ABSTRACT
CONTENTS 7.1 Introduction ................................................................................................................................. 87 7.2 Primary Components of Heterotrimeric G Protein Signaling .................................................... 88
7.2.1 G-Protein-Coupled Receptors (GPCRs) ......................................................................... 88 7.2.2 G Protein α Subunits ...................................................................................................... 89
7.2.2.1 FadA and GpaA .............................................................................................. 90 7.2.2.2 GanB and GpaB ............................................................................................. 91
7.2.3 G Protein β Subunit ........................................................................................................ 91 7.2.4 G Protein γ Subunit ........................................................................................................ 92 7.2.5 Phosducin-Like Proteins (PhLPs) .................................................................................. 92
7.3 Downstream Signaling Branches ................................................................................................ 92 7.3.1 Adenylate Cyclase and cAMP-Dependent Protein Kinases (PKAs) ............................. 92 7.3.2 Mitogen Activated Protein (MAP) Kinases ................................................................... 94 7.3.3 Protein Kinase C (PKC) ................................................................................................. 95
7.4 Negative Regulators of G Protein Signaling: RGSs .................................................................... 96 7.4.1 FlbA and AfFlbA ........................................................................................................... 96 7.4.2 RgsA ............................................................................................................................... 97 7.4.3 Other RGSs ..................................................................................................................... 97
7.5 Conclusions and Prospects .......................................................................................................... 98 Acknowledgments ................................................................................................................................ 99 References ............................................................................................................................................ 99
7.1 Introduction Signal transduction is vital for the biology of all living cells, contributing to the integration of environmental cues into appropriate physiological and biochemical responses. The heterotrimeric G protein (G protein) system is conserved in all eukaryotes and is the most commonly used signal transducing system in eukaryotic cells. Basic elements of G protein signaling include a G protein-coupled receptor (GPCR), a G protein composed of α, β, and γ subunits, and a variety of effector proteins [1-3]. In fungi, G protein signaling controls a diverse range of biological processes including growth, cell division, mating, cell-cell fusion, morphogenesis, chemotaxis, virulence, pathogenesis, and secondary metabolite production [4-9].
