The overall goal of this proposal is to identify the misfolded cytotoxic species populated by light chain amyloidosis (AL) proteins. AL is a rare, fatal misfolding disease characterized by the proliferation of monoclonal plasma cells that secrete immunoglobulin light chains that misfold as amyloid deposits in vital organs. Current treatments reduce the population of the malignant monoclonal plasma cells. Little is known about the misfolding process converting soluble proteins into insoluble AL fibrils and the nature of the toxic species generated during this process;identifying the toxic species is crucial to developing targeted therapies for AL. We have determined that the protein AL-09 forms an altered dimer interface. A single somatic mutation is responsible for the change in the dimer interface, causing loss of thermodynamic stability, and promoting amyloid formation with respect to its germline ('wild type') protein. Our preliminary data show that AL-09 is the most amyloidogenic AL protein studied in our laboratory, it is highly toxic to cardiomyocytes in its soluble form, and its amyloid fibril core is consistent with the altered dimer interface structure. In addition, we want to explore alternative mechanisms of cytotoxicity that would explain the phenomenon observed with some patients who have achieved significant reduction of circulating light chain post-treatment but still have disease progression. Based on this information, our central hypothesis is that soluble AL light chain species are highly toxic. There are different mechanisms that generate AL toxic species. Specific somatic mutations in AL light chains cause the protein to favor one or more cytotoxic mechanisms.
In aim 1, we will test the hypothesis that protein internalization is required for cytotoxicity using toxicity assays on cardiomyocytes and human arteriole dilation assays.
For aim 2, we will test the hypothesis that low thermodynamic stability of some AL fibrils could cause disaggregation that may play a role in cytotoxicity. In addition, we will identify alternative mechanisms of cytotoxicity by testing the hypothesis that some AL proteins are able to cross seed with non-pathogenic light chains present in the normal repertoire of immunoglobulin molecules.
For aim 3, we will test the hypothesis that AL fibril core composition is mostly driven by the predominant dimer structure populated by each AL protein and will correlate to protein cytotoxicity. Our results will have a collective impact because they will provide new knowledge into the mechanism of AL by identifying common cytotoxic species and AL fibril core regions. This knowledge will be essential for the development of rational drug design to ultimately eliminate the devastating consequences of this disease.

Public Health Relevance

Light chain Amyloidosis (AL) is a rare, incurable, and devastating disease that affects vital organs. In this application, """"""""Mechanisms of Aggregation in Light Chain Amyloidosis,"""""""" we propose to study the toxic species that damage these organs to better design future therapeutic approaches for AL.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Biophysics of Neural Systems Study Section (BPNS)
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Wehrle, Janna P
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Mayo Clinic, Rochester
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Blancas-Mejia, Luis M; Misra, Pinaki; Dick, Christopher J et al. (2018) Immunoglobulin light chain amyloid aggregation. Chem Commun (Camb) 54:10664-10674
Blancas-Mejía, Luis M; Misra, Pinaki; Ramirez-Alvarado, Marina (2017) Differences in Protein Concentration Dependence for Nucleation and Elongation in Light Chain Amyloid Formation. Biochemistry 56:757-766
Blancas-Mejía, Luis M; Martin, Emily B; Williams, Angela et al. (2017) Kinetic stability and sequence/structure studies of urine-derived Bence-Jones proteins from multiple myeloma and light chain amyloidosis patients. Biophys Chem 230:89-98
Piehl, Dennis W; Blancas-Mejía, Luis M; Ramirez-Alvarado, Marina et al. (2017) Solid-state NMR chemical shift assignments for AL-09 VL immunoglobulin light chain fibrils. Biomol NMR Assign 11:45-50
Lin, Yi; Marin-Argany, Marta; Dick, Christopher J et al. (2017) Mesenchymal stromal cells protect human cardiomyocytes from amyloid fibril damage. Cytotherapy 19:1426-1437
Marin-Argany, Marta; Lin, Yi; Misra, Pinaki et al. (2016) Cell Damage in Light Chain Amyloidosis: FIBRIL INTERNALIZATION, TOXICITY AND CELL-MEDIATED SEEDING. J Biol Chem 291:19813-25
Blancas-Mejía, Luis M; Ramirez-Alvarado, Marina (2016) Recruitment of Light Chains by Homologous and Heterologous Fibrils Shows Distinctive Kinetic and Conformational Specificity. Biochemistry 55:2967-78
Franco, Daniel A; Truran, Seth; Weissig, Volkmar et al. (2016) Monosialoganglioside-Containing Nanoliposomes Restore Endothelial Function Impaired by AL Amyloidosis Light Chain Proteins. J Am Heart Assoc 5:
Blancas-Mejía, Luis M; Horn, Timothy J; Marin-Argany, Marta et al. (2015) Thermodynamic and fibril formation studies of full length immunoglobulin light chain AL-09 and its germline protein using scan rate dependent thermal unfolding. Biophys Chem 207:13-20
Blancas-Mejía, Luis M; Hammernik, Jared; Marin-Argany, Marta et al. (2015) Differential effects on light chain amyloid formation depend on mutations and type of glycosaminoglycans. J Biol Chem 290:4953-65

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