Heterotrimeric G Proteins
James D. Kim, Patrick Schacht, Amruta Garud, Gyungsoon Park and Katherine A. Borkovich
from: Neurospora: Genomics and Molecular Biology (Edited by: Durgadas P. Kasbekar and Kevin McCluskey). Caister Academic Press, U.K. (2013)
Abstract
One of the major systems used by Neurospora crassa to sense and respond to changes in the environment is the heterotrimeric G protein signaling pathway. This system translates signals detected by G protein coupled receptors (GPCRs) or the cytosolic protein RIC8 to an associated intracellular heterotrimeric G protein (α, β and Gγ subunit) to regulate GDP/GTP exchange on the Gα protein. Gα-GTP and the Gβ γdimer have the potential to regulate downstream effectors. In N. crassa, all five characterized G protein subunits have some function in sexual and asexual growth and development, nutrient sensing or stress responses. Biochemical evidence indicates that the Gβ and Gγ subunits form a heterodimer, and that loss of either subunit leads to degradation of Gα proteins. GPCRs have been implicated in the pheromone response (PRE-1 and PRE-2), perithecial development (GPR-1) and carbon sensing (GPR-4). GTP binding assays using purified proteins demonstrate that RIC8 activates GDP/GTP exchange on two Gα proteins. cAMP is an important second messenger that regulates aspects of asexual and sexual development. Furthermore, metabolomics experiments using 1H-NMR support a role for one G Gα protein in nutrient sensing read more ...
