Nedd4-1 binds and ubiquitylates activated FGFR1 to control its endocytosis and function

Fibroblast growth factor receptor 1 (FGFR1) has critical roles in cellular proliferation and differentiation during animal development and adult homeostasis. Here, we show that human Nedd4 (Nedd4-1), an E3 ubiquitin ligase comprised of a C2 domain, 4 WW domains, and a Hect domain, regulates endocytosis and signalling of FGFR1. Nedd4-1 binds directly to and ubiquitylates activated FGFR1, by interacting primarily via its WW3 domain with a novel non-canonical sequence (non-PY motif) on FGFR1. Deletion of this recognition motif (FGFR1-Delta 6) abolishes Nedd4-1 binding and receptor ubiquitylation, and impairs endocytosis of activated receptor, as also observed upon Nedd4-1 knockdown. Accordingly, FGFR1-Delta 6, or Nedd4-1 knockdown, exhibits sustained FGF-dependent receptor Tyr phosphorylation and downstream signalling (activation of FRS2 alpha, Akt, Erk1/2, and PLC gamma). Expression of FGFR1-Delta 6 in human embryonic neural stem cells strongly promotes FGF2-dependent neuronal differentiation. Furthermore, expression of this FGFR1-Delta 6 mutant in zebrafish embryos disrupts anterior neuronal patterning (head development), consistent with excessive FGFR1 signalling. These results identify Nedd4-1 as a key regulator of FGFR1 endocytosis and signalling during neuronal differentiation and embryonic development. The EMBO Journal (2011) 30, 3259-3273. doi:10.1038/emboj.2011.234; Published online 15 July 2011