Neurite extension and neuronal survival activities of recombinant S100β proteins that differ in the content and position of cysteine residues

S100β produced in Escherichia coli from a synthetic gene (Van Eldik, L.J., J.L. Staecker, and F. Winningham-Major. 1988. J. Biol. Chem. 263:7830-7837) stimulates neurite outgrowth and enhances cell maintenance in cultures of embryonic chick cerebral cortex neurons. In control experiments, the neurite extension activity is reduced by preincubation with antibodies made against bovine brain S100β. When either of the two cysteines in S100β are altered by site-directed mutagenesis, the resultant proteins maintain the overall biochemical properties of S100β, but lose both the neurite extension and neuronal survival activities. However, another S100β mutant, in which the relative position of one of the two cysteines was changed, had neurotrophic activity similar to that of the unmodified protein. These and other results indicate that (a) specific neurite extension activity and neuronal survival activity are two related activities inherent to the S100β molecule; (b) a disulfide-linked form of S100β is required for full biological activity, and (c) the relative position of the cysteines can be modified. These data suggest potential in vivo roles for S100β in the development and maintenance of neuronal function in the central nervous system, and demonstrate the feasibility of the longer term development of selective pharmacological agents based on the S100β structure.