High-Speed AFM Reveals IDR-Mediated Structural Plasticity of EML4-ALK Modulated by ALK Inhibitors

EML4-ALK is a key oncogenic driver in lung cancer, but variant-specific chemoresistance limits the efficacy of current ALK inhibitors. Because the N-terminus contains an intrinsically disordered region (IDR), how ALK inhibitors affect the structure and dynamics of full-length EML4-ALK remains unclear. Here, using high-speed atomic force microscopy (HS-AFM), we visualize the overall structures of three full-length EML4-ALK variants (v1, v3, and v5) at the single-molecule level. We identified a transient globular subdomain (residues 191–217) within the v3 IDR that contributes to distinct oligomerization patterns. Notably, ALK inhibitors compact the IDR subdomain and reduce oligomerization, whereas this effect is abolished by the resistance mutation ALK ^G1202R , suggesting that ALK inhibitors not only affect kinase activity but also modulate IDR dynamics. Our findings shed new light on the structural regulation of EML4-ALK and provide a foundation for developing next-generation targeted therapies that account for IDR-driven molecular behavior.