Chloride ATPase pumps in nature: do they exist?

Abstract

Five widely documented mechanisms for chloride transport across biological membranes are known: anion-coupled antiport, Na+ and H(+)-coupled symport, Cl- channels and an electrochemical coupling process. These transport processes for chloride are either secondarily active or are driven by the electrochemical gradient for chloride. Until recently, the evidence in favour of a primary active transport mechanism for chloride has been inconclusive despite numerous reports of cellular Cl(-)-stimulated ATPases coexisting, in the same tissue, with uphill ATP-dependent chloride transport. Cl(-)-stimulated ATPase activity is a ubiquitous property of practically all cells with the major location being of mitochondrial origin. It also appears that plasma membranes are sites of Cl(-)-stimulated ATPase pump activity. Recent studies of Cl(-) -stimulated ATPase activity and ATP-dependent chloride transport in the same plasma membrane system, including liposomes, strongly suggest a mediation by the ATPase in the net movement of chloride up its electrochemical gradient across the plasma membrane structure. Contemporary evidence points to the existence of Cl(-)-ATPase pumps; however, these primary active transporters exist as either P-, F- or V-type ATPase pumps depending upon the tissue under study.

Functional plasticity of the gut and the Malpighian tubules underlies cold acclimation and mitigates cold-induced hyperkalemia inDrosophila melanogaster

“…In cockroaches, locusts and flies, the main site of ion reabsorption occurs at four areas of thickened epithelia known as rectal pads (Larsen et al, 2014). Studies of ion transport across locust rectum suggest that an apical V-type H + -ATPase at least partially energizes epithelial ion transport (Phillips et al, 1996;Gerencser and Zhang, 2003). Na + /K + -ATPase is also highly expressed in D. melanogaster hindgut, second in abundance only to the Malpighian tubules, and has been localized to the basolateral membrane in Aedes aegypti, yet its function remains unknown (Patrick et al, 2006;Chintapalli et al, 2007).…”

The second sodium pump: from the function to the gene

“…This property defines the two enzymes as ATPases. The fact that the enzyme is stimulated indifferently by different sodium salts essentially excludes the possibility that the Na + -ATPase is an anion-stimulated ATPase, whose existence has been postulated [61]. The Na + -ATPase and the Na + -K + -ATPase can also be differentiated by their slightly different pH optima and different sensitivities to pH.…”

Animals and Environments: Resisting Schisms in Comparative Physiology and Biochemistry

“…The ecophysiology and mechanisms of ion regulation are together a major subdiscipline of comparative physiology (Zanotto and Wheatly 2006, in this issue), and a number of studies are used to illustrate their importance and diversity, for example, the functioning of the basolateral chloride pump (Cl Ϫ -ATPase) in the foregut of the marine molluscan Aplysia, which is a P-type ATPase (Gerencser and Zhang 2003). Heavy metals such as Cu 2ϩ and Zn 2ϩ may be managed using systems routinely employed for Ca 2ϩ (Zanotto and Wheatly 2006).…”