title: In vitro aggregation behavior of a non-amyloidogenic λ light chain dimer deriving from U266 multiple myeloma cells.
abstract: Excessive production of monoclonal light chains due to multiple myeloma can induce aggregation-related disorders, such as light chain amyloidosis (AL) and light chain deposition diseases (LCDD). In this work, we produce a non-amyloidogenic IgE λ light chain dimer from human mammalian cells U266, which originated from a patient suffering from multiple myeloma, and we investigate the effect of several physicochemical parameters on the in vitro stability of this protein. The dimer is stable in physiological conditions and aggregation is observed only when strong denaturating conditions are applied (acidic pH with salt at large concentration or heating at melting temperature T(m) at pH 7.4). The produced aggregates are spherical, amorphous oligomers. Despite the larger β-sheet content of such oligomers with respect to the native state, they do not bind Congo Red or ThT. The impossibility to obtain fibrils from the light chain dimer suggests that the occurrence of amyloidosis in patients requires the presence of the light chain fragment in the monomer form, while dimer can form only amorphous oligomers or amorphous deposits. No aggregation is observed after denaturant addition at pH 7.4 or at pH 2.0 with low salt concentration, indicating that not a generic unfolding but specific conformational changes are necessary to trigger aggregation. A specific anion effect in increasing the aggregation rate at pH 2.0 is observed according to the following order: SO(4)(-)≫Cl(-)>H(2)PO(4)(-), confirming the peculiar role of sulfate in promoting protein aggregation. It is found that, at least for the investigated case, the mechanism of the sulfate effect is related to protein secondary structure changes induced by anion binding.
authors.affiliation: Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich, Zurich, Switzerland.
authors.forename: Paolo
authors.initials: P
authors.lastname: Arosio
authors.forename: Marta
authors.initials: M
authors.lastname: Owczarz
authors.forename: Thomas
authors.initials: T
authors.lastname: Müller-Späth
authors.forename: Paola
authors.initials: P
authors.lastname: Rognoni
authors.forename: Marten
authors.initials: M
authors.lastname: Beeg
authors.forename: Hua
authors.initials: H
authors.lastname: Wu
authors.forename: Mario
authors.initials: M
authors.lastname: Salmona
authors.forename: Massimo
authors.initials: M
authors.lastname: Morbidelli
mesh_terms: D000682:Amyloid / Q000737:chemistry*; D000817:Anilino Naphthalenesulfonates / Q000378:metabolism; D045744:Cell Line, Tumor; D002942:Circular Dichroism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007147:Immunoglobulin Light Chains / Q000737:chemistry* / Q000378:metabolism*; D007700:Kinetics; D008027:Light; D008875:Middle Aged; D009101:Multiple Myeloma / Q000378:metabolism*; D011489:Protein Denaturation; D055503:Protein Multimerization; D055550:Protein Stability; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D012542:Scattering, Radiation; D012996:Solutions; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature
chemical_list: C515594:8-anilino-1-naphthalenesulfonic acid; D000682:Amyloid; D000817:Anilino Naphthalenesulfonates; D007147:Immunoglobulin Light Chains; D012996:Solutions