MicroRNA-370-3p shuttled by breast cancer cell-derived extracellular vesicles induces fibroblast activation through the CYLD/Nf-κB axis to promote breast cancer progression.

Breast cancer is a malignancy arising in the mammary epithelial tissues. Recent studies have indicated the abundance of microRNAs (miRNAs) in extracellular vesicles (EVs), and their interactions have been illustrated to exert crucial roles in the cell-to-cell communication. The present study focused on investigating whether EV-delivered miR-370-3p affects breast cancer. Initially, the miR-370-3p expression pattern was examined in the cancer-associated fibroblasts (CAFs), normal fibroblasts (NFs), and cancerous cells-derived EVs. The relation of miR-370-3p to CYLD was assessed using luciferase activity assay. Afterwards, based on ectopic expression and depletion experiments in the MCF-7 breast cancer cells, we evaluated stemness, migration, invasion, and sphere formation ability, and EMT, accompanied with measurement on the expression patterns of pro-inflammatory factors and nuclear factor-kappa B (NF-κB) signaling-related genes. Finally, tumorigenesis and proliferation were analyzed in vivo using a nude mouse xenograft model. The in vitro experiments revealed that breast cancer cell-derived EVs promoted NF activation, while activated fibroblasts contributed to enhanced stemness, migration, invasion, as well as EMT of cancerous cells. In addition, EVs could transfer miR-370-3p from breast cancer cells to NFs, and EV-encapsulated miR-370-3p was also found to facilitate fibroblast activation. Mechanistically, EV-encapsulated miR-370-3p downregulated the expression of CYLD through binding to its 3'UTR and activated the NF-κB signaling pathway, thereby promoting the cellular functions in vitro and in vivo in breast cancer. Taken together, EVs secreted by breast cancer cells could carry miR-370-3p to aggravate breast cancer through downregulating CYLD expression and activating the NF-κB signaling pathway.

CYLD is a causative gene for frontotemporal dementia - amyotrophic lateral sclerosis.

Frontotemporal dementia and amyotrophic lateral sclerosis are clinically and pathologically overlapping disorders with shared genetic causes. We previously identified a disease locus on chromosome 16p12.1-q12.2 with genome-wide significant linkage in a large European Australian family with autosomal dominant inheritance of frontotemporal dementia and amyotrophic lateral sclerosis and no mutation in known amyotrophic lateral sclerosis or dementia genes. Here we demonstrate the segregation of a novel missense variant in CYLD (c.2155A>G, p.M719V) within the linkage region as the genetic cause of disease in this family. Immunohistochemical analysis of brain tissue from two CYLD p.M719V mutation carriers showed widespread glial CYLD immunoreactivity. Primary mouse neurons transfected with CYLDM719V exhibited increased cytoplasmic localization of TDP-43 and shortened axons. CYLD encodes a lysine 63 deubiquitinase and CYLD cutaneous syndrome, a skin tumour disorder, is caused by mutations that lead to reduced deubiquitinase activity. In contrast with CYLD cutaneous syndrome-causative mutations, CYLDM719V exhibited significantly increased lysine 63 deubiquitinase activity relative to the wild-type enzyme (paired Wilcoxon signed-rank test P = 0.005). Overexpression of CYLDM719V in HEK293 cells led to more potent inhibition of the cell signalling molecule NF-κB and impairment of autophagosome fusion to lysosomes, a key process in autophagy. Although CYLD mutations appear to be rare, CYLD's interaction with at least three other proteins encoded by frontotemporal dementia and/or amyotrophic lateral sclerosis genes (TBK1, OPTN and SQSTM1) suggests that it may play a central role in the pathogenesis of these disorders. Mutations in several frontotemporal dementia and amyotrophic lateral sclerosis genes, including TBK1, OPTN and SQSTM1, result in a loss of autophagy function. We show here that increased CYLD activity also reduces autophagy function, highlighting the importance of autophagy regulation in the pathogenesis of frontotemporal dementia and amyotrophic lateral sclerosis.

CYLD dysregulation in pathogenesis of sporadic inclusion body myositis.

Sporadic inclusion body myositis (sIBM) is the most commonly acquired myopathy in middle-aged and elderly people. The muscle histology is characterized by both inflammation and degeneration, including sarcoplasmic aggregation of TDP-43. Cylindromatosis (CYLD) is a deubiquitinating enzyme that targets Lys63-linked ubiquitin chains and negatively regulates signal transduction pathways, such as NF-κB signalling pathways. We examined localization of CYLD as well as phosphorylated TDP-43, phosphorylated p62, and Lys63-linked ubiquitin in muscle tissues of sIBM patients and muscle-specific wild-type TDP-43 transgenic (TDP-43 TG) mice. We investigated whether overexpression of CYLD can affect muscle toxicity in the cell models treated by endoplasmic reticulum (ER) stress inducers tunicamycin and thapsigargin. CYLD expressed with phosphorylated TDP-43, phosphorylated p62, and Lys63-linked ubiquitin in the nuclear and perinuclear regions of muscle fibres of wild-type TDP-43 TG mice and the degenerative myofibres of sIBM patients with rimmed vacuoles and endomysial cellular infiltration. Although expression levels of CYLD decreased and cell viability was reduced in cells treated with ER stress inducers, wild-type CYLD, but not the catalytic mutant, substantially improved cell viability based on the deubiquitinase activity. Dysregulation of CYLD may reinforce myodegeneration in the pathophysiology of sIBM by attenuating autophagic clearance of protein aggregates. Regulating CYLD in muscle fibres might serve as a novel therapeutic strategy for sIBM treatment.

