Transglutaminase participates in the blockade of neurotransmitter release by tetanus toxin: evidence for a novel biological function.
Inhibition of neuroexocytosis by tetanus neurotoxin (TeNT) involves VAMP-2/synaptobrevin-2 cleavage. However, deletion of the TeNT activity does not completely abolish its inhibitory action. TeNT is a potent activator of the cross-linking enzyme transglutaminase 2 (TGase 2) in vitro. The role of the latter mechanism in TeNT poisoning was investigated in isolated nerve terminals and intact neurons. TeNT-induced inhibition of glutamate release from rat cortical synaptosomes was associated with a simultaneous activation of neuronal transglutaminase (TGase) activity. The TeNT-induced blockade of neuroexocytosis was strongly attenuated by pretreatment of either live Aplysia neurons or isolated nerve terminals with specific TGase inhibitors or neutralizing antibodies. The same treatments completely abolished the residual blockade of neuroexocytosis of a non-proteolytic mutant of TeNT light chain. Electrophysiological studies indicated that TGase activation occurs at an early step of TeNT poisoning and contributes to the inhibition of transmitter release. Bioinformatics and biochemical analyses identified synapsin I and SNAP-25 as potential presynaptic TGase substrates in isolated nerve terminals, which are potentially involved in the inhibitory action of TeNT. The results suggest that neuronal TGase activity plays an important role in the regulation of neuroexocytosis and is one of the intracellular targets of TeNT in neurons.
Facchiano
Francesco
F
Department of Hematology, Oncology and Molecular Medicine, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161, Rome, Italy. francesco.facchiano@iss.it
Deloye
Florence
F
Doussau
Frédéric
F
Innamorati
Giulio
G
Ashton
Anthony C
AC
Dolly
J Oliver
JO
Beninati
Simone
S
Facchiano
Angelo
A
Luini
Alberto
A
Poulain
Bernard
B
Benfenati
Fabio
F
D000109:Acetylcholine / Q000037:antagonists & inhibitors / Q000378:metabolism; D000818:Animals; D002103:Cadaverine / Q000031:analogs & derivatives / Q000494:pharmacology; D003538:Cystamine / Q000494:pharmacology; D008297:Male; D018377:Neurotransmitter Agents / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D051381:Rats; D017207:Rats, Sprague-Dawley; D013379:Substrate Specificity; D013574:Synaptosomes / Q000187:drug effects / Q000201:enzymology; D013744:Tetanus Toxin / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D011503:Transglutaminases / Q000037:antagonists & inhibitors / Q000378:metabolism*
D018377:Neurotransmitter Agents; D013744:Tetanus Toxin; C000717609:Tgm2 protein, rat; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; C008542:monodansylcadaverine; D002103:Cadaverine; D000109:Acetylcholine; D003538:Cystamine