a chemical conjugate of the neuropeptide substance P
and the catalytic A subunit of cholera toxin
targets cells expressing substance P (NK-1) receptor

Targeted CTA conjugates are powerful and specific stimulatory agents. These conjugates use the catalytic A subunit of cholera toxin (CTA) bound to a targeting agent (anything that is recognized on the cell surface and internalized). The targeted conjugate is administered to cells (in vitro or in vivo). The targeting agent seeks out and binds to its target on the cell surface. The conjugate is internalized, CTA activates the cAMP pathway within the cells by ribosylating adenylate cyclase. Cells that do not have the cell surface marker are not affected.

SP-CTA is an exciting tool for use in the research of neurokinin (NK-1) receptor-expressing cells of the central nervous system. It can be used very effectively in vivo for increasing sensitization of these neuronal cells. Selectively targeting the NK-1r-expressing cells with the substance P moiety allows the researcher to stimulate only the cells of interest by amplifying their cAMP production with the CTA, without altering the neighboring cells. This effect lasts for a few days, and gives the researcher an opportunity to study behaviors such as those related to the perception of pain or the control of breathing.

Elimination of Specific Cell Type

• SP-CTA stimulates cells expressing the substance P receptor.
• All other cells are left untouched.