Journal of Neuroscience, Vol 13, 2495-2508, Copyright © 1993 by Society for Neuroscience
Surface and cytoskeletal markers of rostrocaudal position in the mammalian nervous system
Z Kaprielian and PH Patterson
Division of Biology, California Institute of Technology, Pasadena 91125.
To identify cell surface molecules that define position in the mammalian
nervous system, we previously characterized the binding of two monoclonal
antibodies, ROCA1 and ROCA2, to adult rat sympathetic ganglia and
intercostal nerves. The binding of ROCA1 is highest in rostral ganglia and
nerves and declines in a graded manner in the caudal segments. ROCA2 labels
the same cells in ganglia and nerves as ROCA1, but not in a
position-selective manner. We now show by immunoblot analysis that ROCA1
recognizes two antigens in membrane/cytoskeletal fractions of peripheral
nerves and ganglia: (1) a Triton X-100-insoluble, 60 kDa protein and (2) a
Triton x-100- insoluble, 26 kDa protein. The 60 kDa protein is expressed at
higher levels in rostral than in caudal intercostal nerves, and is
identified as the intermediate filament protein peripherin. In contrast, it
is the ROCA1 epitope on the 26 kDa protein, and not the protein itself,
that is preferentially visualized immunohistochemically in rostral nerves
and ganglia. We suggest that the ROCA1 epitope on the 26 kDa protein is
masked in sections of caudal nerves and ganglia. Amino acid sequence data
obtained from the affinity-purified 26 kDa protein indicate significant
homology with human CD9, a cell surface protein implicated in intercellular
signaling in hematopoietic cells. These results suggest that intermediate
filament gene expression and epitope masking on the cell surface may be
involved in functions related to position in the nervous system.