Biological role of immunoglobulin Free light chains interactomes

Background. Monoclonal Gammopathy of Undetermined Significance (MGUS) is a plasma cell disorder that could be diagnosed incidentally and behave like a benign, asymptomatic entity or progress (1% per year) to different haematologic malignancies such as multiple myeloma (MM). Monoclonal plasma cells often secrete high amounts of immunoglobulin free light chains (FLCs) that could induce tissue damage. Recently we showed (Di Noto et al., 2013) that FLCs are internalized in endothelial and myocardial cell lines and secreted in extracellular vesicles (EVs). Our data show that MM EVs internalization is FLCs and GAGs mediated and we could demonstrate that MM EVs induce NfkB nuclear translocation. Blocking FLCs with anti FLCs antibodies or masking the GAGs recognition with heparin altered the EVs intracellular uptake and NfkB nuclear translocation (Di Noto et al., 2014). EVs carry determinant information about the onset of MGUS-MM switching which can be exploited for early assessment of MM onset and progression. Objectives. We aim to identify binding partners that associate with the FLCs in the blood stream (FLCs interactome) and are involved in the EVs generation and cellular uptake. Methods. EVs, purified from serum of control, MGUS and MM patients, were analyzed by a blend of conventional analytical techniques, MALDI TOF analysis and surface plasmon resonance (SPR). Results and Conclusions. In a previous proteomic study immuno-purified FLCs isolated from patients with monoclonal gammopathies were characterised and some proteins such as clusterin and albumin associated with FLCs were identified. We then tracked the binding isotherms of EVs to a heparin-coated sensorchips. The results show a marked difference between the binding isotherms of EVs from healthy individuals and from MM and MGUS patients.