Epithelial-mesenchymal transition (EMT) describes an evolutionary conserved morphogenic process defined by loss of epithelial characteristics and acquisition of mesenchymal phenotype, and altered patterns of intercellular communication, leading to functional changes in cell migration and invasion. In this regard, we have previously reported that oncogenic H-Ras induced EMT in Madin-Darby Canine Kidney (MDCK) cells (21D1 cells) trigger changes in the protein distribution pattern in cells, exosomes, and soluble protein factors (secretome) which modulate the tumor microenvironment. Here, we report that shed microvesicles (also termed microparticles/ectosomes) secreted from MDCK cells following oncogenic H-Ras-induced EMT (21D1-sMVs) are biochemically distinct from exosomes and parental MDCK-sMVs. The protein spectra of RNA-binding proteins and mitochondrial proteins in 21D1-sMVs differ profoundly compared to those of exosomes, likewise proteins associated with suppression of anoikis. We show that 21D1-sMVs promote cell migration, confer anchorage-independent growth, and induce EMT in parental MDCK cells. An unexpected and novel finding was the selective sorting of tissue transglutaminase-2 (TGM2) into 21D1-sMVs; there was no evidence of TGM2 in MDCK-sMVs. Prior treatment of 21D1-sMVs with neutralizing anti-TGM2 or anti-FN1 antibodies attenuates the invasive capability of fibroblasts. These finding suggest that microvesicle-associated TGM2 may play an important contributory role in the EMT process and warrants further investigation.
Keywords: RNA-binding proteins; epithelial-mesenchymal transition; mitochondrial proteins; proteomics; shed microvesicles; tissue transglutaminase-2.
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