Tumor suppressor protein CYLD regulates morphogenesis of dendrites and spines.

Cylindromatosis tumor suppressor protein (CYLD) was initially identified as a tumor suppressor deubiquitylating protein in familial cylindromatosis patients. Proteomic analyses using rodent brain samples revealed enrichment of CYLD in purified postsynaptic density fractions. Here, we report that CYLD regulates dendritic growth and postsynaptic differentiation in mouse hippocampal neurons. CYLD showed diffuse localization in rapidly growing dendrites, but was gradually concentrated in spines. Overexpression and knockdown of CYLD in the early stage of cultured neurons demonstrated that CYLD positively regulated dendritic growth. Phenotypes in dendritic morphogenesis induced by CYLD overexpression and knockdown could be reversed by manipulation of the critical acetylation site of α-tubulin, suggesting tubulin acetylation is a downstream pathway of CYLD-dependent dendritic growth. Overexpression and knockdown of CYLD in the later stage of cultured neurons revealed that CYLD promoted formation of postsynaptic spines. Influence of CYLD on spines was not affected by co-expression of acetylation mutant forms of α-tubulin, indicating that CYLD regulates dendritic growth and spine formation through different molecular mechanisms. Analyses with the truncated and mutated forms of CYLD demonstrated that the first microtubule-binding domain of CYLD was critical for spine formation. These results suggest important roles of CYLD in sequential promotion of dendritic growth and postsynaptic spine maturation.

Cylindromatosis (CYLD), a Deubiquitinase, Attenuates Inflammatory Signaling Pathways by Activating Toll-Like Receptor 3 in Human Mesangial Cells.

BACKGROUND/AIMS: Cylindromatosis (CYLD), a deubiquitinase, negatively regulates nuclear factor-κB in various cells. However, its potential roles in glomerular inflammation remain unclear. Because the activation of the Toll-like receptor 3 (TLR3)/type I interferon (IFN) pathways plays a pivotal role in chronic kidney diseases (CKD), we examined the role of CYLD in the TLR3 signaling in cultured human mesangial cells (MCs). METHODS: We stimulated CYLD-silenced MCs with polyinosinic-polycytidylic acid (poly IC), a synthetic analogue of dsRNA, and studied representative TLR3/IFN-ß pathways (i.e., TLR3/IFN-ß/retinoic acid-inducible gene-I (RIG-I)/CCL5, and TLR3/IFN-ß/melanoma differentiation associated gene 5 (MDA5)/CXCL10 axes) using RT-PCR, western blotting, and ELISA. We also used immunofluorescence staining and microscopy to examine mesangial CYLD expression in biopsied specimens from patients with CKD. RESULTS: CYLD silencing resulted in an increase of poly IC-induced RIG-I and MDA5 protein levels and increased CCL5 and CXCL10 mRNA and protein expression, but unexpectedly decreased mRNA expressions of RIG-I and MDA5. Interestingly, CYLD silencing did not affect IFN-ß or the phosphorylated STAT1 (signal transducers and activator of transcription protein 1). CYLD was highly expressed in biopsied specimens from patients with proliferative lupus nephritis (LN). CONCLUSION: CYLD inhibits post-transcriptional regulation of RIG-I and MDA5 expression following TLR3 activation in MCs. CYLD may be involved in the pathogenesis of CKD, especially pathogenesis of LN.

Dishevelled proteins and CYLD reciprocally regulate each other in CML cell lines.

Dishevelled (Dvl) proteins are activated by Wnt pathway stimulation and have crucial roles in the regulation of ß-catenin destruction complex. CYLD is a tumor suppressor and a deubiquitination enzyme. CYLD negatively regulates the Wnt/ß-catenin signaling pathway by deubiquitinating Dvl proteins. Loss of function and mutations of CYLD were linked to different types of solid tumors. Loss of function in CYLD is associated with Dvl hyper ubiquitination, resulting in the transmission of Wnt signaling to downstream effectors. ß-catenin upregulation is observed during disease progression in chronic myeloid leukemia (CML). Deregulated Dvl signaling may be a reason for ß-catenin activation in CML; and CYLD may contribute to Dvl deregulation. First, we evaluated mRNA expression in three CML cell lines and mRNA expression of the CYLD gene was found to be present in all (K562, MEG01, KU812). Unlike solid tumors sequencing revealed no mutations in the coding sequences of the CYLD gene. DVL genes were silenced by using a pool of siRNA oligonucleotides and gene expression differences in CYLD was determined by RT-PCR and western blot. CYLD protein expression decreased after Dvl silencing. An opposite approach of overexpressing Dvl proteins resulted in upregulated CYLD expression. While previous reports have described CYLD as a regulator of DVL proteins; our data suggests the presence of a more complicated reciprocal regulatory mechanism in CML cell lines.