Abstract
SHP2 is a tyrosine phosphatase involved in the activation of the Ras/ERK signaling pathway downstream of a number of receptor tyrosine kinases. One of the proposed mechanisms involving SHP2 in this context is to dephosphorylate and inactivate inhibitors of the Ras/ERK pathway. Two protein families bearing a unique, common domain, Sprouty and SPRED proteins, are possible candidates because they have been reported to inhibit the Ras/ERK pathway upon FGF activation. We tested whether any of these proteins are likely substrates of SHP2. Our findings indicate that Sprouty2 binds to the C-terminal tail of SHP2, which is an unlikely substrate binding site, whereas SPRED proteins bind to the tyrosine phosphatase domain that is known to be the binding site for its substrates. Overexpressed SHP2 was able to dephosphorylate SPREDs but not Sprouty2. Finally, we found two tyrosine residues on SPRED1 that are required, when phosphorylated, to inhibit Ras/ERK activation and identified Tyr-420 as a specific dephosphorylation target of SHP2. The evidence obtained indicates that SPRED1 is a likely substrate of SHP2, whose tyrosine dephosphorylation is required to attenuate the inhibitory action of SPRED1 in the Ras/ERK pathway.
Highlights
Research (A-STAR), Singapore. □S The on-line version of this article contains supplemental Figs. 1–3. 1 To whom correspondence should be addressed: Institute of Molecular and domains that constitutively binds to Son of Sevenless, a RasGuanine nucleotide exchange factor protein that activates the small membrane-located GTPase Ras
To first ascertain whether and how the Spry proteins bind to SHP2, FLAG-tagged Spry1, Spry2 or Spry4 were transfected into HEK293 cells and activated by overexpressing FGFR1
It is apparent that Spry1 and Spry2 bound to SHP2 upon FGFR1 activation, but Spry4 did not
Summary
In FGFR signaling, SHP2 acts as an adaptor as well as a tyrosine phosphatase, and its phosphatase activity is necessary for a functioning Ras/ERK pathway (4 – 6). There has been considerable interest in identifying the signaling substrate protein of SHP2 in the context of a fully active Ras/ERK pathway. A recent review has comprehensively summarized the theories and suspect proteins that may be the sought-after SHP2 substrates [7] Such potential substrates include Src family kinases and their regulators, signal regulatory protein ␣ (SIRP␣), major vault protein, Csk (via Cbp/ PAG), p120-RasGAP, the inhibitor proteins Sprouty (Spry) and Sprouty-related Ena/vasodilator-stimulated phosphoprotein homology 1-domain-containing protein (SPRED). The most likely SHP2 substrate should ideally be an inhibitor of the Ras/ERK pathway when tyrosine-phosphorylated but should not inhibit when active SHP2 dephosphorylates specific tyrosine residue(s). Spry would be a likely candidate as the sought-after SHP2 substrate if the tyrosine phosphorylated Y55 were a target for active SHP2, there is no compelling evidence for this, currently
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
