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- Björkholm, Patrik, et al.
(författare)
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Identification of novel sphingolipid-binding motifs in mammalian membrane proteins
- 2014
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Ingår i: Biochimica et Biophysica Acta - Biomembranes. - : Elsevier BV. - 0005-2736 .- 1879-2642. ; 1838:8, s. 2066-2070
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Tidskriftsartikel (refereegranskat)abstract
- Specific interactions between transmembrane proteins and sphingolipids is a poorly understood phenomenon, and only a couple of instances have been identified. The best characterized example is the sphingolipid-binding motif VXXTLXXIY found in the transmembrane helix of the vesicular transport protein p24. Here, we have used a simple motif-probability algorithm (MOPRO) to identify proteins that contain putative sphingolipid-binding motifs in a dataset comprising proteomes from mammalian organisms. From these motif-containing candidate proteins, four with different numbers of transmembrane helices were selected for experimental study: i) major histocompatibility complex II Q alpha chain subtype (DQA1), ii) GPI-attachment protein 1 (GAA1), iii) tetraspanin-7 TSN7, and iv), metabotropic glutamate receptor 2 (GRM2). These candidates were subjected to photo-affinity labeling using radiolabeled sphingolipids, confirming all four candidate proteins as sphingolipid-binding proteins. The sphingolipid-binding motifs are enriched in the 7TM family of G-protein coupled receptors, predominantly in transmembrane helix 6. The ability of the motif-containing candidate proteins to bind sphingolipids with high specificity opens new perspectives on their respective regulation and function.
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- Contreras, F.-Xabier, et al.
(författare)
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Molecular recognition of a single sphingolipid species by a protein's transmembrane domain
- 2012
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 481:7382, s. 525-529
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Tidskriftsartikel (refereegranskat)abstract
- Functioning and processing of membrane proteins critically depend on the way their transmembrane segments are embedded in the membrane. Sphingolipids are structural components of membranes and can also act as intracellular second messengers. Not much is known of sphingolipids binding to transmembrane domains (TMDs) of proteins within the hydrophobic bilayer, and how this could affect protein function. Here we show a direct and highly specific interaction of exclusively one sphingomyelin species, SM 18, with the TMD of the COPI machinery protein p24 (ref. 2). Strikingly, the interaction depends on both the headgroup and the backbone of the sphingolipid, and on a signature sequence (VXXTLXXIY) within the TMD. Molecular dynamics simulations show a close interaction of SM 18 with the TMD. We suggest a role of SM 18 in regulating the equilibrium between an inactive monomeric and an active oligomeric state of the p24 protein, which in turn regulates COPI-dependent transport. Bioinformatic analyses predict that the signature sequence represents a conserved sphingolipid-binding cavity in a variety of mammalian membrane proteins. Thus, in addition to a function as second messengers, sphingolipids can act as cofactors to regulate the function of transmembrane proteins. Our discovery of an unprecedented specificity of interaction of a TMD with an individual sphingolipid species adds to our understanding of why biological membranes are assembled from such a large variety of different lipids.
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- Ejerblad, Elisabeth, et al.
(författare)
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Diagnosis according to World Health Organization determines the long-term prognosis in patients with myeloproliferative neoplasms treated with anagrelide : Results of a prospective long-term follow-up
- 2013
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Ingår i: Hematology. - 1024-5332 .- 1607-8454. ; 18:1, s. 8-13
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES:During long term follow-up of a cohort of patients with essential thrombocythemia (ET) and polycythemia vera (PV) a higher than expected incidence of myelofibrosis (MF) was noted. In order to test if the explanation could be found in the diagnostic criteria a re-evaluation of diagnosis using the 2008 WHO diagnostic criteria for ET and MF was performed.METHODS: This prospective study of 60 patients with ET and PV was set up in 1998 to evaluate the long-term efficacy and tolerability of anagrelide treatment. Bone marrow trephine biopsies were requested from study start, after 2 and 7 years of follow-up. A blinded re-evaluation of the bone marrow trephines was performed. The 2008 WHO bone marrow criteria were used for diagnosis and fibrosis grading.RESULTS: Of 40 patients with an initial diagnosis of ET, 21 were confirmed as 'true ET' whereas 17 were reclassified as primary myelofibrosis (PMF) (12 PMF-0, 3 PMF-1, 2 PMF-2) and 2 as myeloproliferative neoplasms of uncertain origin. After 7 years of follow-up, 19 of 21 patients with 'true ET' were alive, none had transformed to MF, leukemia, or myelodysplastic syndrome. In contrast, 4/17 patients reclassified as PMF had died, two patients transformed to myelodysplastic syndrome and 7 patients progressed to overt MF.DISCUSSION:We conclude that a blinded re-evaluation of bone marrow trephines from study start and after 7 years of follow-up using 2008 World Health Organization criteria was able to differentiate between true ET and PMF with a marked difference in follow-up outcome.
