Browsing by Author "Hanna, Michael"

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    Dynamic Glycosylation Governs the Vertebrate COPII Protein Trafficking Pathway.
    (Biochemistry, 2018-01) Cox, Nathan J; Unlu, Gokhan; Bisnett, Brittany J; Meister, Thomas R; Condon, Brett M; Luo, Peter M; Smith, Timothy J; Hanna, Michael; Chhetri, Abhishek; Soderblom, Erik J; Audhya, Anjon; Knapik, Ela W; Boyce, Michael
    The COPII coat complex, which mediates secretory cargo trafficking from the endoplasmic reticulum, is a key control point for subcellular protein targeting. Because misdirected proteins cannot function, protein sorting by COPII is critical for establishing and maintaining normal cell and tissue homeostasis. Indeed, mutations in COPII genes cause a range of human pathologies, including cranio-lenticulo-sutural dysplasia (CLSD), which is characterized by collagen trafficking defects, craniofacial abnormalities, and skeletal dysmorphology. Detailed knowledge of the COPII pathway is required to understand its role in normal cell physiology and to devise new treatments for disorders in which it is disrupted. However, little is known about how vertebrates dynamically regulate COPII activity in response to developmental, metabolic, or pathological cues. Several COPII proteins are modified by O-linked β-N-acetylglucosamine (O-GlcNAc), a dynamic form of intracellular protein glycosylation, but the biochemical and functional effects of these modifications remain unclear. Here, we use a combination of chemical, biochemical, cellular, and genetic approaches to demonstrate that site-specific O-GlcNAcylation of COPII proteins mediates their protein-protein interactions and modulates cargo secretion. In particular, we show that individual O-GlcNAcylation sites of SEC23A, an essential COPII component, are required for its function in human cells and vertebrate development, because mutation of these sites impairs SEC23A-dependent in vivo collagen trafficking and skeletogenesis in a zebrafish model of CLSD. Our results indicate that O-GlcNAc is a conserved and critical regulatory modification in the vertebrate COPII-dependent trafficking pathway.
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    Effect of apixaban compared with warfarin on coagulation markers in atrial fibrillation.
    (Heart (British Cardiac Society), 2019-02) Christersson, Christina; Wallentin, Lars; Andersson, Ulrika; Alexander, John H; Alings, Marco; De Caterina, Raffaele; Gersh, Bernard J; Granger, Christopher B; Halvorsen, Sigrun; Hanna, Michael; Huber, Kurt; Hylek, Elaine M; Lopes, Renato D; Oh, Byung-Hee; Siegbahn, Agneta

    Objectives

    Compare the effect of apixaban and warfarin on coagulation and primary haemostasis biomarkers in atrial fibrillation (AF).

    Methods

    The biomarker substudy from the Apixaban for Reduction in Stroke and Other Thromboembolic Events in Atrial Fibrillation trial included 4850 patients with AF randomised to treatment with apixaban or warfarin. Sixty per cent of patients used vitamin K antagonist (VKA) within 7 days before randomisation. Prothrombin fragment 1+2 (F1+2), D-dimer, soluble CD40 ligand (sCD40L) and von Willebrand factor (vWF) antigen were analysed at randomisation and after 2 months of study treatment.

    Results

    In patients not on VKA treatment at randomisation, F1+2 and D-dimer levels were decreased by 25% and 23%, respectively, with apixaban, and by 59% and 38%, respectively, with warfarin (p<0.0001 for treatment differences for both). In patients on VKA at randomisation, F1+2 and D-dimer levels increased by 41% and 10%, respectively, with apixaban and decreased by 37% and 11%, respectively, with warfarin (p<0.0001 for treatment differences for both). sCD40L levels were slightly increased at 2 months, regardless of VKA or randomised treatment. Apixaban and warfarin also both reduced vWF antigen regardless of VKA treatment. The efficacy (stroke) and safety (bleeding) of apixaban compared with warfarin was similar irrespectively of biomarker levels at 2 months.

    Conclusions

    Treatment with apixaban compared with warfarin for stroke prevention in patients with AF was associated with less reduction in thrombin generation and fibrin turnover. This effect of apixaban could contribute to the clinical results where apixaban was superior to warfarin both in stroke prevention and in reducing bleeding risk.

    Trial registration number

    NCT00412984.
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    ItemOpen Access
    The ABC (age, biomarkers, clinical history) stroke risk score: a biomarker-based risk score for predicting stroke in atrial fibrillation.
    (European heart journal, 2016-05) Hijazi, Ziad; Lindbäck, Johan; Alexander, John H; Hanna, Michael; Held, Claes; Hylek, Elaine M; Lopes, Renato D; Oldgren, Jonas; Siegbahn, Agneta; Stewart, Ralph AH; White, Harvey D; Granger, Christopher B; Wallentin, Lars; ARISTOTLE and STABILITY Investigators

    Aims

    Atrial fibrillation (AF) is associated with an increased risk of stroke, which is currently estimated by clinical characteristics. The cardiac biomarkers N-terminal fragment B-type natriuretic peptide (NT-proBNP) and cardiac troponin high-sensitivity (cTn-hs) are independently associated with risk of stroke in AF. Our objective was to develop and validate a new biomarker-based risk score to improve prognostication of stroke in patients with AF.

    Methods and results

    A new risk score was developed and internally validated in 14 701 patients with AF and biomarkers levels determined at baseline, median follow-up of 1.9 years. Biomarkers and clinical variables significantly contributing to predicting stroke or systemic embolism were assessed by Cox-regression and each variable obtained a weight proportional to the model coefficients. External validation was performed in 1400 patients with AF, median follow-up of 3.4 years. The most important predictors were prior stroke/transient ischaemic attack, NT-proBNP, cTn-hs, and age, which were included in the ABC (Age, Biomarkers, Clinical history) stroke risk score. The ABC-stroke score was well calibrated and yielded higher c-indices than the widely used CHA2DS2-VASc score in both the derivation cohort (0.68 vs. 0.62, P < 0.001) and the external validation cohort (0.66 vs. 0.58, P < 0.001). Moreover, the ABC-stroke score consistently provided higher c-indices in several important subgroups.

    Conclusion

    A novel biomarker-based risk score for predicting stroke in AF was successfully developed and internally validated in a large cohort of patients with AF and further externally validated in an independent AF cohort. The ABC-stroke score performed better than the presently used clinically based risk score and may provide improved decision support in AF.

    Clinicaltrials gov identifier

    NCT00412984, NCT00799903.