bFGF stimulates GAP-43 phosphorylation at ser41 and modifies its intracellular localization in cultured hippocampal neurons.
Cultured hippocampal neurons have been used to study GAP-43 phosphorylation and subcellular distribution. By immunofluorescence, GAP-43 was found associated with adherent membrane patches that remained attached to the substratum after in situ permeabilization with Nonidet-NP40. This association increases during neuronal development and is stabilized by the actin cytoskeleton. Basic fibroblast growth factor (bFGF) promotes GAP-43 translocation from the cytosol to adherent membrane patches and, at the same time, stimulates GAP-43 phosphorylation, mainly at the protein kinase C (PKC) site (Ser41). Inhibition of PKC prevented bFGF-stimulated GAP-43 phosphorylation and translocation, while activation by phorbol esters mimicked bFGF effects, suggesting that phosphorylation at Ser41 regulates GAP-43 subcellular localization. Using biochemical fractionation and phosphorylation analysis, it was found that Ser41 phosphorylation was highest in cytoskeleton-associated GAP-43 and lowest in membrane-associated GAP-43. It is proposed that GAP-43 is continuously cycling between intracellular compartments depending on its phosphorylation state and could be taking part in initial adhesive complexes assembled during growth cone advance.
Tejero-Díez
P
P
Centro de Biología Molecular Severo Ochoa, Departamento de Biología Molecular, Facultad de Ciencias, Universidad Autónoma de Madrid, Cantoblanco, Madrid, 28049, Spain.
Rodríguez-Sánchez
P
P
Martín-Cófreces
N B
NB
Díez-Guerra
F J
FJ
D000199:Actins / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D002451:Cell Compartmentation / Q000187:drug effects* / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D005333:Fetus; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism / Q000494:pharmacology*; D019922:GAP-43 Protein / Q000187:drug effects* / Q000378:metabolism; D020439:Growth Cones / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D006624:Hippocampus / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000187:drug effects / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D051381:Rats; D012694:Serine / Q000187:drug effects* / Q000378:metabolism
D000199:Actins; D019922:GAP-43 Protein; D016222:Fibroblast Growth Factor 2; D012694:Serine; D011493:Protein Kinase C