Molecular Basis of the Interaction of the Human Protein Tyrosine Phosphatase Non-receptor Type 4 (PTPN4) with the Mitogen-activated Protein Kinase p38γ

Abstract

The human protein tyrosine phosphatase non-receptor type 4 (PTPN4) prevents cell death induction in neuroblastoma and glioblastoma cell lines in a PDZ⅐PDZ binding motifs-dependent manner, but the cellular partners of PTPN4 involved in cell protection are unknown. Here, we described the mitogen-activated protein kinase p38␥ as a cellular partner of PTPN4. The main contribution to the p38␥⅐PTPN4 complex formation is the tight interaction between the C terminus of p38␥ and the PDZ domain of PTPN4. We solved the crystal structure of the PDZ domain of PTPN4 bound to the p38␥ C terminus. We identified the molecular basis of recognition of the C-terminal sequence of p38␥ that displays the highest affinity among all endogenous partners of PTPN4. We showed that the p38␥ C terminus is also an efficient inducer of cell death after its intracellular delivery. In addition to recruiting the kinase, the binding of the C-terminal sequence of p38␥ to PTPN4 abolishes the catalytic autoinhibition of PTPN4 and thus activates the phosphatase, which can efficiently dephosphorylate the activation loop of p38␥. We presume that the p38␥⅐PTPN4 interaction promotes cellular signaling, preventing cell death induction. PTPN45 is a non-receptor-tyrosine phosphatase (PTP) with functions in T cell signaling, learning, spatial memory, and cerebellar synaptic plasticity (1-3). Its overexpression reduces cell proliferation in COS-7 cells and suppresses CrkI-mediated cell growth and mobility in HEK293T cells (4, 5). PTPN4 also regulates neuronal cell homeostasis by protecting neurons against apoptosis (5, 6). PTPN4 is a large modular protein containing three domains, an N-terminal FERM domain, a PDZ domain, and a C-terminal catalytic tyrosine phosphatase domain (7). PDZ domains are protein-protein interaction domains, which play a central role in cell signaling by favoring spatial contacts between enzymes and their substrates or, more generally, by assembling and/or regulating protein networks (8, 9). Thus, disrupting the interactions between PDZ domains and PDZ binding motifs (PBM) can trigger profound alterations in cell signaling pathways (10 -12). Such disruptions of PDZ⅐PBM complexes are used by viruses to hijack cell signaling pathways to their own advantage and can also be obtained by treating cells with an excess of cell penetrating peptide encoding a PBM (13). Indeed, we showed that rabies virus (RABV) peptides encoding a PBM can target the PDZ domain of PTPN4 (PTPN4-PDZ) and antagonize the function of PTPN4, leading to cell death (6). We optimized such pro-apoptotic peptides and designed the Cyto8-RETEV sequence, that is so far the most affine ligand of PTPN4-PDZ and the best inducer of cell death (15).Four endogenous partners of PTPN4 have been reported: the glutamate receptor ␦2 and ⑀ subunits, the T-cell receptor subunit, the CrkI oncoprotein, and the TRIF (TIR domain-containing adaptor-inducing interferon-B)-related adaptor molecule TRAM (3,5,16,17). Nevertheless, the natural ligands of PTPN4 involved in the regulation of cell homeos...

miR-181c-5p Exacerbates Hypoxia/Reoxygenation-Induced Cardiomyocyte Apoptosis via Targeting PTPN4

“…Studies have demonstrated that PTPN4 regulates neuronal cell homeostasis by protecting neurons against apoptosis [30]. In neuroblastoma and glioblastoma cell lines, mitogen-activated protein kinase p38 γ served as a cellular partner of PTPN4 [35]. This interaction is mediated by the binding of C terminus of p38 γ to the PDZ domain of PTPN4, which antagonizes the catalytic autoinhibition of PTPN4, leading to cell apoptosis [24, 35].…”

“…In neuroblastoma and glioblastoma cell lines, mitogen-activated protein kinase p38 γ served as a cellular partner of PTPN4 [35]. This interaction is mediated by the binding of C terminus of p38 γ to the PDZ domain of PTPN4, which antagonizes the catalytic autoinhibition of PTPN4, leading to cell apoptosis [24, 35]. Indeed, silencing of PTPN4 or p38 γ gene leads to massive cell death in human osteosarcoma cells [36].…”

Proteinaceous Regulators and Inhibitors of Protein Tyrosine Phosphatases

“…PTPN4 normally protects cells from apoptosis but addition of ligands for the PTPN4 PDZ domain resulted in a marked induction of cell death [ 66 ]. Subsequent studies revealed that the PTPN4 PDZ domain in fact auto-inhibits the enzyme’s catalytic activity, and this is abrogated upon binding of a PDZ domain ligand [ 67 , 68 ]. The segment linking the PDZ and PTP domain in PTPN4 is also contributing to this regulatory principle [ 69 , 70 ].…”

“…Recently, a bidentate molecule (113B7) that prevents the syntenin PDZ domain from binding targets like mutant EGFR (EGFRvIII) was shown to increase radiosensitivity and decrease growth of glioma tumors in vivo [ 154 ]. Then, there is the example of PTPN4, of which the enzyme activity is autoinhibited by its PDZ domain [ 67 , 68 , 69 , 70 ]. Upon ligand binding, the PDZ-mediated inhibition is released and PTPN4 no longer protects glioblastoma cells from apoptosis [ 66 ].…”

Regulation of the Human Phosphatase PTPN4 by the inter-domain linker connecting the PDZ and the phosphatase domains

“…The PBM of p38γ has the highest affinity of all PBM from endogenous partners of PTPN4 and has a similar affinity to the optimized pro-death 13-amino acids peptide Cyto8-RETEV. Both peptides are efficient inducers of cell death after their intracellular delivery 11 , 12 . Furthermore, we showed that the PDZ domain of PTPN4 inhibits the phosphatase activity, while a PBM bound to the PDZ domain abrogates the auto-inhibition of the catalytic activity of PTPN4 11 , 13 .…”