Tetanus neurotoxin light chain (TeNT-LC)

The Tetanus neurotoxin light chain (TeNT-LC) is the catalytic domain of the neurotoxin produced by the anaerobic bacterium Clostridium tetani. It functions as a highly specific zinc-dependent metalloprotease that targets synaptobrevin-2 (VAMP2), a protein essential for the fusion of synaptic vesicles with the presynaptic membrane (UniProt: P04958). Following the toxin's uptake and retrograde transport to the central nervous system, the light chain is translocated into the cytosol of inhibitory interneurons. By cleaving VAMP2 at a specific glutamine-phenylalanine bond, TeNT-LC effectively blocks the release of inhibitory neurotransmitters such as glycine and gamma-aminobutyric acid (GABA) (PubMed: 8221917). This disruption of inhibitory signaling leads to the over-excitation of motor neurons, resulting in the painful muscle contractions and spastic paralysis characteristic of tetanus (StatPearls: NBK459210). From a therapeutic perspective, the light chain is the primary target for neutralizing antibodies provided in tetanus immune globulin (TIG) treatments. It also serves as the basis for the tetanus toxoid vaccine, where the toxin is inactivated but remains immunogenic to elicit protective antitoxin production (PubMed: 10759562). Current research efforts are directed toward identifying small-molecule inhibitors that can block the protease activity of the light chain to treat patients after the toxin has already entered the nervous system.

Other names

TeLCTetanus toxin light chainZinc metalloproteinase tetanolysinTetanus toxin catalytic subunitLight chain of tetanus toxin

The light chain acts as a zinc-dependent endopeptidase that specifically cleaves synaptobrevin-2 (VAMP2) at the Gln76-Phe77 bond, preventing the fusion of synaptic vesicles with the presynaptic membrane and thus blocking neurotransmitter release (UniProt: P04958; PubMed: 8221917).