TAILIEUCHUNG - Báo cáo khoa học: ISC1-encoded inositol phosphosphingolipid phospholipase C is involved in Na+/Li+ halotolerance of Saccharomyces cerevisiae

InSaccharomyces cerevisiae, toxic concentrations of Na + or Li + ions induce the expression of the cation-extrusion ATPase gene,ENA1. Several well-studied signal transduc-tion pathways are known correlating high salinity to the transcriptional activation ofENA1. Nevertheless, informa-tion on the actual sensing mechanism initiating these path-ways is limited. | Eur. J. Biochem. 269 4033-4039 2002 FEBS 2002 doi ISC1-encoded inositol phosphosphingolipid phospholipase C is involved in Na Li halotolerance of Saccharomyces cerevisiae Christian Betz1 Dirk Zajonc1 Matthias Moll2 and Eckhart Schweizer1 1Lehrstuhl fur Biochemie and the 2Lehrstuhl fur Anorganische und Allgemeine Chemie Universitat Erlangen-Nurnberg Erlangen Germany In Saccharomyces cerevisiae toxic concentrations of Na or Li ions induce the expression of the cation-extrusion ATPase gene ENA1. Several well-studied signal transduction pathways are known correlating high salinity to the transcriptional activation of ENA1. Nevertheless information on the actual sensing mechanism initiating these pathways is limited. Here we report that the ISC1-encoded phosphosphingolipid-specific phospholipase C appears to be involved in stimulation of ENA1 expression and consequently in mediating Na and Li tolerance in yeast. Deletion of ISC1 distinctly decreased cellular Na and Li tolerance as growth of the Disc1 HIS5 mutant DZY1 was severely impaired by M NaCl or M LiCl. In contrast K tolerance and general osmostress regulation were unaffected. Isc1A mutant growth with M KCl and glycerol accumulation in the presence of M NaCl or M sorbitol were comparable to that of the wild-type. ENA1-lacZ reporter studies suggested that the increased salt sensitivity of the isc1A mutant is related to a significant reduction of Na Li -stimulated ENA1 expression. Correspondingly Ena1p-dependent extrusion ofNa Li ions was less efficient in the isc1 A mutant than in wild-type cells. It is suggested that ISC1-dependent hydrolysis of an unidentified yeast inositol phosphosphingolipid represents an early event in one of the salt-induced signalling pathways of ENA1 transcriptional activation. Keywords salt-stress signaling sphingolipids sphingolipid phospholipase C yeast. The Saccharomyces cerevisiae gene ISC1 has recently been shown to encode an .

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