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Thema: 3 x 3 (3 Slides in 3 Minutes) Abstract Präsentationen - I 49.15 ESPECIALLY B-LYMPHOCYTES FROM PATIENTS WITH SJÖGREN´S SYNDROME SHOW A DYSREGULATION IN THE GENE EXPRESSION OF COMPONENTS OF THE PROTEASOME SYSTEM Martinez Gamboa L.1, Lesemann K.1, Scheffler S.1, Kuckelkorn U.2, Egerer K.3, Dörner T.4, Burmester G.4, Faustman D.5, Feist E.4 (1) Charite Universitätsmedizin Berlin / Rheumatologie u. Klinische Immunologie, Forschungslabor AG Dr. Eugen Feist, Berlin, (2) Charite Universitätsmedizin Berlin, Institut für Biochemie, Berlin, (3) Charite Universitätsmedizin Berlin / Rheumatologie u. Klinische Immunologie, Rheumatologisches Labor, Berlin, (4) Charité Universitätsmedizin Berlin - Campus Mitte, Med. Klinik III, Schwerpunkt Rheumatologie und Klin. Immunologie, Berlin, (5) Harvard Medical School/Massachusetts General Hospital, Immunobiology Laboratory, Charlestown Zielsetzung Some components of the proteasome system has been shown to be dysregulated in total peripheral blood mononuclear cells (PBMCs) from patients with primary Sjögren's syndrome (pSS), but it is not yet clear which specific blood cell subsets are involved. Due to the central role of the proteasome for the immune response through antigen processing/presentation and in apoptosis, elucidation of the involved cell subset(s) in relation to the proteasome alteration could be important for understanding disease pathogenesis. Therefore, we compared gene expression of constitutive and inducible catalytic subunits of the 20S proteasome in isolated blood immune competent cellular subsets. Additional investigations in vitro included analysis of proteasome activity and of apoptosis after exposure to the proteasome inhibitor Bortezomib. Methodik CD4+ and CD8+ T-lymphocytes, CD19+ B-lymphocytes, CD14+ monocytes and total dendritic cells were sorted from peripheral blood samples of patients and controls. Transcript levels of proteasome system components, including the constitutive catalytic subunits Delta, Z and MB1, and their corresponding inducible ones LMP2, MECL and LMP7, were relative quantified by real time PCR. After proteasome inhibition in vitro, proteasome activity was measured based on hydrolysis of the fluorogenic substrate Suc-LLVY-AMC, and apoptosis was assessed based on the activity of caspase-3 and -7. For statistic analysis, Mann-Whitney test and P-values <0.005 were applied. Ergebnisse Especially B-lymphocytes from pSS showed a marked activation of the proteasome system, with significant up-regulation of all constitutive and inducible subunits. Apart from B-cells, transcript levels of LMP7 were also highly increased in CD8+ T-cells and in monocytes from patients, reflecting the systemic autoimmune process. Preliminary data from further in vitro studies confirm the dysregulation of the proteasome in B-cells: after exposition to Bortezomib, proteasome activity is reduced in a similar degree in PBMCs and Tlymphocytes, but to a lesser extent in B-lymphocytes, and apoptosis is stronger induced in total PBMCs and T-cells than in B-cells. Schlussfolgerung Our results show that the proteasome system is strongly activated specially in B-lymphocytes from patients with Sjögren's syndrome. According to our preliminary data, B-cells seem to be more resistant to the effects of proteasome inhibition with Bortezomib than other cell subsets. These results should encourage further investigations in the field of proteasome inhibition in patients with Sjögren's syndrome.