Genetic interactions among the Arl1 GTPase and intracellular Na+/H+ antiporters in pH homeostasis and cation detoxification

Abstract

The roles of intracellular GTPase Arl1 and organellar cation/H(+) antiporters (Kha1 and Nhx1) in Saccharomyces cerevisiae tolerance to various stress factors were investigated and interesting new phenotypes of strains devoid of these proteins were found. The role of Arl1 GTPase in their tolerance to various cations is not caused by an altered plasma-membrane potential. Besides the known sensitivity of arl1 mutants to high temperature, we discovered their sensitivity to low temperature. We found for the first time that in the absence of Arl1p, Kha1p increases potassium, sodium and lithium tolerance, and can thus be categorized as an antiporter with broad substrate specificity. Kha1p also participates in the detoxification of undesired chemical compounds, pH regulation and growth at nonoptimal temperatures. Cells with the combined deletions of all three genes have considerable difficulty growing under nonoptimal conditions. We conclude that Arl1p, Kha1p and Nhx1p collaborate in survival strategies at nonoptimal pH, temperatures and cation concentrations, but work independent of each other.

Identification of yeast genes that confer resistance to chitosan oligosaccharide (COS) using chemogenomics

“…Arl1 is highly conserved in all eukaryotes with 65% homology to human ADP-ribosylation factor-like protein 1 (Arl1). Arl1 has been shown to be associated with the trans -Golgi and is thought to be required for endosome-Golgi trafficking [45,46]. Arl1- GTP recruits specific receptor proteins to the membrane surface by binding to their GRIP domains, although in yeast, no specific Arl1 binding receptor proteins have yet been identified [44,45].…”

“…Arl1- GTP recruits specific receptor proteins to the membrane surface by binding to their GRIP domains, although in yeast, no specific Arl1 binding receptor proteins have yet been identified [44,45]. Mutations in yeast ARL1 are not lethal [28] but ARL1 mutants do show mild defects in localizing proteins to vacuoles as well as defects in potassium uptake [44,46-48]. arl1 mutants have also been shown to be more sensitive to antifungal agents such as Hygromycin B [46].…”

“…Mutations in yeast ARL1 are not lethal [28] but ARL1 mutants do show mild defects in localizing proteins to vacuoles as well as defects in potassium uptake [44,46-48]. arl1 mutants have also been shown to be more sensitive to antifungal agents such as Hygromycin B [46]. Arl1 can be myristolayted and we hypothesize that through myristoylation, the soluble form of the GTPase could be bound to the membrane bilayer.…”

A novel Na+(K+)/H+ antiporter plays an important role in the growth of Acetobacter tropicalis SKU1100 at high temperatures via regulation of cation and pH homeostasis

“…High temperature could result in an increase in membrane permeability, allowing for greater diffusion of Na + , H + and K + , thus disturbing the internal pH homeostasis (Coote et al, 1991;Konings et al, 2002). In S. cerevisiae, two antiporters involved in K + efflux have been reported to participate in the detoxification and/or cell response to various extracellular stress, including non-optimal temperatures (Marešová and Sychrová, 2010). Moreover, in mammalian cells, it has been reported that there is a linear relationship between thermosensitivity and internal pH, which could be mediated by a Na + /H + antiporter (Liu et al, 1996a;Liu et al, 1996b).…”

“…Growth of Saccharomyces cerevisiae at sub-lethal temperature revealed increasing activity of membrane ATPase, which is responsible for intracellular pH homeostasis (Coote et al, 1991). In addition, the intracellular GTPase Arl1 and organellar cation/H + antiporters (Kha1 and Nhx1) of S. cerevisiae were found to be important for survival at nonoptimal pH, temperature and cation concentration (Marešová and Sychrová, 2010). Such perturbations Abbreviations: AAB, acetic acid bacteria; AO, acridine orange; ISO, inside-out; YPG, yeast extract-peptone-glycerol.…”