14-3-3ζ (also known as tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein, zeta polypeptide) is a member of the 14-3-3 family of proteins which mediate signal transduction by binding to phosphoserine-containing proteins. 14-3-3ζ protein plays a key role in cancer biology by being an important regulator of major cellular processes such as proliferation, differentiation, senescence and apoptosis. 14-3-3ζ protein has been shown to interact with the IRS1 protein, suggesting a role for this protein in regulating insulin sensitivity by interrupting the association between the insulin receptor and IRS1.