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G‐protein Gamma Subunits As Novel Regulators of G‐protein Signaling
Author(s) -
Choudhury Shilpa,
Torres Matthew
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.652.5
Subject(s) - heterotrimeric g protein , g protein coupled receptor , phosphorylation , microbiology and biotechnology , signal transduction , biology , g protein , g protein coupled receptor kinase , protein phosphorylation , protein kinase a , scaffold protein , mapk/erk pathway
G protein signaling systems (GPS), comprised of G protein coupled receptors (GPCRs), heterotrimeric G proteins (Gαβγ) and downstream effectors, are responsible for regulating a wide range of physiological processes including neurotransmitter and hormone signaling. Although the structure and function of GPS proteins are well known, evidence of post‐translational modifications (PTMs) that regulate signal transduction continue to emerge. Using a custom PTM informatics approach (Structural Analysis of PTM Hotspots; SAPH‐ire), we identified the N‐terminal unstructured tail of G protein gamma subunits (Gγ‐Nt) as a phospho‐regulatory element conserved between yeast and humans. Here, we used budding yeast, which harbors a single canonical GPS, to test the hypothesis that phosphorylation of Gγ‐Nt regulates signaling in vivo. We find that Gγ‐Nt in yeast (Ste18‐Nt) is hyper‐phosphorylated upon GPCR activation and in a cell‐cycle dependent manner, both of which events are independent of each other and suggestive of multi‐kinase phosphorylation. A systematic genetic screen revealed the MAPK, Fus3 (orthologous to MAPK‐Erk1), as the primary kinase responsible for GPCR‐dependent phosphorylation. Furthermore, analysis of G protein‐dependent signaling in yeast harboring Ste18‐Nt phosphorylation site mutations suggest that phosphorylation of Gγ N‐terminal tails may be important for regulating the kinetics of G protein pathway activation. Taken together, we have identified the unstructured N‐terminal tail of Gγ subunits as a target of MAPK‐dependent feedback phosphorylation and G protein signal regulation. We further conclude that using SAPH‐ire for computational prediction of biological function can be effective for identifying novel PTM regulatory elements in protein families. Finally, these studies can serve as a model to elucidate the regulatory role of Gγ‐Nt phosphorylation in mammalian G protein signaling systems. Support or Funding Information National Institute of Health (NIH) Funds