ARMc8 indicates aggressive colon cancers and promotes invasiveness and migration of colon cancer cells

MiR-455-3p inhibits gastric cancer progression by repressing Wnt/β-catenin signaling through binding to ARMC8

BACKGROUND

Globally, gastric cancer (GC) is one of the world's most widespread malignancies, with persistent high mortality and morbidity rates. Increasing evidence now suggests that microRNAs (miRNAs) participate in many biological processes, with miR-455-3p having key roles in the progression of diverse cancers. Nevertheless, miR-455-3p function and expression in GC remain unclear.

METHODS

We explored miR-455-3p expression in GC using quantitative polymerase chain reaction (qPCR). To further examine the effect of miR-455-3p in GC, after transfecting miR-455-3p mimics or inhibitors into GC cells, 5-ethynyl-2'-deoxyuridine (EdU) incorporation and colony formation assays were performed to examine cell proliferation. Flow cytometry was used to detect apoptosis, and expression levels of Bax, Bcl-2, Snail, N-cadherin, E-cadherin, and Caspase-3 were assessed by western blotting (WB). Using online databases and luciferase assays, we identified armadillo repeat-containing protein 8 (ARMC8) as a promising target of miR-455-3p. A mouse tumor model was established to investigate actions of miR-455-3p in vivo. Expression levels of C-myc, cyclinD1, and β-catenin were examined using WB and immunofluorescence.

RESULTS

MiR-455-3p expression was attenuated in GC tissue and cell lines. MiR-455-3p overexpression inhibited GC cell proliferation, epithelial-mesenchymal transition (EMT), as well as facilitated apoptosis, while suppression of miR-455-3p had the opposite effects. From luciferase assays, we confirmed that ARMC8 was a novel and direct downstream target gene of miR-455-3p, and that the tumor suppressive role of miR-455-3p was in part reversed due to ARMC8 overexpression. Moreover, miR-455-3p inhibited GC growth in vivo via ARMC8. We also observed that miR-455-3p repressed canonical Wnt pathway activation by binding to ARMC8.

CONCLUSIONS

MiR-455-3p exerted tumor inhibitory effects in GC by targeting ARMC8. Therefore, intervening in the miR-455-3p/ARMC8/Wnt/βcatenin axis could be a promising novel treatment strategy for GC.

RanBP9 controls the oligomeric state of CTLH complex assemblies

The CTLH (C-terminal to lissencephaly-1 homology motif) complex is a multisubunit RING E3 ligase with poorly defined substrate specificity and flexible subunit composition. Two key subunits, muskelin and Wdr26, specify two alternative CTLH complexes that differ in quaternary structure, thereby allowing the E3 ligase to presumably target different substrates. With the aid of different biophysical and biochemical techniques, we characterized CTLH complex assembly pathways, focusing not only on Wdr26 and muskelin but also on RanBP9, Twa1, and Armc8β subunits, which are critical to establish the scaffold of this E3 ligase. We demonstrate that the ability of muskelin to tetramerize and the assembly of Wdr26 into dimers define mutually exclusive oligomerization modules that compete with nanomolar affinity for RanBP9 binding. The remaining scaffolding subunits, Armc8β and Twa1, strongly interact with each other and with RanBP9, again with nanomolar affinity. Our data demonstrate that RanBP9 organizes subunit assembly and prevents higher order oligomerization of dimeric Wdr26 and the Armc8β-Twa1 heterodimer through its tight binding. Combined, our studies define alternative assembly pathways of the CTLH complex and elucidate the role of RanBP9 in governing differential oligomeric assemblies, thereby advancing our mechanistic understanding of CTLH complex architectures.

ARMC Subfamily: Structures, Functions, Evolutions, Interactions, and Diseases

Armadillo repeat-containing proteins (ARMCs) are widely distributed in eukaryotes and have important influences on cell adhesion, signal transduction, mitochondrial function regulation, tumorigenesis, and other processes. These proteins share a similar domain consisting of tandem repeats approximately 42 amino acids in length, and this domain constitutes a substantial platform for the binding between ARMCs and other proteins. An ARMC subfamily, including ARMC1∼10, ARMC12, and ARMCX1∼6, has received increasing attention. These proteins may have many terminal regions and play a critical role in various diseases. On the one hand, based on their similar central domain of tandem repeats, this ARMC subfamily may function similarly to other ARMCs. On the other hand, the unique domains on their terminals may cause these proteins to have different functions. Here, we focus on the ARMC subfamily (ARMC1∼10, ARMC12, and ARMCX1∼6), which is relatively conserved in vertebrates and highly conserved in mammals, particularly primates. We review the structures, biological functions, evolutions, interactions, and related diseases of the ARMC subfamily, which involve more than 30 diseases and 40 bypasses, including interactions and relationships between more than 100 proteins and signaling molecules. We look forward to obtaining a clearer understanding of the ARMC subfamily to facilitate further in-depth research and treatment of related diseases.

