Tyrosine-protein kinase that acts downstream of cell surface receptors and plays a role in the regulation of the actin cytoskeleton, microtubule assembly, cell attachment and cell spreading. Plays a role in FCER1 (high affinity immunoglobulin epsilon receptor)-mediated signaling in mast cells. Acts down-stream of the activated FCER1 receptor and the mast/stem cell growth factor receptor KIT. Plays a role in the regulation of mast cell degranulation. Plays a role in the regulation of cell differentiation and promotes neurite outgrowth in response to NGF signaling. Plays a role in cell scattering and cell migration in response to HGF-induced activation of EZR. Phosphorylates BCR and down-regulates BCR kinase activity. Phosphorylates HCLS1/HS1, PECAM1, STAT3 and TRIM28. ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Kinase activity is tightly regulated. Activated in response to signaling from a cell surface receptor. Activation probably requires binding of a substrate via the SH2 domain, plus autophosphorylation at Tyr-713. Present in an inactive form in the absence of activating stimuli. Homooligomer. Interacts with BCR. Interacts (when activated, via coiled coil domain) with TRIM28. Interacts (via SH2 domain) with phosphorylated EZR, MS4A2/FCER1B and HCLS1/HS1. Interacts with phosphorylated KIT. Interacts with FLT3. Interacts (via F-BAR domain) with soluble tubulin. Interacts (via SH2 domain) with microtubules (By similarity). Distributed throughout the cytosol when the kinase is not activated. Association with microtubules requires activation of the kinase activity. Shuttles between focal adhesions and cell-cell contacts in epithelial cells. Recruited to the lateral cell membrane in polarized epithelial cells by interaction with phosphorylated EZR. Detected at tubular membrane structures in the cytoplasm and at the cell periphery (By similarity). The coiled coil domains are important for regulating the kinase activity. They mediate homooligomerization and probably also interaction with other proteins (By similarity). The N-terminal region including the first coiled coil domain mediates interaction with phosphoinositide-containing membranes. Autophosphorylated on Tyr-713 in response to FGF2. Phosphorylated by LYN in response to FCER1 activation. Phosphorylated by HCK (By similarity). No visible phenotype. Mice are fertile and healthy, display slightly reduced numbers of myeloid cells and are more sensitive to lipopolysaccharide (LPS). Mice lacking both Fps/Fes and Fer activity are viable and fertile, but produce fewer offspring than normal. They display elevated levels of circulating neutrophils, erythrocytes and platelets, while other cell counts are normal. In a BRAF V600E-driven, PTEN deficient and FES deficient melanoma model, tumor growth is accelerated due to an increased proliferation of melanoma cells. Belongs to the protein kinase superfamily. Tyr protein kinase family. Fes/fps subfamily.