Fibrillin-containing microfibrils: structure and function in health and disease.
ABSTRACT Fibrillin-containing microfibrils are a unique class of connective tissue macromolecules whose critical contribution to the establishment and maintenance of diverse extracellular matrices was underlined by the recent linkage of their principal structural component fibrillin to Marfan syndrome, a heritable disorder with pleiotrophic connective tissue manifestations. The complexity of the structure: function relationships of these macromolecules was highlighted by the recent elucidation of the primary structure of fibrillin and characterisation of fibrillin mutations in Marfan patients. This review examines current understanding of the expression and assembly of fibrillin and describes new approaches which are now being applied to elucidate the many outstanding structural, organisational and functional aspects of the fibrillin-containing microfibrils.
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ABSTRACT: The major antigen derived from elastic fiber microfibrils was identified as a Mr = 31,000 glycoprotein, using immunoblotting and immunohistochemical techniques with antisera raised to "reductive guanidine extracts" of fetal bovine nuchal ligament, and to subfractions of these. A second, elastic fiber-derived, but unidentified, antigen of large molecular size (Mr greater than 200,000) was present in these extracts. Antisera raised to the purified 31-kDa glycoprotein were shown, by immunoelectron microscopy, to localize specifically to the elastin-associated microfibrils. Thus, the macro-molecule was called "microfibril-associated glycoprotein" or MAGP. MAGP is an acidic glycoprotein with a distinctive amino acid composition, being exceptionally rich in glutamic acid, rich in cystine, and low in glycine. MAGP was extractable from tissue homogenates using NaCl, urea, or guanidine hydrochloride solutions, only if a strong reducing agent was present. Thus, disulfide bonding is important for the strong association of MAGP with elastic fibers. Immunoblotting with anti-MAGP antiserum identified two additional reactive species, of Mr = 60,000 and Mr approximately 300,000, in tissue extracts. As only the 31-kDa species was detected in fibroblast culture medium, these additional species were probably aggregates, rather than precursors. MAGP did not react with antilysyl oxidase antiserum on immunoblots or by enzyme-linked immunosorbent assay. MAGP is the first macromolecule to have been established to be a constituent of elastin-associated microfibrils in both developing and mature elastic tissues.Journal of Biological Chemistry 09/1986; 261(24):11429-36. · 4.65 Impact Factor
- The Anatomical Record 03/1962; 142:131-7.
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ABSTRACT: The localization of lysyl oxidase was examined in calf and rat aortic connective tissue at the ultrastructural level using polyclonal chicken anti-lysyl oxidase and gold conjugated rabbit anti-chicken immunoglobulin G to identify immunoreactive sites. Electron microscopy of calf aortic specimens revealed discrete gold deposits at the interface between extracellular bundles of amorphous elastin and the microfibrils circumferentially surrounding these bundles. The antibody did not react with microfibrils which were distant from the interface with elastin. There was negligible deposition of gold within the bundles of amorphous elastin and those few deposits seen at these sites appeared to be associated with strands of microfibrils. Lysyl oxidase was similarly localized in newborn rat aorta at the interface between microfibrils and nascent elastin fibers. Gold deposits were not seen in association with extracellular collagen fibers even after collagen-associated proteoglycans had been degraded by chondroitinase ABC. However, the antibody did recognize collagen-bound lysyl oxidase in collagen fibers prepared from purified collagen to which the enzyme had been added in vitro. No reaction product was seen if the anti-lysyl oxidase was preadsorbed with purified lysyl oxidase illustrating the specificity of the antibody probe. The present results are consistent with a model of elastogenesis predicting the radial growth of the elastin fiber by the deposition and crosslinking of tropoelastin units at the fiber-microfibril interface.The Journal of Cell Biology 10/1986; 103(3):1121-8. · 10.82 Impact Factor