Binding of nascent collagen by amyloidogenic light chains and amyloid fibrillogenesis in monolayers of human fibrocytes

Abstract

Light (L) chain dimers expressed by multiple myeloma cells and collected as Bence‐Jones proteins from the urine of human subjects were tested for their ability to form deposits in fibroblast monolayer cell cultures. Bence‐Jones proteins from subjects with primary amyloidosis associated with L chains were shown to form fibrillar deposits by the in vitro assay introduced in this report. Filaments interspersed with nascent collagen could be detected after only 48 h. Deposition of L chains continued over a period of 72 h culminating in the appearance of dense fibrils with widths of 80–100 Å and a variety of lengths. Formation of amyloid‐like fibrils was accompanied by interference with the maturation of the collagen produced by the fibroblast cells. Fibrils composed of the Mcg λ‐type L chain were deposited between collagen fibers, thus expanding them laterally and leading to their partial disintegration. Mature collagen was completely missing from fibroblast monolayers exposed to the Sea λ chain and the Jen κ chain. Collagen with the characteristic striped pattern matured normally in control samples, such as those not dosed with amyloid precursors or those treated with a non‐amyloidogenic Bence‐Jones protein (e.g., the Hud λ chain dimer). By immunochemical techniques using fluorescein‐ and gold‐labeled anti‐L chain antibodies, amyloidogenic L chains were shown to decorate the strands of nascent collagen. This observation suggests that amyloidogenic L chains are concentrated in the extracellular matrix by monovalent antigen–antibody type reactions. The capacity of the Mcg L chain dimer to bind collagen‐derived sequences was tested by soaking crystals with a collagenase substrate, PZ‐Pro‐Leu‐Gly‐Pro‐D‐Arg. Difference Fourier analysis at 2.7 Å resolution indicated that the PZ‐peptide is a site‐filling ligand. It could not be removed from the active site by perfusion of the crystal with ammonium sulfate crystallizing media. Similar experiments with the collagen‐derived peptide (Pro‐Pro‐Gly)5 showed substantial hysteresis effects extending from one end of the Mcg dimer to the other. After the ligand was withdrawn, the active site of the Mcg dimer could no longer bind the PZ‐peptide. However, if the active site was first blocked by the PZ‐peptide and subsequently exposed to the (Pro‐Pro‐Gly)5 peptide, the difference Fourier map was indistinguishable from that obtained with the PZ‐peptide alone. We concluded that amyloidogenic L chains such as the Mcg dimer could be concentrated in the perivascular space by binding to normal tissue constituents. These components include nascent collagen, which can be deterred from maturing as a result of this binding. Participation in such pathological activity is also self‐destructive to the amyloidogenic L chains, which lose their binding capabilities for collagen‐derived peptides and also become susceptible to irreversible conversion to amyloid fibrils. All of these events may be prevented by prior treatment of the amyloidogenic L chains with site‐filling ligands. Copyright © 20...

Bence Jones KWR protein structures determined by X-ray crystallography

“…Thus, it is possible that some proteolysis could have occurred after the crystals had grown. Such a process was also suggested after an in vivo analysis of the AL amyloid fibrils by Harris et al (2000). It is unlikely in our experiment, however, that such proteolysis was exclusively the case.…”

Exceptional Amyloid β Peptide Hydrolyzing Activity of Nonphysiological Immunoglobulin Variable Domain Scaffolds

“…Lane 1, IgV L2 -t 2E6 stained with silver. Ig light chain homodimers overproduced by cancerous B cells in multiple myeloma patients can bind certain antigens (39,40). There is no naturally occurring Ig homolog of IgV L2 -t 2E6, a heterodimer of two V L domains.…”

“…5 legend). Smaller signals for the following peptide products were also detected as follows: A␤-(1-15), A␤-(1-20), A␤- (16 -40), and A␤- (21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40). The corresponding scissile bonds in A␤40 are Gln 15 -Lys 16 and Phe 20 -Ala 21 .…”

Dangerous small B-cell clones

“…As first reported by Comenzo et al, 12 LCs derived from the 6a germ line gene are preferentially associated with kidney involvement possibly through receptor-mediated interactions with mesangial cells. 13 Recognition of specific epitopes by LC dimers retaining antibody-binding activity 14 can also play a role in tissue specificity.…”