Hen egg lysozyme fibrils act as amyloid nucleating agents for β-lactoglobulin and insulin

Understanding the mechanism of amyloid cross-seeding has become fundamentally important for unraveling the molecular basis of amyloid-associated diseases. Hence, the intrinsic crosstalk potential between different amyloidogenic proteins has become an important area of investigation that explores how the amyloid fibrils of one type of protein would induce amyloid aggregation of other protein types. Here, we have explored the cross-seeding effect of lysozyme amyloid fibrils on two important amyloidogenic proteins: type II diabetes-linked insulin hormone and food protein β-lactoglobulin. The lysozyme amyloid fibrils were found to effectively induce cross-seeding reactions in insulin and β-lactoglobulin, leading to their amyloid aggregation. Experimental and computational data showed that both monomeric and fibrillar structures of lysozyme have strong binding affinity for insulin as well as β-lactoglobulin via stable non-covalent interactions dominated by H-bonds and hydrophobic contacts. Our data clearly demonstrate that the cross-β structure of lysozyme can trap native structures of both insulin and β-lactoglobulin; however, the marginally higher affinity for the monomers of β-lactoglobulin resulted in faster kinetics of the cross-seeding reactions. At the monomeric level, we also observed a rapid coaggregation process for heteromeric combinations of these proteins. The results signify that amyloid cross-seeding/coaggregation could be central to the mechanism for the formation of heterogenous amyloid structures and targeting cross-seeding and coaggregation may help in developing better anti-amyloid strategies.