Prokineticins are small proteins expressed in the GI tract and other tissues that regulate contraction of GI smooth muscle, angiogenesis and other responses. Two closely related receptors for prokineticins have been cloned, PKR1 and PKR2. PKR2 is expressed in ileocecum, in brain and in endocrine tissues. PKR2 is Gq coupled and has been shown to be activated by mamba intestinal toxin (MIT1). This PKR2-expressing cell line displays a very robust calcium response and is useful as a target for drug discovery.