The yeast trimeric guanine nucleotide-binding protein alpha subunit, Gpa2p, controls the meiosis-specific kinase Ime2p activity in response to nutrients.
Saccharomyces cerevisiae Gpa2p, the alpha subunit of a heterotrimeric guanine nucleotide-binding protein (G protein), is involved in the regulation of vegetative growth and pseudohyphal development. Here we report that Gpa2p also controls sporulation by interacting with the regulatory domain of Ime2p (Sme1p), a protein kinase essential for entrance of meiosis and sporulation. Protein-protein interactions between Gpa2p and Ime2p depend on the GTP-bound state of Gpa2p and correlate with down-regulation of Ime2p kinase activity in vitro. Overexpression of Ime2p inhibits pseudohyphal development and enables diploid cells to sporulate even in the presence of glucose or nitrogen. In contrast, overexpression of Gpa2p in cells simultaneously overproducing Ime2p results in a drastic reduction of sporulation efficiency, demonstrating an inhibitory effect of Gpa2p on Ime2p function. Furthermore, deletion of GPA2 accelerates sporulation on low-nitrogen medium. These observations are consistent with the following model. In glucose-containing medium, diploid cells do not sporulate because Ime2p is inactive or expressed at low levels. Upon starvation, expression of Gpa2p and Ime2p is induced but sporulation is prevented as long as nitrogen is present in the medium. The negative control of Ime2p kinase activity is exerted at least in part through the activated form of Gpa2p and is released as soon as nutrients are exhausted. This model attributes a switch function to Gpa2p in the meiosis-pseudohyphal growth decision.
Donzeau
M
M
Institut für Genetik und Mikrobiologie, Ludwig-Maximilians-Universität München, D-80638 Munich, Germany.
Bandlow
W
W
D001483:Base Sequence; D018797:Cell Cycle Proteins; D003470:Culture Media; D017931:DNA Primers / Q000235:genetics; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D044385:GTP-Binding Protein alpha Subunits; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020962:Heterotrimeric GTP-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008540:Meiosis; D008954:Models, Biological; D008969:Molecular Sequence Data; D009584:Nitrogen / Q000378:metabolism; D011487:Protein Conformation; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D013172:Spores, Fungal / Q000235:genetics / Q000378:metabolism
D018797:Cell Cycle Proteins; D003470:Culture Media; D017931:DNA Primers; D005656:Fungal Proteins; D044385:GTP-Binding Protein alpha Subunits; D047908:Intracellular Signaling Peptides and Proteins; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D011494:Protein Kinases; C064979:IME2 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; D019204:GTP-Binding Proteins; C083907:Gpa2 protein, S cerevisiae; D020962:Heterotrimeric GTP-Binding Proteins; D009584:Nitrogen