title: Novel mechanisms in nutrient activation of the yeast protein kinase A pathway.
abstract: In yeast the Protein Kinase A (PKA) pathway can be activated by a variety of nutrients. Fermentable sugars, like glucose and sucrose, trigger a spike in the cAMP level, followed by activation of PKA and phosphorylation of target proteins causing a.o. mobilization of reserve carbohydrates, repression of stress-related genes and induction of growth-related genes. Glucose and sucrose are sensed by a G-protein coupled receptor system that activates adenylate cyclase and also activates a bypass pathway causing direct activation of PKA. Addition of other essential nutrients, like nitrogen sources or phosphate, to glucose-repressed nitrogen- or phosphate-starved cells, also triggers rapid activation of the PKA pathway. In these cases cAMP is not involved as a second messenger. Amino acids are sensed by the Gap1 transceptor, previously considered only as an amino acid transporter. Recent results indicate that the amino acid ligand has to induce a specific conformational change for signaling. The same amino acid binding site is involved in transport and signaling. Similar results have been obtained for Pho84 which acts as a transceptor for phosphate activation of the PKA pathway. Ammonium activation of the PKA pathway in nitrogen-starved cells is mediated mainly by the Mep2 transceptor, which belongs to a different class of transporter proteins. Hence, different types of sensing systems are involved in control of the yeast PKA pathway by nutrients.
authors.affiliation: Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, Katholieke Universiteit Leuven, Belgium. johan.thevelein@bio.kuleuven.be
authors.forename: Johan M
authors.initials: JM
authors.lastname: Thevelein
authors.forename: Beatriz Monge
authors.initials: BM
authors.lastname: Bonini
authors.forename: Dries
authors.initials: D
authors.lastname: Castermans
authors.forename: Steven
authors.initials: S
authors.lastname: Haesendonckx
authors.forename: Johan
authors.initials: J
authors.lastname: Kriel
authors.forename: Wendy
authors.initials: W
authors.lastname: Louwet
authors.forename: Palvannan
authors.initials: P
authors.lastname: Thayumanavan
authors.forename: Yulia
authors.initials: Y
authors.lastname: Popova
authors.forename: Marta
authors.initials: M
authors.lastname: Rubio-Texeira
authors.forename: Wim
authors.initials: W
authors.lastname: Schepers
authors.forename: Patrick
authors.initials: P
authors.lastname: Vandormael
authors.forename: Griet
authors.initials: G
authors.lastname: Van Zeebroeck
authors.forename: Peter
authors.initials: P
authors.lastname: Verhaert
authors.forename: Matthias
authors.initials: M
authors.lastname: Versele
authors.forename: Karin
authors.initials: K
authors.lastname: Voordeckers
mesh_terms: D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D005502:Food; D005656:Fungal Proteins; D012440:Saccharomyces / Q000502:physiology*; D015398:Signal Transduction
chemical_list: D005656:Fungal Proteins; D017868:Cyclic AMP-Dependent Protein Kinases