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Nikolajev L.,Pharmacology and Therapeutics and | Laporte S.A.,McGill University
The Journal of biological chemistry | Year: 2014

β-Arrestins are signaling adaptors that bind to agonist-occupied G protein-coupled receptors (GPCRs) and target them for endocytosis; however, the mechanisms regulating receptor/β-arrestin complexes and trafficking in endosomes, remain ill defined. Here we show, in live cells, differential dynamic regulation of endosomal bradykinin B2 receptor (B2R) complexes with either β-arrestin-1 or -2. We find a novel role for MAPK in the B2R/β-arrestin-2 complex formation, receptor trafficking and signaling mediated by an ERK1/2 regulatory motif in the hinge domain of the rat β-arrestin-2 (PET(178)P), but not rat β-arrestin-1 (PER(177)P). While the ERK1/2 regulatory motif is conserved between rat and mouse β-arrestin-2, it is surprisingly not conserved in human β-arrestin-2 (PEK(178)P). However, mutation of lysine 178 to threonine is sufficient to confer MAPK sensitivity to the human β-arrestin-2. Furthermore, substitution for a phosphomimetic residue in both the rat and the human β-arrestin-2 (T/K178D) significantly stabilizes B2R/β-arrestin complexes in endosomes, delays receptor recycling to the plasma membrane and maintains intracellular MAPK signaling. Similarly, the endosomal trafficking of β2-adrenergic, angiotensin II type 1 and vasopressin V2 receptors was altered by the β-arrestin-2 T178D mutant. Our findings unveil a novel subtype specific mode of MAPK-dependent regulation of β-arrestins in intracellular trafficking and signaling of GPCRs, and suggest differential endosomal receptor/β-arrestin-2 signaling roles among species. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.


PubMed | McGill University and Pharmacology and Therapeutics and.
Type: Journal Article | Journal: The Journal of biological chemistry | Year: 2014

-Arrestins are signaling adaptors that bind to agonist-occupied G protein-coupled receptors (GPCRs) and target them for endocytosis; however, the mechanisms regulating receptor/-arrestin complexes and trafficking in endosomes, remain ill defined. Here we show, in live cells, differential dynamic regulation of endosomal bradykinin B2 receptor (B2R) complexes with either -arrestin-1 or -2. We find a novel role for MAPK in the B2R/-arrestin-2 complex formation, receptor trafficking and signaling mediated by an ERK1/2 regulatory motif in the hinge domain of the rat -arrestin-2 (PET(178)P), but not rat -arrestin-1 (PER(177)P). While the ERK1/2 regulatory motif is conserved between rat and mouse -arrestin-2, it is surprisingly not conserved in human -arrestin-2 (PEK(178)P). However, mutation of lysine 178 to threonine is sufficient to confer MAPK sensitivity to the human -arrestin-2. Furthermore, substitution for a phosphomimetic residue in both the rat and the human -arrestin-2 (T/K178D) significantly stabilizes B2R/-arrestin complexes in endosomes, delays receptor recycling to the plasma membrane and maintains intracellular MAPK signaling. Similarly, the endosomal trafficking of 2-adrenergic, angiotensin II type 1 and vasopressin V2 receptors was altered by the -arrestin-2 T178D mutant. Our findings unveil a novel subtype specific mode of MAPK-dependent regulation of -arrestins in intracellular trafficking and signaling of GPCRs, and suggest differential endosomal receptor/-arrestin-2 signaling roles among species.


PubMed | Pharmacology and Therapeutics and and Roswell Park Cancer Institute
Type: Journal Article | Journal: The Journal of biological chemistry | Year: 2014

Tyrosine kinase inhibitors such as imatinib can effectively target the BCR-ABL oncoprotein in a majority of patients with chronic myeloid leukemia (CML). Unfortunately, some patients are resistant primarily to imatinib and others develop drug resistance, prompting interest in the discovery of new drug targets. Although much of this resistance can be explained by the presence of mutations within the tyrosine kinase domain of BCR-ABL, such mutations are not universally identified. Interferon regulatory factor-8 (IRF-8) is a transcription factor that is essential for myelopoiesis. Depressed IRF-8 levels are observed in a majority of CML patients and Irf-8(-/-) mice exhibit a CML-like disease. The underlying mechanisms of IRF-8 loss in CML are unknown. We hypothesized that BCR-ABL suppresses transcription of IRF-8 through STAT5, a proximal BCR-ABL target. Treatment of primary cells from newly diagnosed CML patients in chronic phase as well as BCR-ABL(+) cell lines with imatinib increased IRF-8 transcription. Furthermore, IRF-8 expression in cell line models was necessary for imatinib-induced antitumor responses. We have demonstrated that IRF-8 is a direct target of STAT5 and that silencing of STAT5 induced IRF-8 expression. Conversely, activating STAT5 suppressed IRF-8 transcription. Finally, we showed that STAT5 blockade using a recently discovered antagonist increased IRF-8 expression in patient samples. These data reveal a previously unrecognized BCR-ABL-STAT5-IRF-8 network, which widens the repertoire of potentially new anti-CML targets.


PubMed | Hematology and Oncology., Nicolaus Copernicus University and Pharmacology and Therapeutics and.
Type: Journal Article | Journal: Experimental and therapeutic medicine | Year: 2014

The pathogenesis of viral bronchiolitis is poorly understood. The aim of this study was to analyze interleukin (IL)-15, IL-18 and interferon (IFN)- concentrations and the activity of NK cells and CD4

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