Tetanus Toxin Biotinylation and Localization of Binding Sites in Catecholaminergic Cultures and Granules

Abstract

Tetanus toxin (TT), the 150-kD protein secreted by Clostridium tetani bacteria, is a very powerful neurotoxin which produces spastic paralysis and death in humans in the range of ng/ kg body weight.¹ The pharmacokinetics of TT entry to the central nervous system target²include the following main steps: (1) selective binding of TT on the surface of the peripheral motor neuron terminals;³ (2) TT internalization into a vesicular compartment which delivers TT by retrograde axonal transport to the spinal cord perikarya and dendrites;⁴ (3) TT release from the motor neuron in the spinal cord;⁵ (4) trans-synaptic transfer of TT and uptake into the presynaptic terminals of the inhibitory intemeurons.⁵ (5) Thereafter, the constitutive release of gamma amino butyric acid and/or glycine is blocked, resulting with a syndrome of motor neuron dysinhibition;⁶ (6) the results are muscular spastic contractions, spasms, and convulsive seizures leading to musculature rigidity, respiratory failure, and death.⁷ It is believed that the binding of TT to neuronal G 1 b polysialogangliosides is involved in these pharmacokinetic steps and is the initial step triggering axonal transport and inhibition of neurotransmitter release.^8–9 For many years this TT-specific recognition has been used as a diagnostic and basic research tool for marking central and peripheral neuronal,¹⁰ as well as neurosecretory cells such as thyroid C, anterior pituitary, pancreatic islet cells, and derived tumors (insulinoma, pheochromocytoma, neuroblastoma).^11–13 All these cells express on their surface G1b polysialogangliosides of different sugar compositions, therefore binding TT.