Research Description:

The Effect of a Substance P Cholera Toxin Conjugate on NK1 Receptors and Cyclic Adenosine Monophosphate Activity

The focus of this experiment is to plot the time course of cyclic-adenosine monophosphate (cAMP) activity once the cholera toxin has entered the cell. With this information an effective timeline can be created. The secondary objective is to determine the concentration of SP-CTA required to cross the threshold and stimulate NK1 receptors, which will induce cAMP production. This experiment will be executed by using cell lines of Chinese hamster ovary cells.

In earlier studies done by Dr. Caudle, he found that cholera toxins suppressed the increase in prodynorphin, which is associated with persistent pain. This toxin may also inhibit two of the most troubling symptoms of chronic pain, allodynia and hyperalgesia. Allodynia is pain to normally non-painful stimuli, and hyperalgesia is an enhanced response to noxious stimulus. If cholera toxin is proven to treat these chronic pain symptoms, then this would be a significant advancement in the study of pain. The toxins that are currently used to treat chronic pain (saporin, diphtheria toxin and pseudomonas exotoxin) are lethal, which leads to permanent destruction of the targeted pathways. The lethality of these conjugates restricts their use to severely debilitated individuals and the terminally ill. A cholera toxin conjugate can be used to treat chronic pain without the liability of permanently damaging the nervous system.

Dr. Caudle and his team of colleagues developed a neuropeptide (substance P) conjugate with the A subunit of cholera toxin (SP-CTA). Unlike the lethal toxin conjugates, SP-CTA does not cause cell death. Instead it uncouples the g-protein Gs from the receptors and enhances the activity of adenylate cyclase in the targeted cells. This results in elevation of cyclic adenosine monophosphate (cAMP) activity. Large changes in cell function are caused by cAMP because it acts as a secondary messenger biochemical pathway.