A halocin acting on Na+/H+ exchanger of Haloarchaea as a new type of inhibitor in NHE of mammals

Abstract

The capability of halocin H6 (a bacteriocin-like protein produced by haloarchaea Haloferax gibbonsii) to inhibit Na+/H+ exchanger (NHE) in mammalian cells and its cardio-protective efficacy on the ischemic and reperfused myocardium were evaluated in the present study. H6 inhibits NHE activity (measured by a flow cytometry method) in a dose-dependent form of cell lines of mammalian origin (HEK293, NIH3T3, Jurkat and HL-1) as well as in primary cell culture from human skeletal muscle (myocytes and fibroblasts). In vivo, an ischemia-reperfusion model in dogs by coronary arterial occlusion was used (two hours of regional ischemia and three hours of reperfusion). In animals treated with halocin H6 there was a significant reduction of premature ventricular ectopic beats and infarct size, whereas blood pressure and heart rate remained unchanged. Up to date, halocin H6 is the only described biological molecule that exerts a specific inhibitory activity in NHE of eukaryotic cells.

Antimicrobial peptides and proteins in the face of extremes: Lessons from archaeocins

“…gibbonsii Ma2.39, from Spanish salt ponds in Alicante [37], was initially named halocin H7 in the first studies [22], and both nomenclatures are found in the literature. A halocin-overproducing mutant of the Ma2.39 strain, named strain Alicante SPH7 is also reported to produce HalH6 [37,38]. HalH6 was revealed by SDS-PAGE analysis to be a 32 kDa protein, but the amino acid sequence was not determined [36,37].…”

“…This transmembrane protein, which controls cytosolic pH and intracellular Na þ concentration in all living organisms, is of primary importance for Halobacteriales, where it constitutes the central unit for cell adaptation to highly saline environments [39]. Interestingly, a latter study showed that HalH6 could also inhibit the eukaryotic NHE [38], implying similarities in the structure of these proteins from the archaeal and the eukaryotic domains. It is currently unknown whether HalH6 has any effect on the function of this transporter in bacteria.…”

“…Inhibitors of the eukaryotic NHE could therefore be interesting drug candidates [75]. In fact, one study has demonstrated that halH6 is also capable of inhibiting the eukaryotic NHE in different mammalian cell types [38]. In a dog model of myocardial ischaemia and reperfusion, halH6 protected the myocardium, provoking a decrease of infarct size and the number of ectopic beats [38,76].…”

Features and Applications of Halophilic Archaea

“…Some of these characterized halocines were isolated from Halobacterium, Haloferax, and other haloarchaeon strains and could have applications in this field (O'Connor and Shand, 2002;Shand and Leyva, 2007). Currently, halocins are not considered for use as antibiotics in medicine, but some experiments showed that they could be used as compounds for the control of blood pressure and related pharmacological uses, including potential applications for the reduction of injury in organ transplantation (Meseguer et al, 1995;Alberola et al, 1998;Lequerica et al, 2006;Shand and Leyva, 2007).…”

Halophiles, Industrial Applications

“…This property can protect tissues including the myocardium from damage caused when blood returns after ischemic conditions. Currently, halocin H6 is the only known biological molecule that exerts a specific inhibitory effect on the NHE of mammalian cells (94).…”