E.T.V. TREVISOL1*, A.D. PANEK1, J.F. DE MESQUITA2, E.C.A. ELEUTHERIO1
1 Programa de Pós-graduação em Bioquímica, Instituto de Química, Universidade Federal do Rio de Janeiro,
2 Programa de Pós-graduação em Genética e Biologia Molecular, Instituto Biomédico, Universidade Federal do Estado do Rio de Janeiro,
Trehalose is a non-reducing disaccharide of glucose widely found in nature.It was originally thought to serve as a reserve carbohydrate, but several works have suggested it as an important stress protectant.In the yeast Saccharomyces cerevisiae, trehalose is synthesized by a large complex (TPS). Trehalose-6-phosphate synthase (Tps1) catalyzes the synthesis of trehalose-6-phosphate (T6P), which is dephosphorylated to free trehalose by trehalose-6-phosphate phosphatase (Tps2). TPS complex also includes Tsl1 and Tps3, which seem to have regulatory functions. However, until now the precise role played by these proteins has not been demonstrated. Therefore, in this work we aimed to analyze more closely the regulatory mechanisms played by Tps3 and Tsl1 on trehalose synthesis in response to heat shock and during the stress recovery. According to our results, we do not observed any increase in Tps1 activity in tsl1 cells in response to a heat stress, while in tps3 cells we only observed a reduced Tps1 activity. Besides, in the wild-type strain, Tps1 was inhibited by both T6P and adenosine triphosphate (ATP).Mg2+ in the presence of cAMP, a phosphorylation cocktail. Tps1 was not inhibited by phosphorylation in tps3 cells, which accumulated a higher portion of T6P after stress. This last information is supported by an absence of Tps2 induction in heat stressed tps3 cells. Taken together these results suggest that Tsl1 is a decisive subunit for activity of the TPS complex since in its absence no trehalose synthesis occurred. Tps3 seems to be an activator of Tps2. To perform this task, Tps3 must be non-phosphorylated. In order to readily stop trehalose synthesis during recovery from stress, Tps3 must be phosphorylated by cAMP-dependent protein kinase, decreasing Tps2 activity and, consequently, increasing the concentration of T6P which, in turn, would inhibit Tps1.
Finnancial support: CAPES and CNPq; Area: Biochemistry
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