Non-receptor protein-tyrosine kinase that plays an essential role in regulating cell migration, adhesion, spreading, reorganization of the actin cytoskeleton, formation and disassembly of focal adhesions and cell protrusions, cell cycle progression, cell proliferation and apoptosis. Required for early embryonic development, embryonic angiogenesis, normal cardiomyocyte migration and proliferation, and normal heart development. Regulates axon growth and neuronal cell migration, axon branching and synapse formation; required for normal development of the nervous system. Plays a role in osteogenesis and differentiation of osteoblasts. Functions in integrin signal transduction, but also in signaling downstream of numerous growth factor receptors, G-protein coupled receptors (GPCR), ephrin receptors, netrin receptors and LDL receptors. Forms multisubunit signaling complexes with SRC and SRC family members upon activation; this leads to the phosphorylation of additional tyrosine residues, creating binding sites for scaffold proteins, effectors and substrates. Regulates numerous signaling pathways. Promotes activation of phosphatidylinositol 3-kinase and the AKT1 signaling cascade. Promotes activation of MAPK1/ERK2, MAPK3/ERK1 and the MAP kinase signaling cascade. Promotes localized and transient activation of guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs), and thereby modulates the activity of Rho family GTPases. Signaling via CAS family members mediates activation of RAC1. Regulates P53/TP53 activity and stability. Phosphorylates SRC; this increases SRC kinase activity. Isoform 2 (FRNK) does not contain a kinase domain and inhibits PTK2/FAK1 phosphorylation and signaling. ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Subject to autoinhibition, mediated by interactions between the FERM domain and the kinase domain. Activated by autophosphorylation at Tyr-397. This promotes interaction with SRC and phosphorylation at Tyr-576 and Tyr-577 in the kinase activation loop. Phosphorylation at Tyr-576 and Tyr-577 is required for maximal kinase activity. Inhibited by TAE226. Interacts with ARHGAP26, GRB7, DCC, PIK3R1, PXN and SRC. Interacts with the ARP2/3 complex. Constituent of focal adhesions. Detected at microtubules (By similarity). The carboxy-terminal region is the site of focal adhesion targeting (FAT) sequence which mediates the localization of FAK1 to focal adhesions. Phosphorylated on tyrosine residues upon activation, e.g. upon integrin signaling. Tyr-397 is the major autophosphorylation site, but other kinases can also phosphorylate this residue. Phosphorylation at Tyr-397 promotes interaction with SRC and SRC family members, leading to phosphorylation at Tyr-576, Tyr-577 and at additional tyrosine residues. Isoform 2 is phosphorylated on serine or threonine residues, but apparently not on tyrosine residues. Belongs to the protein kinase superfamily. Tyr protein kinase family. FAK subfamily.