Interaction of ribosomal protein L22 with casein kinase 2α: A novel mechanism for understanding the biology of non-small cell lung cancer

Dysfunction of ribosomal proteins (RPs) may play an important role in molecular tumorigenesis, such as lung cancer, acting in extraribosomal functions. Many protein-protein interaction studies and genetic screens have confirmed the extraribosomal capacity of RPs. As reported, ribosomal protein L22 (RPL22) dysfunction could increase cancer risk. In the present study, we examined RPL22-protein complexes in lung cancer cells. Tandem affinity purification (TAP) was used to screen the RPL22-protein complexes, and GST pull-down experiments and confocal microscopy were used to assess the protein-protein interaction. The experiment of kinase assay was used to study the function of the RPL22-protein complexes. The results showed that several differentially expressed proteins were isolated and identified by LC-MS/MS, which revealed that one of the protein complexes included casein kinase 2 alpha (CK2 alpha). RPL22 and CK2 alpha interact in vitro. RPL22 also inhibited CK2 alpha substrate phosphorylation in vitro. This is the first report of the RPL22-CK2 alpha relationship in lung cancer. Dysregulated CK2 may impact cell proliferation and apoptosis, key features of cancer cell biology. Our results indicate that RPL22 may be a candidate anticancer agent due to its CK2 alpha-binding and -inhibitory functions in human lung cancer.