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- Kristinsson, Sigurdur Y, et al.
(författare)
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Arterial and venous thrombosis in monoclonal gammopathy of undetermined significance and multiple myeloma : a population-based study
- 2010
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Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 115:24, s. 4991-4998
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Tidskriftsartikel (refereegranskat)abstract
- Patients with multiple myeloma (MM) have an increased risk of venous thrombosis. Interestingly, excess risk of venous thromboembolism has been observed among patients with monoclonal gammopathy of undetermined significance (MGUS). Using population-based data from Sweden, we assessed the risks of venous and arterial thrombosis in 18,627 MM and 5326 MGUS patients diagnosed from 1958 to 2006, compared with 70,991 and 20,161 matched controls, respectively. At 1, 5, and 10 years after MM diagnosis, there was an increased risk of venous thrombosis: hazard ratios (95% confidence intervals) were 7.5 (6.4-8.9), 4.6 (4.1-5.1), and 4.1 (3.8-4.5), respectively. The corresponding results for arterial thrombosis were 1.9 (1.8-2.1), 1.5 (1.4-1.6), and 1.5 (1.4-1.5). At 1, 5, and 10 years after MGUS diagnosis, hazard ratios were 3.4 (2.5-4.6), 2.1 (1.7-2.5), and 2.1 (1.8-2.4) for venous thrombosis. The corresponding risks for arterial thrombosis were 1.7 (1.5-1.9), 1.3 (1.2-1.4), and 1.3 (1.3-1.4). IgG/IgA (but not IgM) MGUS patients had increased risks for venous and arterial thrombosis. Risks for thrombosis did not vary by M-protein concentration (> 10.0 g/L or < 10.0 g/L) at diagnosis. MGUS patients with (vs without) thrombosis had no excess risk of MM or Waldenström macroglobulinemia. Our findings are of relevance for future studies and for improvement of thrombosis prophylaxis strategies.
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| 7. |
- Kristinsson, Sigurdur Y, et al.
(författare)
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Monoclonal gammopathy of undetermined significance and risk of skeletal fractures : a population-based study
- 2010
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Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 116:15, s. 2651-2655
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Tidskriftsartikel (refereegranskat)abstract
- Patients with multiple myeloma (MM) have an increased risk of fractures. On the basis of small numbers, patients with monoclonal gammopathy of undetermined significance (MGUS) have been reported to have an increased fracture risk. Using population-based data from Sweden, we assessed the risks of fractures in 5326 MGUS patients diagnosed from 1958 to 2006, compared with 20 161 matched controls. MGUS patients had an increased risk of any fracture at 5 (hazard ratio [HR] = 1.74; 95% confidence interval [CI], 1.58-1.92) and 10 (HR = 1.61; 95% CI, 1.49-1.74) years. The risk was significantly higher for axial (skull, vertebral/pelvis, and sternum/costae) compared with distal (arm and leg) fractures (P < .001). On the basis of 10 years of follow-up, there was an increased risk of vertebral/pelvic (HR = 2.37; 95% CI, 2.02-2.78), sternal/costae (HR = 1.93; 95% CI, 1.5-2.48), arm (HR = 1.23; 95% CI, 1.06-1.43), leg (HR = 1.40; 95% CI, 1.26-1.56), and other/multiple fractures (HR = 4.25; 95% CI, 3.29-5.51). Risks for fractures did not differ by isotype or M protein concentration at diagnosis. MGUS patients with (versus without) fractures had no excess risk of MM or Waldenström macroglobulinemia. Our results suggest that bone alterations are present in early myelomagenesis. Our findings may have implications for the development of better prophylaxis for bone disease in MGUS, and they provide novel clues on pathogenesis of MM bone disease.
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