Botox is an exotoxin secreted by Clostridium botulinum. This organism primarily causes spoilage of canned foods that have not been effectively heat treated. Consumption of the toxin could prove to be fatal. Botox is recently used in the cosmetic industry as treatment to wrinkles. This toxin has 2 subunits- heavy and light chain. The heavy subunit is the binding subunit and binds to the glycoprotein receptors on the cholinergic nerve endings. By receptor-mediated endocytosis, it is engulfed into the cell. The 2 chains dissociate followed by the release of the light chain from the vesicle into the cytoplasm. It then cleaves off the SNARE proteins on the inner surface of the cell membrane of the axon endings that are essential for the fusion of acetylcholine containing vesicles with the cell membrane and subsequent release of the neurotransmitter. The cleaving of the SNARE proteins does not allow this to happen thereby causing paralysis of the striated (voluntary) muscles. These muscles remain flaccid and cannot be activated by stimuli.
