TD-60 links RalA GTPase function to the CPC in mitosis

NudCL2 is required for cytokinesis by stabilizing RCC2 with Hsp90 at the midbody

Cytokinesis is required for faithful division of cytoplasmic components and duplicated nuclei into two daughter cells. Midbody, a protein-dense organelle that forms at the intercellular bridge, is indispensable for successful cytokinesis. However, the regulatory mechanism of cytokinesis at the midbody still remains elusive. Here, we unveil a critical role for NudC-like protein 2 (NudCL2), a co-chaperone of heat shock protein 90 (Hsp90), in cytokinesis regulation by stabilizing regulator of chromosome condensation 2 (RCC2) at the midbody in mammalian cells. NudCL2 localizes at the midbody, and its downregulation results in cytokinesis failure, multinucleation, and midbody disorganization. Using iTRAQ-based quantitative proteomic analysis, we find that RCC2 levels are decreased in NudCL2 knockout (KO) cells. Moreover, Hsp90 forms a complex with NudCL2 to stabilize RCC2, which is essential for cytokinesis. RCC2 depletion mirrors phenotypes observed in NudCL2-downregulated cells. Importantly, ectopic expression of RCC2 rescues the cytokinesis defects induced by NudCL2 deletion, but not vice versa. Together, our data reveal the significance of the NudCL2/Hsp90/RCC2 pathway in cytokinesis at the midbody.

RPGR is a guanine nucleotide exchange factor for the small GTPase RAB37 required for retinal function via autophagy regulation

Although the small GTPase RAB37 acts as an organizer of autophagosome biogenesis, the upstream regulatory mechanism of autophagy via guanosine diphosphate (GDP)-guanosine triphosphate (GTP) exchange in maintaining retinal function has not been determined. We found that retinitis pigmentosa GTPase regulator (RPGR) is a guanine nucleotide exchange factor that activates RAB37 by accelerating GDP-to-GTP exchange. RPGR directly interacts with RAB37 via the RPGR-RCC1-like domain to promote autophagy through stimulating exchange. Rpgr knockout (KO) in mice leads to photoreceptor degeneration owing to autophagy impairment in the retina. Notably, the retinopathy phenotypes of Rpgr KO retinas are rescued by the adeno-associated virus-mediated transfer of pre-trans-splicing molecules, which produce normal Rpgr mRNAs via trans-splicing in the Rpgr KO retinas. This rescue upregulates autophagy through the re-expression of RPGR in KO retinas to accelerate GDP-to-GTP exchange; thus, retinal homeostasis reverts to normal. Taken together, these findings provide an important missing link for coordinating RAB37 GDP-GTP exchange via the RPGR and retinal homeostasis by autophagy regulation.

Leucine zipper protein 1 (LUZP1) regulates the constriction velocity of the contractile ring during cytokinesis

There has been a great deal of research on cell division and its mechanisms; however, its processes still have many unknowns. To find novel proteins that regulate cell division, we performed the screening using siRNAs and/or the expression plasmid of the target genes and identified leucine zipper protein 1 (LUZP1). Recent studies have shown that LUZP1 interacts with various proteins and stabilizes the actin cytoskeleton; however, the function of LUZP1 in mitosis is not known. In this study, we found that LUZP1 colocalized with the chromosomal passenger complex (CPC) at the centromere in metaphase and at the central spindle in anaphase and that these LUZP1 localizations were regulated by CPC activity and kinesin family member 20A (KIF20A). Mass spectrometry analysis identified that LUZP1 interacted with death-associated protein kinase 3 (DAPK3), one regulator of the cleavage furrow ingression in cytokinesis. In addition, we found that LUZP1 also interacted with myosin light chain 9 (MYL9), a substrate of DAPK3, and comprehensively inhibited MYL9 phosphorylation by DAPK3. In line with a known role for MYL9 in the actin-myosin contraction, LUZP1 suppression accelerated the constriction velocity at the division plane in our time-lapse analysis. Our study indicates that LUZP1 is a novel regulator for cytokinesis that regulates the constriction velocity of the contractile ring.

RCC2 promotes prostate cancer cell proliferation and migration through Hh/GLI1 signaling pathway and cancer stem-like cells

BACKGROUND

Regulator of chromosome condensation 2 (RCC2) was a telophase disk-binding protein on mitosis, and functions as an oncogene in many human cancers. However, its role on prostate cancer (PCa) was unknown. The goal of this study is to explore the function of RCC 2 on PCa development.

METHODS

The expression of RCC2 and its methylation level, its correlation with lymph node metastasis or disease-free survival (DFS) was analyzed using TCGA database. The effect of RCC2 on PCa cell proliferation, migration and invasion were detected using CCK-8, cell colony formation, Transwell and wood healing assays. RNA-seq and GSEA analysis were used to search the downstream genes and pathways of RCC2 in mediated PCa progression. Western blot was used to detect the proteins in PCa cells transfected with indicated siRNAs or plasmids.

