Tyrosine 785 is a major determinant of Trk - Substrate interaction

Department of Molecular Biology, Max-Planck-Institut für Biochemie, Martinsried, Germany.
The EMBO Journal (Impact Factor: 10.43). 04/1993; 12(3):933-41.
Source: PubMed


Interaction of the nerve growth factor (NGF) receptor/Trk with cellular substrates was investigated by transient co-overexpression in human 293 fibroblasts using ET-R, a chimeric receptor consisting of the epidermal growth factor receptor (EGF-R) extracellular ligand binding domain and the Trk transmembrane and intracellular signal-generating sequences. The chimera was fully functional, and associated with and phosphorylated phospholipase C gamma (PLC gamma), ras GTPase-activating protein (GAP) and the non-catalytic subunit of phosphatidylinositol-3'-kinase, p85, in a ligand-dependent manner. Deletion of 15 C-terminal amino acids, including tyrosine 785 (Y-785) abrogated receptor and substrate phosphorylation activities. Mutation of Y-785 to phenylalanine somewhat impaired receptor phosphorylation activity, which was reflected in reduced GAP and p85 phosphorylation. In contrast, ET-YF phosphorylation of PLC gamma was significantly reduced, while the high affinity association potential with this substrate was abrogated by this point mutation in vitro and in intact cells. Furthermore, a tyrosine-phosphorylated synthetic C-terminal peptide competitively inhibited Trk cytoplasmic domain association with PLC gamma. Thus, the short C-terminal tail appears to be a crucial structural element of the Trk cytoplasmic domain, and phosphorylated Y-785 is a major and selective interaction site for PLC gamma.

