S-100 PROTEIN AND ANNEXIN II2-P11(2) (CALPACTIN-I) ACT IN CONCERT TO REGULATE THE STATE OF ASSEMBLY OF GFAP INTERMEDIATE FILAMENTS IN-VITRO

S-100 protein and annexin II2-p11(2) were reported to inhibit and to s timulate the assembly of glial fibrillary acidic protein (GFAP), respe ctively, in a Ca2+-dependent manner. Here we show by a number of exper imental approaches that S-100 protein contrasts all the effects of ann exin II2-p11(2) on GFAP assembly and, conversely, that annexin II2-p11 (2) contrasts the inhibitory effects of S-100 protein on GFAP assembly , in a dose-dependent manner in both cases. Altogether, these data sug gest that two specific Ca2+ effecters, i.e., annexin II2-p11(2) and S- 100 protein, might regulate the state of assembly of glial filaments i n a concerted manner. (C) 1995 Academic Press, Inc.