Abstract
E10 chick sympathetic ganglion cells display a cell contact-dependent rise in choline acetyltransferase (ChAT) specific activity over the first several days in culture. This effect can be mimicked by addition of crude membrane fractions prepared from E10 retina and adult chicken brain, but not by those from E10 brain. The effects of both cell-cell and membrane-cell contact are inhibited by the addition of anti-NCAM Fab fragments. The membranes capable of increasing ChAT and those which are ineffective all contain NCAM, however their relative levels of NCAM polysialic acid differ. Whereas membranes with high polysialic acid NCAM are ineffective, selective enzymatic removal of polysialic acid renders them capable of producing an increase in ChAT. The inhibition of NCAM-mediated adhesion produced by Fab fragments can be compensated for by addition of wheat germ agglutinin, but only with membranes whose NCAM has low levels of polysialic acid. Taken together, these data suggest that NCAM can regulate cell contact-mediated increases in ChAT activity. We propose that NCAM-mediated adhesion promotes contact between cell membranes to allow the transmission of an otherwise NCAM-independent signal. In addition, NCAM's polysialic acid moiety appears to influence the ability of cells to transmit this signal, even in the presence of an alternative adhesion mechanism.