Isolation of a gene encoding a G protein α subunit involved in the regulation of cAMP levels in the yeastKluyveromyces lactis

Saviñón‐Tejeda, Alma L.; Ongay‐Larios, Laura; Ramı́rez, Jorge; Coria, Roberto

doi:10.1002/(sici)1097-0061(19960915)12:11<1125::aid-yea7>3.0.co;2-2

Cited by 21 publications

(2 citation statements)

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“…This further supports the finding that glucose does not stimulate cAMP synthesis through intracellular acidification. Our results also fit with results obtained in the other yeast species S.pombe (Isshiki et al ., 1992; Nocero et al ., 1994) and K.lactis (Saviñon‐Tejeda et al ., 1996) where a GPA2 homologue was found to be required for glucose‐induced stimulation of cAMP synthesis. Previously, the inability of a Ras2 val19 mutant to mediate glucose‐induced cAMP signalling was interpreted as indicating a role for the Ras proteins in transmission of the glucose signal (Mbonyi et al ., 1988).…”

Section: Discussionmentioning

confidence: 99%

“…In spite of this, it was concluded that Gpa2 is an element of the nitrogen‐sensing machinery that regulates pseudohyphal differentiation by modulating cAMP levels. On the other hand, in Schizosaccharomyces pombe (Isshiki et al ., 1992; Nocero et al ., 1994) and Kluyveromyces lactis (Saviñon‐Tejeda et al ., 1996), Gα proteins appear to be involved in the stimulation of cAMP levels in response to glucose.…”

Section: Introductionmentioning

confidence: 99%

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Involvement of distinct G-proteins, Gpa2 and Ras, in glucose-and intracellular acidification-induced cAMP signalling in the yeast Saccharomyces cerevisiae

et al. 1998

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S.Colombo and P.Ma contributed equally to this workAdenylate cyclase activity in Saccharomyces cerevisiae is dependent on Ras proteins. Both addition of glucose to glucose-deprived (derepressed) cells and intracellular acidification trigger an increase in the cAMP level in vivo. We show that intracellular acidification, but not glucose, causes an increase in the GTP/GDP ratio on the Ras proteins independent of Cdc25 and Sdc25. Deletion of the GTPase-activating proteins Ira1 and Ira2, or expression of the RAS2 val19 allele, causes an enhanced GTP/GDP basal ratio and abolishes the intracellular acidification-induced increase. In the ira1Δ ira2Δ strain, intracellular acidification still triggers a cAMP increase. Glucose also did not cause an increase in the GTP/GDP ratio in a strain with reduced feedback inhibition of cAMP synthesis. Further investigation indicated that feedback inhibition by cAPK on cAMP synthesis acts independently of changes in the GTP/GDP ratio on Ras. Stimulation by glucose was dependent on the Gα-protein Gpa2, whose deletion confers the typical phenotype associated with a reduced cAMP level: higher heat resistance, a higher level of trehalose and glycogen and elevated expression of STRE-controlled genes. However, the typical fluctuation in these characteristics during diauxic growth on glucose was still present. Overexpression of Ras2 val19 inhibited both the acidification-and glucose-induced cAMP increase even in a protein kinase A-attenuated strain. Our results suggest that intracellular acidification stimulates cAMP synthesis in vivo at least through activation of the Ras proteins, while glucose acts through the Gpa2 protein. Interaction of Ras2 val19 with adenylate cyclase apparently prevents its activation by both agonists.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Involvement of distinct G-proteins, Gpa2 and Ras, in glucose-and intracellular acidification-induced cAMP signalling in the yeast Saccharomyces cerevisiae

et al. 1998

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The Gβ(KlSte4p) subunit of the heterotrimeric G protein has a positive and essential role in the induction of mating in the yeast Kluyveromyces lactis

Kawasaki

Saviñón‐Tejeda

Ongay‐Larios

et al. 2005

Yeast

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In the yeast Saccharomyces cerevisiae the Gβγ dimer of the heterotrimeric G protein transduces a pheromone signal from serpentine receptor to a MAP kinase cascade that activates the mating response pathway. Haploid cells lacking the Gβ subunit do not respond to sexual pheromone, leading to sterility. In this work we demonstrate that the β-subunit of Kluyveromyces lactis, encoded by the KlSTE4 gene, is a component of the G protein, and that its disruption gives rise to sterile cells. However, unlike Ste4p in S. cerevisiae, its overexpression does not induce growth arrest or promote mating. It has been shown that in K. lactis, the Gα subunit has a positive role in the mating process, hence the resulting double Gα Gβ mutant was viable and sterile. Here we show that the overproduction of Gβ subunit fails to rescue Gα mutant from sterility and that expression of a constitutive active allele of Gα enhances transcription of the KlSTE4 gene. The mating pathway triggered by the Gβ-subunit requires a functional KlSte12p transcription factor. Gβ has a 10-fold higher association rate with the Gα1 subunit involved in pheromone response than with Gα2, the protein involved in cAMP regulation in K. lactis. Additionally, the Gβ-subunit from K. lactis is able to interact with the Gα-subunit from S. cerevisiae but fails to restore the mating deficiency of Scste4 mutant. The data presented indicate that the mating pathway of K. lactis is positively and cooperatively regulated by both the Gα and the Gβ subunits.

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The KlSTE2 and KlSTE3 genes encode MATα‐ and MATa‐specific G‐protein‐coupled receptors, respectively, which are required for mating of Kluyveromyces lactis haploid cells

Torres-Quiroz

Kawasaki

Rodríguez-González

et al. 2006

Yeast

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Mating in yeast is initiated by binding of pheromone to G-protein-coupled receptors expressed in haploid cells. We analysed the role of KlSte2p and KlSte3p receptors in the Kluyveromyces lactis mating pathway. By sequence analysis, KlSte2p and KlSte3p are the homologues of the Saccharomyces cerevisiae α-pheromone and a-pheromone receptors, respectively. However, by expression experiments, we determined that KlSTE2 gene is expressed in the cells typified as MAT α and therefore is the receptor for the K. lactis a-pheromone and KlSTE3 gene is expressed in the MAT a cells and binds the α-pheromone. The KlSTE2 gene is silent in MAT a cells, while it is highly expressed in MATα cells, and conversely the KlSTE3 gene is expressed in MAT a cells and repressed in MATα cells. Disruption mutants of both genes were found to be sterile, and this defect is reversed by plasmidic copies of each gene. The cytoplasmic C-terminus of KlSte3p interacts strongly with the KlGpa1p (Gα) subunit, which is involved in the transduction of the pheromone stimulus to induce mating. Remarkably, this same domain does not interact with a constitutive active allele of the Gα subunit, indicating that the C-terminus is able to discriminate between the active (GTP-bound) and inactive (GDP-bound) forms of the Gα subunit.

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Isolation of a gene encoding a G protein α subunit involved in the regulation of cAMP levels in the yeastKluyveromyces lactis

Cited by 21 publications

References 30 publications

Involvement of distinct G-proteins, Gpa2 and Ras, in glucose-and intracellular acidification-induced cAMP signalling in the yeast Saccharomyces cerevisiae

Involvement of distinct G-proteins, Gpa2 and Ras, in glucose-and intracellular acidification-induced cAMP signalling in the yeast Saccharomyces cerevisiae

The Gβ(KlSte4p) subunit of the heterotrimeric G protein has a positive and essential role in the induction of mating in the yeast Kluyveromyces lactis

The KlSTE2 and KlSTE3 genes encode MATα‐ and MATa‐specific G‐protein‐coupled receptors, respectively, which are required for mating of Kluyveromyces lactis haploid cells

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