title: Tetanus Toxin Hc Fragment Induces the Formation of Ceramide Platforms and Protects Neuronal Cells against Oxidative Stress.
abstract: Tetanus toxin (TeTx) is the protein, synthesized by the anaerobic bacteria Clostridium tetani, which causes tetanus disease. TeTx gains entry into target cells by means of its interaction with lipid rafts, which are membrane domains enriched in sphingomyelin and cholesterol. However, the exact mechanism of host membrane binding remains to be fully established. In the present study we used the recombinant carboxyl terminal fragment from TeTx (Hc-TeTx), the domain responsible for target neuron binding, showing that Hc-TeTx induces a moderate but rapid and sustained increase in the ceramide/sphingomyelin ratio in primary cultures of cerebellar granule neurons and in NGF-differentiated PC12 cells, as well as induces the formation of ceramide platforms in the plasma membrane. The mentioned increase is due to the promotion of neutral sphingomyelinase activity and not to the de novo synthesis, since GW4869, a specific neutral sphingomyelinase inhibitor, prevents neutral sphingomyelinase activity increase and formation of ceramide platforms. Moreover, neutral sphingomyelinase inhibition with GW4869 prevents Hc-TeTx-triggered signaling (Akt phosphorylation), as well as the protective effect of Hc-TeTx on PC12 cells subjected to oxidative stress, while siRNA directed against nSM2 prevents protection by Hc-TeTx of NSC-34 cells against oxidative insult. Finally, neutral sphingomyelinase activity seems not to be related with the internalization of Hc-TeTx into PC12 cells. Thus, the presented data shed light on the mechanisms triggered by TeTx after membrane binding, which could be related with the events leading to the neuroprotective action exerted by the Hc-TeTx fragment.
authors.affiliation: Departament de Bioquímica i Biologia Molecular and Institut de Neurociències, Universitat Autònoma de Barcelona, Bellaterra, Catalunya, Spain.
authors.forename: Roger
authors.initials: R
authors.lastname: Cubí
authors.forename: Ana
authors.initials: A
authors.lastname: Candalija
authors.forename: Arturo
authors.initials: A
authors.lastname: Ortega
authors.forename: Carles
authors.initials: C
authors.lastname: Gil
authors.forename: José
authors.initials: J
authors.lastname: Aguilera
mesh_terms: D000814:Aniline Compounds / Q000494:pharmacology; D000818:Animals; D001597:Benzylidene Compounds / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D002491:Central Nervous System Agents / Q000494:pharmacology; D002518:Ceramides / Q000378:metabolism*; D002531:Cerebellum / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D018696:Neuroprotective Agents / Q000494:pharmacology*; D018384:Oxidative Stress / Q000187:drug effects* / Q000502:physiology; D016716:PC12 Cells; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism / Q000494:pharmacology; D013108:Sphingomyelin Phosphodiesterase / Q000037:antagonists & inhibitors / Q000378:metabolism; D013744:Tetanus Toxin / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D000814:Aniline Compounds; D001597:Benzylidene Compounds; D002491:Central Nervous System Agents; D002518:Ceramides; C468773:GW 4869; D018696:Neuroprotective Agents; D010446:Peptide Fragments; D011994:Recombinant Proteins; D013744:Tetanus Toxin; C040635:tetanus toxin fragment C; D051057:Proto-Oncogene Proteins c-akt; D013108:Sphingomyelin Phosphodiesterase