Myristoylation-Dependent Palmitoylation of the Receptor Tyrosine Kinase Adaptor FRS2?.
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ABSTRACT: An early step in signaling from activated receptor tyrosine kinases (RTKs) is the recruitment of cytosolic adaptor proteins to autophosphorylated tyrosines in the receptor cytoplasmic domains. Fibroblast growth factor receptor substrate 2? (FRS2?) associates via its phosphotyrosine-binding domain (PTB) to FGF receptors (FGFRs). Upon FGFR activation, FRS2? undergoes phosphorylation on multiple tyrosines, triggering recruitment of the adaptor Grb2 and the tyrosine phosphatase Shp2, resulting in stimulation of PI3K/AKT and MAPK signaling pathways. FRS2? also undergoes N-myristoylation, which was shown to be important for its localization to membranes and its ability to stimulate downstream signaling events (Kouhara et al., 1997). Here we show that FRS2? is also palmitoylated in cells and that cysteines 4 and 5 account for the entire modification. We further show that mutation of those two cysteines interferes with FRS2? localization to the plasma membrane (PM), and we quantify this observation using fluorescence fluctuation spectroscopy approaches. Importantly, prevention of myristoylation by introduction of a G2A mutation also abrogates palmitoylation, raising the possibility that signaling defects previously ascribed to the G2A mutant may actually be due to a failure of that mutant to undergo palmitoylation. Our results demonstrate that FRS2? undergoes coupled myristoylation and palmitoylation. Unlike stable cotranslational modifications, such as myristoylation and prenylation, palmitoylation is reversible due to the relative lability of the thioester linkage. Therefore, palmitoylation may provide a mechanism, in addition to phosphorylation, for dynamic regulation of FRS2 and its downstream signaling pathways.
SUBMITTER: Barylko B
PROVIDER: S-EPMC6800032 | biostudies-literature | 2019 Jun
REPOSITORIES: biostudies-literature
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