Journal of Neuroscience, Vol 8, 231-241, Copyright © 1988 by Society for Neuroscience
Nerve growth factor receptors on cultured rat Schwann cells
PS DiStefano and EM Johnson Jr
Department of Pharmacology, Washington University School of Medicine, St. Louis, Missouri 63110.
Neonatal rat Schwann cells were grown in tissue culture and assayed for NGF
receptors with time in culture. NGF receptor levels on freshly prepared
Schwann cells (day 0) were low but increased dramatically during the first
week in culture. Characterization of 125I-NGF binding to resuspended cells
grown for 4 d in culture revealed that binding was not saturable at high
ligand concentrations (50-70 nM) and that a high- capacity, low-affinity
NGF binding component existed on these cells as compared to PC12 cells. The
monoclonal antibody, 192-IgG, which recognizes the rat NGF receptor, was
used as an immunohistochemical tool to verify the presence of NGF receptors
on the cultured rat Schwann cells. In contrast to radiolabeled NGF,
125I-192-IgG demonstrated saturable binding to Schwann cells in suspension,
with Kd and Bmax values of 4 nM and 115 fmol/10(6) cells, respectively.
Schwann cells showed no evidence of slow dissociation or internalization of
NGF binding at any of several NGF concentrations. 192-IgG was used to
immunoprecipitate 125I-NGF chemically crosslinked to cell membranes.
SDS-PAGE and subsequent autoradiography of the immunoprecipitated NGF
receptors revealed that 2 species of NGF receptors were precipitated from
Schwann cells and PC12 cells. In PC12 cells, 2 bands with molecular weights
of 90 and 210 kDa were identified. The Schwann cell NGF receptor species
migrated slower on the gels, with apparent molecular weights of 95 and 220
kDa. Further analysis of glial cell NGF receptors showed that Schwann cells
isolated from the vagus nerve of neonatal rats also expressed NGF receptors
in culture; however, astrocytes cultured from neonatal rat cerebral cortex,
cultured under conditions reported here, were devoid of detectable NGF
receptors. These results show that NGF receptor levels on Schwann cells
increase with time in culture, and this resembles what is observed in
Schwann cells in vivo when adult peripheral nerve is injured. The data are
discussed in terms of a supportive role for the Schwann cell in
facilitating peripheral nerve development and regeneration.