Journal of Neuroscience, Vol 6, 3721-3730, Copyright © 1986 by Society for Neuroscience
Synthesis of a growth-associated protein by embryonic rat cerebrocortical neurons in vitro
NI Perrone-Bizzozero, SP Finklestein and LI Benowitz
Proteins synthesized by embryonic rat cortical cultures were studied under
conditions that were either permissive or nonpermissive to neurite
outgrowth. Freshly dissected cortex from embryonic day 17 rat pups was
mechanically dissociated and plated on poly(L-lysine) substrate in the
presence of (1) serum-free media, which allowed neuronal survival but no
outgrowth; (2) serum, which allowed survival of both neurons and glia as
well as neurite outgrowth; or (3) a hormone- supplemented defined media,
which allowed preferential survival and outgrowth of neurons. In addition,
postnatal tissue was cultured as a source of glia. Cultures were
pulse-labeled with 35S-methionine 48 hr after plating and the protein
synthesis patterns examined by 2- dimensional gel electrophoresis followed
by fluorography. The expression of an acidic 50 kDa protein, associated
with the particulate fraction of cells, was found to be a prominent
correlate of neurite outgrowth. This protein was synthesized in serum- or
hormone-treated embryonic cultures showing neurite outgrowth but was
undetectable in embryonic cultures without outgrowth or in postnatal glial
cultures. By virtue of its migration position on 2-dimensional gels, its
presence in a light membrane fraction, and its cleavage products after
Staphylococcus aureus protease treatment, the 50 kDa protein appears to be
identical to an acidic 43-49 kDa protein that has been identified in
several developing and regenerating neural pathways, as well as to the B-50
phosphoprotein. These findings lend support for a critical role of this
protein in neural development and demonstrate the feasibility of using
primary CNS cell cultures to study its biosynthesis and function.