Glucose-sensing and -signalling mechanisms in yeast.

Glucose has dramatic effects on the regulation of carbon metabolism and on many other properties of yeast cells. Several sensing and signalling pathways are involved. For many years attention has focussed on the main glucose-repression pathway which is responsible for the downregulation of respiration, gluconeogenesis and the transport and catabolic capacity of alternative sugars during growth on glucose. The hexokinase 2- dependent glucose-sensing mechanism of this pathway is not well understood but the downstream part of the pathway has been elucidated in great detail. Two putative glucose sensors, the Snf3 and Rgt2 non-transporting glucose carrier homologs, control the expression of many functional glucose carriers. Recently, several new components of this glucose-induction pathway have been identified. The Ras-cAMP pathway controls a wide variety of cellular properties in correlation with cellular proliferation. Glucose is a potent activator of cAMP synthesis. In this case glucose sensing is carried out by two systems, a G-protein-coupled receptor system and a still elusive glucose-phosphorylation-dependent system. The understanding of glucose sensing and signalling in yeast has made dramatic advances in recent years and has become a strong paradigm for the elucidation of nutrient-sensing mechanisms in other eukaryotic organisms.