1999 — 2002 |
Howard, Eric W |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Regulation of Cell Migration in Vascular Remodeling @ University of Oklahoma Hlth Sciences Ctr
The pathogenic remodeling of blood vessels often involves smooth muscle proliferation and migration. As in other instances of cell movement, smooth muscle cell migration into the neointima involves a regulated series of adhesion and de-adhesion events regulated by cell-surface receptors and surface-associated proteases. The matrix metalloproteinase (MMP), gelatinase A, plays a significant role in this process by enabling cells to overcome matrix barriers, and also regulates cell-matrix adhesion during migration. It does this through its interaction with its specific activator, MT1-MMP, a membrane-associated proteinase that initiates cleavage of the gelatinase A pro-peptide in a complex process involving multiple interactions with cell-surface proteins. One such interaction involves MT1-MMP itself, which bindings gelatinase A through a bridge with the MMP inhibitor, TIMP-2, a critical mediator of gelatinase A activation. TIMP-2 binds the active site of MT1-MMP and the carboxyl domain of gelatinase A, forming a triplex which positions gelatinase A appropriate for subsequent activation by another MT1-MMP molecule. The carboxyl domain of gelatinase A also binds the integrin, alphavbeta3, which also plays a role in the activation process. Finally, cell bind TIMP-2 to other, as yet unknown sites which may also be key elements of gelatinase A activation. Interestingly, fibroblasts and smooth muscle cells rapidly respond to changes in cell shape by activating and binding gelatinase A in a process independent of new protein synthesis, suggesting that the components of the activation mechanism are present on cells but preventing from interacting appropriately. In this study, the role of TIMP-2 in both the cell binding and activation of gelatinase A will be explored. First, the biochemical basis for the role of TIMP-2 in both the cell binding and activation of gelatinase A will be explored. First, the biochemical basis for TIMP-2's specificity for MT1-MMP will be deduced using chimeric TIMP molecules in which TIMP-2 sequence will be exchanged for sites within TIMP-2, a highly homologous inhibitor with virtually no specificity for MT1-MMP. Net, the non-MMP cell-surface binding sites for TIMP-2 will be characterized, and the critical amino acid sequences within TIMP-2 that confer this binding will be determined. Finally, the contribution of TIMP-2 to gelatinase A binding and activation will be modeled. Understanding this mechanism will be important in defining the biochemical events that occur during vascular remodeling in both normal and disease processes.
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0.958 |
2002 — 2005 |
Howard, Eric W |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Regulation of Angiogenesis During Wound Healing @ University of Oklahoma Hlth Sciences Ctr
Description (provided by applicant): Wound healing requires the formation of new vasculature in a complex process that is dependent on stabilization and destabilization signals. The endothelial cell-specific receptor tyrosine kinase, Tie2, when stimulated by its primary ligand, angiopoietin-1 (Ang1), promotes blood vessel stability by stimulating cell viability, basement membrane integrity, and perivascular cell recruitment. Ang2, an antagonist of the Tie2 receptor, blocks these signals by competing for Ang1 binding, and is necessary for the locaiized vessel instability associated with angiogenesis. Thus, the ratio of Ang1 to Ang2 is a critical factor in the regulation of neovascularization; altering Ang1 or Ang2 expression can lead to profound vascular defects. This study focuses on evidence that Ang2 expression is regulated post-transcriptionally; endothelial and smooth muscle cell culture models demonstrate profound changes in Ang2 mRNA half-life in response to certain growth factors. This induced change in message stability is dependent on new transcription, presumably of factors associated with regulated mRNA turnover. It is hypothesized that such post-traiascriptional regulation is critical for the maintenance of appropriate Ang2 levels during tissue repair. To test this, the putative mRNA control elements within the human, mouse, and rat Ang2 MRNAs that regulate induced message stability/instability or translation will be identified and characterized. Their role in regulating Ang2 expression will then be tested in vivo by introducing these elements into reporter constructs; which will then be used to develop transgenic mice. The biological roles of these mRNA control elements will be further analyzed in mice in which these elements are ablated by conditional homologous recombination. These mouse models will be used to test the effects of dysfunctional Ang2 post-transcriptional regulation on wound healing. These studies will indicate the relative importance of post-transcriptional regulation of Ang2, and whether eliminating the ability of cells to regulate Ang2 mRNA stability or translation impacts vessel structure during the wound healing process.
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0.958 |