ABSTRACT
Rab GTPases are major mediators that ensure the proper spatiotemporal regulation of intracellular trafficking. Functional impairment and altered expression of Rab proteins have been revealed in various human cancers. There is an emerging evidence about the role of Rab proteins in the biogenesis of extracellular vesicles (EVs). In hepatocellular carcinoma (HCC), using RNA sequencing comparing expression profiles of adjacent non-tumorous tissues and HCC, Rab20 is identified to be the most frequently downregulated Rab member in HCC. Functionally, restoration of Rab20 in metastatic HCC cells results in the release of EVs with a diminished activity to promote cell growth, motility and metastasis. Conversely, EVs released from normal liver cells with Rab20 knockdown loses suppressive effect on HCC cell growth and motility. Proteomic profiling revealed the level of triosephosphate isomerase 1 (TPI1), a glycolytic enzyme, in EVs to be positively associated with Rab20 expression of the releasing cells. TPI1 targeted to be expressed in EVs released by Rab20 knockdown cells compromises the oncogenic activity of EVs. Besides, EVs released by TPI1 knockdown cells recapitulates the promoting effect of EVs derived from HCC cells with Rab20 underexpression. Aerobic glycolysis is beneficial to the survival and proliferation of tumour cells. Here, we observed that the enhanced cell growth and motility are driven by the enhanced aerobic glycolysis induced by EVs with reduced TPI1. The addition of glycolytic inhibitor blocks the promoting effect of EVs with reduced TPI1. Taken together, our study provides a mechanistic link among tumour cell-derived EVs and glucose metabolism in HCC with Rab20 deregulation.
Subject(s)
Carcinogenesis/metabolism , Carcinoma, Hepatocellular/metabolism , Extracellular Vesicles/metabolism , Glycolysis , Liver Neoplasms/metabolism , Triose-Phosphate Isomerase/metabolism , rab GTP-Binding Proteins/metabolism , Carcinoma, Hepatocellular/genetics , Cell Line, Tumor , Cell Movement , Gene Expression Profiling , Gene Expression Regulation, Neoplastic , Gene Knockdown Techniques , Humans , Liver Neoplasms/genetics , Sequence Analysis, RNA , Triose-Phosphate Isomerase/genetics , rab GTP-Binding Proteins/geneticsABSTRACT
ortho-Phthalaldehyde (OPA) and its derivatives are found to react chemoselectively with amino groups on peptides and proteins rapidly and tracelessly under the physiological condition via formation of phthalimidines, which provides a novel and promising approach when performing bioconjugation on native proteins. The notable advantages of this method over the existing native protein lysine-labeling approaches include a traceless process, a self-reacting, specific and fast reaction, ease of operation, and the ability to use nonhydrolyzable reagents. Its applications have been effectively demonstrated including conjugation of peptides and proteins, and generation of an active PEGlyated l-asparaginase.
Subject(s)
Immobilized Proteins/chemistry , Phthalimides/chemistry , Asparaginase/chemistry , Luminescent Proteins/chemistry , Molecular Structure , Polyethylene Glycols/chemistry , Red Fluorescent ProteinABSTRACT
A germline mutation (A339V) in thyroid transcription factor-1 (TITF1/NKX2.1) was shown to be associated with multinodular goiter (MNG) and papillary thyroid carcinoma (PTC) pathogenesis. The overexpression of A339V TTF1 significantly promoted hormone-independent growth of the normal thyroid cells, representing a cause of MNG and/or PTC. Nevertheless, the underlying mechanism still remains unclear. In this study, we used liquid chromatography (LC)-tandem mass spectrometry (MS/MS)-based shotgun proteomics comparing the global protein expression profiles of normal thyroid cells (PCCL3) that overexpressed the wild-type or A339V TTF1 to identify key proteins implicated in this process. Proteomic pathway analysis revealed that the aberrant activation of epidermal growth factor (EGF) signaling is significantly associated with the overexpression of A339V TTF1 in PCCL3, and clathrin heavy chain (Chc) is the most significantly up-regulated protein of the pathway. Intriguingly, dysregulated Chc expression facilitated a nuclear accumulation of pStat3, leading to an enhanced cell proliferation of the A339V clones. Down-regulation and abrogation of Chc-mediated cellular trafficking, respectively, by knocking-down Chc and ectopic expression of a dominant-negative (DN) form of Chc could significantly reduce the nuclear pStat3 and rescue the aberrant cell proliferation of the A339V clones. Subsequent expression analysis further revealed that CHC and pSTAT3 are co-overexpressed in 66.7% (10/15) MNG. Taken together, our results suggest that the A339V TTF1 mutant protein up-regulates the cellular expression of Chc, resulting in a constitutive activation of Stat3 pathway, and prompting the aberrant growth of thyroid cells. This extensive growth signal may promote the development of MNG.
