The elastic properties of many vertebrate tissues are due largely to elastic fibers made up of two morphologically and biochemically distinct components: (1) the amorphous component made up entirely of the protein elastin, (2) the microfibrillar component made up of several proteins, whose exact number has yet to be determined. The elastin amorphous component is largely responsible for the elastic properties of the fibers; the function of the microfibrillar component is not well defined, but it appears to have some role in organizing the fiber or in controlling fiber formation. Microfibrils also appear in several tissues which do not contain elastin and here they may serve an anchoring or other function. In order to expand our understanding of microfibrillar structure and function, the investigators are continuing a concerted collaborative effort focused on the protein previously called fibrillin-like protein (FLP) and now called latent TGF-beta-binding protein (LTBP-2) which was cloned in their laboratories. They hypothesize that expression of LTBP-2 is largely controlled by transcription and that expression of LTBP-2- isoforms is developmentally controlled in a tissue-specific manner. They further hypothesize the LTBP-2 plays an important role in the assembly of the elastic fiber. In order to test these hypotheses, they propose: (1) to isolate and characterize the large transcript form (9.0 kb) of LTBP-2, to complete the cloning of the gene, and to define elements controlling transcription of the gene, (2) to determine the tissue and developmental pattern of expression of the two forms of LTBP-2, (3) to investigate binding interactions between LTBP-2 and tropoelastin, other microfibrillar proteins and TGF-beta and to determine the role of LTBP-2 in elastic fiber assembly. The potential function of LTBP-2 isoforms encoded by the two different transcripts will also be investigated. The studies will employ a wide variety of molecular biology (cloning and sequencing, transfection, recombinant synthesis of protein), cell biology (cell culture, in vitro fiber assembly) immunologic (production of monospecific antibody, immunohistochemical and EM analyses), and protein (peptide synthesis, and sequencing, protein-protein interactions) methods, all of which are currently on-going in the investigator's laboratories. Elastic fibers are critical components of the extracellular matrix of many fetal tissues, including major blood vessels, the lung, the bladder, and the dermis. Derangements in the fibers probably play a decisive role in the pathology of a variety of heritable (i.e., Marfan's Syndrome) and acquired (i.e., emphysema) diseases. Definition of the molecular structure of the fibers and the mechanism involved in their synthesis and assembly are requisite to understanding these derangements and devising cures.
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