Exploring the interaction of cisplatin with β2-microglobulin: new insights into a chemotherapeutic drug

Abstract

Cisplatin is one of the most widely used anticancer platinum drugs and the interactions between cisplatin and proteins are deemed to be associated with its severe side-effects and drug resistance generated in the chemotherapy process. Here, the interaction of cisplatin with b2-microglobulin was investigated using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FTICR MS). High resolution MS data revealed that b2-microglobulin (b2M) can quickly react with cisplatin in 5 mM NH 4 OAc aqueous solution (pH 7.0) and up to five platinated complexes were bound to b2M in 24 h. The primary monoadduct was determined to be b2-microglobulin-Pt(NH 3 ). Besides, the oxidation of Met99 to methionine sulfoxide decreased the reaction velocity of b2M and cisplatin. Four binding sites for cisplatin to b2M have been identified using FTICR MS combined with a bottom-up approach without complex liquid chromatography separation. Met99 and His51 were identified as the main binding sites.Besides, His84 and His31 were the other two binding sites. What's more, the platination of b2M disrupts the conformation of the protein, and coordination of different platinum species induced different conformation changes of b2M. Interestingly, a Pt(II) bridged dimer of b2M was observed under physiological conditions. This work highlights the ability of high resolution mass spectrometry to study the interactions between b2M and cisplatin, but also provides unique insights into the mechanism of side-effects of cisplatin at a molecular level.

Mass spectrometry based strategy for studies of binding sites and structural changes of cisplatin binding to myoglobin

“…A study showed that within 24 h of intravenous injection, 65–98% of platinum is bound to proteins in the blood . There are considerable studies about the interactions of platinum metallodrugs with a variety of proteins such as human serum albumin (HSA), myoglobin, cytochrome c, ubiquitin, calmodulin, insulin, transferrin, lysozyme, copper‐containing proteins, beta 2‐microglobulin, and so on.…”