Conversion of embryonic form to adult forms of N-CAM in vitro: results from de novo synthesis of adult forms
Open Access
- 1 August 1985
- journal article
- research article
- Published by Rockefeller University Press in The Journal of cell biology
- Vol. 101 (2), 412-419
- https://doi.org/10.1083/jcb.101.2.412
Abstract
During normal development, the neural cell adhesion molecule N-CAM changes at the cell-surface from a sialic acid-rich embryonic, or E form, to several adult, or A forms that have less sialic acid (E-to-A conversion). To investigate the cellular and molecular mechanisms that underlie these changes, we have established conditions under which E-to-A conversion occurs in cultured explants of central nervous system tissues. Mouse cerebellum, chick spinal cord, and chick retina that express the E form of N-CAM were dissected and cultured on collagen gels. After 3-6 d in culture, increased proportions of A forms were synthesized, as revealed by specific immunoprecipitation and immunoblotting. The rate of E-to-A conversion and the proportions of the different A forms synthesized in vitro were similar to those observed for the tissues in vivo at comparable times. In addition, the explants incorporated radioactive precursors of amino sugars into N-CAM, and the electrophoretic mobilities of the E and A forms of N-CAM were altered by treatment with neuraminidase in a way comparable to that found for N-CAM obtained directly from tissue. These results suggest that the post translational processing in vitro was similar to that in vivo. Logistic studies on cell division and death in the explants suggested that E-to-A conversion resulted mainly from a specific increase in synthesis of A forms in individual cells rather than as a consequence of differential birth or death within distinct cell populations. The data were consistent with the possibility that the increase in synthesis of A forms occurred either in cells that had previously synthesized E forms or in a distinct population of cells that already synthesized A forms. Cells dissociated from embryonic central nervous system tissues and cultured in vitro were also found to undergo E-to-A conversion at the same rate as the explant cultures, which suggests that if intercellular signals were responsible for initiation of the change in synthetic pattern, they had already occurred in vivo before the time of culture. In pulse-chase experiments, the E form of N-CAM that was synthesized during the first day after explantation persisted as E form for several days, at times when newly synthesized N-CAM was predominantly in A forms. These results indicate that in cultured neural tissue, the E form of N-CAM is not processed into A forms but is gradually degraded and replaced by newly synthesized A forms.(ABSTRACT TRUNCATED AT 400 WORDS)This publication has 39 references indexed in Scilit:
- Comparison of the 34,000-Da pp60src substrate and a 38,000-Da phosphoprotein identified by monoclonal antibodies.Journal of Biological Chemistry, 1983
- Electrophoretic transfer of proteins from polyacrylamide gels to nitrocellulose sheets: procedure and some applications.Proceedings of the National Academy of Sciences, 1979
- Adhesion among neural cells of the chick embryo. IV. Role of the cell surface molecule CAM in the formation of neurite bundles in cultures of spinal ganglia.The Journal of cell biology, 1978
- Adhesion among neural cells of the chick embryo. I. An immunological assay for molecules involved in cell-cell binding.Journal of Biological Chemistry, 1977
- Adhesion among neural cells of the chick embryo. II. Purification and characterization of a cell adhesion molecule from neural retina.Journal of Biological Chemistry, 1977
- Surface Modulation in Cell Recognition and Cell GrowthScience, 1976
- NS-4 (nervous system antigen-4), a cell surface antigen of developing and adult mouse brain and spermDevelopmental Biology, 1975
- Brain specific synaptosomal membrane proteins demonstrated by crossed immunoelectrophoresisJournal of Neurochemistry, 1974
- COLLAGEN SUBSTRATA FOR STUDIES ON CELL BEHAVIORThe Journal of cell biology, 1972
- Cleavage of Structural Proteins during the Assembly of the Head of Bacteriophage T4Nature, 1970