The human GID complex engages two independent modules for substrate recruitment

The human GID (hGID) complex is a conserved E3 ubiquitin ligase regulating diverse biological processes, including glucose metabolism and cell cycle progression. However, the biochemical function and substrate recognition of the multi-subunit complex remain poorly understood. Using biochemical assays, cross-linking mass spectrometry, and cryo-electron microscopy, we show that hGID engages two distinct modules for substrate recruitment, dependent on either WDR26 or GID4. WDR26 and RanBP9 cooperate to ubiquitinate HBP1 in vitro, while GID4 is dispensable for this reaction. In contrast, GID4 functions as an adaptor for the substrate ZMYND19, which surprisingly lacks a Pro/N-end degron. GID4 substrate binding and ligase activity is regulated by ARMC8α, while the shorter ARMC8β isoform assembles into a stable hGID complex that is unable to recruit GID4. Cryo-EM reconstructions of these hGID complexes reveal the localization of WDR26 within a ring-like, tetrameric architecture and suggest that GID4 and WDR26/Gid7 utilize different, non-overlapping binding sites. Together, these data advance our mechanistic understanding of how the hGID complex recruits cognate substrates and provides insights into the regulation of its E3 ligase activity.

Downregulation of ARMC8 promotes tumorigenesis through activating Wnt/β-catenin pathway and EMT in cutaneous squamous cell carcinomas

BACKGROUND

Aberrant expression of Armadillo repeat containing 8 (ARMC8) plays crucial roles in tumor growth and metastasis of various cancers. The specific role of ARMC8 in cutaneous squamous cell carcinoma (cSCC) is yet to be elucidated.

OBJECTIVE

The present study aimed to investigate the molecular mechanisms of ARMC8 and epithelial-mesenchymal transition (EMT) in cSCC development and provide translational insights for future therapeutics.

METHODS

cSCC tumor specimens were used to determine the ARMC8 by immunohistochemistry. Three cSCC cell lines including HSC-1, HSC-5 and A431 as well as BALB/C mouse tumor model was utilized to study the potential mechanisms in tumorigenesis.

RESULTS

Our data identified ARMC8 as a direct downstream target of miR-664. We found that ARMC8 was remarkably low expression in cSCC patient specimens and cSCC cell lines. Knockdown of ARMC8 promotes tumorigenic behaviors such as increased cell proliferation, migration and invasion capacities in vitro and enhanced tumorigenicity in xenograft mouse model. Whereas ARMC8 over-expression inhibits tumorigenesis in cSCC. Together, it revealed ARMC8 functions as a tumor suppressor via restraining Wnt/β-catenin pathway and epithelial-mesenchymal transition in cSCC.

CONCLUSION

Our data verifies that aberrant expression of ARMC8 plays a vital role in carcinogenesis of cSCC. And overexpression of ARMC8 will facilitate future development of cSCC therapeutic interventions.

The CTLH Complex in Cancer Cell Plasticity

Cancer cell plasticity is the ability of cancer cells to intermittently morph into different fittest phenotypic states. Due to the intrinsic capacity to change their composition and interactions, protein macromolecular complexes are the ideal instruments for transient transformation. This review focuses on a poorly studied mammalian macromolecular complex called the CTLH (carboxy-terminal to LisH) complex. Currently, this macrostructure includes 11 known members (ARMC8, GID4, GID8, MAEA, MKLN1, RMND5A, RMND5B, RANBP9, RANBP10, WDR26, and YPEL5) and it has been shown to have E3-ligase enzymatic activity. CTLH proteins have been linked to all fundamental biological processes including proliferation, survival, programmed cell death, cell adhesion, and migration. At molecular level, the complex seems to interact and intertwine with key signaling pathways such as the PI3-kinase, WNT, TGFβ, and NFκB, which are key to cancer cell plasticity. As a whole, the CTLH complex is overexpressed in the most prevalent types of cancer and may hold the key to unlock many of the biological secrets that allow cancer cells to thrive in harsh conditions and resist antineoplastic therapy.

