👤 Yong Hwangbo

Fibroblast-like synoviocytes (FLSs) play a crucial role in the pathogenesis of arthritis. However, the impact of small extracellular vesicles (sEVs) secreted by FLSs on osteoclastogenesis remains incompletely understood. In this study, we aimed to investigate the role of tumor necrosis factor (TNF)- and lysophosphatidic acid (LPA)-activated FLSs in sEV-mediated release of osteoclastogenic miRNAs and elucidate their functional contribution to osteoclastogenesis. Stimulation of SW982 cells with LPA or TNF significantly increased sEV secretion. TNF upregulated autotaxin expression and promoted sEV release; however, small interfering RNA (siRNA)-mediated knockdown (KD) of LPAR1 attenuated the increase in sEV release induced by the TNF-autotaxin-LPA axis. Notably, stimulation with TNF or LPA elevated syntenin-1 expression without altering its mRNA level. Furthermore, KD of the syntenin-1 gene (SDCBP) suppressed the LPA-induced increase in sEV release, indicating that syntenin-1 may mediate sEV secretion induced by the TNF-autotaxin-LPA-LPAR1 axis. sEVs derived from TNF- or LPA-treated SW982 cells stimulated osteoclastogenesis. We identified miR-31-5p as an osteoclastogenic miRNA enriched in sEVs. Expression levels of miR-31-5p in sEVs from TNF- and LPA-stimulated rheumatoid arthritis (RA) FLSs were significantly higher than in those from unstimulated RA FLSs. Treatment with a miR-31-5p mimic enhanced osteoclastogenesis by targeting large tumor suppressor kinase 2 (LATS2), whereas treatment with its inhibitor suppressed the sEV-mediated promotion of osteoclastogenesis. These findings reveal a mechanism by which TNF- and LPA-activated FLSs may facilitate sEV-mediated delivery of osteoclastogenic miRNAs, such as miR-31-5p, to osteoclast precursors, thereby contributing to osteoclast formation and bone destruction. Show less

Mitogen- and stress-activated protein kinase 1 (MSK1), a Ser/Thr kinase, phosphorylates nuclear proteins to increase their stability and DNA-binding affinity. Despite the role of MSK1 in promoting cancer progression in colorectal cancer (CRC), the precise molecular mechanisms remain unelucidated. Here we show that MSK1 expression induces the epithelial-mesenchymal transition (EMT) process and increases CRC cell metastasis. Furthermore, we discovered that MSK1 interacts with Snail, a key EMT regulator, and increases its stability by inhibiting ubiquitin-mediated proteasomal degradation. Importantly, MSK1 increased Snail protein stability by promoting deubiquitination rather than inhibiting its ubiquitination. Finally, we identified USP5 as an essential deubiquitinase that binds to Snail protein phosphorylated by MSK1. Based on the experimental data, in CRC, MSK1-Snail-USP5 axis can promote EMT and metastasis of CRC. Together, our findings provide potential biomarkers and novel therapeutic targets for further research in CRC. Show less

Breast cancer remains a significant health concern, with triple-negative breast cancer (TNBC) being an aggressive subtype with poor prognosis. Epithelial-mesenchymal transition (EMT) is important in early-stage tumor to invasive malignancy progression. Snail, a central EMT component, is tightly regulated and may be subjected to proteasomal degradation. We report a novel proteasomal independent pathway involving chaperone-mediated autophagy (CMA) in Snail degradation, mediated via its cytosolic interaction with HSC70 and lysosomal targeting, which prevented its accumulation in luminal-type breast cancer cells. Conversely, Snail predominantly localized to the nucleus, thus evading CMA-mediated degradation in TNBC cells. Starvation-induced CMA activation downregulated Snail in TNBC cells by promoting cytoplasmic translocation. Evasion of CMA-mediated Snail degradation induced EMT, and enhanced metastatic potential of luminal-type breast cancer cells. Our findings elucidate a previously unrecognized role of CMA in Snail regulation, highlight its significance in breast cancer, and provide a potential therapeutic target for clinical interventions. Show less