The downstream of kinase family (Dok-1-7) are members of a class of docking proteins that interact with receptor tyrosine kinases and, via this interaction, mediate biological responses within the body. Dok-4 (Downstream of kinase-4) is a 326 amino acid protein that contains one PH domain and one IRS-type PTB domain and belongs to the Dok family of interacting proteins. Expressed in a variety of tissues with highest expression in liver, heart, kidney and skeletal muscle, Dok-4 plays an important role in Ret-mediated neurite outgrowth and may link Ret with downstream effectors during neuronal differentiation. Additionally, Dok-4 is thought to play a positive role in the activation of MAPK pathways and may participate in T-cell induced immune system regulation. Overexpression of Dok-4 is associated with clear cell renal cell carcinoma, suggesting a role for Dok-4 in tumorigenesis.