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Mol. Cell. Biol., 03 1995, 1431-1438, Vol 15, No. 3
S Arkinstall, M Payton and K Maundrell
The fission yeast Schizosaccharomyces pombe has no detectable endogenous
receptor tyrosine kinases or associated signalling apparatus, and we have
used this cell system to reconstitute mammalian platelet-derived growth
factor beta (PDGF beta) receptor-linked activation of phospholipase C gamma
2 (PLC gamma 2). The PDGF beta receptor migrates as a glycosylated protein
of 165 kDa associated exclusively with membrane fractions. No tyrosine
autophosphorylation was detected when PDGF beta was expressed alone. PLC
gamma 2 appears as a 140-kDa protein distributed between particulate and
soluble fractions which exhibits characteristic selectivity for
phosphatidylinositol 4,5- bisphosphate and is sensitive to powerful
activation by Ca2+. When coexpressed, both PDGF beta and PLC gamma 2
undergo tyrosine phosphorylation, and this is accompanied by a > 26-fold
increase in [3H]inositol 4,5-biphosphate ([3H]IP2) and [3H]inositol 1,4,5-
triphosphate [3H]IP3 production. Treatment with the tyrosine phosphatase
inhibitor pervanadate further increased PLC gamma 2 tyrosine
phosphorylation as well as [3H]IP2 and [3H]IP3 generation. Phosphorylated
PLC gamma 2 was found predominantly in membrane fractions. To test a
nonreceptor tyrosine kinase, we then expressed the human proto-oncogene
c-src together with its negative regulator Csk. These were immunodetectable
as bands at 60 kDa (c-Src) and 50 kDa (Csk) and distributed between
membrane and cytosolic fractions. When yeast coexpressing c-Src, Csk, and
PLC gamma 2 was incubated with pervanadate, PLC gamma 2 was tyrosine
phosphorylated and [3H]IP2 and [3H]IP3 production increased 11.0- and
7.0-fold, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Copyright © 1995, American Society for Microbiology
Activation of phospholipase C gamma in Schizosaccharomyces pombe by coexpression of receptor or nonreceptor tyrosine kinases
Glaxo Institute for Molecular Biology, Plan-les-Ouates, Geneva, Switzerland.
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