Fibroblast growth factor receptor 4-beta-Klotho complex (FGFR4-KLB complex)

The Fibroblast growth factor receptor 4-beta-Klotho (FGFR4-KLB) complex is a specialized receptor system primarily expressed in the liver, where it functions as the primary mediator for the endocrine hormone FGF19 (UniProt: P22607, Q86Z14). Beta-Klotho acts as an essential scaffold that enables FGFR4 to bind FGF19 with high affinity, triggering intracellular signaling pathways such as MAPK/ERK and PI3K/AKT (PubMed: 28103437). This complex is a master regulator of bile acid metabolism, specifically inhibiting the rate-limiting enzyme CYP7A1 to prevent bile acid overproduction. In various cancers, particularly hepatocellular carcinoma, the FGF19-FGFR4-KLB axis is often hyperactivated through ligand amplification or receptor overexpression, promoting tumor cell proliferation and survival (PubMed: 30842634). Therapeutic targeting of this complex involves highly selective small-molecule inhibitors designed to block FGFR4 kinase activity while sparing other FGFR isoforms to avoid systemic toxicities like hyperphosphatemia. Clinical trials for these inhibitors frequently utilize FGF19 expression as a biomarker to identify patients most likely to respond to therapy (ClinicalTrials.gov: NCT02508467).

Other names

FGFR4-beta-KlothoFGFR4-KLBFGF19 receptor complexFibroblast growth factor receptor 4-KLB complex

Selective inhibition of the FGFR4 tyrosine kinase domain or disruption of the FGF19-FGFR4-KLB binding interface to suppress downstream oncogenic and metabolic signaling.