Regulation of EGFR surface levels by COPII-dependent trafficking

The clathrin adaptor complex-1 and Rab12 regulate post-golgi trafficking of WT epidermal growth factor receptor (EGFR)

The epidermal growth factor receptor (EGFR) plays important roles in cancer progression and is one of the major drug targets for targeted cancer therapy. Although fundamentally important, how newly synthesized EGFR is delivered to the cell surface to perform its cellular functions remains to be further investigated. In this study, we found using the approaches of gene knockout, siRNA knockdown, streptavidin pull-down, and co-immunoprecipitation assays that the clathrin adaptor complex-1 (AP-1) and Rab12 interact with EGFR and regulate the export of EGFR out of the trans-Golgi network (TGN). In addition, the tyrosine residue at the 998 position on human EGFR is critical to bind to AP-1, and this residue is important for TGN export of EGFR. We demonstrate that AP-1 and Rab12 are important for epidermal growth factor-induced phosphorylation of EGFR, cell elongation, and proliferation, suggesting that AP-1-mediated and Rab12-mediated post-Golgi trafficking is important for EGFR signaling. Moreover, TGN export of the constitutively activated mutant form of EGFR (EGFR^L858R) is independent of AP-1 and Rab12. Our results reveal insights into the molecular mechanisms that mediate the TGN-to-cell surface delivery of EGFR and indicate that TGN export of WT EGFR and EGFR^L858R depends on different cellular factors.

Fucosyltransferase 4 shapes oncogenic glycoproteome to drive metastasis of lung adenocarcinoma

BACKGROUND

Aberrant fucosylation plays a critical role in lung cancer progression. Nevertheless, the key fucosyltransferase with prognostic significance in lung cancer patients, the enzyme's intracellular targets, and complex molecular mechanisms underlying lung cancer metastasis remain incompletely understood.

METHODS

We performed a large-scale transcriptome-clinical correlation to identify major fucosyltransferases with significant prognostic values. Invasion, migration, cell adhesion assays were performed using lung cancer cells subject to genetic manipulation of FUT4 levels. Genome-wide RNA-seq and immunoprecipitation-mass spectrometry were used to characterize major cellular processes driven by FUT4, as well as profiling its intracellular protein targets. We also performed lung homing and metastasis assays in mouse xenograft models to determine in vivo phenotypes of high FUT4-expressing cancer cells.

FINDINGS

We show that FUT4 is associated with poor overall survival in lung adenocarcinoma patients. High FUT4 expression promotes lung cancer invasion, migration, epithelial-to-mesenchymal transition, and cell adhesion. FUT4-mediated aberrant fucosylation markedly activates multiple cellular processes, including membrane trafficking, cell cycle, and major oncogenic signaling pathways. The effects are independent of receptor tyrosine kinase mutations. Notably, genetic depletion of FUT4 or targeting FUT4-driven pathways diminishes lung colonization and distant metastases of lung cancer cells in mouse xenograft models.

INTERPRETATION

We propose that FUT4 can be a prognostic predictor and therapeutic target in lung cancer metastasis. Our data provide a scientific basis for a potential therapeutic strategy using targeted therapy in a subset of patients with high FUT4-expressing tumors with no targetable mutations.

An integrated approach to infer cross-talks between intracellular protein transport and signaling pathways

Background

The endomembrane system, known as secretory pathway, is responsible for the synthesis and transport of protein molecules in cells. Therefore, genes involved in the secretory pathway are essential for the cellular development and function. Recent scientific investigations show that ER and Golgi apparatus may provide a convenient drug target for cancer therapy. On the other hand, it is known that abundantly expressed genes in different cellular organelles share interconnected pathways and co-regulate each other activities. The cross-talks among these genes play an important role in signaling pathways, associated to the regulation of intracellular protein transport.

Results

In the present study, we device an integrated approach to understand these complex interactions. We analyze gene perturbation expression profiles, reconstruct a directed gene interaction network and decipher the regulatory interactions among genes involved in protein transport signaling. In particular, we focus on expression signatures of genes involved in the secretory pathway of MCF7 breast cancer cell line. Furthermore, network biology analysis delineates these gene-centric cross-talks at the level of specific modules/sub-networks, corresponding to different signaling pathways.

Conclusions

We elucidate the regulatory connections between genes constituting signaling pathways such as PI3K-Akt, Ras, Rap1, calcium, JAK-STAT, EFGR and FGFR signaling. Interestingly, we determine some key regulatory cross-talks between signaling pathways (PI3K-Akt signaling and Ras signaling pathway) and intracellular protein transport.

Electronic supplementary material

The online version of this article (10.1186/s12859-018-2036-2) contains supplementary material, which is available to authorized users.