Nutrient sensing and transceptor-mediated metabolic control in yeast

Abstract

The yeast Saccharomyces cerevisiae coordinates growth, metabolism, and stress adaptation through signaling pathways that respond to changes in nutrient availability. Classical nutrient-sensing systems, including the cAMP–protein kinase A (PKA), Snf1/AMP-activated protein kinase, target of rapamycin complex 1 (TORC1)–Sch9, Ssy1–Ptr3–Ssy5, and general amino acid control pathways, have revealed how yeast senses and responds to extracellular carbon, nitrogen, phosphate, and amino acid levels. In addition to these established pathways, plasma-membrane nutrient transporters also function in signaling rather than solely mediating substrate uptake. These dual-function proteins, termed nutrient transceptors, couple nutrient transport or extracellular nutrient recognition to rapid intracellular responses, often activating PKA without detectable changes in cAMP levels. This review focuses on yeast nutrient transceptors, specifically Gap1, Mep2, Pho84, Sul1/Sul2, Can1, Ftr1, and Zrt1. These proteins link extracellular nutrient availability to intracellular regulatory responses, including trehalose mobilization, stress resistance, growth resumption, filamentous development, and, in some cases, TORC1–Sch9 signaling. Mechanistic insights, including transport-signaling uncoupling and potential physical association with downstream protein kinases, are also discussed. Collectively, this evidence establishes nutrient transceptors as an essential additional layer of nutrient sensing in yeast, highlighting their role in translating extracellular nutrient cues into cellular responses.