title: Peptides induce persistent signaling from endosomes by a nutrient transceptor.
abstract: The yeast Gap1 transceptor mediates amino acid activation of the protein kinase A pathway and undergoes endocytic internalization following amino acid transport. We identified three specific γ-glutamyl dipeptides that cause persistent cyclic AMP-independent activation of protein kinase A, prevent Gap1 vacuolar sorting and cause Gap1 accumulation in endosomes. To our knowledge, these are the first examples of persistent agonists of a transceptor. In yeast mutants blocked in multivesicular body sorting, L-citrulline mimicked persistent signaling, further supporting that the internalized Gap1 transceptor keeps signaling. Unexpectedly, these dipeptides were transported by Gap1 and not by the regular dipeptide transporters. Their uptake was unusually sensitive to external pH and caused transient intracellular acidification. High external pH, NHA1 deletion or V-ATPase inhibition overcame the vacuolar sorting defect. Hence, this work has identified specific dipeptides that cause enhanced proton influx through the Gap1 symporter, resulting in its defective vacuolar sorting, and independently transform it into a persistently signaling transceptor.
authors.affiliation: Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Flanders, Belgium.
authors.forename: Marta
authors.initials: M
authors.lastname: Rubio-Texeira
authors.forename: Griet
authors.initials: G
authors.lastname: Van Zeebroeck
authors.forename: Johan M
authors.initials: JM
authors.lastname: Thevelein
mesh_terms: D026905:Amino Acid Transport Systems / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism; D002956:Citrulline / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004151:Dipeptides / Q000378:metabolism* / Q000494:pharmacology*; D011992:Endosomes / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism
chemical_list: D026905:Amino Acid Transport Systems; D027682:Cation Transport Proteins; D004151:Dipeptides; C491145:GAP1 protein, S cerevisiae; C000631624:NHA1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D017923:Sodium-Hydrogen Exchangers; D002956:Citrulline; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases