Disease relevance of Grb2

• Furthermore, Grb2 is rate limiting for mammary carcinomas induced by polyomavirus middle T antigen [1].
• A direct binding site for the Grb2 adapter protein is required for the induction of fatal chronic myeloid leukemia (CML)-like disease in mice by Bcr-Abl [2].
• Introduction of a mutation that results in failure to bind Grb2 abrogates the ability of Sf-Stk to induce colonies in response to Friend virus, while the Grb2 binding site from EGFR restores this response [3].
• Here we investigated Grb2 expression in liver lesions in N-nitrosodimethylamine (NDMA)-treated Helicobacter hepaticus-infected and -noninfected A/J mice at 1 year of age [4].
• Involvement of Grb2 was confirmed by immunoblotting of similarly infected mice at 9 to 18 months of age, showing a 2.5- to 3.3-fold increase in Grb2 protein in infected livers (p < 0.05 compared with uninfected controls) as well as in preneoplastic foci, adenomas, and carcinomas [4].

High impact information on Grb2

• Mammalian Grb2 regulates multiple steps in embryonic development and malignant transformation [1].
• Analysis of mutant embryonic stem cells, embryos, and chimeras reveals that Grb2 is required during embyrogenesis for the differentiation of endodermal cells and formation of the epiblast [1].
• Shc is subsequently phosphorylated at tyrosine 317 and recruits Grb2 [5].
• Uncoupling of Grb2 from the Met receptor in vivo reveals complex roles in muscle development [6].
• Activation of growth factor receptors results in tyrosine autophosphorylation and recruitment of SH2 domain-containing effectors, including Grb2 [7].

Chemical compound and disease context of Grb2

• When crossed with mice expressing activated forms of the Neu receptor tyrosine kinase that selectively couple to the Grb2 or Shc signaling pathways the activated type I receptor increased the latency of mammary tumor formation but also enhanced the frequency of extravascular lung metastasis [8].
• A tyrosine-phosphorylated protein of 140 kD is constitutively associated with the phosphotyrosine binding domain of Shc and the SH3 domains of Grb2 in acute myeloid leukemia cells [9].
• BACKGROUND: The v-abl oncogene of the Abelson murine leukemia virus (A-MuLV) encodes a cytoplasmic tyrosine kinase that can associate with phosphoinositide 3-kinase, Shc and Grb2, and activate the pathway that leads from Ras to mitogen-activated protein (MAP) kinase [10].

Biological context of Grb2

• Disruption of T cell signaling networks and development by Grb2 haploid insufficiency [11].
• Tyr209 within the C-terminal SH3 domain of Grb2 was identified as one of the tyrosine phosphorylation sites, and phosphorylation of Tyr209 abolished the binding of the SH3 domain to a proline-rich Sos peptide in vitro [12].
• The ShcC protein is predicted to have a C-terminal SH2 domain, a CH1 region with a putative Grb2-binding site, and an N-terminal PTB domain [13].
• Since the ubiquitously expressed adaptor protein Grb2 plays an important role in several tyrosine kinase signal transduction pathways, we used a filter binding assay to identify osteoclast proteins that bind to Grb2 [14].
• We propose that the Grb2-independent recruitment of Gab proteins to Met is necessary but not sufficient to promote epithelial morphogenesis [15].

Anatomical context of Grb2

• 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 [16].
• Thus, PTEN/phosphatidylinositol 3' kinase signaling requires Grb2 during both embryonic development and fibroblast survival, but Grb2 heterozygosity does not effect tumorigenesis in pten-deficient mice [17].
• Mitogenic signaling of NGF in NIH 3T3 cells ectopically expressing Trk receptors also takes place without detectable association between Grb2 and Trk [18].
• Embryonic and hematopoietic stem cells express a novel SH2-containing inositol 5'-phosphatase isoform that partners with the Grb2 adapter protein [19].
• Mona/Gads is a Grb2-related, Src homology 3 (SH3) and SH2 domain-containing adapter protein whose expression is restricted to cells of hematopoietic lineage (i.e., monocytes and T lymphocytes) [20].

