title: Global assessment of protein turnover in recombinant antibody producing myeloma cells.
abstract: The global turnover rates of cellular proteins and the secretion rate of a recombinant immunoglobulin G (IgG) in a myeloma cell line, NS0, were determined using SILAC proteomic analysis. After complete labeling of cellular proteins with (13)C(6), (15)N(4)-arginine, cells were transferred to unlabeled medium and the decay of the labeled arginine in proteins was monitored during exponential cell growth. After PAGE separation and mass-spectrometric identification of proteins, those detected with high confidence over at least three time points were used for the determination of turnover rates. Among the 224 proteins quantified with a protein half-life, about 15% have a degradation rate constant lower than one-tenth of specific growth rate. For most proteins, the turnover rate is insignificant in its overall dynamics. Only 6.3% of proteins have a half-life shorter than the cell doubling time. For IgG secretion, both heavy and light chain molecules follow the same kinetic behavior with a half-life estimated to be 2h. The label decay curve appears to show a second region with very slow kinetics, raising the possibility of two populations of IgG molecules with different secretion characteristics.
authors.affiliation: Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455-0132, USA.
authors.forename: Joon Chong
authors.initials: JC
authors.lastname: Yee
authors.forename: Nitya M
authors.initials: NM
authors.lastname: Jacob
authors.forename: Karthik P
authors.initials: KP
authors.lastname: Jayapal
authors.forename: Yee-Jiun
authors.initials: YJ
authors.lastname: Kok
authors.forename: Robin
authors.initials: R
authors.lastname: Philp
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Griffin
authors.forename: Wei-Shou
authors.initials: WS
authors.lastname: Hu
mesh_terms: D000911:Antibodies, Monoclonal / Q000096:biosynthesis*; D002460:Cell Line; D006801:Humans; D007074:Immunoglobulin G / Q000235:genetics / Q000378:metabolism*; D007553:Isotope Labeling / Q000379:methods; D013058:Mass Spectrometry / Q000379:methods*; D008657:Metabolic Clearance Rate; D009101:Multiple Myeloma / Q000378:metabolism*; D009194:Myeloma Proteins / Q000378:metabolism*; D010449:Peptide Mapping / Q000379:methods*; D020543:Proteome / Q000378:metabolism; D011994:Recombinant Proteins / Q000096:biosynthesis*
chemical_list: D000911:Antibodies, Monoclonal; D007074:Immunoglobulin G; D009194:Myeloma Proteins; D020543:Proteome; D011994:Recombinant Proteins