tailieunhanh - Báo cáo khoa học: Collagenous Alzheimer amyloid plaque component assembles amyloid fibrils into protease resistant aggregates

Recently, a novel plaque-associated protein, collagenous Alzheimer amy-loid plaque component (CLAC), was identified in brains from patients with Alzheimer’s disease. CLAC is derived from a type II transmembrane colla-gen precursor protein, termed CLAC-P (collagen XXV). The biological function and the contribution of CLAC to the pathogenesis of Alzheimer’s disease and plaque formation are unknown. | ềFEBS Journal Collagenous Alzheimer amyloid plaque component assembles amyloid fibrils into protease resistant aggregates Linda Sỏderberg1 Camilla Dahlqvist1 z Hiroyoshi Kakuyama1 Johan Thyberg2 Akira Ito3 Bengt Winblad1 Jan Naslund1 and Lars O. Tjernberg1 1 Karolinska Institute and Sumitomo Pharmaceuticals Alzheimer Center KASPAC Neurotec Novum Huddinge Sweden 2 Karolinska Institutet Department of Celland Molecular Biology Stockholm Sweden 3 Sumitomo Pharmaceuticals Research Center Osaka Japan Keywords Alzheimer s disease amyloid CLAC fibrils thioflavin T Correspondence C. Dahlqvist Karolinska Institutet Neurotec Novum KASPAC pl. 5 SE-141 57 Huddinge Sweden Fax 46 8585 836 10 Tel 46 8585 836 21 E-mail Note These authors contributed equally to this work. Received 28 January 2005 revised 25 February 2005 accepted 7 March 2005 doi Recently a novel plaque-associated protein collagenous Alzheimer amyloid plaque component CLAC was identified in brains from patients with Alzheimer s disease. CLAC is derived from a type II transmembrane collagen precursor protein termed CLAC-P collagen XXV . The biological function and the contribution of CLAC to the pathogenesis of Alzheimer s disease and plaque formation are unknown. In vitro studies indicate that CLAC binds to fibrillar but not to monomeric amyloid b-peptide Ab . Here we examined the effects of CLAC on Ab fibrils using assays based on turbidity thioflavin T binding sedimentation analysis and electron microscopy. The incubation of CLAC with preformed Ab fibrils led to increased turbidity indicating that larger aggregates were formed. In support of this contention more Ab was sedimented in the presence of CLAC as determined by gel electrophoresis. Moreover electron microscopy revealed an increased amount of Ab fibril bundles in samples incubated with CLAC. Importantly the frequently used thioflavin T-binding assay failed to reveal these effects of CLAC. .