Portunus trituberculatus:a molecular correlate for salt-tolerant trait

“…NKCC is an integral membrane protein responsible for the simultaneous transport of one Na + , one K + , and two Cl − ions from the external to the internal side of epithelial cells (Kang et al 2010). Although previous studies suggest that NKCC plays a critical role in the osmoregulatory endurance of fish (Kang et al 2010;Watson et al 2014;LorinNebel et al 2006;Ip et al 2013;Chandrasekar et al 2014), its role in salinity adaptations has been little studied in crustaceans compared to other ion transport genes (i.e., Na + , K + -ATPase, V-type H + -ATPase, carbonic anhydrase (CA)) (Tsai and Lin 2007;Lucu et al 2008;Firmino et al 2011;Han et al 2015).…”