I'm going to go way back and tell you all a little bit about botulinum toxins, which are produced by the bacteria Clostridium botulinum. Botulinum neurotoxins are the most poisonous substances on Earth. They cause paralysis by targeting a specific protein in the synaptic vesicle and plasma membrane
of neurons. These toxins prevent acetylcholine from being released and cause botulism.
There are seven known serotypes of botulinum neurotoxins, all of which are classified as category A bioterrorism agents!
In small doses, these toxins can be used to block the release of neurotransmitters that cause pain, muscle spasms and other symptoms associated with diseases like arthritis, asthma, and psoriasis. Interestingly, the protein that botulinum toxin targets exists in non-nerve cells also, but these cells lack the receptors needed for the toxin to enter and work in the cell. In recent experiments, botulinum toxin was attached to a molecule that non-nerve cells do have receptors for. These engineered botulinum toxins block the release of a protein from immune cells linked to inflammation, which is a major problem in many diseases. This very dangerous toxin could potentially be beneficial to people with chronic inflammatory diseases! Go figure.