Armc8 is an evolutionarily conserved armadillo protein involved in cell-cell adhesion complexes through multiple molecular interactions

Armadillo-repeat-containing protein 8 (Armc8) belongs to the family of armadillo-repeat containing proteins, which have been found to be involved in diverse cellular functions including cell-cell contacts and intracellular signaling. By comparative analyses of armadillo repeat protein structures and genomes from various premetazoan and metazoan species, we identified orthologs of human Armc8 and analyzed in detail the evolutionary relationship of Armc8 genes and their encoded proteins. Armc8 is a highly ancestral armadillo protein although not present in yeast. Consequently, Armc8 is not the human ortholog of yeast Gid5/Vid28.Further, we performed a candidate approach to characterize new protein interactors of Armc8. Interactions between Armc8 and specific δ-catenins (plakophilins-1, -2, -3 and p0071) were observed by the yeast two-hybrid approach and confirmed by co-immunoprecipitation and co-localization. We also showed that Armc8 interacts specifically with αE-catenin but neither with αN-catenin nor with αT-catenin. Degradation of αE-catenin has been reported to be important in cancer and to be regulated by Armc8. A similar process may occur with respect to plakophilins in desmosomes. Deregulation of desmosomal proteins has been considered to contribute to tumorigenesis.

C14orf159 suppresses gastric cancer cells' invasion and proliferation by inactivating ERK signaling

Background

C14orf159, a new protein, has been identified recently. But its expression in tissues and clinicopathologic correlation is still unknown.

Patients and methods

We carried out immunohistochemistry staining in 144 gastric cancer cases in this study. Then Western blot was used to detect the expression of protein. MTT and matrigel invasion assay were used to assess the biological effects.

Results

The immunohistochemical results indicated that the expression of C14orf159 in normal gastric mucosa close to cancer tissue was remarkably higher than that in stomach carcinoma samples (63.9% and 34.7%, respectively, P<0.001). Negative C14orf159 expression was dramatically related to high TNM stages (P=0.033) and positive lymph node metastasis (P=0.008). Once C14orf159 was overexpressed, the expression levels of phosphorylated ERK and its regulated downstream molecules, such as Snail, phosphorylated P90RSK and Cyclin D1, were decreased, while the expression level of E-cadherin was increased. Finally, the invasion and proliferation capacity of gastric cancer cells was inhibited.

Conclusion

In other words, loss of C14orf159 is associated with the progression of gastric cancer. The role of C14orf159 in repression of proliferation and invasion may be due to resuming E-cadherin and abolishing Snail and Cyclin D1 expression through inactivating ERK–P90RSK pathway.

The micro RNA hsa-miR-377-3p inhibits tumor growth in malignant melanoma

Background/Aims: Most recently, micro RNAs (miRNAs/miRs) have been suggested to play a key role in various physiological and pathological processes by regulating the expression of specific genes. The influence of miR-377-3p on multitudinous cancer cells has been investigated; however, its function in melanoma remains undiscovered. Armadillo repeat-containing protein 8 (ARMC8), a target of miR-377-3p, plays essential roles in proliferation, differentiation and apoptosis. Our research aimed to detect the specific roles of miR-377-3p in melanoma. Methods: The MiRNA and mRNA expressions were evaluated by a real-time quantitative polymerase chain reaction in the A375 and HEMa-LP cell lines. We predicted the possible interactions between microRNA and mRNAs by bioinformatics database and constructed them with the Cytoscape software. The proliferation and migration activities were investigated using a cell counting kit-8 (CCK8) and wound-healing assay. Validation of the correlation between miR-377-3p and ARMC8 was implemented by the luciferase reporter assay and PCR. Results: The expression of miR-377-3p was found to be lower in malignant melanoma cells. The upregulation of miR-377-3p inhibited the melanoma cell proliferation, migration, and ARMC8 expression. miR-377-3p was identified to bind to the 3′UTR region of ARMC8 directly; this indicated that miR-377-3p suppressed melanoma cell growth partly mediated via the ARMC8 expression. Conclusion: These findings show that miR-377-3p negatively regulates tumor growth in malignant melanoma, which may thus provide a potential biological target for melanoma treatment and subsequently lead to the development of potential treatments.

We have demonstrated that miR-377-3p inhibits melanoma cell growth by binding to the ARMC8 mRNA in the A375 cell line.

