Beta-amyloid-induced synthesis of the ganglioside GD3 is a requisite for cell cycle reactivation and apoptosis in neurons.
We have shown that cortical neurons challenged with toxic concentrations of beta-amyloid peptide (betaAP) enter the S phase of the cell cycle before apoptotic death. Searching for a signaling molecule that lies at the border between cell proliferation and apoptotic death, we focused on the disialoganglioside GD3. Exposure of rat cultured cortical neurons to 25 microm betaAP(25-35) induced a substantial increase in the intracellular levels of GD3 after 4 hr, a time that precedes neuronal entry into S phase. GD3 levels decreased but still remained higher than in the control cultures after 16 hr of exposure to betaAP(25-35). Confocal microscopy analysis showed that the GD3 synthesized in response to betaAP colocalized with nuclear chromatin. The increase in GD3 was associated with a reduction of sphingomyelin (the main source of the ganglioside precursor ceramide) and with the induction of alpha-2,8-sialyltransferase (GD3 synthase), the enzyme that forms GD3 from the monosialoganglioside GM3. A causal relationship between GD3, cell-cycle activation, and apoptosis was demonstrated by treating the cultures with antisense oligonucleotides directed against GD3 synthase. This treatment, which reduced betaAP(25-35)-stimulated GD3 formation by approximately 50%, abolished the neuronal entry into the S phase and was protective against betaAP(25-35)-induced apoptosis.
Copani
Agata
A
Department of Pharmaceutical Sciences, University of Catania, 95125 Catania, Italy. acopani@katamail.com
Melchiorri
Daniela
D
Caricasole
Andrea
A
Martini
Francesca
F
Sale
Patrizio
P
Carnevale
Roberto
R
Gradini
Roberto
R
Sortino
Maria Angela
MA
Lenti
Luisa
L
De Maria
Ruggero
R
Nicoletti
Ferdinando
F
D016229:Amyloid beta-Peptides / Q000494:pharmacology*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002452:Cell Count; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002843:Chromatin / Q000378:metabolism; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005732:Gangliosides / Q000096:biosynthesis*; D008856:Microscopy, Fluorescence; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology*; D012333:RNA, Messenger / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016196:S Phase / Q000187:drug effects / Q000502:physiology; D012799:Sialyltransferases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D013109:Sphingomyelins / Q000378:metabolism; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase
D016229:Amyloid beta-Peptides; D002843:Chromatin; D018691:Excitatory Amino Acid Antagonists; D005732:Gangliosides; D016376:Oligonucleotides, Antisense; D010446:Peptide Fragments; D012333:RNA, Messenger; D013109:Sphingomyelins; C074636:amyloid beta-protein (25-35); C026226:ganglioside, GD3; D012799:Sialyltransferases; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase