TrkA

TrkA, encoded by the NTRK1 gene, is the high-affinity receptor tyrosine kinase for nerve growth factor (NGF). Ligand-induced dimerization activates the intracellular kinase and initiates RAS/MAPK, PI3K/AKT, and PLC-gamma signaling that supports survival and differentiation of sympathetic and sensory neurons during development. Inactivating mutations of NTRK1 cause congenital insensitivity to pain with anhidrosis, a rare disorder characterized by loss of pain perception and impaired thermoregulation. Chromosomal rearrangements generating NTRK1 fusion proteins with constitutive kinase activity occur in papillary thyroid carcinoma, infantile fibrosarcoma, and other tumors, and are targetable with TRK inhibitors such as larotrectinib and entrectinib.