RESULTS

RCC2 had high expression and low promoter methylation level in PCa, and its expression was correlated with regional node metastasis and disease-free survival. Cell proliferation, migration, invasion and EMT of PCa cells in vitro were greatly enhanced after RCC2 overexpression, while the RCC2 knockdown suppressed these processes. RNA-seq and GSEA results showed the Hedgehog signaling regulator Gli1 and Gli3 were involved in RCC2 knockdown DU145 cells. Gli1 was also a marker of cancer stem-like cells (CSCs). Mechanistically, RCC2 induced cell growth, EMT, CSCs markers through Gli1; inhibiting Gli1 expression using siGli1 or GLI inhibitor suppressed cell progression in vitro and tumor growth in vivo.

CONCLUSION

In summary, RCC2 promoted PCa development through Hh/Gli1 signaling pathway via regulating EMT and CSCs.

A human pan-cancer system analysis of regulator of chromatin condensation 2

Regulation of chromosome condensation 2 (RCC2) is associated with the cell cycle and is a crucial regulator of the chromatin condensation 1 (RCC1) family. The members of this family were normally regulators in the process of DNA replication and nucleocytoplasmic transport. RCC2 overexpression may lead to tumor formation and poor prognosis in some tumors including breast cancer and lung adenocarcinoma. However, the possible role of RCC2 in tumor formation and its prognostic function remains unclear. In this study, expression analysis from databases including The Cancer Genome Atlas (TCGA) and Clinical Proteomic Tumor Analysis Consortium (CPTAC) were combined to perform the first integrative and comprehensive analysis of RCC2 in human pan-cancer. RCC2 was highly expressed in most tumors which may lead to a poor prognosis. RCC2 expression was associated with immune/stromal infiltration, immune checkpoints, tumor mutational burden, and microsatellite instability. Thus, RCC2 could be a novel biomarker for prognosis and a promising cancer therapy target.

Comprehensive analysis of the expression profile and clinical implications of regulator of chromosome condensation 2 in pan-cancers

The Regulator of Chromosome Condensation 2 (RCC2) is an important gene that regulates mitosis and cytoplasmic division in the cell cycle. Although there have been reported in several individual tumors, an integrative analysis of RCC2 and its clinical significance across diverse cancer types is poorly elucidated. In this study, we performed integrative bioinformatics analyses to profile the expression landscape and assess the prognostic value of RCC2 in pan-cancers. Correlations between RCC2 expression and tumor-infiltrating immune cells, tumor mutation burden (TMB), microsatellite instability (MSI), chemokine and their receptors were analyzed using TCGA, ESTIMATE algorithm, and TISIDB database. We also explored the potential molecular functions of RCC2 through functional enrichment analysis and protein interaction networks. We discovered that RCC2 was highly expressed in various tumor tissues and was closely associated with cancer prognosis. Different RCC2-associated immune infiltration patterns were exhibited in different tumor-infiltrating immune cells. In addition, the RCC2 had a potential role in regulating the tumor immune microenvironment and the formation of cancer-associated fibroblasts (CAFs). Meanwhile, RCC2 showed a significant correlation with TMB, MSI, chemokines and their receptors in different tumor types. The role of RCC2 as a clinical therapeutic target was further revealed from the perspective of the immune microenvironment. In conclusion, RCC2 is closely associated with tumorigenesis and cancer-immune infiltration, and could be a promising prognostic and therapeutic biomarker in diverse cancers.

The mitotic regulator RCC2 promotes glucose metabolism through BACH1-dependent transcriptional upregulation of hexokinase II in glioma

Weighted gene co-expression network analysis (WGCNA) identified a cell-cycle module that is associated with poor prognosis and aggressiveness of glioma. One of the core members, Regulator of chromatin condensation 2 (RCC2) is a component of the chromosome passenger complex. Accumulating evidence suggests that RCC2 plays a vital role in the mitotic process and that abnormal RCC2 expression is involved in cancer development. Gene silencing experiments show that RCC2 is required for glioma cell proliferation and migration. RNA-Sequencing analysis reveals a dual role of RCC2 in both the cell cycle and metabolism. Specifically, RCC2 regulates G2/M progression via CDC2 phosphorylation at Tyrosine 15. Metabolomic analysis identifies a role for RCC2 in promoting the glycolysis and pentose phosphate pathway. RCC2 exerts effects on metabolism by stabilizing the transcription factor BACH1 at its C-terminus leading to the transcriptional upregulation of hexokinase 2 (HK2). These findings elucidate a novel PTEN/RCC2/BACH1/HK2 signaling axis that drives glioma progression through the dual regulation of mitotic cell cycle and glycolytic events.

