Gene Summary: The protein encoded by this gene is a member of the fibroblast growth factor receptor family, where amino acid sequence is highly conserved between members and throughout evolution. FGFR family members differ from one another in their ligand affinities and tissue distribution. A full-length representative protein would consist of an extracellular region, composed of three immunoglobulin-like domains, a single hydrophobic membrane-spanning segment and a cytoplasmic tyrosine kinase domain. The extracellular portion of the protein interacts with fibroblast growth factors, setting in motion a cascade of downstream signals, ultimately influencing mitogenesis and differentiation. The genomic organization of this gene, compared to members 1-3, encompasses 18 exons rather than 19 or 20. Although alternative splicing has been observed, there is no evidence that the C-terminal half of the IgIII domain of this protein varies between three alternate forms, as indicated for members 1-3. This particular family member preferentially binds acidic fibroblast growth factor and, although its specific function is unknown, it is overexpressed in gynecological tumor samples, suggesting a role in breast and ovarian tumorigenesis.General information above from NCBI
Catalytic activity: ATP + a [protein]-L-tyrosine = ADP + a [protein]-L-tyrosine phosphate.
Enzyme regulation: Present in an inactive conformation in the absence of bound ligand. Ligand binding leads to dimerization and activation by autophosphorylation on tyrosine residues.
Subunit structure: Monomer. Homodimer after ligand binding. Interacts with FGF1, FGF2, FGF4, FGF6, FGF8, FGF9, FGF16, FGF17, FGF18, FGF19, FGF21 and FGF23 (in vitro). Binding affinity for FGF family members is enhanced by interactions between FGFs and heparan sulfate proteoglycans. Interacts with KLB; this strongly increases the affinity for FGF19 and FGF23. Affinity for FGF19 is strongly increased by KLB and sulfated glycosaminoglycans. KLB and KL both interact with the core-glycosylated FGFR4 in the endoplasmic reticulum and promote its degradation, so that only FGFR4 with fully mature N-glycans is expressed at the cell surface. Identified in a complex with NCAM1, CDH2, PLCG1, FRS2, SRC, SHC1, GAP43 and CTTN. Interacts with MMP14 and HIP1.
Subcellular location: Cell membrane; Single-pass type I membrane protein. Endosome. Endoplasmic reticulum. Note=Internalized from the cell membrane to recycling endosomes, and from there back to the cell membrane.
Isoform 2: Secreted.
Tissue specificity: Expressed in gastrointestinal epithelial cells, pancreas, and gastric and pancreatic cancer cell lines.
Post-translational: N-glycosylated. Full maturation of the glycan chains in the Golgi is essential for high affinity interaction with FGF19.
Ubiquitinated. Subject to proteasomal degradation when not fully glycosylated.
Autophosphorylated. Binding of FGF family members together with heparan sulfate proteoglycan or heparin promotes receptor dimerization and autophosphorylation on tyrosine residues. Autophosphorylation occurs in trans between the two FGFR molecules present in the dimer.
Sequence similarity: Belongs to the protein kinase superfamily. Tyr protein kinase family. Fibroblast growth factor receptor subfamily.
Contains 3 Ig-like C2-type (immunoglobulin-like) domains.
Contains 1 protein kinase domain.
General information above from UniProt