title: Lysine 58-cleaved beta2-microglobulin is not detectable by 2D electrophoresis in ex vivo amyloid fibrils of two patients affected by dialysis-related amyloidosis.
abstract: The lysine 58 cleaved and truncated variant of beta(2)-microglobulin (DeltaK58-beta2m) is conformationally unstable and present in the circulation of a large percentage of patients on chronic hemodialysis, suggesting that it could play a role in the beta2-microglobulin (beta2m) amyloid fibrillogenesis associated with dialysis-related amyloidosis (DRA). However, it has yet to be detected in the amyloid deposits of such patients. Here, we extracted amyloid fibrils, without denaturation or additional purification, from different amyloidotic tissues of two unrelated individuals suffering from DRA, and characterized them by high-sensitivity bidimensional gel electrophoresis (2D-PAGE), immunoblotting, MALDI time-of-flight mass spectrometry, and protein sequencing. To confirm whether or not this species could be identified by our proteomic approaches, we mapped its location in 2D-PAGE, in mixtures of pure DeltaK58-beta2m, and extracts of amyloid fibrils from patients, to a discrete region of the gel distinct from other isoforms of beta2m. Using this approach, the two known principal isoforms found in beta2m amyloid were identified, namely, the full-length protein and the truncated species lacking six N-terminal amino acid residues (DeltaN6-beta2m). In contrast, we found no evidence for the presence of DeltaK58-beta2m.
authors.affiliation: Department of Biochemistry, University of Pavia-Laboratori di Biotecnologie, IRCCS Policlinico San Matteo, via Taramelli 3b, 27100 Pavia, Italy.
authors.forename: Sofia
authors.initials: S
authors.lastname: Giorgetti
authors.forename: Monica
authors.initials: M
authors.lastname: Stoppini
authors.forename: Glenys A
authors.initials: GA
authors.lastname: Tennent
authors.forename: Annalisa
authors.initials: A
authors.lastname: Relini
authors.forename: Loredana
authors.initials: L
authors.lastname: Marchese
authors.forename: Sara
authors.initials: S
authors.lastname: Raimondi
authors.forename: Maria
authors.initials: M
authors.lastname: Monti
authors.forename: Sara
authors.initials: S
authors.lastname: Marini
authors.forename: Ole
authors.initials: O
authors.lastname: Østergaard
authors.forename: Niels H H
authors.initials: NH
authors.lastname: Heegaard
authors.forename: Piero
authors.initials: P
authors.lastname: Pucci
authors.forename: Gennaro
authors.initials: G
authors.lastname: Esposito
authors.forename: Giampaolo
authors.initials: G
authors.lastname: Merlini
authors.forename: Vittorio
authors.initials: V
authors.lastname: Bellotti
mesh_terms: D000682:Amyloid / Q000737:chemistry / Q000378:metabolism*; D000686:Amyloidosis / Q000378:metabolism*; D015180:Electrophoresis, Gel, Two-Dimensional; D006801:Humans; D015151:Immunoblotting; D008239:Lysine / Q000737:chemistry / Q000378:metabolism*; D018625:Microscopy, Atomic Force; D006435:Renal Dialysis; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D001613:beta 2-Microglobulin / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000682:Amyloid; D001613:beta 2-Microglobulin; D008239:Lysine