Biomedical Sciences Graduate Program(s)
Biomedical Sciences Graduate Programs
The overall goal of our research is to undestand how the large number of G protein
α and βγ isoforms lead to specificity in cell signaling, especially
how the multiple isoforms of the βγ dimer selectively regulate signaling.
We are currently pursuing three major projects. The goal of this work is to understand
the interaction between two major signaling pathways in the cell membrane, one
utilized by Gi linked recceptors to activate hematopoietic cells and another used
by Gs linked receptors to inhibit inflammation. In neutrophils and macrophages,
activation of Gi coupled receptors release the G protein βγ dimer and
activate superoxide production, cell shape changes and cell migration. Cellular
targets for Gβγ dimers include phosphatidylinositol 3-kinase (PI 3 kinase)
and the Rac guanine nucleotide exchange factor (GEF), P-Rex1. Activation of PI
3-kinase generates PIP3 in the plasma membrane and Rac is a central mediator in
cardiovascular physiology and pathophysiology. As P-Rex1 activation is modulated
by PIP3 and the G protein βγ subunit, the synergistic actions of the Gβγ
dimer on PI 3-kinase and P-Rex1 combine to activate cells such as neutrophils
Receptors which raise cyclic AMP levels inhibit the activation of hematopoietic
cells. Thus, phosphorylation of important regulatory sites via the cyclic AMP
depended protein kinase in hematopoietic cells is central to the inhibitory response.
Both PI 3-kinase and P-Rex1 can be phosphorylated in vitro by the cyclic AMP depended
protein kinase (PKA). This event inhibits the activity of both of these enzymes.
Our work examines the ability of pure G protein α and βγ subunits
to regulate PI 3-kinase and P-Rex1 in synthetic lipid vesicles containing PIP3
and PI 3-kinase or Rac to determine which G protein subunits modify the activity
of these enzymes. In another project we are phosphorylating pure, recombinant
PI 3-kinase and P-Rex1 with the cyclic AMP depended protein kinase and measuring
the effect of phoshorylation on their activity in the presence of PIP3 and the
G protein subunits.In a third project, we are examining how PI 3-kinase and P-Rex1
respond to activation of G protein coupled receptors in HEK-293 cells, macrophages
and neutrophils. We are also using small, inhibitory RNA's delivered to these
cells by transfection or stable infection with lentiviruses to determine which
isoforms of G proteins regulate PI 3-kinase and P-Rex1 activity in a cellular
context. Other effectors examined in these experiments include: adenylyl cyclase,
PLC-β, PtdIns 3-kinase and production of certain cytokines such as TNF-α.
Mayeenuddin, L.H., McIntire, W.E. & J.C. Garrison. Differential Sensitivity of P-Rex1 to Isoforms of G Protein beta/gamma Dimers. Journal of Biological Chemistry, 281, 1913-1920, 2006.
Mayeenuddin, L.H. & J.C. Garrison. Phosphorylation of P-Rex1 by the cyclic AMP-Dependent Protein Kinase Inhibits the PIP3 and G beta/gamma Mediated Regulation of Its Activity. Journal of Biological Chemistry, 281, 1921-1928, 2006.
Chen, X., Talley, E.M., Patel, N., Gomez, A, McIntire, W.E., Viana, F., Garrison, J.C. and D.A. Bayliss. Inhibition of a Background Potassium Channel by Gq protein alpha subunits. Proceedings of the National Academy of Sciences, USA, 103, 3422-3427, 2006.
DePuy, S.D., Yao, J., Hu, C., McIntire, W.E., Bidaud, I., Lory, P., Rastinejad, F., Gonzales, C., Garrison, J.C. and P.Q. Barrett. The Molecular Basis for T-type Ca Channel Inhibition by G-protein beta-2\gamma-2 Subunits. Proceedings of the National Academy of Sciences, USA, 103, 14590-14595, 2006.
PubMed Listings for this Faculty Member
(Find Out How to Update Your Faculty Profile)
||PO Box 800735 Jordan Hall 5th Fl, 5013,
||+1 434-924-5618, +1 434-924-9976