Pseudohyphal and invasive growth in the yeast Saccharomyces cerevisiae require a signaling pathway that is mediated by the G protein beta-subunit Gpa2p and its coupled receptor Gpr1. Gpr1p is a low affinity glucose receptor that responds to high concentrations of glucose in the environment. Transmission of a signal from Gpr1p to Gpa2p results in phenotypes associated with high levels of intracellular cAMP. We have recently identified KRH1 and KRH2 as genes that encode components of the Gpa2p signaling pathway. We have shown that Krh1p and Krh2p act downstream of adenylyl cyclase to inhibit protein kinase A (PKA) by a process that does not involve production of intracellular cAMP. Activation of Gpa2p is thought to relieve the inhibition of PKA by Krh1p and Krh2p, resulting in high levels of PKA activity. The long-term objectives of this project are: 1) To obtain a complete description of the molecular processes that comprise the Gpa2p signal transduction pathway;2) To understand the biological function of the Gpa2p pathway in terms of an entire cell population undergoing pseudohyphal growth. The first specific aim of this project is to determine how Krh1p and Krh2p regulate PKA. These studies will investigate whether binding of Krh1p and Krh2p to PKA is direct and whether binding inhibits PKA kinase activity. The second specific aim is to determine whether Krh1p and Krh2p control signaling by affecting the localization of PKA. The third specific aim is to investigate whether the GTP-bound form of Gpa2p blocks the inhibitory function of Krh1p and Krh2p by determining the effects of non-activatable and constitutive alleles of GPA2 on Krh1p and Krh2p function. The fourth specific aim is to test whether Gpa2p is specifically activated in cells at the edge of a growing colony in order to suppress stress and starvation responses and to promote growth and pseudohyphal development. The goal of this aim is to develop a reporter system to allow detection of activated Gpa2p at the level of a whole colony undergoing pseudohyphal growth. These studies will provide new information about G protein-mediated signaling pathways, which are essential for the proper functioning of many physiological processes in humans.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
3R01GM074242-04S1
Application #
8003041
Study Section
Special Emphasis Panel (ZRG1-CDF-3 (90))
Program Officer
Maas, Stefan
Project Start
2010-02-12
Project End
2010-12-31
Budget Start
2010-02-12
Budget End
2010-12-31
Support Year
4
Fiscal Year
2010
Total Cost
$158,081
Indirect Cost
Name
Icahn School of Medicine at Mount Sinai
Department
Biology
Type
Schools of Medicine
DUNS #
078861598
City
New York
State
NY
Country
United States
Zip Code
10029
Budhwar, Roli; Fang, Guoqiang; Hirsch, Jeanne P (2011) Kelch repeat proteins control yeast PKA activity in response to nutrient availability. Cell Cycle 10:767-70
Budhwar, Roli; Lu, Ailan; Hirsch, Jeanne P (2010) Nutrient control of yeast PKA activity involves opposing effects on phosphorylation of the Bcy1 regulatory subunit. Mol Biol Cell 21:3749-58
Niranjan, Thiruvur; Guo, Xuedong; Victor, Jacob et al. (2007) Kelch repeat protein interacts with the yeast Galpha subunit Gpa2p at a site that couples receptor binding to guanine nucleotide exchange. J Biol Chem 282:24231-8
Lu, Ailan; Hirsch, Jeanne P (2005) Cyclic AMP-independent regulation of protein kinase A substrate phosphorylation by Kelch repeat proteins. Eukaryot Cell 4:1794-800