B-50 GAP-43 MESSENGER-RNA EXPRESSION IN CULTURED PRIMARY SCHWANN-CELLS IS REGULATED BY CYCLIC-AMP/

FOLLOWING peripheral nerve crush or transection, B-50 mRNA expression increased dramatically in the distal nerve stump. This increase has be en fully attributed to an up-regulation of B-50 synthesis in reactive Schwann cells. Here we describe that B-50 mRNA expression in primary S chwann cell cultures is strongly down-regulated by cyclic AMP. Treatme nt of neonatal Schwann cell cultures with as low as 20 nM forskolin de creased B-50 mRNA expression. We show that B-50 promoter P2, but not P 1, is active in Schwann cells and that the activity of P2 is inhibited 2.5 fold by forskolin. P2 does not contain a consensus sequence of a known cyclic AMP responsive element suggesting that the effect of fors kolin is indirect.