Garrison, James C.

James C. Garrison

James C. Garrison

Primary Appointment


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 <br /> &#945 and &#946&#947 isoforms lead to specificity in cell signaling, especially <br /> how the multiple isoforms of the &#946&#947 dimer selectively regulate signaling. <br /> We are currently pursuing three major projects. The goal of this work is to understand <br /> the interaction between two major signaling pathways in the cell membrane, one <br /> utilized by Gi linked recceptors to activate hematopoietic cells and another used <br /> by Gs linked receptors to inhibit inflammation. In neutrophils and macrophages, <br /> activation of Gi coupled receptors release the G protein &#946&#947 dimer and <br /> activate superoxide production, cell shape changes and cell migration. Cellular <br /> targets for G&#946&#947 dimers include phosphatidylinositol 3-kinase (PI 3 kinase) <br /> and the Rac guanine nucleotide exchange factor (GEF), P-Rex1. Activation of PI <br /> 3-kinase generates PIP3 in the plasma membrane and Rac is a central mediator in <br /> cardiovascular physiology and pathophysiology. As P-Rex1 activation is modulated <br /> by PIP3 and the G protein &#946&#947 subunit, the synergistic actions of the G&#946&#947 <br /> dimer on PI 3-kinase and P-Rex1 combine to activate cells such as neutrophils <br /> and macrophages.<br/><br /> Receptors which raise cyclic AMP levels inhibit the activation of hematopoietic <br /> cells. Thus, phosphorylation of important regulatory sites via the cyclic AMP <br /> depended protein kinase in hematopoietic cells is central to the inhibitory response. <br /> Both PI 3-kinase and P-Rex1 can be phosphorylated in vitro by the cyclic AMP depended <br /> protein kinase (PKA). This event inhibits the activity of both of these enzymes. <br /> Our work examines the ability of pure G protein &#945 and &#946&#947 subunits <br /> to regulate PI 3-kinase and P-Rex1 in synthetic lipid vesicles containing PIP3 <br /> and PI 3-kinase or Rac to determine which G protein subunits modify the activity <br /> of these enzymes. In another project we are phosphorylating pure, recombinant <br /> PI 3-kinase and P-Rex1 with the cyclic AMP depended protein kinase and measuring <br /> the effect of phoshorylation on their activity in the presence of PIP3 and the <br /> G protein subunits.In a third project, we are examining how PI 3-kinase and P-Rex1 <br /> respond to activation of G protein coupled receptors in HEK-293 cells, macrophages <br /> and neutrophils. We are also using small, inhibitory RNA's delivered to these <br /> cells by transfection or stable infection with lentiviruses to determine which <br /> isoforms of G proteins regulate PI 3-kinase and P-Rex1 activity in a cellular <br /> context. Other effectors examined in these experiments include: adenylyl cyclase, <br /> PLC-&#946, PtdIns 3-kinase and production of certain cytokines such as TNF-&#945.

Selected Publications