New dimensions in G protein signalling: G beta 5 and the RGS proteins.
The beta gamma complex of G-proteins regulates effectors independently of the G alpha subunits, such that upon activation G proteins give may signal downstream along one or both pathways. The G beta 5 isoform exhibits much less homology with other G beta isoforms (approximately 50%) and is preferentially expressed in brain. The G beta 5 isoform exhibits novel properties in its activation of effector pathways such as MAPK, phospholipase C-beta, and adenylyl cyclase type II when compared to G beta 1. Recently specific native complexes between G beta 5 and the regulator of G protein signaling (RGS) protein-7 (RGS7) and between G beta 5L (a splice variant with a 42 amino acid N-terminal extension) and RGS9 have been isolated from different retinal fractions. Such findings are not accounted for by current models as only the G alpha subunits and not G beta had been previously implicated in RGS protein function. These recent novel observations further reinforce the view of G beta 5 as a unique and highly specialized G protein subunit.
Simonds
W F
WF
Metabolic Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA. wfs@helix.nih.gov
Zhang
J H
JH
D000595:Amino Acid Sequence; D000818:Animals; D019204:GTP-Binding Proteins / Q000502:physiology*; D006801:Humans; D008969:Molecular Sequence Data; D020710:RGS Proteins / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*
D020710:RGS Proteins; D019204:GTP-Binding Proteins