G protein signal integration by multifunctional proteins

  • Siderovski, David (PI)
  • Sondek, John (PI)

Project Details


DESCRIPTION (provided by applicant): G protein-mediated signaling underlies the
action of many growth factors, hormones, and neurotransmitters. Although
initially conceived as linear and unidirectional, many G protein-related cell
signaling pathways now are known to converge (and diverge) at many levels. For
example, members of the large family of RGS proteins exhibit multiple
biochemical activities in addition to their signature capacity to promote
G-alpha-mediated GTP hydrolysis. This program project (PPG) applies a
multidisciplinary approach to gain mechanistic and structural insight into
important examples of multifunctional proteins in G protein signaling. We have
assembled investigators with expertise in cancer biology (Der), in signaling in
yeast (Dohlman), and in the molecular pharmacology/biochemistry (Harden),
molecular biology/bioinformatics (Siderovski), and structure (Sondek) of G
protein signaling. A Protein Core will play a central role in the PPG by
facilitating high-throughput cloning, expression, purification, and biophysical
characterization of proteins. The mechanism(s) of R7-family RGS proteins in
"upstream" regulation of receptor/G protein interaction and cross-talk among
heterotrimeric G proteins will be determined in Project I through studies with
mammalian and C. elegans proteins. The multifunctional nature of the newly
identified PLC-epsilon isozyme will be delineated in Project II through studies
identifying interactors for the N-terminal RasGEF and C-terminal
Ras-association domains, the role of PLC-epsilon in Ras-promoted cell
transformation, and the domain(s) in PLC-epsilon that interacts with
G-alpha-subunits. Project III will focus on the yeast protein Sst2, which was
the first RGS protein discovered, and which contains an N-terminal DEP domain
of unknown function also found in the mammalian R7-family RGS proteins studied
in Projects I and IV. Yeast two-hybrid screens have identified proteins that
bind the Sst2 N-terminal domain, and which activate the stress response signal.
The domains of Sst2 responsible for G protein effector activity will be
defined, as will the mechanism(s) of stress response signaling. Project IV will
establish the structural basis for several functional interactions mediating
cross-talk in G protein signaling by solving the structures of the beta5-R7
dimer and the GoLoco domain of R12-family RGS proteins, which has been shown to
inhibit GDP release by G-alpha-i-subunits. This PPG will provide major new
mechanistic insights into the molecular complexities that function across G
protein signaling pathways and should illuminate new drug targets within
fundamental processes that underlie diseases as diverse as cancer, heart
disease, and mental disorders.
Effective start/end date10/04/0231/03/03