BPS2026 – Investigating the effects of oncogenic mutations on EGFR endocytosis

Epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase central to cell proliferation and survival. In non-small cell lung cancer (NSCLC), activating mutations, most frequently exon 19 deletions (Ex19) and the L858R point mutation, drive oncogenesis and therapeutic resistance, yet their effects on receptor endocytosis remain poorly defined. We investigated how oncogenic EGFR variants alter clathrin-mediated endocytosis (CME) using total internal reflection fluorescence microscopy (TIRFM) and quantitative image analysis. We recorded EGFR and AP-2 dynamics during the first 30 min after EGF stimulation, a critical window for endocytic pathway selection. Wild-type EGFR exhibited significant reduction in surface intensity within 30 min, consistent with efficient internalization. We then compared Ex19 variants (including E746-A750del and L747-A750>P) and the L858R mutant to wild-type by quantifying receptor surface intensity and the number of puncta formed over time. These analyses revealed distinct patterns of endocytic engagement, with differences in both baseline and EGF-stimulated dynamics, indicating that the mutations differentially influence CME behavior. By linking structural alterations to endocytic behavior, this work provides mechanistic insight into NSCLC pathogenesis and highlights receptor trafficking as a potential therapeutic target. Targeting mutant-specific endocytic defects may complement kinase inhibition strategies, offering new opportunities to overcome drug resistance in EGFR-driven cancers.