Cell Cycle Regulation by Integrin-Mediated Adhesion

Cell cycle and cell adhesion are two interdependent cellular processes regulating each other, reciprocally, in every cell cycle phase. The cell adhesion to the extracellular matrix (ECM) via integrin receptors triggers signaling pathways required for the cell cycle progression; the passage from the G1 to S phase and the completion of cytokinesis are the best-understood events. Growing evidence, however, suggests more adhesion-dependent regulatory aspects of the cell cycle, particularly during G2 to M transition and early mitosis. Conversely, the cell cycle machinery regulates cell adhesion in manners recently shown driven mainly by cyclin-dependent kinase 1 (CDK1). This review summarizes the recent findings regarding the role of integrin-mediated cell adhesion and its downstream signaling components in regulating the cell cycle, emphasizing the cell cycle progression through the G2 and early M phases. Further investigations are required to raise our knowledge about the molecular mechanisms of crosstalk between cell adhesion and the cell cycle in detail.

Fine-tuning cell organelle dynamics during mitosis by small GTPases

During mitosis, the allocation of genetic material concurs with organelle transformation and distribution. The coordination of genetic material inheritance with organelle dynamics directs accurate mitotic progression, cell fate determination, and organismal homeostasis. Small GTPases belonging to the Ras superfamily regulate various cell organelles during division. Being the key regulators of membrane dynamics, the dysregulation of small GTPases is widely associated with cell organelle disruption in neoplastic and non-neoplastic diseases, such as cancer and Alzheimer's disease. Recent discoveries shed light on the molecular properties of small GTPases as sophisticated modulators of a remarkably complex and perfect adaptors for rapid structure reformation. This review collects current knowledge on small GTPases in the regulation of cell organelles during mitosis and highlights the mediator role of small GTPase in transducing cell cycle signaling to organelle dynamics during mitosis.

The RAL Enigma: Distinct Roles of RALA and RALB in Cancer

RALA and RALB are highly homologous small G proteins belonging to the RAS superfamily. Like other small GTPases, the RALs are molecular switches that can be toggled between inactive GDP-bound and active GTP-bound states to regulate diverse and critical cellular functions such as vesicle trafficking, filopodia formation, mitochondrial fission, and cytokinesis. The RAL paralogs are activated and inactivated by a shared set of guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs) and utilize similar sets of downstream effectors. In addition to their important roles in normal cell biology, the RALs are known to be critical mediators of cancer cell survival, invasion, migration, and metastasis. However, despite their substantial similarities, the RALs often display striking functional disparities in cancer. RALA and RALB can have redundant, unique, or even antagonistic functions depending on cancer type. The molecular basis for these discrepancies remains an important unanswered question in the field of cancer biology. In this review we examine the functions of the RAL paralogs in normal cellular physiology and cancer biology with special consideration provided to situations where the roles of RALA and RALB are non-redundant.

Roles of regulator of chromosome condensation 2 in cancer: Beyond its regulatory function in cell cycle

Regulator of chromosome condensation 2 (RCC2) is an essential protein in order for mitosis to proceed properly. It localizes in the centrosome of chromosomes where is involved in chromosome segregation and cytokinesis. Furthermore, RCC2 associates with integrin networks at the plasma membrane where participates in the control of cell movement. Because of its known role in cell cycle, RCC2 has been linked with cancer progression. Several reports show that RCC2 induces cancer hallmarks, but the mechanisms explaining how RCC2 exerts these roles are widely unknown. Here, we aim to summarize the main findings explaining the roles and mechanisms of RCC2 in cancer promotion. RCC2 is overexpressed in different cancers, including glioblastoma, lung, ovarian, and esophageal which is related to proliferation, migration, invasion promotion in vitro and tumor progression and metastasis in vivo. Besides, RCC2 overexpression induces epithelial-mesenchymal transition and causes poorer prognosis in cancer patients. RCC2 overexpression has also been linked with resistance development to chemotherapy and radiotherapy by inhibiting apoptosis and activating cancer-promoting transcription factors. Unfortunately, not RCC2 inhibitors are currently available for further pre-clinical and clinical assays. Therefore, these findings emphasize the potential use of RCC2 as a targetable biomarker in cancer and highlight the importance for designing RCC2 chemical inhibitors to evaluate its efficacy in animal studies and clinical trials.

Regulator of Chromosome Condensation 2 Modulates Cell Cycle Progression, Tumorigenesis, and Therapeutic Resistance

Accurate regulation of cell cycle is important for normal tissue development and homeostasis. RCC2 (Regulator of Chromosome Condensation 2) play a role as chromosomal passenger complex (CPC) implicated in all cell cycle phases. RCC2 was initially identified as Ran guanine exchange factor (GEF) for small G proteins. Therefore, RCC2 plays a key role in oncogenesis of most cancers. RCC2 is implicated in Colorectal Cancer (CRC), Lung Adenocarcinoma (LUAD), breast cancer, and ovarian cancer. Expression level of RCC2 protein determines regulation of tumor cell proliferation, invasion, metastasis, and radio-chemotherapeutic resistance. In this review, we explored proteins that interact with RCC2 to modulate tumor development and cancer therapeutic resistance by regulation of cell cycle process through various signaling pathways.

