Katacalcin is a polypeptide encoded by the calc-1 gene that is also known as crustacean cardioactive peptide (CCAP or CCP1). Katacalcin exhibits immunomodulatory activity. Katacalcin activates PKA and decreases intracellular Ca2+ levels, inducing migration of CD14+ peripheral blood mononuclear cells and deactivating chemotaxis. Katacalcin may be used as a biomarker for medullary thyroid tumors. Additionally, this peptide may play a role in signaling cascade elicited by treatments for mood disorders, such as antipsychotic medications.