Verbatim): This research program focuses on the function of alpha2-macroglobulin (a2M) as a regulator of growth factor activity. a2M binds diverse growth factors with limited sequence identity, including transforming growth factor-n (TGFB), platelet-derived growth factor-beta (PDGF-beta), and nerve growth factor-B (NGF-f3). In cell culture, a2M antagonizes growth factor activity. Similar interactions may explain abnormalities in a2M gene knock-out mice that are challenged with inflammatory stimuli. By analyzing a library of a2M peptide-GST fusion proteins, we identified a sequence (an 591-774), near the center of the a2M subunit that binds TGF-B, PDGF-BB, and NGF-B with high affinity. A 16-amino acid peptide (P3) that binds both TGF-beta and PDGF-BB was subsequently identified. In the next five years, our major objectives are: to fully characterize a2M-growth factor interactions on a molecular level; to determine whether the function of a2M as a growth factor-binding protein is responsible for abnormalities in the a2M gene knock-out mouse; and to explore strategies for using our novel growth factor-binding peptides as therapeutics in cancer.
Four specific aims are proposed.
In Specific Aim 1, the function of P3 and related peptides as regulators of growth factor activity will be determined.
In Specific Aim 2, the sequence of human aM will be modified by site-directed mutagenesis to determine the function of the P3 region in the intact protein.
In Specific Aim 3, novel transgenic mice that express mutated forms of murinoglobulin will be generated. Crossbreeding experiments will then be performed with the a2M gene knock-out mouse to determine whether the phenotype of the a2M gene knock-out mouse can be rescued by reversing the deficiency in growth factor regulation. Finally, in aim 4, we will assess the ability of naturally-occurring a2M and a2M-derived growth factor-binding peptides to limit cancer growth and metastasis. The emerging function of a2M as a regulator of diverse growth factors indicates that this protein may have undiscovered activities in a variety of disease states. The combination of approaches proposed here, including molecular analyses and physiology studies, offers the opportunity to elucidate the function of a2M in various diseases including cancer and to exploit this knowledge in rational drug design.
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