The RAL signaling network: Cancer and beyond

The RAL proteins RALA and RALB belong to the superfamily of small RAS-like GTPases (guanosine triphosphatases). RAL GTPases function as molecular switches in cells by cycling through GDP- and GTP-bound states, a process which is regulated by several guanine exchange factors (GEFs) and two heterodimeric GTPase activating proteins (GAPs). Since their discovery in the 1980s, RALA and RALB have been established to exert isoform-specific functions in central cellular processes such as exocytosis, endocytosis, actin organization and gene expression. Consequently, it is not surprising that an increasing number of physiological functions are discovered to be controlled by RAL, including neuronal plasticity, immune response, and glucose and lipid homeostasis. The critical importance of RAL GTPases for oncogenic RAS-driven cellular transformation and tumorigenesis still attracts most research interest. Here, RAL proteins are key drivers of cell migration, metastasis, anchorage-independent proliferation, and survival. This chapter provides an overview of normal and pathological functions of RAL GTPases and summarizes the current knowledge on the involvement of RAL in human disease as well as current therapeutic targeting strategies. In particular, molecular mechanisms that specifically control RAL activity and RAL effector usage in different scenarios are outlined, putting a spotlight on the complexity of the RAL GTPase signaling network and the emerging theme of RAS-independent regulation and relevance of RAL.

RCC2 Promotes Esophageal Cancer Growth by Regulating Activity and Expression of the Sox2 Transcription Factor

Regulator of chromosome condensation 2 (RCC2) is a protein located in the centrosome, which ensures that cell division proceeds properly. Previous reports show that RCC2 is overexpressed in some cancers and could play a key role in tumor development, but the mechanisms concerning how this occurs are not understood. Furthermore, no evidence exists regarding its role in esophageal cancer. We studied the relevance of RCC2 in esophageal cancer growth and its regulation on Sox2, an important transcription factor promoting esophageal cancer. RCC2 was overexpressed in esophageal tumors compared with normal tissue, and this overexpression was associated with tumorigenicity by increasing cell proliferation, anchorage-independent growth, and migration. These oncogenic effects were accompanied by overexpression of Sox2. RCC2 upregulated and stabilized Sox2 expression and its target genes by inhibiting ubiquitination-mediated proteasome degradation. Likewise, RCC2 increased the transcriptional activity and promoter binding of Sox2. In vivo studies indicated that RCC2 and Sox2 were overexpressed in esophageal tumors compared with normal tissue, and this upregulation occurs in the esophageal basal cell layer for both proteins. In conditional knockout mice, RCC2 deletion decreased the tumor nodule formation and progression in the esophagus compared with wild-type mice. Proliferating cell nuclear antigen expression, a cell proliferation marker, was also downregulated in RCC2 knockout mice. Overall, our data show for the first time that RCC2 is an important protein for the stabilization and transcriptional activation of Sox2 and further promotion of malignancy in esophageal cancer. IMPLICATIONS: This study shows that RCC2 controls Sox2 expression and transcriptional activity to mediate esophageal cancer formation.

RCC2 contributes to tumor invasion and chemoresistance to cisplatin in hepatocellular carcinoma

Tumor metastasis and chemoresistance are the main causes of treatment failure and high mortality in hepatocellular carcinoma (HCC). Therefore, it is critical to clarify the biological action and potential mechanisms in HCC cells to develop novel therapeutics. The regulator of chromosome condensation 2 (RCC2), a component of the chromosomal passenger complex, was shown to have important roles in tumor development and radio-chemotherapy resistance. However, its role in the aggressive phenotypes and cisplatin (DDP)-resistance of HCC is not known. Therefore, this study aimed to investigate the role of RCC2 in HCC pathogenesis. Interestingly, we found that RCC2 was upregulated in HCC patient specimens and HCC cell lines and was correlated with the pathological grade of HCC. To evaluate the function of RCC2 in HCC cell, lentivirus vector-based shRNAs were transfected into HCC cells. Silencing RCC2 inhibited the HCC cell proliferation, migration, invasion, and increased the apoptosis rate upon DDP treatment. Further analysis showed that RCC2-mediated downregulation of the expression of survival proteins occurred via the AKT and Bcl2 pathways. Our results suggest that RCC2 might act as an oncogenic protein promoting metastatic behaviors and cisplatin resistance in HCC cells, and thereby could be a potential prognostic biomarker and therapeutic target for HCC.

RCC2 Expression Stimulates ER-Positive Breast Tumorigenesis

Objective

Regulator of chromosome condensation 2 (RCC2) has been reported to be involved in the regulation of cell cleavage. This study investigated the effect of RCC2 expression on breast tumorigenesis.

Methods

MCF-7 cells originating from estrogen receptor-positive (ER+) breast cancer were transfected with anti-RCC2 siRNA or RCC2-expressing plasmids. Cell proliferation, apoptosis, migration, and cytokine production in the transfected cells were examined using the CCK-8 assay, wound healing assay, and flow cytometry, respectively. PCR array was used to investigate the tumorigenic pathway of RCC2 in MCF-7 cells transfected with the anti-RCC2 siRNA. MCF-7 cells were also transfected with lentivirus-containing anti-RCC2 short hairpin RNA and were injected into BALB/c nude mice to generate tumor-bearing mice. Tumor growth in the mouse model was examined using magnetic resonance imaging by diffusion-weighted imaging analysis.

