Journal of Neuroscience, Vol 15, 385-393, Copyright © 1995 by Society for Neuroscience
Neuron-specific enolase: a neuronal survival factor in the retinal extracellular matrix?
A Li, WS Lane, LV Johnson, GJ Chader and J Tombran-Tink
Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892.
To identify soluble proteins of the retinal interphotoreceptor matrix
(IPM), we isolated IPM from the bovine eye by gentle lavage and subjected
it to SDS-PAGE. In the resultant gel, a 46 kDa band was particularly
prominent and appeared to be a single protein. This protein was
electroblotted to nitrocellulose membrane, digested with trypsin, and
selected peptides were isolated by HPLC and subjected to Edman
microsequencing. The amino acid sequences of the peptides were found to be
virtually identical to that of human neuron-specific enolase (NSE). A
monoclonal antibody specific for human NSE confirmed the presence of this
enzyme in the bovine IPM by both Western blotting and immunocytochemical
analysis. Immunofluorescence microscopy demonstrated that NSE is mainly
localized to the basal domain of the IPM surrounding photoreceptor cells
but is also prominent in the inner segments of the cone photoreceptor
neurons. When NSE was added to cultures of human retinoblastoma cells, no
effect on morphology was observed. However, a positive effect on cell
growth and/or survival was readily apparent. It thus seems that not only is
NSE a significant component of the retinal extracellular matrix, but that
it could function as a survival (neuronotrophic) factor for photoreceptor
neurons.