Protein-tyrosine kinase 7 (PTK17) is a member of the receptor protein tyrosine kinase family of proteins that transduce extracellular signals across the cell membrane. PTK17 lacks detectable catalytic tyrosine kinase activity. It is involved in the Wnt signaling pathway and plays a role in multiple cellular processes including polarity and adhesion [taken from NCBI Entrez Gene (Gene ID: 5754)].