Results

Western blotting and immunohistochemistry detected significantly increased expression of RCC2 in ER + breast tumor tissues compared with breast fibroadenoma samples. Inhibiting RCC2 expression decreased cell migration and stimulated apoptosis in MCF-7 cells, while overexpressing RCC2 stimulated cell migration and inhibited apoptosis. The inhibition of RCC2 expression significantly decreased breast tumor growth and IL-6 levels in the tumor-bearing mice. PCR array demonstrated that inhibiting RCC2 expression significantly decreased the expression of IGF1 and TWIST1, two well-known tumor-enhancing genes, in MCF-7 cells; conversely, overexpressing RCC2 increased the expression levels of these two genes in the transfected cells. This result was verified in the mouse model following inhibition of RCC2 expression in MCF-7 cells. Additionally, estradiol-17β suppressed MCF-7 cell apoptosis, stimulated cell proliferation and cell migration, and increased RCC2, IGF1, and TWIST1 expression. The siRNA-mediated inhibition of RCC2 expression alleviated the inhibitory effects of estrogen on apoptosis in MCF-7 cells, while overexpressing RCC2 enhanced the estrogen-driven inhibition of apoptosis. Modifying RCC2 expression had no impact on MCF-7 cell proliferation in the presence or absence of estradiol-17β.

Conclusions

Our results suggest that estrogen-induced RCC2 expression prompts IGF1, TWIST1, and IL-6 expression, stimulates cell migration, and inhibits apoptosis to contribute to ER + breast tumorigenesis.

RCC2 Interacts with Small GTPase RalA and Regulates Cell Proliferation and Motility in Gastric Cancer

Background

Regulator of chromosome condensation 2 (RCC2), also known as TD-60, is associated with various human malignant cancers. RCC2 has been shown to exhibit guanine exchange factor (GEF) activity and contribute to early mitosis. However, the role and mechanism of RCC2 in gastric cancer remain unclear.

Materials and Methods

RCC2 expression in gastric cancer was studied using qPCR, Western blotting and immunochemistry staining of clinical specimens, and its roles in the cytobiology, mouse model and related molecular pathways were evaluated using gastric cell lines.

Results

RCC2 was frequently overexpressed in gastric cancer. RCC2 knockdown significantly inhibited cell proliferation, migration and invasion in vitro, which was further confirmed by the RCC2 overexpression results in gastric cancer cells. Moreover, RCC2 knockdown inhibited tumor progression in vivo. Further study revealed the interaction between RCC2 and RalA. The level of RalA-GTP was decreased in gastric cancer cells after RCC2 knockdown, while an increased phosphorylation level in MAPK/JNK was found. Furthermore, the changes in the level of RalA-GTP as well as cell proliferation, migration and invasion abilities were further confirmed using RBC8, a specific small-molecule inhibitor of the intracellular actions of Ral GTPases, in gastric cancer cells.

Conclusion

RCC2 plays an important role in gastric cancer. RCC2 knockdown inhibits cell growth, cell motility and tumor progression, which may act through RalA and affect the MAPK/JNK pathway.

RCC2 promotes breast cancer progression through regulation of Wnt signaling and inducing EMT

Regulator of chromosome condensation 2 (RCC2), also known as TD-60, is an RCC1 family member and plays an essential role in mitosis. However, the roles of RCC2 in breast cancer are still unclear. In this study, RCC2 was found to exert oncogenic activities in breast cancer. Samples of breast cancer tissue revealed an increased level of RCC2 and a high level of RCC2 was associated with poor overall survival rate of breast cancer patients. Overexpression of RCC2 significantly enhanced cell proliferation and migration abilities of breast cancer cells in vitro and in vivo. Mechanistically, RCC2 induced epithelial-mesenchymal transition (EMT) through the activation of Wnt signaling pathway. Collectively, our study indicates that RCC2 contributes to breast cancer progression and functions as an important regulator of EMT through the activation of Wnt signaling.

RCC2 promotes proliferation and radio-resistance in glioblastoma via activating transcription of DNMT1

Regulator of chromosome condensation 2 (RCC2) is a regulator of cell-cycle progression linked in multiple cancers to pro-tumorigenic phenomena including promotion of tumor growth, tumor metastases and poorer patient prognoses. However, the role of RCC2 in GBM remains under-investigated. Here, we sought to determine the relevance of RCC2 in GBM, as well as its roles in GBM development, progression and prognosis. Initial clinical evaluation determined significant RCC2 enrichment in GBM when compared to normal brain tissue, and elevated expression was closely associated with a poorer prognosis in glioma patients. Via shRNA inhibition, we determined that RCC2 is essential to tumor proliferation and tumorigenicity in vitro and in vivo. Additionally, RCC2 was determined to promote radioresistance of GBM tumor cells. Investigation of the underlying mechanisms implicated DNA mismatch repair, JAK-STAT pathway and activated transcription of DNA methyltransferase 1 (DNMT1). For validation, pharmacologic inhibition via administration of a DNMT1 inhibitor demonstrated attenuated GBM tumor growth both in vitro and in vivo. Collectively, this study determined a novel therapeutic target for GBM in the form of RCC2, which plays a pivotal role in GBM proliferation and radio-resistance via regulation of DNMT1 expression in a p-STAT3 dependent manner.

