TAILIEUCHUNG - Báo cáo khoa học: Regulated cleavage of intracellular glycosylphosphatidylinositol in a trypanosome Peroxisome-to-endoplasmic reticulum translocation of a phospholipase C

Cell exposure to hypo-osmolarity and alkalinity triggers a spectrum of responses including activation of phospholipases. Glycosylphosphatidyl-inositol-specific phospholipase C (GPI-PLC) is expressed in Trypanosoma brucei, a protozoan parasite that causes human African trypanosomia-sis. | iFEBS Journal Regulated cleavage of intracellular glycosylphosphatidylinositol in a trypanosome Peroxisome-to-endoplasmic reticulum translocation of a phospholipase C Sandesh Subramanya and Kojo Mensa-Wilmot Department of Cellular Biology University of Georgia Athens GA USA Keywords glycosylphosphatidylinositol phospholipase C protein trafficking Trypanosoma brucei trypanosomiasis Correspondence K. Mensa-Wilmot Department of Cellular Biology University of Georgia Athens GA 30602 USA Fax 1 706 542 4271 Tel 1 706 542 3355 E-mail mensawil@ Received 8 October 2005 revised 27 February 2006 accepted 13 March 2006 doi Cell exposure to hypo-osmolarity and alkalinity triggers a spectrum of responses including activation of phospholipases. Glycosylphosphatidylinositol-specific phospholipase C GPI-PLC is expressed in Trypanosoma brucei a protozoan parasite that causes human African trypanosomiasis. We examined possible contributions of GPI-PLC to the response of T. brucei to hypo-osmotic or mildly alkaline conditions. GPIs were detected at the endoplasmic reticulum ER . They were cleaved after exposure of T. brucei to hypo-osmolarity or mild alkalinity which also strikingly caused translocation of GPI-PLC from glycosomes peroxisomes to the ER. A catalytically inactive Gln81Leu mutant of GPI-PLC failed to cleave GPIs despite being transported from glycosomes to the ER after hypo-osmotic or mild alkaline treatment of the parasites. In contrast a Cys347-Ser mutant of the enzyme could not exit glycosomes after treatment of cells expressing the protein with mild base or hypo-osmotic buffer. We conclude that a GPI-PLC contributes to loss of GPIs in T. brucei treated with hypo-osmotic or mildly alkaline buffer b access of GPI-PLC to its substrate in vivo can be regulated post-translationally c translocation of GPI-PLC from glycosomes to the ER is important for in vivo cleavage of GPIs d Cys347 is part of a peptide motif required for .

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