J. Biol. Chem., Vol. 265, Issue 24, 14315-14320, Aug, 1990
cAMP promotes the synthesis in early G1 of gp115, a yeast glycoprotein containing glycosyl-phosphatidylinositol
R Grandori, L Popolo, M Vai and L Alberghina
Sezione di Biochimica Comparata, Dipartimento di Fisiologia e Biochimica Generali, Milano, Italy.
The glycoprotein gp115 (Mr = 115,000, pI 4.8-5) is localized in the plasma
membrane of Saccharomyces cerevisiae cells and maximally expressed during
G1 phase. To gain insight on the mechanism regulating its synthesis, we
have examined various conditions of cell proliferation arrest. We used
pulse-labeling experiments with [35S]methionine and two-dimensional gel
electrophoresis analysis, which allow the detection of the well
characterized 100-kDa precursor of gp115 (p100). In the cAMP-requiring
mutant cyr1, p100 synthesis is active during exponential growth, shut off
by cAMP removal, and induced when growth is restored by cAMP readdition.
The inhibition of p100 synthesis also occurs in TS1 mutant cells
(ras1ras2-ts1) shifted from 24 to 37 degrees C. During nitrogen starvation
of rca1 cells, a mutant permeable to cAMP, p100 synthesis is also
inhibited. cAMP complements the effect of ammonium deprivation, promoting
p100 synthesis, even when added to cells which have already entered G0.
Experiments with the bcy1 and cyr1bcy1 mutants have indicated the
involvement of the cAMP- dependent protein kinases in the control of p100
synthesis. Moreover, the synthesis of p100 was unaffected in A364A cells,
terminally arrested at START B by alpha-factor. These results indicate that
the switch operating on p100 synthesis is localized in early G1 (START A)
and is one of the multiple events controlled by the cAMP pathway.
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