Meta-Biol

• Pathways

FGFRL1 is a fifth member of the FGFR family of receptors that shares 40% sequence similarity with the extracellular region of FGFR1-4, but FGFRL1 lacks the internal kinase domain required for typical downstream FGFR signaling. Instead, FGFRL1 has a short intracellular domain with a C-terminal histidine rich region that has been shown to interact with the MAP kinase regulator SPRED proteins (Sleeman et al, 2001; Zhuang et al, 2011; reviewed in Trueb et al, 2013). FGFRL1 forms constitutive dimers and has been shown to bind to a wide range of FGF ligands, including FGF3,4,8,10, 22 and with lower affinity to FGF2,5,17,18 and 23 (Reickman et al, 2008; Steinberg et al, 2010). FGFRL1 knockout mice die shortly after birth from lung and renal defects (Gerber et al, 2009; Gerber et al, 2012; Trueb et al, 2013). FGFRL1 has been postulated to act as a decoy receptor that sequesters ligand away from canonical FGF receptors; more recently, however, alternate roles for FGFRL1 in enhancing ERK1/2 activation or promoting FGFR1-mediated signaling have been suggested (Sleeman et al, 2001; Steinberg et al, 2010; Silva et al, 2013; Amann and Trueb, 2013). Further work will be required to elucidate the role(s) of FGFRL1.