Transcriptomic analysis of gills provides insights into the molecular basis of molting in Chinese mitten crab (Eriocheir sinensis)

Chinese mitten crab (Eriocheir sinensis) is an economically important freshwater aquaculture species and is a model species for research on the mechanism of molting. This study aimed to identify important candidate genes associated with the molting process and to determine the role of gills in the regulation of molting with the help of transcriptomic analysis. The transcriptomes of crabs at different molting stages—postmolt (PoM), intermolt (InM), premolt (PrM) and ecdysis (E)—were de novo assembled to generate 246,232 unigenes with a mean length of 851 bp. A total of 86,634 unigenes (35.18% of the total unigenes) were annotated against reference databases. Significantly upregulated genes were identified in postmolt compared to intermolt (1,475), intermolt compared to premolt (65), premolt compared to ecdysis (1,352), and ecdysis compared to postmolt (153), and the corresponding numbers of downregulated genes were 1,276, 32, 1,573 and 171, respectively. Chitin synthase, endochitinase, chitinase A, chitinase 3, chitinase 6 and chitin deacetylase 1 were upregulated during the postmolt and ecdysis stages, while phosphoglucomutase 3 (PGM3), glucosamine 6-phosphate deaminase (GNPDA) and glucosamine glycoside hydrolase (nagZ) were upregulated during the intermolt and premolt stages compared to the other stages. The upregulated genes were enriched in several lipid-related metabolic pathways, such as “fatty acid elongation”, “glycerophospholipid metabolism” and “sulfur metabolism”. Meanwhile, three signaling pathways, including the “phosphatidylinositol signaling system”, the “calcium signaling pathway” and the “GnRH signaling pathway” were also enriched. Tetraspanin-18, an important effector gene in the lysosomal pathway involved in cell apoptosis, up-regulate with the beginning of molting (in premolt stage) and reach the top in the ecdysis stage, and barely expressed in the intermolt stage. The expression variations in the tetraspanin-18 gene indicated that it may play an important role in the beginning of molting cycle, which might be regulated by the stress of salinity. This study revealed that the gills could participate in chitin degradation, in reestablishment of the exoskeleton and the signaling process. Based on transcriptomic analysis of the gills, we not only explored novel molecular mechanisms of molting in E. sinensis but also acquired foundational genetic data for E. sinensis.

Developmental fidelity is imposed by genetically separable RalGEF activities that mediate opposing signals

The six C. elegans vulval precursor cells (VPCs) are induced to form the 3°-3°-2°-1°-2°-3° pattern of cell fates with high fidelity. In response to EGF signal, the LET-60/Ras-LIN-45/Raf-MEK-2/MEK-MPK-1/ERK canonical MAP kinase cascade is necessary to induce 1° fate and synthesis of DSL ligands for the lateral Notch signal. In turn, LIN-12/Notch receptor is necessary to induce neighboring cells to become 2°. We previously showed that, in response to graded EGF signal, the modulatory LET-60/Ras-RGL-1/RalGEF-RAL-1/Ral signal promotes 2° fate in support of LIN-12. In this study, we identify two key differences between RGL-1 and RAL-1. First, deletion of RGL-1 confers no overt developmental defects, while previous studies showed RAL-1 to be essential for viability and fertility. From this observation, we hypothesize that the essential functions of RAL-1 are independent of upstream activation. Second, RGL-1 plays opposing and genetically separable roles in VPC fate patterning. RGL-1 promotes 2° fate via canonical GEF-dependent activation of RAL-1. Conversely, RGL-1 promotes 1° fate via a non-canonical GEF-independent activity. Our genetic epistasis experiments are consistent with RGL-1 functioning in the modulatory 1°-promoting AGE-1/PI3-Kinase-PDK-1-AKT-1 cascade. Additionally, animals lacking RGL-1 experience 15-fold higher rates of VPC patterning errors compared to the wild type. Yet VPC patterning in RGL-1 deletion mutants is not more sensitive to environmental perturbations. We propose that RGL-1 functions to orchestrate opposing 1°- and 2°-promoting modulatory cascades to decrease developmental stochasticity. We speculate that such switches are broadly conserved but mostly masked by paralog redundancy or essential functions.

