Changes in intracellular and extracellular proteins after ERGIC3 knockdown in lung cancer: Proteins interacting with ERGIC3, HORN, and FLNA

Objective: Endoplasmic reticulum-Golgi intermediate compartment 3 (ERGIC3) promotes cell proliferation and metastasis in lung cancer, but its molecular mechanism is unclear. Methods: The GLC-82 cells were randomly divided into the ERGIC3i group and the negative control group. The cells were transfected with ERGIC3 siRNA or control siRNA in the groups, respectively. The ERGIC3-interacting proteins expressed in cells or extracellularly were isolated by the immunoprecipitation method and detected by isobaric tags for relative and absolute quantitation and liquid chromatography-tandem mass spectrometry. The differentially expressed proteins were determined by bioinformatic methods. Results: After ERGIC3 knockdown, 88 extracellular differentially expressed proteins, 41 up regulated and 47 down-regulated, were detected in the supernatant of cultured cells. Among 52 intracellular differentially expressed proteins, 33 were up-regulated and 19 down-regulated. Cluster analysis showed that the extracellular differential proteins are mainly involved in Ca2+ binding and transport and I-kappa B kinase/NF-kappa B signal transduction. The upregulated proteins are mainly involved in the biological process of H3-K27 and H3-K4 methylation in cells. Co-immunoprecipitation assay showed that proteins interacting with ERGIC3 were rich in cytoskeleton construction and RHO GTPases activated p21-activated kinases. The intersection of these two research methods shows that ERGIC3 interacts with HORN and filamin A (FLNA). Conclusion: Proteomic analyses reveal that ERGIC3 acts as a vesicle transmembrane protein on the distribution of various extracellular and intracellular proteins and regulates the extracellular and intracellular biological processes by specifically binding hornin (HORN) and FLNA proteins. These findings maybe provide new methods and ideas for ERGIC3 as a therapeutic target for lung cancer.