Sprouty2 association with B-Raf is regulated by phosphorylation and kinase conformation.
Sprouty2 is a feedback regulator that controls the Ras/Raf/MEK/extracellular signal-regulated kinase mitogen-activated protein kinase (MAPK) pathway at multiple levels, one way being through direct interaction with Raf kinases. Consistent with a role as a tumor suppressor, Sprouty2 expression is often down-regulated in human cancers. However, Sprouty2 is up-regulated in some cancers, suggesting the existence of posttranscriptional mechanisms that permit evasion of Sprouty2-mediated antitumorigenic properties. We report that MAPK activation induces Sprouty2 phosphorylation on six serine residues, which reduced Sprouty2 association with wild-type B-Raf. Mutation of these six serines to nonphosphorylatable alanines increased the ability of Sprouty2 to inhibit growth factor-induced MAPK activation. Oncogenic B-Raf mutants such as B-Raf V600E did not associate with Sprouty2, but this resistance to Sprouty2 binding was not due to phosphorylation. Instead, the active kinase conformation induced by oncogenic mutation prevents Sprouty2 binding. These results reveal a dual mechanism that affects the Sprouty2/B-Raf interaction: Sprouty phosphorylation and B-Raf conformation.
Brady
Suzanne C
SC
The Beatson Institute for Cancer Research, Glasgow, United Kingdom.
Coleman
Mathew L
ML
Munro
June
J
Feller
Stephan M
SM
Morrice
Nicolas A
NA
Olson
Michael F
MF
D000818:Animals; D001665:Binding Sites; D004789:Enzyme Activation; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D008565:Membrane Proteins; D051379:Mice; D009154:Mutation; D041681:NIH 3T3 Cells; D009369:Neoplasms / Q000201:enzymology* / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D011487:Protein Conformation; D048493:Proto-Oncogene Proteins B-raf / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C485561:SPRY2 protein, human; D048493:Proto-Oncogene Proteins B-raf
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