Global transition of human serum albumin to prefibrillar aggregates induced by temsirolimus: Insight into implications of anti-renal cancer drug

In our study, we have characterized the prefibrillar aggregates of human serum albumin (HSA) induced by temsirolimus, anti-renal cancer drug. Molecular docking was retorted to confirm binding of HSA and temsirolimus. Temsirolimus caused the structural transition of native HSA to non-native species after prolonged incubation of 20 days. These non-native species were characterized as prefibrillar aggregates as evident by decreased intrinsic fluorescence and enhanced 8-anilino-1-naphthalene-sulphonic acid (ANS) fluorescence. Further, enhanced thioflavin T fluorescence and shift in congo red (CR) spectra of temsirolimus-incubated HSA as compared to native HSA are suggestive of global transition of HSA in presence of temsirolimus towards prefibrillar aggregates. Circular dichroism spectroscopy revealed α to β transition upon prolonged incubation with temsirolimus suggesting the formation of prefibrillar aggregates as aggregates are known to possess high β content. Scanning electron microscopy confirmed these non-native species to be prefibrillar aggregates evident by observed sheath-like structures. Comet assay was retorted to confirm genotoxic nature of these prefibrillar aggregates; DNA damage was observed for temsirolimus-incubated HSA confirming the genotoxic nature of prefibrillar aggregates. These prefibrillar aggregates are observed at heart of many pathological conditions, thus making our study clinically significant.