Tyrosine-protein kinase that acts downstream of cell surface receptors for growth factors and plays a role in the regulation of the actin cytoskeleton, microtubule assembly, lamellipodia formation, cell adhesion, cell migration and chemotaxis. Acts downstream of EGFR, KIT, PDGFRA and PDGFRB. Acts downstream of EGFR to promote activation of NF-kappa-B and cell proliferation. May play a role in the regulation of the mitotic cell cycle. Plays a role in the insulin receptor signaling pathway and in activation of phosphatidylinositol 3-kinase. Acts downstream of the activated FCER1 receptor and plays a role in FCER1 (high affinity immunoglobulin epsilon receptor)-mediated signaling in mast cells. Plays a role in the regulation of mast cell degranulation. Plays a role in leukocyte recruitment and diapedesis in response to bacterial lipopolysaccharide (LPS). Plays a role in synapse organization, trafficking of synaptic vesicles, the generation of excitatory postsynaptic currents and neuron-neuron synaptic transmission. Plays a role in neuronal cell death after brain damage. Phosphorylates CTTN, CTNND1, PTK2/FAK1, GAB1, PECAM1 and PTPN11. May phosphorylate JUP and PTPN1. Can phosphorylate STAT3, but the biological relevance of this depends on cell type and stimulus. ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Activated by phosphatidic acid binding. Activated by hydrogen peroxide (in vitro). Activated by reactive oxygen species (ROS). Homotrimer. Interacts with ARHGDIA, IRS1, JAK1, NRP1, PIK3R1, PLEC and TMF1. Interacts with PPP1CA and regulates its phosphorylation at 'Thr-320' (By similarity). Interacts with CTNND1, EGFR, FLT3, PECAM1, PDGFR and STAT3. Interacts (via SH2 domain) with CTTN. Interacts with HSP90; this stabilizes phosphorylated FER and protects FER against proteasomal degradation. Component of a complex that contains at least FER, CTTN and PTK2/FAK1. Associated with the chromatin. Detected on microtubules in polarized and motile vascular endothelial cells. Colocalizes with F-actin at the cell cortex. Colocalizes with PECAM1 and CTNND1 at nascent cell-cell contacts. Isoform 1 is detected in normal colon and in fibroblasts (at protein level). Isoform 3 is detected in normal testis, in colon carcinoma-derived metastases in lung, liver and ovary, and in colon carcinoma and hepato carcinoma cell lines (at protein level). Isoform 3 is not detected in normal colon or in normal fibroblasts (at protein level). Widely expressed. The coiled coil domains mediate homooligomerization and are required for location at microtubules. The N-terminal region including the first coiled coil domain mediates interaction with phosphoinositide-containing membranes. Autophosphorylated. Polyubiquitinated; this leads to proteasomal degradation. Produced by alternative promoter usage. Belongs to the protein kinase superfamily. Tyr protein kinase family. Fes/fps subfamily.