Immunoglobulin Structure, Stability and Aging

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DESCRIPTION (provided by applicant): The parent grant continues to have three aims. The first is to elucidate how the molecular chaperones BiP and GRP94 react to misfolded Ig in the cell and how this interaction can be employed to reduce the aggregation that leads to amyloid formation. Aim 2 is to understand the structural basis of the polymerization reaction and Aim 3 is to develop a mouse model for light chain amyloidosis. The requested competitive revision evolved from our work on Aim 1, showing that in addition to immunoglobulins, production of insulin-like growth factors requires GRP94. This discovery allowed us to devise IGF-dependent cells whose survival depends on the functionality of GRP94. We demonstrated that this assay is suitable for screening mutants and in Aim 1 of this project we will exploit it to define functional residues and active sites of GRP94. The mutations will be designed to pinpoint the client binding site and other known biochemical features of this essential stress protein. Aim 2 will extend the use of the cell-based assay to human aging. Since low IGF production is associated with longer lifespan, we hypothesize that among the sequence variants in human GRP94 are those that lead to partial IGF chaperoning activity. Proof of concept had been obtained with one SNP in the middle domain of GRP94. This hypothesis will be tested by genotyping and deep sequencing of human GRP94 in subject with the lowest or highest 15% levels of systemic IGF-1 in the large population of the Health ABC consortium. Variants that are likely to change function will be tested in the survival assay, to relate the genotype to function directly. PUBLIC HEALTH RELEVANCE: This competitive revision takes advantage of discoveries about the interactions of molecular chaperones with aggregation-prone immunoglobulins (made under will grant AG18001) and expands the scope of research to a related novel topic with extremely high relevance to human aging - the control of insulin-like growth factor signaling by chaperones.