Protein kinases Elm1 and Sak1 of Saccharomyces cerevisiae exerted different functions under high-glucose and heat shock stresses.

Phosphorylation catalyzed by protein kinases is the most common and important regulatory pathway in the adaptive physiological responses to the changes in nutrition and environment of yeast. This study focused on the functions of Elm1, Sak1, and Tos3, which are three upstream protein kinases of Snf1 in Saccharomyces cerevisiae, in response to high-glucose and heat shock stresses. Results suggested that changing the gene dosage of ELM1/SAK1/TOS3 had different effects under high-glucose and heat shock stresses. ELM1 and SAK1 overexpressions could enhance the tolerance of S. cerevisiae to high-glucose and heat shock stresses, respectively. Nevertheless, the overexpression of TOS3 decreased the tolerance to high-glucose stress, and a native level of Tos3 was important for the normal adaptation to heat shock condition. The overexpression of ELM1 increased the accumulation of trehalose and ergosterol and altered the composition of fatty acids with altered gene expressions involved in the metabolism of three metabolites. Enhanced resistance to heat shock stress in SAK1 overexpression might be related to the enhanced accumulation of trehalose and ergosterol and upregulated transcription of genes related to the metabolism of trehalose and ergosterol. Furthermore, Elm1 might regulate the metabolism of trehalose, ergosterol, and fatty acids in a Snf1-independent form under high-glucose stress. A Snf1-independent pathway might be involved in the regulation of trehalose metabolism by Sak1 under heat shock condition. However, Sak1 and Snf1 may have an indirect relationship in the regulation of ergosterol synthesis. KEY POINTS: • Altering the gene dosage of ELM1/SAK1/TOS3 had different effects on stress responses • Elm1 regulated high-glucose response in a Snf1-independent manner • Sak1 and Snf1 had an indirect relationship in the regulation of heat shock response.