Sodium Acetate Responses in Saccharomyces cerevisiae and the Ubiquitin Ligase Rsp5.

Akaraphol Watcharawipas,Hiroshi Takagi,Daisuke Watanabe

doi:10.3389/fmicb.2018.02495

Akaraphol Watcharawipas, Hiroshi Takagi + Show 1 more

Open Access

https://doi.org/10.3389/fmicb.2018.02495

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Abstract

Recent studies have revealed the feasibility of sodium acetate as a potentially novel inhibitor/stressor relevant to the fermentation from neutralized lignocellulosic hydrolysates. This mini-review focuses on the toxicity of sodium acetate, which is composed of both sodium and acetate ions, and on the involved cellular responses that it elicits, particularly via the high-osmolarity glycerol (HOG) pathway, the Rim101 pathway, the P-type ATPase sodium pumps Ena1/2/5, and the ubiquitin ligase Rsp5 with its adaptors. Increased understanding of cellular responses to sodium acetate would improve our understanding of how cells respond not only to different stimuli but also to composite stresses induced by multiple components (e.g., sodium and acetate) simultaneously. Moreover, unraveling the characteristics of specific stresses under industrially related conditions and the cellular responses evoked by these stresses would be a key factor in the industrial yeast strain engineering toward the increased productivity of not only bioethanol but also advanced biofuels and valuable chemicals that will be in demand in the coming era of bio-based industry.

Highlights

The budding yeast Saccharomyces cerevisiae is an important microorganism for the production of alcoholic beverages, bread, and bioethanol, as well as other biochemicals due to its wellknown ability during the fermentation process
Yeast cells lacking RIM101 exhibit impaired vacuole acidification, leading to acidic cytosolic pH under propionic acid stress (Mira et al, 2009). These findings suggested that both the high-osmolarity glycerol (HOG) and the Rim101 pathways potentially participate in the cellular responses to composite stress from a salt and weak acid — in this case, sodium and acetate
Our study found that disruption of HOG1 conferred sodium acetate sensitivity on yeast cells, but did not significantly affect the accumulation of intracellular sodium in yeast cells under sodium acetate stress conditions, suggesting that Hog1 mediated sodium acetate responses via other components e.g., glycerol (Watcharawipas et al, 2017)

Summary

INTRODUCTION

The budding yeast Saccharomyces cerevisiae is an important microorganism for the production of alcoholic beverages, bread, and bioethanol, as well as other biochemicals due to its wellknown ability during the fermentation process. Yeast cells lacking RIM101 exhibit impaired vacuole acidification, leading to acidic cytosolic pH under propionic acid stress (Mira et al, 2009) Taken together, these findings suggested that both the HOG and the Rim101 pathways potentially participate in the cellular responses to composite stress from a salt and weak acid — in this case, sodium and acetate. The plasma membrane H+-ATPase Pma was shown to be mono-ubiquitinated by Rsp, leading to its internalization and vacuolar degradation, in response to the loss of V-ATPase activity (Smardon and Kane, 2014), suggesting that Rsp plays a role in the regulation of cytosolic pH homeostasis in yeast cells. Previous studies have shown that acetate stress in the presence of sodium at pH 6.8 exhibits a growth-inhibitory effect and triggers Hog MAPK

Conserved domain

Plasma membrane Plasma membrane

CONCLUSION