Aberrant trafficking of NSCLC-associated EGFR mutants through the endocytic recycling pathway promotes interaction with Src.
BACKGROUND
Epidermal growth factor receptor (EGFR) controls a wide range of cellular processes, and altered EGFR signaling contributes to human cancer. EGFR kinase domain mutants found in non-small cell lung cancer (NSCLC) are constitutively active, a trait critical for cell transformation through activation of downstream pathways. Endocytic trafficking of EGFR is a major regulatory mechanism as ligand-induced lysosomal degradation results in termination of signaling. While numerous studies have examined mutant EGFR signaling, the endocytic traffic of mutant EGFR within the NSCLC milieu remains less clear.


RESULTS
This study shows that mutant EGFRs in NSCLC cell lines are constitutively endocytosed as shown by their colocalization with the early/recycling endosomal marker transferrin and the late endosomal/lysosomal marker LAMP1. Notably, mutant EGFRs, but not the wild-type EGFR, show a perinuclear accumulation and colocalization with recycling endosomal markers such as Rab11 and EHD1 upon treatment of cells with endocytic recycling inhibitor monensin, suggesting that mutant EGFRs preferentially traffic through the endocytic recycling compartments. Importantly, monensin treatment enhanced the mutant EGFR association and colocalization with Src, indicating that aberrant transit through the endocytic recycling compartment promotes mutant EGFR-Src association.


CONCLUSIONS
The findings presented in this study show that mutant EGFRs undergo aberrant traffic into the endocytic recycling compartment which allows mutant EGFRs to engage in a preferential interaction with Src, a critical partner for EGFR-mediated oncogenesis.
Chung
Byung Min
BM
Eppley Institute for Cancer and Allied Diseases, University of Nebraska Medical Center, 985950 Nebraska Medical Center, Omaha, NE 68198-5950, USA. chungj@unmc.edu
Raja
Srikumar M
SM
Clubb
Robert J
RJ
Tu
Chun
C
George
Manju
M
Band
Vimla
V
Band
Hamid
H
D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D004705:Endocytosis; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism*; D051907:Lysosomal Membrane Proteins / Q000378:metabolism; D009154:Mutation; D011485:Protein Binding; D021381:Protein Transport; D015398:Signal Transduction; D014168:Transferrin / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism*; D052118:Lysosomal-Associated Membrane Protein 1
D066246:ErbB Receptors; D051907:Lysosomal Membrane Proteins; D014168:Transferrin; D019061:src-Family Kinases; C489116:LAMP1 protein, human; D052118:Lysosomal-Associated Membrane Protein 1; C512478:EGFR protein, human