Role of Bicaudal C1 in renal gluconeogenesis and its novel interaction with the CTLH complex

Altered glucose and lipid metabolism fuel cystic growth in polycystic kidneys, but the cause of these perturbations is unclear. Renal cysts also associate with mutations in Bicaudal C1 (Bicc1) or in its self-polymerizing sterile alpha motif (SAM). Here, we found that Bicc1 maintains normoglycemia and the expression of the gluconeogenic enzymes FBP1 and PEPCK in kidneys. A proteomic screen revealed that Bicc1 interacts with the C-Terminal to Lis-Homology domain (CTLH) complex. Since the orthologous Gid complex in S. cerevisae targets FBP1 and PEPCK for degradation, we mapped the topology among CTLH subunits and found that SAM-mediated binding controls Bicc1 protein levels, whereas Bicc1 inhibited the accumulation of several CTLH subunits. Under the conditions analyzed, Bicc1 increased FBP1 protein levels independently of the CTLH complex. Besides linking Bicc1 to cell metabolism, our findings reveal new layers of complexity in the regulation of renal gluconeogenesis compared to lower eukaryotes.

Polycystic kidney diseases (PKD) are incurable inherited chronic disorders marked by fluid-filled cysts that frequently cause renal failure. A glycolytic metabolism reminiscent of cancerous cells accelerates cystic growth, but the mechanism underlying such metabolic re-wiring is poorly understood. PKD-like cystic kidneys also develop in mice that lack the RNA-binding protein Bicaudal-C (Bicc1), and mutations in a single copy of human BICC1 associate with renal cystic dysplasia. Here, we report that Bicc1 regulates renal gluconeogenesis. A screen for interacting factors revealed that Bicc1 binds the C-Terminal to Lis-Homology domain (CTLH) complex, which in lower eukaryotes mediates degradation of gluconeogenic enzymes. By contrast, Bicc1 and the mammalian CTLH complex regulated each other, and Bicc1 stimulated the accumulation of the rate-limiting gluconeogenic enzyme even in cells depleted of CTLH subunits. Our finding that Bicc1 is required for normoglycemia implies that renal gluconeogenesis may be important to inhibit cyst formation.

Silencing of Armadillo Repeat-Containing Protein 8 (ARMc8) Inhibits TGF-β-Induced EMT in Bladder Carcinoma UMUC3 Cells

Armadillo repeat-containing protein 8 (ARMc8) is a key factor in regulating cell migration, proliferation, tissue maintenance, and tumorigenesis. However, its role in bladder cancer remains unknown. Thus, in this study we sought to investigate the effect of ARMc8 on the epithelial-to-mesenchymal transition (EMT) progress in bladder cancer cells induced by transforming growth factor-β1 (TGF-β1). Our results found that ARMc8 was highly expressed in bladder cancer cell lines. ARMc8 silencing inhibited the TGF-β1-induced migration and invasion and suppressed the EMT progress in bladder cancer cells. Furthermore, ARMc8 silencing inhibited the TGF-β1-induced expression of β-catenin, cyclin D1, and c-myc in bladder cancer cells. In conclusion, the present study demonstrates a novel function for ARMc8, which acts as a mediator for TGF-β1-induced cell migration/invasion through modulation of the Wnt/β-catenin signaling pathway in bladder cancer cells. This study suggests that ARMc8 may be a potential therapeutic target for the development of therapies for bladder cancer.

Armadillo Repeat-Containing Protein 8 (ARMC8) Silencing Inhibits Proliferation and Invasion in Osteosarcoma Cells

Armadillo repeat-containing protein 8 (ARMC8) plays an important role in regulating cell migration, proliferation, tissue maintenance, signal transduction, and tumorigenesis. However, the expression pattern and role of ARMC8 in osteosarcoma are still unclear. In this study, our aims were to examine the effects of ARMC8 on osteosarcoma and to explore its underlying mechanism. Our results demonstrated that ARMC8 was overexpressed in osteosarcoma cell lines. Knockdown of ARMC8 significantly inhibited osteosarcoma cell proliferation in vitro and markedly inhibited xenograft tumor growth in vivo. ARMC8 silencing also suppressed the epithelial-mesenchymal transition (EMT) phenotype, as well as inhibited the migration and invasion of osteosarcoma cells. Furthermore, knockdown of ARMC8 obviously inhibited the expression of β-catenin, c-Myc, and cyclin D1 in MG-63 cells. In conclusion, this report demonstrates that ARMC8 silencing inhibits proliferation and invasion of osteosarcoma cells. Therefore, ARMC8 may play an important role in the development and progression of human osteosarcoma and may represent a novel therapeutic target in the treatment of osteosarcoma.