Fig. 2.

The structure of annexin A4 (AnxA4) and related mechanisms of platinum resistance. a No treatment. AnxA4 is localized in the cytoplasm before exposure to platinum drugs. b After platinum drug exposure. Exposure to platinum drugs leads to AnxA4 relocalization from the cytoplasm to the cell membrane. AnxA4 has four annexin repeats that are packed into an α-helical disk within the C-terminal polypeptide core, which contains Ca²⁺-binding sites. These Ca²⁺-binding sites are involved in platinum resistance. c After platinum drug exposure. AnxA4 is attached to the membrane surface through bound Ca²⁺ ions and contributes to the efflux of platinum drugs via platinum transporters