Interaction between Glycosaminoglycans and Immunoglobulin Light Chains

Primary amyloidosis (AL) results from overproduction of unstable monoclonal immunoglobulin light chains (LCs) and the deposition of insoluble fibrils in tissues, leading to fatal organ disease. Glycosaminoglycans (GAGs) are associated with AL fibrils and have been successfully targeted in the treatment of other forms of amyloidosis. We investigated the role of GAGs in LC fibrillogenesis. Ex vivo tissue amyloid fibrils were extracted and examined for structure and associated GAGs. The GAGs were detected along the length of the fibril strand, and the periodicity of heparan sulfate (HS) along the LC fibrils generated in vitro was similar to that of the ex vivo fibrils. To examine the role of sulfated GAGs on AL oligomer and fibril formation in vitro, a 1 LC purified from urine of a patient with AL amyloidosis was incubated in the presence or absence of GAGs. The fibrils generated in vitro at physiologic concentration, temperature, and pH shared morphologic characteristics with the ex vivo 1 amyloid fibrils. The presence of HS and over-O-sulfatedheparin enhanced the formation of oligomers and fibrils with HS promoting the most rapid transition. In contrast, GAGs did not enhance fibril formation of a non-amyloidogenic 1 LC purified from urine of a patient with multiple myeloma. The data indicate that the characteristics of the full-length 1 amyloidogenic LC, containing post-translational modifications, possess key elements that influence interactions of the LC with HS. These findings highlight the importance of the variable and constant LC regions in GAG interaction and suggest potential therapeutic targets for treatment.Amyloid deposition is hypothesized to play a role in many diseases including rheumatoid arthritis and diabetes, as well as the amyloidoses themselves (1). The amyloidoses are a group of systemic and localized diseases that exhibit deposition of insoluble fibrillar proteins in organs and tissues. Primary amyloidosis (AL) 2 is the most common systemic form in the UnitedStates. It results from a plasma cell dyscrasia in which clonal B cells produce an excess of amyloidogenic immunoglobulin light chains (LCs), which circulate and deposit as insoluble fibrils throughout the body (2). A structural rearrangement from nonfibril-prone oligomers to more fibril-prone conformers is required for protofilament formation (3). Nascent protofilaments can nucleate and elongate through the addition of partially folded oligomeric intermediates to the ends of the growing protofilaments. Protofilaments can further intertwine to form protofibrils and fibrils (4, 5). Glycosaminoglycans (GAGs) are one of the major components of the extracellular matrix. They consist of disaccharide repeating units that are unbranched and attached to a serine residue of a core protein through a trisaccharide linker. Each GAG has a unique sequence, and post-assembly modifications, which can be induced by a number of factors, lead to alterations in sulfation, acetylation, or length of chain (6). Recently, Staples et al. (7) showed that the fu...

Section: Discussionmentioning

confidence: 86%

Role of Glycosaminoglycan Sulfation in the Formation of Immunoglobulin Light Chain Amyloid Oligomers and Fibrils

Ren

Hong

Gong³

et al. 2010

“…CR competes with sulfated GAGs for binding with prion proteins, suggesting that they bind to same sites, most likely through sulfates (9). A previous study showed that several V L 's, including SMA, interact with GAGs by electrostatic interactions between the sulfate groups of GAGs and the positively charged residues of the proteins (59). These interactions may be responsible for the enhanced fibrillogenesis of proteins in the presence of GAGs which, analogously to CR, may favor population of partially unfolded, aggregation competent protein species.…”

Section: Discussionmentioning

confidence: 99%

Congo Red Populates Partially Unfolded States of an Amyloidogenic Protein to Enhance Aggregation and Amyloid Fibril Formation

Kim

Randolph

Manning

et al. 2003

Self Cite

116

Congo red (CR) has been reported to inhibit or enhance amyloid fibril formation by several proteins. To gain insight into the mechanism(s) for these apparently paradoxical effects, we studied as a model amyloidogenic protein, a dimeric immunoglobulin light chain variable domain. With a range of molar ratios of CR, i.e. r ‫؍‬ [CR]/[protein dimer], we investigated the aggregation kinetics, conformation, hydrogen-deuterium exchange, and thermal stability of the protein. In addition, we used isothermal titration calorimetry to characterize the thermodynamics of CR binding to the protein. During incubation at 37°C or during thermal scanning, with CR at r ‫؍‬ 0.3, 1.3, and 4.8, protein aggregation was greatly accelerated compared with that measured in the absence of the dye. In contrast, with CR at r ‫؍‬ 8.8, protein unfolding was favored over aggregation. The aggregates formed with CR at r ‫؍‬ 0 or 0.3 were typical amyloid fibrils, but mixtures of amyloid fibrils and amorphous aggregates were formed at r ‫؍‬ 1.3 and 4.8. CR decreased the apparent thermal unfolding temperature of the protein. Furthermore, CR perturbed the tertiary structure of the protein without significantly altering its secondary structure. Consistent with this result, CR also increased the rate of hydrogen-deuterium exchange by the protein. Isothermal titration calorimetry showed that CR binding to the protein was enthalpically driven, indicating that binding was mainly the result of electrostatic interactions. Overall, these results demonstrate that at low concentrations, CR binding to the protein favors a structurally perturbed, aggregation-competent species, resulting in acceleration of fibril formation. At high CR concentration, protein unfolding is favored over aggregation, and fibril formation is inhibited. Because low concentrations of CR can promote amyloid fibril formation, the therapeutic utility of this compound or its analogs to inhibit amyloidoses is questionable.

“…Early in vitro studies showed an interaction between light chain proteins and various GAGs (27). Trinkaus-Randall et al (28) later showed that cardiac fibroblast cells incubated with AL light chains internalized the protein, up-regulated GAG production, and secreted highly sulfated GAGs.…”

mentioning

confidence: 99%

Differential Effects on Light Chain Amyloid Formation Depend on Mutations and Type of Glycosaminoglycans

Blancas‐Mejia¹,

Hammernik

Argany³

et al. 2015

Background: Extracellular amyloid deposits involve glycosaminoglycans (GAGs). Results: Fibrillation of AL proteins was accelerated by heparan sulfate and inhibited by chondroitin sulfate A. Conclusion: Endogenous GAGs can modulate amyloid formation, and their effect is determined by the amyloidogenic properties of AL proteins studied. Significance: Biologically relevant molecules like GAGs play a major role in the amyloidogenicity of AL proteins.