S100B-mediated inhibition of the phosphorylation of GFAP is prevented by TRTK-12.
S100B belongs to a family of calcium-binding proteins involved in cell cycle and cytoskeleton regulation. We observed an inhibitory effect of S100B on glial fibrillary acidic protein (GFAP) phosphorylation, when stimulated by cAMP or Ca2+/calmodulin, in a cytoskeletal fraction from primary astrocyte cultures. We found that S100B has no direct effect on CaM KII activity, the major kinase in this cytoskeletal fraction able to phosphorylate GFAP. The inhibition of GFAP phosphorylation is most likely due to the binding of S100B to the phosphorylation sites on this protein and blocking the access of these sites to the protein kinases. This inhibition was dependent on Ca2+. However, Zn2+ could substitute for Ca2+. The inhibitory effect of S100B was prevented by TRTK-12, a peptide that blocks S100B interaction with several target proteins including glial fibrillary acidic protein. These data suggest a role for S100B in the assembly of intermediate filaments in astrocytes.
Frizzo
Juliana Karl
JK
Departamento de Bioquímica, ICBS, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil. julianadk@iname.com
Tramontina
Francine
F
Bortoli
Erica
E
Gottfried
Carmen
C
Leal
Rodrigo B
RB
Lengyel
Imre
I
Donato
Rosario
R
Dunkley
Peter R
PR
Gonçalves
Carlos-Alberto
CA
D000818:Animals; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D051347:CapZ Actin Capping Protein; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism*; D009414:Nerve Growth Factors / Q000037:antagonists & inhibitors / Q000502:physiology*; D009842:Oligopeptides / Q000494:pharmacology*; D010446:Peptide Fragments; D010766:Phosphorylation; D051381:Rats; D017208:Rats, Wistar; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*
D051347:CapZ Actin Capping Protein; D005904:Glial Fibrillary Acidic Protein; D009414:Nerve Growth Factors; D009842:Oligopeptides; D010446:Peptide Fragments; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins; C579158:S100b protein, rat; C475482:TRTK-12 peptide; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases