Garrison, James C.

James C. Garrison

James C. Garrison

Primary Appointment

Professor, Pharmacology

Contact Information

Jordan Hall 5th Fl Bx 800735, 5013
Charlottesville, VA 22908
Telephone: 434-924-5618

Research Interests

<body>Role of the G protein &alpha and &beta&gamma Subunits in Cell Signaling </body>

Research Description

The overall goal of our research is to undestand how the large number of G protein &#945 and &#946&#947 isoforms lead to specificity in cell signaling, especially how the multiple isoforms of the &#946&#947 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 &#946&#947 dimer and activate superoxide production, cell shape changes and cell migration. Cellular targets for G&#946&#947 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 &#946&#947 subunit, the synergistic actions of the G&#946&#947 dimer on PI 3-kinase and P-Rex1 combine to activate cells such as neutrophils and macrophages.

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 &#945 and &#946&#947 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-&#946, PtdIns 3-kinase and production of certain cytokines such as TNF-&#945.