High-Speed Atomic Force Microscopy Reveals Disordered Region-Mediated Structural Plasticity of Anaplastic Lymphoma Kinase Fusion Proteins Induced by 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 inhibit kinase activity but also modulate IDR dynamics. Our study reveals a structural basis linking IDR dynamics to variant-specific oligomerization in EML4-ALK, offering further insights into the regulation of oncogenic signaling and the development of targeted therapies.