Sprouty1 and Sprouty2 provide a control mechanism for the Ras/MAPK signalling pathway

Abstract

Sprouty (Spry) inhibits signalling by receptor tyrosine kinases; however, the molecular mechanism underlying this function has not been defined. Here we show that after stimulation by growth factors Spry1 and Spry2 translocate to the plasma membrane and become phosphorylated on a conserved tyrosine. Next, they bind to the adaptor protein Grb2 and inhibit the recruitment of the Grb2-Sos complex either to the fibroblast growth factor receptor (FGFR) docking adaptor protein FRS2 or to Shp2. Membrane translocation of Spry is necessary for its phosphorylation, which is essential for its inhibitor activity. A tyrosine-phosphorylated octapeptide derived from mouse Spry2 inhibits Grb2 from binding FRS2, Shp2 or mouse Spry2 in vitro and blocks activation of the extracellular-signal-regulated kinase (ERK) in cells stimulated by growth factor. A non-phosphorylated Spry mutant cannot bind Grb2 and acts as a dominant negative, inducing prolonged activation of ERK in response to FGF and promoting the FGF-induced outgrowth of neurites in PC12 cells. Our findings suggest that Spry functions in a negative feedback mechanism in which its inhibitor activity is controlled rapidly and reversibly by post-translational mechanisms.

Sprouty4 negatively regulates protein kinase C activation by inhibiting phosphatidylinositol 4,5-biphosphate hydrolysis

“…Sprouty4 inhibits FGF-mediated ERK activation, where the N-terminal tyrosine Y53 plays an essential role. The phosphorylated N-terminal tyrosine residue of Sprouty2 has been shown to interact with Grb2 and inhibits Grb2-SOS complex to the FGF receptor (FGFR) docking adaptor protein FRS2 or to Shp2 (Hanafusa et al, 2002). However, this tyrosine residue is not required for the suppression of VEGF-A-mediated ERK activation.…”

“…In addition, three Sprouty-related genes, Spreds were identified (Sprouty-related Ena/VASP homology 1 domain-containing proteins) . Mammalian Sproutys and Spreds inhibit growth factor-induced cellular responses by inhibiting the RTK-dependent ERK signaling pathway (Gross et al, 2001;Impagnatiello et al, 2001;Lee et al, 2001;Sasaki et al, 2001Sasaki et al, , 2003Yigzaw et al, 2001;Hanafusa et al, 2002;Yusoff et al, 2002). Sproutys are considered to be a candidate of anti-oncogenes, as reduced expression of Sproutys has been shown in several cancers Lo et al, 2006).…”

“…It is clear that Spred1 is involved in the suppression of the Ras-ERK pathway in vivo, as a loss-of-function mutation of SPRED1 gene was found in human NCFC syndrome, which is caused by dysregulation of the RTK/Ras/ERK pathway (Brems et al, 2007). On the other hand, several mechanisms for the Sprouty-mediated inhibition of the RTK/Ras/ERK pathway have been proposed, including the avoidance of Grb2-Sos recruitment (Gross et al, 2001;Hanafusa et al, 2002) or the inhibition of Raf Sasaki et al, 2003).…”

“…Sprouty2 and Sprouty4 mutants, in which tyrosine residues (Y55 for Sprouty2 and Y53 for Sprouty4) in the N-terminal region are replaced by a non-phosphorylatable residue, have been shown to act as a dominant-negative form for the FGF-induced ERK kinase activation. Therefore, the phosphorylation of these N-terminal tyrosine residues seems to be essential for the inhibitory activity of Sproutys on FGF-induced ERK activation (Sasaki et al, 2001;Hanafusa et al, 2002). However, in the case of VEGF-A signaling, the N-terminal region including Y53 of Sprouty4 is not necessary for suppression, whereas the CR domain is indispensable (Sasaki et al, 2003).…”

Inhibition of Sprouty2 polarizes macrophages toward an M2 phenotype by stimulation with interferon γ andPorphyromonas gingivalislipopolysaccharide

“…The interaction between Grb2 and RTK is prevented and RTK signaling is inhibited as a result of the interaction between Spry2 and Grb2 21, 38. In addition to the Ras/ERK pathway, Spry2 can also suppress the PI3K/AKT signaling pathway by promoting the activation and stability of phosphatase and tensin homolog (PTEN) 39, 40, 41.…”