title: Aberrant processing forms of lung surfactant proteins SP-B and SP-C revealed by high-resolution mass spectrometry.
abstract: The mutation (g.1286T>C) of the pulmonary surfactant-associated protein C gene (SFTPC) leads to the I73T substitution in the precursor protein (pro-SP-C) and results in interstitial lung disease with the histological pattern of non-specific interstitial pneumonia and pulmonary alveolar proteinosis. Central for the disease is the abnormal processing of the SP-C pro-protein to mature SP-C; however little is known about the nature of intermediates and processing products. We report here the application of high resolution Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry to the characterization of processing intermediates of hydrophobic pulmonary surfactant proteins SP-B and SP-C in intra- alveolar surfactant material of a patient with I73T mutation. SP-C and SP-B processing forms were separated from broncho-alveolar lavage fluid using chloroform/methanol extraction and sodium dodecyl sulfate poly acrylamide gel electrophoreis, detected by Western blot and identified by electrospray- and matrix-assisted laser desorption/ionization-FT-ICR mass spectrometry. The mass spectrometric and immuno-analytical results show the intra-alveolar accumulation of an aberrant C-terminal SP-C processing products in which the mature SP-C protein part is missing and aberrant processing intermediates of SP-B.
authors.affiliation: Laboratory of Analytical Chemistry and Biopolymer Structure Analysis, Department of Chemistry, University of Konstanz, Box M 73178457 Konstanz, Germany.
authors.forename: Dmitry
authors.initials: D
authors.lastname: Galetskiy
authors.forename: Markus
authors.initials: M
authors.lastname: Woischnik
authors.forename: Jan
authors.initials: J
authors.lastname: Ripper
authors.forename: Matthias
authors.initials: M
authors.lastname: Griese
authors.forename: Michael
authors.initials: M
authors.lastname: Przybylski
mesh_terms: D000595:Amino Acid Sequence; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D005583:Fourier Analysis; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods*; D008969:Molecular Sequence Data; D037701:Pulmonary Surfactant-Associated Protein B / Q000737:chemistry* / Q000235:genetics; D037721:Pulmonary Surfactant-Associated Protein C / Q000737:chemistry* / Q000235:genetics; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D037701:Pulmonary Surfactant-Associated Protein B; D037721:Pulmonary Surfactant-Associated Protein C; C489679:SFTPC protein, human