Developmental signals are increasingly conceptualized in the context of networks rather than linear pathways. Patterning of C. elegans vulval fates is mostly governed by two major signaling cascades that operate antagonistically to induce two cell identities. An additional pair of minor cascades support each of the major cascades. All components in this system are conserved in mammalian oncogenic signaling networks. We find that RGL-1, a component of one of the minor cascades, performs two antagonistic functions. Its deletion appears to abolish both opposing modulatory signals, resulting in a 15-fold increase in the basal error rate in development of these cells. We hypothesize that the bifunctional RGL-1 protein defines a novel mechanism by which signaling networks are interwoven to mitigate developmental errors.

RCC2, a regulator of the RalA signaling pathway, is identified as a novel therapeutic target in cisplatin-resistant ovarian cancer

Currently, cisplatin (DDP) is the first-line chemotherapeutic agent used for treatment of ovarian cancer, but gradually acquired drug resistance minimizes its therapeutic outcomes. We aimed to identify crucial genes associated with DDP resistance in ovarian cancer and uncover potential mechanisms. Two sets of gene expression data were downloaded from Gene Expression Omnibus, and bioinformatics analysis was conducted. In our study, the differentially expressed genes between DDP-sensitive and DDP-resistant ovarian cancer were screened in GSE15709 and GSE51373 database, and chromosome condensation 2 regulator (RCC2) and nucleoporin 160 were identified as 2 genes that significantly up-regulated in DDP-resistant ovarian cancer cell lines compared with DDP-sensitive cell lines. Moreover, RCC2, Ral small GTPase (RalA), and Ral binding protein-1 (RalBP1) expression was found to be significantly higher in DDP-resistant ovarian cancer tissues than in DDP-sensitive tissues. RCC2 plays a positive role in cell proliferation, apoptosis, and migration in DDP-resistant ovarian cancer cell lines in vitro and in vivo. Furthermore, RCC2 could interact with RalA, thus promoting its downstream effector RalBP1. RalA knockdown could reverse the effects of RCC2 overexpression on DDP-resistant ovarian cancer cell proliferation, apoptosis, and migration. Similarly, RalA overexpression could alleviate the effects of RCC2 knockdown in DDP-resistant ovarian cancer cells. Taken together, RCC2 may function as an oncogene, regulating the RalA signaling pathway, and intervention of RCC2 expression might be a promising therapeutic strategy for DDP-resistant ovarian cancer.-Gong, S., Chen, Y., Meng, F., Zhang, Y., Wu, H., Li, C., Zhang, G. RCC2, a regulator of the RalA signaling pathway, is identified as a novel therapeutic target in cisplatin-resistant ovarian cancer.

Overexpression of CDCA8 promotes the malignant progression of cutaneous melanoma and leads to poor prognosis

Cutaneous melanoma is very aggressive and results in high mortality rates for cancer patients. Determining molecular targets is important for developing novel therapies for cutaneous melanoma. Cell division cycle associated 8 (CDCA8) is a putative oncogene that is upregulated in multiple types of cancer. The present study aimed to examine the role of CDCA8 in cutaneous melanoma, with a focus on the association of its expression to prognosis and metastasis. First, the mRNA expression of CDCA8 in cutaneous melanoma tissues was investigated using the ONCOMINE and Gene Expression Omnibus (GEO) databases. Furthermore, the relationship between the expression of CDCA8 and cutaneous melanoma patient survival was analyzed using a Kaplan‑Meier plot and Log Rank test. In addition, the effects of CDCA8 on proliferation, migration and invasion of cutaneous melanoma cell lines were investigated using reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR), Cell Counting kit‑8, colony formation assay, wound healing and Matrigel assay. Finally, the expression levels of key proteins related to the Rho‑associated coiled‑coil‑containing protein kinase (ROCK) signaling pathway were measured by western blot assay. The results demonstrated that CDCA8 was overexpressed in cutaneous melanoma tissues and cells lines compared with normal tissues, and high expression of CDCA8 was significantly associated with poorer prognosis in patients with cutaneous melanoma. In in vitro experiments, CDCA8 knockdown inhibited A375 and MV3 cell proliferation, migration and invasion. In addition, CDCA8 knockdown reduced the phosphorylation levels of ROCK1 and myosin light chain, two downstream effector proteins of the ROCK pathway. In summary, the present findings suggested that CDCA8 may be a promising therapeutic target for the treatment of cutaneous melanoma.

WBSCR16 Is a Guanine Nucleotide Exchange Factor Important for Mitochondrial Fusion

Regulated inter-mitochondrial fusion/fission is essential for maintaining optimal mitochondrial respiration and control of apoptosis and autophagy. In mammals, mitochondrial fusion is controlled by outer membrane GTPases MFN1 and MFN2 and by inner membrane (IM) GTPase OPA1. Disordered mitochondrial fusion/fission contributes to various pathologies, and MFN2 or OPA1 mutations underlie neurodegenerative diseases. Here, we show that the WBSCR16 protein is primarily associated with the outer face of the inner mitochondrial membrane and is important for mitochondrial fusion. We provide evidence of a WBSCR16/OPA1 physical interaction in the intact cell and of a WBSCR16 function as an OPA1-specific guanine nucleotide exchange factor (GEF). Homozygosity for a Wbscr16 mutation causes early embryonic lethality, whereas neurons of mice heterozygous for the mutation have mitochondria with reduced membrane potential and increased susceptibility to fragmentation upon exposure to stress, suggesting roles for WBSCR16 deficits in neuronal pathologies.

