Aging of lens fibers. Mapping membrane proteins with monoclonal antibodies.

Lens fiber proteins with apparent molecular weights 57,000, 70,000, 82,000, and 100,000 were components in urea insoluble, membrane-rich fractions. Monoclonal antibodies against these proteins labeled membranes by immunofluorescence microscopy of sheep lens cryosections and are thus referred to as membrane proteins MP57, MP70, MP82, and MP100. MP70 has previously been localized in fiber junctional membranes (Kistler et al 1985, J Cell Biol 101:28-35). Using radioimmunoassays, the authors found a different membrane protein composition for the cortical and nuclear sheep lens regions. In addition, the membrane protein composition altered with the overall lens age. All the above membrane antigens were eventually cleaved by proteolysis in older fibers, and their degradation patterns could be grouped into distinct classes. The results are of basic importance for cataract research.