Effects of gangliosides GM1 and GD1a on GAP-43 phosphorylation and dephosphorylation in isolated growth cones.
Phosphorylation of the nervous system-specific protein GAP-43 in growth cones in vivo increases as the growth cones near their targets, at a time when the gangliosides GM1 and GD1a are being accumulated in the growth cone membrane, thus raising the possibility that the gangliosides could modulate GAP-43 behavior. We used a subcellular fraction of intact isolated growth cones to show that both GM1 and GD1a affected the calcium-dependent posttranslational regulation of GAP-43 in several similar ways. Both gangliosides induced rapid incorporation of phosphate into GAP-43; however, the induction was undetectable with our antibody 2G12 that is specific for kinase C-phosphorylated GAP-43. Furthermore, neither ganglioside stimulated kinase C activity in isolated growth cones, suggesting that the rapid phosphorylation may not be on Ser41, the kinase C site. However, both gangliosides did induce a slower accumulation of GAP-43 phosphorylated on Ser41, apparently by inhibiting a phosphatase. Finally, calcium-dependent proteolysis of GAP-43 was also stimulated by both GM1 and GD1a. In contrast, GD1a, but not GM1, caused the redistribution of GAP-43 into the isolated growth cone cytoskeleton. The results demonstrate that both gangliosides can modulate the calcium-dependent regulation of GAP-43.
Meiri
K F
KF
Department of Pharmacology, SUNY Health Science Center, Syracuse 13210.
Beverly
M
M
D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn; D001369:Axons / Q000378:metabolism* / Q000648:ultrastructure; D002458:Cell Fractionation; D002499:Centrifugation, Density Gradient; D003599:Cytoskeleton / Q000378:metabolism; D005677:G(M1) Ganglioside / Q000494:pharmacology*; D019922:GAP-43 Protein; D005732:Gangliosides / Q000494:pharmacology*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D016548:Prosencephalon / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D051381:Rats; D012694:Serine / Q000378:metabolism
D019922:GAP-43 Protein; D005732:Gangliosides; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; C021298:ganglioside, GD1a; D005677:G(M1) Ganglioside; D012694:Serine