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© The Rockefeller University Press, 0021-9525/1998//1177 $5.00
The Journal of Cell Biology, Volume 140, Number 5, , 1998 1177-1186

Article

Regulation of Neural Cell Adhesion Molecule Polysialylation: Evidence for Nontranscriptional Control and Sensitivity to an Intracellular Pool of Calcium



Juan L. Brusés* and Urs Rutishauser*,{ddagger}

* Department of Neurosciences and {ddagger} Department of Genetics, Case Western Reserve University, Cleveland, Ohio 44106

The up- and downregulation of polysialic acid–neural cell adhesion molecule (PSA–NCAM) expression on motorneurons during development is associated respectively with target innervation and synaptogenesis, and is regulated at the level of PSA enzymatic biosynthesis involving specific polysialyltransferase activity. The purpose of this study has been to describe the cellular mechanisms by which that regulation might occur. It has been found that developmental regulation of PSA synthesis by ciliary ganglion motorneurons is not reflected in the levels of polysialyltransferase-1 (PST) or sialyltransferase-X (STX) mRNA. On the other hand, PSA synthesis in both the ciliary ganglion and the developing tectum appears to be coupled to the concentration of calcium in intracellular compartments. This study documents a calcium dependence of polysialyltransferase activity in a cell-free assay over the range of 0.1–1 mM, and a rapid sensitivity of new PSA synthesis, as measured in a pulse–chase analysis of tissue explants, to calcium ionophore perturbation of intracellular calcium levels. Moreover, the relevant calcium pool appears to be within a specific intracellular compartment that is sensitive to thapsigargin and does not directly reflect the level of cytosolic calcium. Perturbation of other major second messenger systems, such as cAMP and protein kinase–dependent pathways, did not affect polysialylation in the pulse chase analysis. These results suggest that the shuttling of calcium to different pools within the cell can result in the rapid regulation of PSA synthesis in developing tissues.

Abbreviations used in this paper: CG, ciliary ganglion; endo H, endoglycosidase H; endo N, endoneuraminidase N; IC, intracellular compartments; NCAM, neural cell adhesion molecule; PSA, polysialic acid; PST, polysialyltransferase-1; RT, reverse transcriptase; St, embryonic stage; STX, sialyltransferase-X.

The authors acknowledge the excellent technical assistance of Denice Major.


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