Disease relevance of FRS2

• These experiments demonstrate that FRS2 couples both ligand-regulated and oncogenic forms of RET, with the MAP kinase signaling cascade as part of the response of RET under normal biological conditions and pathological conditions, such as MEN 2 and papillary thyroid carcinomas [1].
• We found that the L5 VRT produced rapid (24 h after transection), robust and prolonged (56 days) bilateral mechanical allodynia, to a similar extent to that in rats with L5 spinal nerve transection (L5 SNT), cold allodynia and short-term thermal hyperalgesia (14 days) [2].
• In addition, mRNA encoding tumor protein D52 was overexpressed in 60% of breast cancer specimens, while transcripts encoding SNT-1 signal adaptor protein were downregulated in 70% of these cases [3].

High impact information on FRS2

• In this report, we describe the purification, cloning, and characterization of a novel protein, designated FRS2, that is tyrosine phosphorylated and binds to Grb2/Sos in response to FGF or NGF stimulation [4].
• We find that FRS2 is myristylated and that this modification is essential for membrane localization, tyrosine phosphorylation, Grb2/Sos recruitment, and MAPK activation [4].
• These experiments reveal a novel MAPK-mediated, negative feedback mechanism for control of signaling pathways that are dependent on FRS2 and a mechanism for heterologous control of signaling via FGF receptors [5].
• SNT adaptor proteins transduce activation of fibroblast growth factor receptors (FGFRs) and neurotrophin receptors (TRKs) to common signaling targets [6].
• The SNT-1 phosphotyrosine binding (PTB) domain recognizes activated TRKs at a canonical NPXpY motif and, atypically, binds to nonphosphorylated FGFRs in a region lacking tyrosine or asparagine [6].

Biological context of FRS2

• Using deletion and alanine scanning mutagenesis as well as peptide competition assays, we demonstrate that the PTB domains of the FRS2 proteins specifically recognize two different primary structures in two different receptors in a phosphorylation-dependent or -independent manner [7].
• The PTB domains of the FRS2 proteins bind to a highly conserved sequence in the juxtamembrane region of FGFR1 [7].
• In contrast, tyrosine phosphorylation of FRS2 was not evident with FGFR-1L [8].
• NPXY is the consensus sequence for phosphotyrosine binding (PTB) domains, and notably, FRS2 and SHC contain PTB domains [9].
• Identification of SNT/FRS2 docking site on RET receptor tyrosine kinase and its role for signal transduction [10].

Anatomical context of FRS2

• FRS2 proteins recruit intracellular signaling pathways by binding to diverse targets on fibroblast growth factor and nerve growth factor receptors [7].
• VEGF treatment of human umbilical vein endothelial cells (HUVECs) and KDR-transfected porcine aortic endothelial cells leads to the rapid tyrosine phosphorylation of FRS2 [11].
• SNT1/FRS2 mediates germinal vesicle breakdown induced by an activated FGF receptor1 in Xenopus oocytes [12].
• It is likely that FRS2 serves as an anchoring protein for targeting activated atypical PKCs to the cell plasma membrane in signaling pathways [13].
• We report here that FRS2 was associated with PKC lambda when Swiss 3T3 cells were stimulated with basic fibroblast growth factor [13].

Associations of FRS2 with chemical compounds

• The multiple interactions mediated by FRS2 appear to play an important role in target selection and in defining the specificity of several families of receptor tyrosine kinases [7].
• The FRS2 PTB domain recognizes tyrosine-phosphorylated TRKs at an NPXpY (where pY is phosphotyrosine) motif, whereas its constitutive association with FGFR involves a receptor juxtamembrane region lacking Tyr and Asn residues [14].
• Mutation of the alanine residue (Ala-120) to glutamate in the pseudo-substrate region of PKC lambda results in a constitutively active kinase that exhibited more than 2-fold greater binding to FRS2 in vitro than its "closed" wild-type counterpart [13].
• Bisindolylmaleimide I Suppresses Fibroblast Growth Factor-mediated Activation of Erk MAP Kinase in Chondrocytes by Preventing Shp2 Association with the Frs2 and Gab1 Adaptor Proteins [15].
• Phosphorylation of the adapter protein FGF receptor substrate 2 is much more robust in the cells expressing the C3 variant of FGFR2 compared with the C1 variant [16].
• Inactivation of the FGFR1 kinase and substitutions of tyrosine phosphorylation sites of FGFR1, but not FRS2alpha, reduced binding of FGFR1 with FRS2alpha [17].
• We found that FRS2 binding to FGFR2 IIIb is required for increased FRS2 tyrosine phosphorylation and enhanced transforming activity by Y770F mutation [18].

