Microtubule-dependent relocation of branchial V-H+-ATPase to the basolateral membrane in the Pacific spiny dogfish (Squalus acanthias): a role in base secretion

Abstract

SUMMARY We have previously shown that continuous intravenous infusion of NaHCO3 for 24 h (∼1000 μmol kg-1 h-1)results in the relocation of V-H+-ATPase from the cytoplasm to the basolateral membrane in the gills of the Pacific dogfish. To further investigate this putative base-secretive process we performed similar experiments with the addition of colchicine, an inhibitor of cytoskeleton-dependent cellular trafficking processes. Blood pH and plasma total CO2 were significantly higher in the colchicines-treated,HCO3--infused fish compared with fish infused with HCO3- alone. The effect of colchicine was highest after 24 h of infusion (8.33±0.06 vs 8.02±0.03 pH units,15.72±3.29 vs 6.74±1.34 mmol CO2l-1, N=5). Immunohistochemistry and western blotting confirmed that colchicine blocked the transit of V-H+-ATPase to the basolateral membrane. Furthermore, western blotting analyses from whole gill and cell membrane samples suggest that the short-term (6 h) response to alkaline stress consists of relocation of V-H+-ATPases already present in the cell to the basolateral membrane, while in the longer term (24 h) there is both relocation of preexistent enzyme and upregulation in the synthesis of new units. Our results strongly suggest that cellular relocation of V-H+-ATPase is necessary for enhanced HCO3- secretion across the gills of the Pacific dogfish.

Physiological and molecular responses of the spiny dogfish shark (Squalus acanthias) to high environmental ammonia: scavenging for nitrogen

“…2) located, in contrast to teleosts. Instead, all current models for the elasmobranch gill indicate that H + -ATPase functions basolaterally in those ionocytes, which excrete base (Piermarini and Evans, 2001;Piermarini et al, 2002;Tresguerres et al, 2005;Reilly et al, 2011), so that H + ions are returned to the blood when HCO 3 -is excreted apically at times of blood alkalosis (Tresguerres et al, 2005;Tresguerres et al, 2006;Tresguerres et al, 2007;Roa et al, 2014). In the present study, there was a slight tendency towards alkalosis during HEA exposure, with a significant rise in plasma [HCO 3 -] (Fig.…”

Feeding through your gills and turning a toxicant into a resource: how the dogfish shark scavenges ammonia from its environment

“…The Rh transcripts expressed in the gills (Rhbg and Rhp2) are thought to be basolaterally located (Nawata et al, 2015a,b). Together with basolaterally located V-type H + -ATPase (Tresguerres et al, 2005(Tresguerres et al, , 2006, these Rh proteins could function as a metabolon to pump ammonia-N from gill cells to blood, analogous to the apical Rhcg metabolon that pumps ammonia-N from gill cells to the external water in teleosts (Wright andWood, 2009, 2012). In the kidney of another elasmobranch, Triakis scyllium, Nakada et al (2010) have similarly proposed that basolateral Rhp2 serves to recover ammonia-N from the urine.…”

“…Unfortunately, as yet, there are no pharmacological blockers of Rh proteins to test these ideas. However, there are both pharmacological and physiological tools available to manipulate the expression of Vtype H + -ATPase on the basolateral gill membranes of the dogfish shark (Tresguerres et al, 2005(Tresguerres et al, , 2006, providing an exciting pathway forward for future research.…”

Recent advances in understanding trans-epithelial acid-base regulation and excretion mechanisms in cephalopods

“…78,81 However, a basolateral orientation of the VHA has been associated with base secretory processes through cooperating with apical pendrin (SLC26A4) to secrete base in type B intercalated cells of the mammalian kidney 78,83 or in branchial epithelia of some elasmobranchs. 84,85 Also in dipteran insect larvae, a basal VATPase that is coupled to apical anion exchange is responsible for a net import of HCO 3 ¡ into the luminal space to drive luminal alkalinization. 86,87 Also in euryhaline killifish, Japanese medaka (Oryzias latipes), a basolateral VHA is found in ionocytes co-expressing the Na C -Cl ¡ cotransporter (NCC).…”