The purpose of these studies is to define the molecular mechanisms by which ligand occupancy of integrin receptors and other cell surface proteins alters the capacity of insulin-like growth factor-I (IGF-I) to stimulate smooth muscle cell (SMC) replication and migration. The studies will determine the role of ligand occupancy of the (_v133integrin in regulating recruitment of SHP-2 tyrosine phosphatase to the plasma membrane and subsequently to the IGF-I receptor. The tyrosine kinase that phosphorylates 133will be identified and how ligand occupancy of (_v133activates the kinase to alter SHP-2 recruitment will be analyzed. A protein that transfers SHP-2 to 133will be isolated and reagents prepared to determine how ECM protein binding to o_v63 stimulates this transfer protein to enhance SHP-2 recruitment. The molecular mechanism by which integrin receptor antagonists function to alter SHP-2 recruitment to IGF-IR will be further defined. The next series of studies will determine how failure to recruit SHP-2 to IGF-IR and to insulin receptor substrate 1 (IRS-1) leads to failure to activate downstream signaling components in the PI-3 and MAP kinase pathways. We will deter- mine whether other cell surface proteins that are involved in SHP-2 recruitment such as SHPS-1 directly alter IGF-IR activity and ability of IGF-IR to activate downstream signaling molecules such as Shc. We will deter- mine the role of SHP-2 transfer to p85 in regulating the activation of Rac-1 and Cdc-42. The necessity of SHP. 2 transfer to GTP exchange factors such as VAV-2 for MAP kinase activation will also be determined. Further studies will analyze the effects of altering ligand occupancy of SHPS-1 in controlling IGF-IR activation and SHP-2 recruitment to IGF-IR. SHPS-1 ligands will be isolated and their effects on these processes determined. The physiologic significance of the SHPS-l-integrin associated protein (lAP) interaction will be defined in several cell types by disrupting this interaction and determining the consequences for IGF-I signaling. The importance of this process for atherosclerotic lesion development will be studied directly in pigs. The SHPS-1/ lAP interaction will be inhibited and the effect on atherosclerotic lesion size determined. The results of these studies should help us to define molecular mechanisms by which the cell surface proteins function coordinately with IGF-IR to stimulate smooth muscle cell migration and replication and may suggest novel strategies for interfering with these processes to alter the progression of atherosclerosis.

National Institute of Health (NIH)
National Institute on Aging (NIA)
Method to Extend Research in Time (MERIT) Award (R37)
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Special Emphasis Panel (NSS)
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Kohanski, Ronald A
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University of North Carolina Chapel Hill
Internal Medicine/Medicine
Schools of Medicine
Chapel Hill
United States
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Xi, Gang; Wai, Christine; White, Morris F et al. (2017) Down-regulation of Insulin Receptor Substrate 1 during Hyperglycemia Induces Vascular Smooth Muscle Cell Dedifferentiation. J Biol Chem 292:2009-2020
Xi, Gang; Shen, Xinchun; Wai, Christine et al. (2015) Hyperglycemia stimulates p62/PKC? interaction, which mediates NF-?B activation, increased Nox4 expression, and inflammatory cytokine activation in vascular smooth muscle. FASEB J 29:4772-82
Shen, Xinchun; Xi, Gang; Wai, Christine et al. (2015) The coordinate cellular response to insulin-like growth factor-I (IGF-I) and insulin-like growth factor-binding protein-2 (IGFBP-2) is regulated through vimentin binding to receptor tyrosine phosphatase ? (RPTP?). J Biol Chem 290:11578-90
Xi, Gang; Shen, Xin-Chun; Wai, Christine et al. (2013) Recruitment of Nox4 to a plasma membrane scaffold is required for localized reactive oxygen species generation and sustained Src activation in response to insulin-like growth factor-I. J Biol Chem 288:15641-53
Xi, Gang; Solum, Melissa A; Wai, Christine et al. (2013) The heparin-binding domains of IGFBP-2 mediate its inhibitory effect on preadipocyte differentiation and fat development in male mice. Endocrinology 154:4146-57
DeMambro, Victoria E; Maile, Laura; Wai, Christine et al. (2012) Insulin-like growth factor-binding protein-2 is required for osteoclast differentiation. J Bone Miner Res 27:390-400
Shen, Xinchun; Xi, Gang; Maile, Laura A et al. (2012) Insulin-like growth factor (IGF) binding protein 2 functions coordinately with receptor protein tyrosine phosphatase ? and the IGF-I receptor to regulate IGF-I-stimulated signaling. Mol Cell Biol 32:4116-30
Xi, Gang; Shen, Xinchun; Maile, Laura A et al. (2012) Hyperglycemia enhances IGF-I-stimulated Src activation via increasing Nox4-derived reactive oxygen species in a PKC?-dependent manner in vascular smooth muscle cells. Diabetes 61:104-13
Clemmons, David R (2012) Metabolic actions of insulin-like growth factor-I in normal physiology and diabetes. Endocrinol Metab Clin North Am 41:425-43, vii-viii
Maile, Laura A; DeMambro, Victoria E; Wai, Christine et al. (2011) An essential role for the association of CD47 to SHPS-1 in skeletal remodeling. J Bone Miner Res 26:2068-81

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