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    • "Tyrosine residues at positions 670, 674, and 675 are located in the activation loop of the human TrkA tyrosine kinase domain. Tyrosine 490 forms a PTB binding motif (NPXpY) known to bind SHC and FRS2 (Obermeier et al., 1993b; Ong et al., 2000) and tyrosine 785 binds to PLCγ (Obermeier et al., 1993a). The juxtamembrane KFG motif is an ubiquitination site involved in receptor localization. "
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    ABSTRACT: The classic neurotrophins Nerve Growth Factor (NGF), Brain Derived Neurotrophic Factor (BDNF) and Neurotrophins NT-3 and NT-4 are well known to regulate various aspects of neuronal differentiation, survival and growth. They do this by binding to their cognate receptors, members of the Tropomyosin-related kinase (Trk) receptor tyrosine kinase family, namely TrkA, TrkB, and TrkC. These receptors are then internalized and localized to different cellular compartments, where signal transduction occurs. Conversely, members of the suppressor of cytokine signaling (SOCS) family are best known as negative regulators of signaling via the JAK/STAT pathway. Some members of the family, and in particular SOCS2, have roles in the nervous system that at least partially overlap with that of neurotrophins, namely neuronal differentiation and neurite outgrowth. Recent evidence suggests that SOCS2 is a novel regulator of NGF signaling, altering TrkA cellular localization and downstream signaling to affect neurite growth but not neuronal survival. This review first discusses regulation of Trk receptor signaling, followed by the role of SOCS2 in the nervous system and finishes with a discussion of possible mechanisms by which SOCS2 may regulate TrkA function.
    Frontiers in Molecular Neuroscience 05/2014; 7:39. DOI:10.3389/fnmol.2014.00039 · 4.08 Impact Factor
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    • "Inhibition of trkB-fl signaling does not induce NSC to differentiate into glial cells Some evidence suggests that trkB-t exerts its biologic effects by sequestering BDNF so that it cannot bind to and activate trkB-fl, or by forming a heterodimer with trkB-fl and thereby preventing homodimerization of trkB-fl which is required for signaling (Eide et al. 1996; Ninkina et al. 1996). BDNF binding to trkB-fl results in receptor dimerization, activation of the receptor tyrosine kinase activity and transphosphorylation of tyrosine residues in the cytoplasmic domain of trkBfl (Obermeier et al. 1993). These changes in the cytoplasmic domain of trkB-fl promote binding of adaptor proteins containing phosphotyrosine-binding or shc-homology-2 motifs (Pawson and Nash 2000; Huang and Reichardt 2001) which, in turn, engage intracellular signaling cascades including PLC, the Ras/ERK protein kinase pathway and the phosphatidylinositol-3-kinase/Akt kinase pathway (Kaplan and Miller 2000; Huang and Reichardt 2001). "
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    ABSTRACT: During development of the mammalian cerebral cortex neural stem cells (NSC) first generate neurons and subsequently produce glial cells. The mechanism(s) responsible for this developmental shift from neurogenesis to gliogenesis is unknown. Brain-derived neurotrophic factor (BDNF) is believed to play important roles in the development of the mammalian cerebral cortex; it enhances neurogenesis and promotes the differentiation and survival of newly generated neurons. Here, we provide evidence that a truncated form of the BDNF receptor tyrosine kinase B (trkB-t) plays a pivotal role in directing embryonic mouse cortical NSC to a glial cell fate. Expression of trkB-t promotes differentiation of NSC toward astrocytes while inhibiting neurogenesis both in cell culture and in vivo. The mechanism by which trkB-t induces astrocyte genesis is not simply the result of inhibition of full-length receptor with intrinsic tyrosine kinase activity signaling. Instead, binding of BDNF to trkB-t activates a signaling pathway (involving a G-protein and protein kinase C) that induced NSC to become glial progenitors and astrocytes. Thus, the increased expression of trkB-t in the embryonic cerebral cortex that occurs coincident with astrocyte production plays a pivotal role in the developmental transition from neurogenesis to gliogenesis. Our findings suggest a mechanism by which a single factor (BDNF) regulates the production of the two major cell types in the mammalian cerebral cortex.
    Journal of Neurochemistry 04/2007; 100(6):1515-30. DOI:10.1111/j.1471-4159.2006.04337.x · 4.28 Impact Factor
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    • "ments involving mutation of tyro - sine 490 to phenylalanine indicate a role for the NPXY motif in NGF - induced PC12 cell differentiation ( Obermeier et al . 1994 ) , although there is also a requirement for tyrosine 785 phosphorylation ( Obermeier et al . 1994 ; Stephens et al . 1994 ) . Phosphotyrosine 785 is the binding site for PLCc1 on Trk ( Obermeier et al . 1993a ) . Further emphasis on the importance of this site in PC12 cell differentiation was shown by experiments with a chimeric EGF receptor containing the Trk juxtamembrane domain including the NPXY motif ( Yoon et al . 1997 ) . EGF induces PC12 cell differentiation in cells expressing this chimeric recep - tor . Furthermore , this was corre"
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    ABSTRACT: Brain-derived neurotrophic factor (BDNF) and other neurotrophins induce a unique prolonged activation of mitogen-activated protein kinase (MAPK) compared with growth factors. Characterization and kinetic and spatial modeling of the signaling pathways underlying this prolonged MAPK activation by BDNF will be important in understanding the physiological role of BDNF in many complex systems in the nervous system. In addition to Shc, fibroblast growth factor receptor substrate 2 (FRS2) is required for the BDNF-induced activation of MAPK. BDNF induces phosphorylation of FRS2. However, BDNF does not induce phosphorylation of FRS2 in cells expressing a deletion mutant of TrkB (TrkBDeltaPTB) missing the juxtamembrane NPXY motif. This motif is the binding site for SHC. NPXY is the consensus sequence for phosphotyrosine binding (PTB) domains, and notably, FRS2 and SHC contain PTB domains. This NPXY motif, which contains tyrosine 484 of TrkB, is therefore the binding site for both FRS2 and SHC. Moreover, the proline containing region (VIENP) of the NPXY motif is also required for FRS2 and SHC phosphorylation, which indicates this region is an important component of FRS2 and SHC recognition by TrkB. Previously, we had found that the phosphorylation of FRS2 induces association of FRS2 and growth factor receptor binding protein 2 (Grb2). Now, we have intriguing data that indicates BDNF induces association of the SH2 domain containing protein tyrosine phosphatase, Shp2, with FRS2. Moreover, the PTB association motif of TrkB containing tyrosine 484 is required for the BDNF-induced association of Shp2 with FRS2 and the phosphorylation of Shp2. These results imply that FRS2 and Shp2 are in a BDNF signaling pathway. Shp2 is required for complete MAPK activation by BDNF, as expression of a dominant negative Shp2 in cells attenuates BDNF-induced activation of MAPK. Moreover, expression of a dominant negative Shp2 attenuates Ras activation showing that the protein tyrosine phosphatase is required for complete activation of MAPKs by BDNF. In conclusion, Shp2 regulates BDNF signaling through the MAPK pathway by regulating either Ras directly or alternatively, by signaling components upstream of Ras. Characterization of MAPK signaling controlled by BDNF is likely to be required to understand the complex physiological role of BDNF in neuronal systems ranging from the regulation of neuronal growth and survival to the regulation of synapses.
    Journal of Neurochemistry 06/2006; 97(3):834-45. DOI:10.1111/j.1471-4159.2006.03789.x · 4.28 Impact Factor
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