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Thermodynamic instability of human lambda 6 light chains: correlation with fibrillogenicity.
1Human Immunology and Cancer Program, University of Tennessee Graduate School of Medicine at Knoxville 37920-6999, USA. jwall@mc.utmck.edu
Biochemistry
|October 21, 1999
Summary
Monoclonal lambda 6 proteins associated with AL amyloidosis are less stable and form amyloid fibrils faster in vitro. Stabilizing interactions within the V L domain influence light chain fibrillogenicity.
Area of Science:
- Biochemistry
- Molecular Biology
- Immunology
Background:
- Certain human light chains, particularly monoclonal lambda 6 proteins, are preferentially associated with AL amyloidosis, suggesting they have a propensity to form pathological amyloid fibrils.
- The specific molecular features that make these light chains amyloidogenic remain largely unelucidated.
- A link exists between the thermodynamic stability of light chains and their in vitro aggregation propensity.
Purpose of the Study:
- To compare the thermodynamic properties and fibrillogenic potential of two recombinant V lambda 6 molecules.
- To investigate the molecular features contributing to the differential deposition of light chains as amyloid fibrils versus tubular casts.
Main Methods:
- Generated two recombinant (r) V lambda 6 molecules from patients with distinct light chain deposition patterns (AL amyloidosis vs. renal tubular casts).
- Determined thermodynamic stabilities using chaotropic and thermal denaturation studies, analyzing parameters like Delta GH2O, Delta H, Delta G25°C, Tm, and Cm.
- Assessed fibril formation kinetics using a novel in vitro fibril forming assay under physiologic conditions.
Main Results:
- The recombinant V lambda 6 molecule from the amyloidosis patient (rV lambda 6Wil) was less thermodynamically stable than the non-amyloidogenic counterpart (rV lambda 6Jto).
- Both recombinant V lambda 6 proteins formed fibrils in vitro, but rV lambda 6Wil exhibited a shorter lag time and faster fibril formation kinetics.
- Sequence analysis identified primary structural features in the non-amyloidogenic Jto protein that likely contribute to its increased stability.
Conclusions:
- Thermodynamic instability is associated with the amyloidogenic potential of V lambda 6 light chains.
- Stabilizing interactions within the V L domain can influence the kinetics of light chain fibrillogenicity, impacting pathological deposition.
- This study provides the first evidence linking V L domain stability to the rate of light chain fibril formation.