Activation of numerous G-protein-coupled receptors (GPCRs) results in cell proliferation that contributes to the progression of diseases such as Kaposi's sarcoma. We have recently reported that GPCRs activate nuclear factor kappa B (NF-kappaB), which induces the expression of a large number of genes responsible for cell growth and survival. The NF-KappaB activation mechanims have been extensively characterized using model cytokines such as TNFalpha, but little is known about the G-protein pathways that activate this important transcription factor. Using pharmacological inhibitors and dominant negative DNA constructs that disrupt G-protein signaling, we have found that G-proteins vary in their ability to activate NF-KappaB. While many Galpha and Gbetagamma subunits mediate NF-KappaB activation, certain Galpha subunits can also inhibit NF-KappaB. Experiments are proposed in 3 specific aims to determine the mechanisms by which G-proteins regulate NFKappaB activation.
In Aim 1, we will investigate the signaling pathways utilized by G13 for NF-KappaB activation. We hypothesize that signaling effectors downstream of the G13-p115RhoGEF-RhoA pathway play a critical role in NF-KappaB activation through p65 transactivation.
Aim 2 is focused on Gbetagamma dimers in the differential activation of PI-3 kinases and Src protein tyrosine kinases, both leading to NF-KappaB activation but with different 1kappabetaalpha kinetics. We propose to identify the factors that determine the activation of these effectors of Gbetaalpha. The role of beta-arrestins in Gbetagamma-mediated NF-KappaB activation will also be examined.
In Aim 3, we will determine how NF-KappaB activation is negatively regulated by G-proteins. A working hypothesis is that Galphai proteins have the opposite function of Gbetagamma in that they mediate inhibition of NF-KappaB activation in cells stimulated with proinflammatory agents. We will investigate a possible role of Galphai2 in suppression of NF-KappaB. A potential link to Galkphai-mediated inhibition of Raf-1 pathway will be examined. Collectively, these studies are expected to reveal how G-protein mediated proximal signaling events lead to different cytoplasmic and nuclear signaling and transcriptional regulation, and to identify potential sites for therapeutic intervention.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM066182-02
Application #
6874915
Study Section
Pharmacology A Study Section (PHRA)
Program Officer
Lograsso, Philip
Project Start
2004-04-01
Project End
2008-03-31
Budget Start
2005-04-01
Budget End
2006-03-31
Support Year
2
Fiscal Year
2005
Total Cost
$260,400
Indirect Cost
Name
University of Illinois at Chicago
Department
Pharmacology
Type
Schools of Medicine
DUNS #
098987217
City
Chicago
State
IL
Country
United States
Zip Code
60612
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