Mutational and genetic determinants of λ6 light chain amyloidogenesis

Abstract

Approximately 25% of the k6 light chains have glycine rather than arginine at position 25, which is an allelic variant of the IGLV6-57 (6a) locus. The Gly25 variant has been shown to decrease the folding stability of the germline k6 V L protein 6aJL2 by 1.7 kcalÁmol À1. In this work, we compared the thermodynamic and fibrillogenic properties of the amyloidosis (AL) derived recombinant (r) V L protein AR, which contains the allelic variant Gly25, with those of germline rV L 6aJL2-R25G and the k6 diseaseassociated V L proteins Wil (AL) and Jto (myeloma). Our experiments show that of the four proteins AR is the least stable; forms amyloid fibrils at physiological temperature, pH and ionic strength; has the shortest lag time; and elongates homologous seeds most efficiently. We conclude that the Gly25 allelic variant, together with the somatic mutations, contributes importantly to the extremely low stability and high amyloidogenicity of the AL-derived protein AR.

Stabilizing an amyloidogenic λ6 light chain variable domain

“…The aim of this approach was to understand the stabilizing effects of certain back mutations all over the variable domain. AR showed 14 mutations and an extra Glycine compared with recombinant germ line 6aJL2, a high sequence identity between them, around 85%, and all the mutations were distributed throughout all the sequence highlighting the somatic hypermutagenic origin of this light chain [17]. Furthermore, AR was the first amyloidogenic k6 V L reported [18,19].…”

“…The relevance of Trp35 is that it can be used as a reporter revealing hydrophobic core compaction because its fluorescence is mediated through local hydrophobicity and quenched by the proximity of the nearby disulfide bridge Cys23-Cys88 [23,24]. Since the T m values are very different between AR and 6aJL2, 33 and 49.9°C respectively [17], it can be proposed that the high intrinsic fluorescence intensity of AR might be attributable to an inadequate hydrophobic core packing of the native state. 2).…”

“…The aim of this approach was to understand the stabilizing effects of certain back mutations all over the variable domain. This domain, named AR, has been reported as the least stable and the most fibrillogenic k6 LC, capable of forming amyloid fibrils in approximately half an hour [17]. Furthermore, AR was the first amyloidogenic k6 V L reported [18,19].…”

“…This domain, named AR, has been reported as the least stable and the most fibrillogenic k6 LC, capable of forming amyloid fibrils in approximately half an hour [17]. The aim of this approach was to understand the stabilizing effects of certain back mutations all over the variable domain.…”

A Substantial Structural Conversion of the Native Monomer Leads to in‐Register Parallel Amyloid Fibril Formation in Light‐Chain Amyloidosis

“…The model protein 6aJL2, a recombinant (r) V L protein within the λ6 subgroup, has a particularly amyloidogenic mutant 6aJL2‐R24G (one should note that here we use continuous numbering of the amino‐acid residues along the protein; an alternative numbering scheme in which Gly24 becomes Gly25 exists). Both proteins have been comprehensively characterized by in vitro fibrillization, and their monomer structures have been determined by X‐ray crystallography and solution‐state NMR .…”