Quantitative Proteomics Reveals a Novel Role of Karyopherin Alpha 2 in Cell Migration through the Regulation of Vimentin–pErk Protein Complex Levels in Lung Cancer

Karyopherin alpha 2 (KPNA2) is overexpressed
in various human cancers
and is associated with cancer invasiveness and poor prognosis. Herein,
to understand the essential role of KPNA2 protein complexes in cancer
progression, we applied stable isotope labeling with amino acids in
cell culture (SILAC)-based quantitative proteomic strategy combined
with immunoprecipitation (IP) to investigate the differential KPNA2
protein complexes in lung adenocarcinoma cell lines with different
invasiveness potentials. We found that 64 KPNA2-interaction proteins
displayed a 2-fold difference in abundance between CL1-5 (high invasiveness)
and CL1-0 (low invasiveness) cells. Pathway map analysis revealed
that the formation of complexes containing KPNA2 and cytoskeleton-remodeling-related
proteins, including actin, beta tubulin, tubulin heterodimers, vimentin,
keratin 8, keratin 18, and plectin, was associated with cancer invasiveness.
IP demonstrated that the levels of KPNA2–vimentin–pErk
complexes were significantly higher in CL1-5 cells than in CL1-0 cells.
The KPNA2–vimentin–pErk complex was also up-regulated
in the advanced stage compared with the early-stage lung adenocarcinoma
tissues. Importantly, the levels of pErk as well as cell migration
ability were significantly reduced in KPNA2-knockdown cells; however,
migration was restored by treatment with pErk phosphatase inhibitors.
Collectively, our results demonstrate the usefulness of a SILAC-based
proteomic strategy for identifying invasiveness-associated KPNA2 protein
complexes and provide new insight into the KPNA2-mediated modulation
of cell migration.