Annexin II2-p11(2) (calpactin I) stimulates the assembly of GFAP in a calcium- and pH-dependent manner.
Annexin II2-p11(2) (calpactin I) was tested as a potential regulator of GFAP assembly into glial filaments (GF), following the observation that it interacts with GFAP and cosediments with GF in a sedimentation assay. Under conditions where GFAP assembly is reduced, e.g., at pH values > 6.8, annexin II2-p11(2) stimulates GF formation in a Ca(2+)- and dose-dependent manner. Concomitantly, an ever larger fraction of annexin 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, although with a smaller efficacy as compared to annexin II2-p11(2), but does not cosediment with GF to a large extent, whereas p11 neither cosediments with GF nor affects GFAP assembly. On the other hand, the in vitro reconstituted annexin II2-p11(2) heterotetramer mimics native annexin II2-p11(2), and perturbation of the integrity of annexin II2-p11(2) by a mild treatment with alpha-chymotrypsin results in the nearly complete abolition of the stimulatory effect of annexin II2-p11(2) on GFAP assembly. These data suggest that annexin II2-p11(2) might be involved in the regulation of the state of assembly of GF, possibly in concert with other proteins.
Garbuglia
M
M
Department of Experimental Medicine and Biochemical Sciences, University of Perugia, Italy.
Bianchi
R
R
Verzini
M
M
Giambanco
I
I
Donato
R
R
D000818:Animals; D017306:Annexin A2 / Q000302:isolation & purification / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology*; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D005904:Glial Fibrillary Acidic Protein / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008168:Lung
D017306:Annexin A2; D005904:Glial Fibrillary Acidic Protein; D002118:Calcium