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Protein Tyrosine Phosphatase 1B (PTP1B) is the prototypical protein tyrosine phosphatase and plays an essential role in the regulation of several kinase-driven signalling pathways. PTP1B displays a preference for bisphosphorylated substrates. Here we identify PTP1B as an inhibitor of IL-6 and show that, in vitro, it can dephosphorylate all four members of the JAK family. In order to gain a detailed understanding of the molecular mechanism of JAK dephosphorylation, we undertook a structural and biochemical analysis of the dephosphorylation reaction. We identified a product-trapping PTP1B mutant that allowed visualisation of the tyrosine and phosphate products of the reaction and a substrate-trapping mutant with a vastly decreased off-rate compared to those previously described. The latter mutant was used to determine the structure of bisphosphorylated JAK peptides bound to the enzyme active site. These structures revealed that the downstream phosphotyrosine preferentially engaged the active site, in contrast to the analogous region of IRK. Biochemical analysis confirmed this preference. In this binding mode, the previously identified second aryl binding site remains unoccupied and the non-substrate phosphotyrosine engages Arg47. Mutation of this arginine disrupts the preference for the downstream phosphotyrosine. This study reveals a previously unappreciated plasticity in how PTP1B interacts with different substrates. Structural and biochemical characterization of the phosphastase and immune checkpoint PTP1B reveals the molecular basis of PTBP1B/JAK interaction and plasticity of substrate recognition by PTP1B. [ABSTRACT FROM AUTHOR]

Purpose: Mapping the ischaemic penumbra in acute stroke is of considerable clinical interest. For this purpose, mapping tissue hypoxia with F-misonidazole (FMISO) PET is attractive, and is straightforward compared to O PET. Given the current emphasis on penumbra imaging using diffusion/perfusion MR or CT perfusion, investigating the relationships between FMISO uptake and abnormalities with these modalities is important. Methods: According to a prospective design, three patients (age 54-81 years; admission NIH stroke scale scores 16-22) with an anterior circulation stroke and extensive penumbra on CT- or MR-based perfusion imaging successfully completed FMISO PET, diffusion-weighted imaging and MR angiography 6-26 h after stroke onset, and follow-up FLAIR to map the final infarction. All had persistent proximal occlusion and a poor outcome despite thrombolysis. Significant FMISO trapping was defined voxel-wise relative to ten age-matched controls and mapped onto coregistered maps of the penumbra and irreversibly damaged ischaemic core. Results: FMISO trapping was present in all patients (volume range 18-119 ml) and overlapped mainly with the penumbra but also with the core in each patient. There was a significant ( p ≤ 0.001) correlation in the expected direction between FMISO uptake and perfusion, with a sharp FMISO uptake bend around the expected penumbra threshold. Conclusion: FMISO uptake had the expected overlap with the penumbra and relationship with local perfusion. However, consistent with recent animal data, our study suggests FMISO trapping may not be specific to the penumbra. If confirmed in larger samples, this preliminary finding would have potential implications for the clinical application of FMISO PET in acute ischaemic stroke. [ABSTRACT FROM AUTHOR]

LNK is a member of the SH2B family of adaptor proteins and is a non-redundant regulator of cytokine signalling. Cytokines are secreted intercellular messengers that bind to specific receptors on the surface of target cells to activate the Janus Kinase-Signal Transducer and Activator of Transcription (JAK-STAT) signalling pathway. Activation of the JAK-STAT pathway leads to proliferative and often inflammatory effects, and so the amplitude and duration of signalling are tightly controlled. LNK binds phosphotyrosine residues to signalling proteins downstream of cytokines and constrains JAK-STAT signalling. Mutations in LNK have been identified in a range of haematological and inflammatory diseases due to increased signalling following the loss of LNK function. Here, we review the regulation of JAK-STAT signalling via the adaptor protein LNK and discuss the role of LNK in haematological diseases. [ABSTRACT FROM AUTHOR]

Introduction: Stroke is the third most common cause of death in most developed countries. It is a worldwide problem; about 4.5 million people die from stroke each year. Stroke can occur at any age, but half of all strokes occur in people aged over 70 years. About 80% of all acute strokes are ischaemic, usually resulting from thrombotic or embolic occlusion of a cerebral artery. The remainder are caused either by intracerebral or subarachnoid haemorrhage., Methods and Outcomes: We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of specialised care in people with acute stroke? What are the effects of medical treatment in people with acute ischaemic stroke? What are the effects of decompressive hemicraniectomy in acute ischaemic stroke? What are the effects of surgical evacuation for intracerebral haematomas? We searched: Medline, Embase, The Cochrane Library, and other important databases up to August 2010 (Clinical Evidence reviews are updated periodically, please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA)., Results: We found 41 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions., Conclusions: In this systematic review we present information relating to the effectiveness and safety of the following interventions: acute reduction in blood pressure, aspirin, evacuation (early surgical evacuation, or conservative treatment), decompressive hemicraniectomy, neuroprotective agents (calcium channel blockers, citicoline, gamma-aminobutyric acid agonists, glycine antagonists, lubeluzole, magnesium, N-methyl-D-aspartate antagonists), specialised stroke care, systemic anticoagulation (heparinoids, specific thrombin inhibitors, low molecular weight heparin, oral anticoagulants, unfractionated heparin), and thrombolysis.

Introduction: Stroke is the third most common cause of death in most resource-rich countries. It is a worldwide problem; about 4.5 million people die from stroke each year. Stroke can occur at any age, but half of all strokes occur in people aged over 70 years. About 80% of all acute strokes are ischaemic, usually resulting from thrombotic or embolic occlusion of a cerebral artery. The remainder are caused either by intracerebral or subarachnoid haemorrhage., Methods and Outcomes: We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of specialised care in people with acute stroke? What are the effects of medical treatment in people with acute ischaemic stroke? What are the effects of surgical treatment for intracerebral haematomas? We searched: Medline, Embase, The Cochrane Library, and other important databases up to June 2007 (BMJ Clinical Evidence reviews are updated periodically, please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA)., Results: We found 42 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions., Conclusions: In this systematic review we present information relating to the effectiveness and safety of the following interventions: acute reduction in blood pressure, aspirin, evacuation (early surgical evacuation, or conservative treatment), neuroprotective agents (calcium channel antagonists, citicoline, gamma-aminobutyric acid agonists, glycine antagonists, lubeluzole, magnesium, N-methyl-D-aspartate antagonists, tirilazad), specialised stroke care, systemic anticoagulation (heparinoids, low or specific thrombin inhibitors, molecular weight heparin, oral anticoagulants, unfractionated heparin), and thrombolysis.