Leukocyte receptor tyrosine kinase (LTK) is a member of the ALK/LTK receptor family of receptor tyrosine kinases (RTKs). Closely related to the insulin receptor family of RTKs. Tyrosine-specific phosphorylation of proteins is a key to the control of diverse pathways leading to cell growth and differentiation. And LTK has been shown to interact with IRS-1, Shc, and PIK3R1.