The lab studies signal transduction that contributes to the pathophysiology of:
- Restenosis of angioplastied vessels
- Vein graft neointimal hyperplasia
Signal transduction pertinent to these pathologic processes substantially involves cell surface receptor protein tyrosine kinases, like those for platelet-derived growth factor (PDGF) and epidermal growth factor (EGF), among several others.
Ongoing work has shown that a variety of receptor protein tyrosine kinases are regulated by G protein-coupled receptor kinases (GRKs) -2 and -5.
In addition, we have recently shown that G protein-coupled receptor signaling through the adaptor protein beta-arrestin2 contributes to atherogenesis.
We are currently focused on three areas, related by their importance in the pathogenesis of atherosclerosis:
Determining mechanisms important to the regulation of receptor protein tyrosine kinases by GRKs 2 and 5, which are expressed widely in mammalian tissues. Model systems for this project include:
- Atherosclerotic mice with smooth-muscle-specific deletions of GRKs
- Smooth muscle cells and fibroblasts from mice genetically deficient in specific G protein-coupled receptor kinases, and cognate wild type cells
- Transfected and recombinant virus-infected cells
- siRNA-treated cells
- Purified proteins
Investigating beta-arrestin2-mediated signaling in vascular smooth muscle and endothelial cells; seeking to determine the roles of beta-arrestins in neointimal hyperplasia and atherosclerosis. Model systems for these projects include:
- Beta-arrestin-deficient (knockout) mice that are also deficient in the LDL receptor
- Endothelial and smooth muscle cells from WT and knockout mice
- RNAi-treated cells
- Co-cultures of macrophages with either smooth muscle cells or endothelial cells
- Mouse inferior vena cava-to-carotid artery interposition ("bypass") grafts
- Carotid arterial grafts
Exploring how genetic variation in the arterial wall affects susceptibility to atherosclerosis, by testing candidate genes identified by our collaborators in the Duke Center for Human Genetics.
To answer this question, we implant carotid arterial grafts from a variety of knockout mice into the common carotid of apolipoprotein-E-deficient (atherosclerosis-prone) mice, and compare the extent of atherosclerosis in these grafts with that observed in carotid grafts taken from congenic control (wild type) mice. We also perform aortic atherosclerosis studies in double- and single-gene knockout mice.
- Kim J, Zhang L, Peppel K, Wu JH, Zidar DA, Brian L, DeWire SM, Exum ST, Lefkowitz RJ, Freedman NJ. ß-arrestins regulate Atherosclerosis and Neointimal Hyperplasia by Controlling Smooth Muscle Cell Proliferation and Migration. Circulation Research 2008; 103: 70-79.
- Zhang L, Sivashunmugam P, Wu JH, Brian L, Exum ST, Freedman NJ, Peppel K. Tumor necrosis factor receptor-2 signaling attenuates vein graft neointima formation by promoting endothelial recovery. Arteriosclerosis Thrombosis and Vascular Biology 2008; 28: 284-9.
- Zhang L, Peppel K, Sivashanmugam P, Orman ES, Brian L, Exum ST, Freedman NJ. Expression of tumor necrosis factor receptor-1 in arterial wall cells promotes atherosclerosis. Arteriosclerosis Thrombosis andVascular Biology 2007; 27: 1087-94.
- Wu J-H, Goswami R, Cai X, Exum ST, Huang X, Zhang L, Brian L, Premont RT, Peppel K, Freedman NJ. Regulation of the platelet-derived growth factor receptor-b by G protein-coupled receptor kinase-5 in vascular smooth muscle cells involves the phosphatase Shp2. The Journal of Biological Chemistry 2006; 281: 37758-72.
- Wu J-H, Goswami R, Kim LK, Miller WE, Peppel K, Freedman NJ. The platelet-derived growth factor receptor-beta phosphorylates and activates G protein-coupled receptor kinase-2: a mechanism for feedback inhibition.The Journal of Biological Chemistry 2005; 280: 31027-35.
Neil J. Freedman, MD, Director
Office: 447 Clinical and Research Labs, Durham, NC, 27710
Campus mail: DUMC Box 3187, Durham, NC, 27710