Extracellular signals such as nutrients and hormones cue intracellular pathways to produce adaptive responses. Cells often need to coordinate their responses to multiple signals to achieve an appropriate outcome. In this study, we demonstrate that components of a glucose-sensing pathway directly influence the heterotrimeric guanine nucleotide-binding protein (G protein)-mediated pheromone signaling pathway in Saccharomyces cerevisiae. We show that the G protein α subunit Gpa1 undergoes phosphorylation under conditions of reduced glucose availability, and this modification contributes to diminished pheromone-dependent activation of mitogen-activated protein kinases (MAPKs), gene transcription, cell morphogenesis, and mating efficiency. The kinases Elm1, Sak1, and Tos3—known for phosphorylating and activating Snf1, the yeast homolog of adenosine monophosphate-activated protein kinase (AMPK)—also phosphorylate Gpa1 and play a role in attenuating the mating response. Additionally, Reg1, the regulatory subunit of the protein phosphatase PP1 that targets Snf1, is required to reverse Gpa1 phosphorylation and sustain mating competence. These findings reveal that the same kinases and phosphatase regulating Snf1 also modulate Gpa1, indicating direct crosstalk between nutrient-sensing and G protein signaling pathways. This coordination allows cells to prioritize metabolic homeostasis over reproductive processes during periods of energy stress.
The regulation of G protein signaling is fundamental across eukaryotes. In yeast, pheromone signaling triggers a cascade leading to cell fusion between haploid MATa and MATα cells. The process begins when the α-factor pheromone binds to the Ste2 G protein-coupled receptor (GPCR), which activates the heterotrimeric G protein composed of Gpa1 (Gα), Ste4 (Gβ), and Ste18 (Gγ). Dissociation of Gβγ from Gα initiates a kinase cascade culminating in the activation of MAPKs Fus3 and Kss1. This leads to gene expression changes, cell cycle arrest at G1, and morphological alterations including shmoo formation. While G protein activity is traditionally linked to hormonal inputs, emerging evidence shows that metabolic status can modulate such signaling. Here, we establish that glucose availability directly regulates Gpa1 via phosphorylation, thereby fine-tuning the mating response in a context-dependent manner.
We first observed that Gpa1 migration shifts on SDS-PAGE gels under low-glucose conditions, indicating phosphorylation. This modification occurs rapidly and persists even after 60 minutes of starvation. Although deletion of Elm1 alone does not abolish phosphorylation, combined deletion of Elm1, Sak1, and Tos3 eliminates it at early time points, suggesting functional redundancy among these kinases. Notably, phosphorylated Gpa1 remains detectable even in snf1Δ mutants, ruling out Snf1 as the kinase responsible. Furthermore, Reg1-deficient cells accumulate phosphorylated Gpa1 even under high-glucose conditions, demonstrating that Reg1-Glc7 phosphatase activity is essential for dephosphorylating Gpa1.Neratinib manufacturer Coimmunoprecipitation experiments confirmed stable interactions between Gpa1 and both Sak1 and Reg1, supporting direct regulation.
Functional assays revealed that phosphorylation of Gpa1 dampens the pheromone response.Ataluren Purity Strains lacking Elm1, Sak1, and Tos3 exhibit enhanced sensitivity to α-factor and increased Fus3 activation, although full activation is delayed.PMID:34840081 Conversely, reg1Δ cells show reduced Fus3 phosphorylation and decreased pheromone-induced gene expression. These results indicate that the Snf1-activating kinases act as negative regulators of mating, while Reg1 promotes maximal signaling output. Consistent with this, limiting glucose reduces Fus3 activation, gene transcription, shmoo formation, and mating efficiency. Importantly, bypassing Gpa1 through constitutively active Ste11 enhances pathway activity regardless of glucose levels, suggesting that inhibition occurs upstream of MAPK activation.
In summary, our work uncovers a previously unrecognized mechanism by which metabolic state controls sexual development in yeast. By linking glucose sensing to G protein signaling through shared regulatory enzymes, cells ensure that mating—a metabolically costly process—is suppressed during energy scarcity. This model illustrates how conserved signaling networks integrate diverse stimuli to maintain cellular fitness. Given the evolutionary conservation of both G protein and AMPK pathways, similar mechanisms may operate in higher eukaryotes, offering new insights into diseases involving metabolic and signaling dysregulation such as diabetes and cancer.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com