DESCRIPTION OF RESEARCH INTERESTS:

Dr. Myers' research is focused on the structure, function and expression of two human collagen proteins, type XV and type XIX.

Type XV and type XIX molecules were originally discovered from the sequence of cDNA clones. Polyclonal antibodies were developed for the amino and carboxy noncollagenous domains of each protein using synthetic peptides and bacteria-expressed recombinant proteins. Immunoblotting of human placenta tissue extract using the type XV antibody revealed a 116-kDa collagen chain, significantly smaller than expected from the primary structure. Accordingly, identification of the type XV forms expressed in human cultured cells showed two poly-peptides, the same size 116-kDa chain found in placenta and also a 210-kDa protein which we believe to be the precursor of the smaller product. This processing event will be characterized in time-course and pulse-chase biosynthetic studies. The Myers lab is also in the process of purifying type XV from placenta by differential salt precipitations and column chromatography. Protein microsequencing will be employed to locate the position of the cleavage site which is expected to be near the end of the amino-terminal domain. Future experiments will be aimed at identification of the processing enzyme and inhibition of its activity.

The type XIX protein monomer in tissue and cell culture was found to be a 165-kDa collagenase-sensitive chain, consistent with the expected molecular weight. They intend to also isolate this protein, which together with type XV, will be examined by rotary shadowing electron microscopy to elucidate the ultra-structure of these native trimer molecules, and the existence of end-terminal intermolecular interactions. To investigate the distribution of these collagens within tissue structures, immunohistochemical analysis was conducted. In eight tissues examined, both type XV and type XIX were found to exhibit a widespread presence in basement membrane zones, i.e. some epithelial, and all endothelial, perineural and muscle. While many similarities in their localization were identified, there was a differential expression of these two collagens in a number of epithelial basement membrane zones. This observation will be pursued by immunogold electron microscopy. We hypothesize that these two collagens are prominent components of an undefined structural complex, which serves to mediate the adherence of basement membrane to the underlying stroma. Definition of this putative network should lead to establishing the role of these proteins in inherited diseases of connective tissue and other pathologic processes.

1. Myers, J.C., D. Li, V. Bageris, A.S. Dion and P.S. Amenta (1997) Biochemical and immunohistochemical characterization of human type XIX defines a novel class of basement membrane zone collagens. Am. J. Pathol. 151:1729-1740.
2. Myers, J.C., A.S. Dion, V. Abraham and P.S. Amenta (1996) Type XV collagen exhibits a widespread distribution in human tissues but a distinct localization in basement membrane zones. Cell Tissue Res. 286:493-505.
3. Myers, J.C., H. Yang, J.A. D'Ippolito, A. Presente, M.K. Miller and A.S. Dion (1994) The triple helical region of human type XIX collagen consists of multiple collagenous subdomains and exhibits limited sequence homology to a1(XVI). J. Biol. Chem. 269:18549-18557.
4. Myers, J.C., Sun, M.J., D'Ippolito, J.A., Jabs, E.W., Neilson, E.G. and Dion, A.S. (1993) Human cDNA clones transcribed from an unusually high molecular weight RNA encode a new collagen chain. Gene 123:211-217.
5. Myers, J.C., S. Kivirikko, M.K. Gordon, A.S. Dion and T. Philajaniemi (1992) Identification of a previously unrecognized human collagen chain, a1(XV), characterized by extensive interruptions in the triple-helical region. Proc. Natl. Acad. Sci. U.S.A. 89:10144-10148.