Associations of Grb2 with chemical compounds

• Expression of GrpL is restricted to hematopoietic tissues, and it is distinguished from Grb2 by having a proline-rich region [21].
• The latter effect probably abates Grb2 inhibition of the phosphotyrosine displacement process that is required specifically for Src dephosphorylation and causes a mitotic increase in transient PTPalpha-Src binding [22].
• The molecular adapter c-Cbl is rapidly tyrosine phosphorylated following stimulation through the TCR and associates with Src homology domain-2 (SH2)/SH3 domain-containing adapters such as Grb2, Crk, and Crk-L, which interact with guanine nucleotide exchange factors specific for the Ras family [23].
• Srcasm is capable of interacting with Grb2 and the regulatory subunit of phosphoinositide 3-kinase, p85, in a phosphorylation-dependent manner [24].
• This involves serine phosphorylation-dependent differential modulation of the affinity of Tyr(P)789 for the Src and Grb2 SH2 domains [25].

Physical interactions of Grb2

• The Grb2 SH2 domain binds to Tyr1068 of EGFR and Tyr317 of Shc while its SH3 domains bind to mSos1 [26].
• E3 or laminin-1 increase Grb2-binding and Rac1 activation [27].
• Fms also formed complexes with Grb2 and Sos1, and neither contained phosphotyrosine [28].
• These results demonstrate that tyrosine-phosphorylated Shc specifically interacts with the SH2 domain of Grb2 [29].
• Furthermore, we show that this interaction is direct and that Grb2 binds to phospho-AbetaPP via its Src homology 2 region [30].

Enzymatic interactions of Grb2

• In FGF-2 treated proliferating EC, FRS2 as well as Shc are tyrosine phosphorylated and interact with Grb2 [31].
• Pyk2 became phosphorylated at the major autophosphorylation site (Tyr-402) and the potential Grb2-binding site (Tyr-881) during EMT [32].

Regulatory relationships of Grb2

• Overexpression of mutants of Grb2 with inactive SH2 or SH3 domains also blocks cytokine-stimulated Gab2 phosphorylation [33].
• In response to pressure overload, cardiac p38 MAPK and JNK activation was inhibited and cardiac hypertrophy and fibrosis was blocked in Grb2(+/-) mice [34].
• Further, tyrosine phosphorylation of Vav and the costimulation-dependent activation of Jun N-terminal kinase was blocked in cells defective in CD28/Grb2 binding [35].
• Dominant-negative mutants of Grb2 induced reversal of the transformed phenotypes caused by the point mutation-activated rat HER-2/Neu [36].
• PDGF action triggers both mechanisms of Grb2 disassembly, which probably operate in concert with GAP to attenuate p21ras signaling [37].

Other interactions of Grb2

• Molecular cloning of the mouse grb2 gene: differential interaction of the Grb2 adaptor protein with epidermal growth factor and nerve growth factor receptors [18].
• How c-Cbl interacts with proteins, such as Grb2, phosphatidylinositol 3-kinase, and phosphorylated receptors, is well understood, but its role in these complexes is unclear [38].
• Together, these data suggest that Grap, unlike Grb2, acts as a negative regulator of TCR-stimulated intracellular signaling by downregulating signal relay through the Ras/Erk pathway [39].
• Grb2-mSos1 bound to both EGFR- and Shc-derived phosphopeptides with higher affinities (KD of 0.3 microM and 31 nM, respectively) than Grb2 alone [26].
• Activation of both PKB and Erk as well as survival in low serum-containing media are all rescued by reexpression of Grb2 containing mutations within the N-terminal Src homology 3 (SH3) domain, but not by C-terminal SH3 domain mutants [17].

Analytical, diagnostic and therapeutic context of Grb2

• By immunoblotting and immunoprecipitation, we further demonstrate the association of tyrosine phosphoproteins with Grb2, an adaptor protein serving as a key intermediate for Ras activation [40].
• From kinetic studies using surface plasmon resonance, it was deduced that a conformation change occurred in the SH2 protein as well as the full-length Grb2 after binding [41].
• Immunoprecipitation of Grb2 followed by SOS immunoblotting demonstrated a disassociation of the SOS-Grb2 complex that paralleled the decrease in SOS electrophoretic mobility [42].
• (J. Immunol. 1994. 153: 623) receptor ligation leads to tyrosine phosphorylation of SHC and to the formation of a phospho-SHC/Grb2/Sos complex [43].
• Since Grb2 is a known signal transducer for several major human oncogenes, this approach may have applications for a wider range of human cancers [44].

References