Quantitative study of the interactome of PKCζ involved in the EGF-induced tumor cell chemotaxis

Chemotaxis plays an important role in metastasis. In our previous studies, we reported that protein kinase C ζ (PKCζ) mediated cancer cell chemotaxis by regulating cytoskeleton rearrangement and cell adhesion. To further study the molecular mechanism of chemotaxis, mass spectrometry-based approaches were employed to investigate the interactome of PKCζ and its changes upon stimulation by epidermal growth factor (EGF). As a result, 233 proteins were identified as potential PKCζ binding partners. Label free quantification was applied to examine the quantitative changes of these interactions involved in the EGF induced chemotaxis. Fifteen identified proteins were enriched and 9 proteins were reduced in the presence of EGF (≥ 1.5 folds, p ≤ 0.05). The interaction between cofilin-1 (CFL1) and PKCζ was evidenced and this interaction was enhanced in the EGF induced chemotaxis signaling transduction. In addition, novel PKCζ interacting proteins potentially related with chemotaxis were characterized, such as isoform 1 of nucleophosmin (NPM1). Furthermore, Western blotting and chemotaxis assays were also applied to validate the proteomics result and explore its biological implications. Collectively, the combination of quantitative proteomics and biological assays provides a powerful strategy for elucidating the signaling pathway of tumor cell chemotaxis.