Extracellular carbohydrate-signal triggering cAMP-dependent protein kinase-dependent neuronal actin-reorganization.
Cell surface glycoconjugates are thought to mediate cell-cell recognition and to play roles in neuronal development and functions. We demonstrated here that exposure of neuronal cells to nanomolar levels of glyco-chains with an N-acetylgalactosamine (GalNAc) residue at the non-reducing termini (GalNAc-S) such as GalNAcbeta4(Neu5Acalpha3)Galbeta4GlcCer (GM2) ganglioside, its oligosaccharide portion, GalNAcbeta4Galbeta4GlcCer (Gg(3)) Cer, GalNAcalpha3GalNAcbeta3Galalpha4Galbeta4GlcCer (Gb(5)) Cer (Forssman hapten) and alpha1-4 linked oligomers of GalNAc, induced a rapid and transient activation of cAMP-dependent protein kinase (PKA) in subplasmalemma. The treatment was accompanied by peripheral actin polymerization and filopodia formation in NG108-15 cells and primary cultured hippocampal neurons, but not in glial cells. A cAMP-dependent protein kinase (PKA) selective inhibitor and an adenylate cyclase inhibitor blocked both PKA activation and the subsequent filopodia formation. A small GTPase cdc42 was a potential downstream target of GalNAc-S-activated PKA. These results suggest that extracellular GalNAc-S serve as potential regulators of the filopodia formation in neuronal cells by triggering the activation of PKA followed by cdc42 up-regulation via a cell surface receptor-like component. Filopodia formation induced by GalNAc-S may have a physiological relevance because long-term exposure to GalNAc-S enhanced F-actin-rich dendrite generation of primary cultured hippocampal neurons, and PKA-dependent dendritic outgrowth and branch formation of primary cultured cerebellar Purkinje neurons, in which actin isoforms were localized to motile structures in dendrites. These findings provide evidence for a novel GalNAc/PKA-signaling cascade in regulating some neuronal maturation.
Chen
N
N
Mitsubishi Kagaku Institute of Life Sciences, 11-Go, Minamioya, Machida, Tokyo 194-8511, Japan.
Furuya
S
S
Shinoda
Y
Y
Yumoto
M
M
Ohtake
A
A
Sato
K
K
Doi
H
H
Hashimoto
Y
Y
Kudo
Y
Y
Higashi
H
H
D000116:Acetylgalactosamine / Q000494:pharmacology*; D000199:Actins / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D045604:Extracellular Fluid / Q000187:drug effects / Q000201:enzymology; D006624:Hippocampus / Q000187:drug effects / Q000201:enzymology*; D009474:Neurons / Q000187:drug effects / Q000201:enzymology*; D011554:Pseudopodia / Q000187:drug effects / Q000201:enzymology; D051381:Rats
D000199:Actins; D004791:Enzyme Inhibitors; D017868:Cyclic AMP-Dependent Protein Kinases; D000116:Acetylgalactosamine