M. Garbuglia et al., ANNEXIN II2-P11(2) (CALPACTIN-I) STIMULATES THE ASSEMBLY OF GFAP IN ACALCIUM-DEPENDENT AND PH-DEPENDENT MANNER, Biochemical and biophysical research communications, 208(3), 1995, pp. 901-909
Annexin II2-p11(2) (calpactin I) was tested as a potential regulator o
f GFAP assembly into glial filaments (GF), following the observation t
hat it interacts with GFAP and cosediments with GF in a sedimentation
assay. Under conditions where GFAP assembly is reduced, e.g.,at pH val
ues > 6.8, annexin II2-p11(2) stimulates GF formation in a Ca2+- and d
ose-dependent manner. Concomitantly, an ever larger fraction of annexi
n II2-p11(2) can be recovered in GF pellets as the pH is raised from 6
.8 to 7.35. Monomeric annexin II also stimulates GFAP assembly, althou
gh with a smaller efficacy as compared to annexin II2-p11(2), but does
not cosediment with GF to a large extent, whereas pll neither cosedim
ents with GF nor affects GFAP assembly. On the other hand, the in vitr
o reconstituted annexin II2-p11(2) heterotetramer mimics native annexi
n II2-p11(2), and perturbation of the integrity of annexin II2-p11(2)
by a mild treatment with a-chymotrypsin results in the nearly complete
abolition of the stimulatory effect of annexin II2-p11(2) on GFAP ass
embly. These data suggest that annexin II2-p11(2) might be involved in
the regulation of the state of assembly of GF, possibly in concert wi
th other proteins. (C) 1995 Academic Press, Inc.