Physical interactions of FRS2

• Here we show that the PTB domains of both the alpha and beta isoforms of FRS2 bind directly to the FGF or NGF receptors [7].
• In this report, we demonstrate that FRS2 forms a complex with the N-terminal SH2 domain of the protein tyrosine phosphatase Shp2 in response to FGF stimulation [19].
• Here we show by isothermal titration calorimetry that the FRS2alpha PTB domain binding to peptides derived from TRKs or FGFR is thermodynamically different [14].

Enzymatic interactions of FRS2

• These results indicate a ligand-stimulated negative regulatory feedback loop in which activated ERK1/2 phosphorylates FRS2 on serine/threonine residues thereby down-regulating its tyrosine phosphorylation [20].
• We have isolated a human cDNA for the signaling adapter molecule FRS-2/suc1-associated neurotrophic factor target and shown that it is tyrosine-phosphorylated in response to nerve growth factor (NGF) stimulation [21].
• We found that IR can directly phosphorylate FRS2 [22].
• Fibroblast growth factor-1 stimulation leads to phosphorylation of the adaptor protein Suc1-associated neurotrophic factor-induced tyrosine-phosphorylated target (SNT-1) on C-terminal tyrosine residues, whereas it is constitutively bound through its N-terminal phosphotyrosine-binding domain (PTB) to FGF receptors (FGFRs) [23].

Regulatory relationships of FRS2

• Our findings support a broader role of FRS2 in EGFR-controlled signaling pathways in A-431 cells and provide insight into a molecular mechanism for ligand-stimulated feedback regulation with FRS2 as a central regulatory switch point [20].
• BDNF induces phosphorylation of FRS2 [9].
• Notably, tyrosine phosphorylation of FRS2 is enhanced when ERK1/2 activation is inhibited after both EGF and FGF stimulation [20].
• Phosphorylation by ectopic FGFR1 that promotes malignancy was much more intense and yielded a phosphorylated 85-kDa SNT1 [24].
• However, overexpression of FRS2 but not Shc potentiates mitogen-activated protein (MAP) kinase activation by RET oncoproteins [1].

Other interactions of FRS2

• This involves the direct interaction of the FRS2 PTB domain with the EGFR and results in a significantly altered mobility of FRS2 in SDS-PAGE which is also observed in FGF stimulated cells [20].
• The ability of FRS2 to recruit cell-signaling proteins to the cell is significant because it provides a mechanism for enhancing the repertoire of VEGF-induced signaling pathways [11].
• Now, we have intriguing data that indicates BDNF induces association of the SH2 domain containing protein tyrosine phosphatase, Shp2, with FRS2 [9].
• SNT/FRS2 is a lipid anchored docking protein that contains an amino-terminal myristylation signal, followed by a phosphotyrosine-binding (PTB) domain and a carboxy-terminal region with multiple tyrosine residues [10].
• Here we provide evidence that FRS2 can also play a role in epidermal growth factor (EGF) signaling [20].

Analytical, diagnostic and therapeutic context of FRS2

• Genomic organization and comparative sequence analysis of the mouse and human FRS2, FRS3 genes [25].
• To assay potential differences in their patterns of expression, RT-PCR analysis was used to assay FRS2 and FRS3 expression in the developing embryo and neural tube (NT) during the time of neurogenesis [25].
• Quantitative evaluation of SNT in biological material is currently hindered by many methodological problems [26].

References