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.
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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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    • "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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