 In many cases, the FGFs themselves can also activate more than one receptor (i.e., FGF1, which binds all seven principal FGFRs).FGF7, however, can only activate FGFR2b, and FGF18 was recently shown to activate FGFR3.A gene for a fifth FGFR protein, FGFR5, has also been identified.