(Verbatim from the application): Injury of the arterial wall results in accelerated vascular smooth muscle cell (SMC) proliferation and directed migration from the media to the intima, leading to intimal hyperplasia and thickening. This process contributes significantly to the pathogenesis of atherosclerosis and related complications. The molecular mechanisms underlying the abnormal SMC proliferation and migration in this process are not well defined but are key to understanding the basis of the development of atherosclerotic lesions. Insulin-like growth factor-I (IGF-1) is a potent regulator of SMC proliferation and directed migration. The growth-promoting and chemotactic actions of IGF-1 are mediated through the IGF-1 receptor (IGF-1R), but how the activation of the same receptor by the same ligand leads to distinct growth and chemotactic responses is unknown. Recently we have discovered that IGF-1 utilizes distinct signaling pathways to stimulate SMC growth and migration. Our further studies indicate that SMCs secrete several high-affinity IGF binding proteins (IGFBPs) and that these IGFBPs may play a critical role in determining whether SMCs will migrate and/or proliferate in response to IGF-1. Our goal in this proposal is to understand how IGF-1, IGF-1R, and IGFBPs interact with each other to regulate SMC proliferation and migration.
The first aim i n this proposal is to elucidate the divergent growth and chemotactic signaling pathways activated by ligand occupancy of IGF-1R in SMCs.
The second aim focuses on the distinct roles of different IGFBPs in determining SMC response to IGF-1. Site-directed mutations will also be generated to determine the specific structural motifs that are essential for the distinct biological actions of different IGFBPs. In the third aim, we will determine the role of cell-surface-associated IGFBP5 in promoting SMC migration towards an IGF-1 gradient. Furthermore, we will test the hypothesis that IGFBP-5 is translocated into SMC nuclei and that the nuclear IGFBP-5 alters SMC motility through a novel mechanism that is independent of the IGF-1R-mediated signaling pathways. The proposed studies will lead us towards an understanding of the molecular interactions between IGF-1, IGF-1R, and IGFBPs and will provide novel information on the regulation of SMC proliferation and migration, as well as a conceptual model of the molecular mechanisms that determine the specific physiological outcomes of IGF-1 stimulation. It is our belief that a complete elucidation of the mechanisms of IGF-1, IGF-1R and IGFBP actions in SMCs should have many ramifications including the development of future therapeutic strategies that may correct or circumvent atherosclerosis and related complications.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL060679-02
Application #
6389978
Study Section
Experimental Cardiovascular Sciences Study Section (ECS)
Program Officer
Applebaum-Bowden, Deborah
Project Start
2000-04-01
Project End
2004-03-31
Budget Start
2001-04-01
Budget End
2002-03-31
Support Year
2
Fiscal Year
2001
Total Cost
$228,000
Indirect Cost
Name
University of Michigan Ann Arbor
Department
Biology
Type
Schools of Arts and Sciences
DUNS #
791277940
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
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Xu, Qijin; Li, Shenghua; Zhao, Yang et al. (2004) Evidence that IGF binding protein-5 functions as a ligand-independent transcriptional regulator in vascular smooth muscle cells. Circ Res 94:E46-54

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