RAL GTPases: Biology and Potential as Therapeutic Targets in Cancer

More than a hundred proteins comprise the RAS superfamily of small GTPases. This family can be divided into RAS, RHO, RAB, RAN, ARF, and RAD subfamilies, with each shown to play distinct roles in human cells in both health and disease. The RAS subfamily has a well-established role in human cancer with the three genes, HRAS, KRAS, and NRAS being the commonly mutated in tumors. These RAS mutations, most often functionally activating, are especially common in pancreatic, lung, and colorectal cancers. Efforts to inhibit RAS and related GTPases have produced inhibitors targeting the downstream effectors of RAS signaling, including inhibitors of the RAF-mitogen-activated protein kinase/extracellular signal-related kinase (ERK)-ERK kinase pathway and the phosphoinositide-3-kinase-AKT-mTOR kinase pathway. A third effector arm of RAS signaling, mediated by RAL (RAS like) has emerged in recent years as a critical driver of RAS oncogenic signaling and has not been targeted until recently. RAL belongs to the RAS branch of the RAS superfamily and shares a high structural similarity with RAS. In human cells, there are two genes, RALA and RALB, both of which have been shown to play roles in the proliferation, survival, and metastasis of a variety of human cancers, including lung, colon, pancreatic, prostate, skin, and bladder cancers. In this review, we summarize the latest knowledge of RAL in the context of human cancer and the recent advancements in the development of cancer therapeutics targeting RAL small GTPases.

Overexpression of RCC2 Enhances Cell Motility and Promotes Tumor Metastasis in Lung Adenocarcinoma by Inducing Epithelial-Mesenchymal Transition

Purpose: Investigate the role of regulator of chromosome condensation 2 (RCC2) on lung adenocarcinoma (LUAD) metastasis.Experimental Design: Clinical specimens were used to assess the impact of RCC2 on LUAD metastasis. Mouse models, cytobiology, and molecular biology assays were performed to elucidate the function and underlying mechanisms of RCC2 in LUAD.Results: RCC2 expression was frequently increased in LUADs (88/122, 72.13%). It was confirmed by analysis of a larger cohort of TCGA RNA-seq data containing 488 LUADs and 58 normal lung tissues (P < 0.001). Importantly, increased level of RCC2 was significantly associated with T status of tumor (P = 0.002), lymph node metastasis (P = 0.004), and advanced clinical stage (P = 0.001). Patients with LUAD with higher expression of RCC2 had shorter overall survival. Cox regression analysis demonstrated that RCC2 was an independent poorer prognostic factor for patients with LUAD. Moreover, forced expression of RCC2 promoted intrapulmonary metastasis in vivo and significantly enhanced LUAD cell migration, invasion, and proliferation in vitro Further study found that RCC2 induced epithelial-mesenchymal transition (EMT) and also stimulated the expression of MMP-2 and MMP-9. In addition, RCC2 was able to activate JNK, while inhibition of JNK suppressed the effect of RCC2 on LUAD cell migration, invasion, EMT, and the expression of MMP-2 and MMP-9.Conclusions: RCC2 plays a pivotal role in LUAD metastasis by inducing EMT via activation of MAPK-JNK signaling. Clin Cancer Res; 23(18); 5598-610. ©2017 AACR.

MicroRNA profiles involved in trifluridine resistance

Trifluridine (FTD) is a key component of the novel oral antitumor drug trifluridine/tipiracil, which is approved for the treatment of patients with metastatic colorectal cancer refractory to standard chemotherapies. A microRNA analysis of three colorectal cell lines was conducted to investigate causes of FTD resistance. Drug resistant sublines of DLD-1, HCT-116, and RKO cells were developed by continuous administration of increasing doses of FTD for 5 months. The let-7d-5p gene, which maps to chromosome 9q22.32, was downregulated in the FTD-resistant DLD-1 sublines. DLD-1 cells became more resistant to FTD when let-7d-5p was knocked down and more sensitive when let-7d-5p was overexpressed. The FTD-resistant sublines were not cross-resistant to 5-fluorouracil (5-FU); 5-FU sensitivity was affected only slightly when let-7d-5p as overexpressed or knocked down. These data indicate that let-7d-5p increases sensitivity of FTD but not 5-FU and that let-7d-5p is a potential clinical marker of treatment sensitivity.

The long non-coding RNA LINC00152 is essential for cell cycle progression through mitosis in HeLa cells

In recent years, long non-coding RNA (lncRNA) research has identified essential roles of these transcripts in virtually all physiological cellular processes including tumorigenesis, but their functions and molecular mechanisms are poorly understood. In this study, we performed a high-throughput siRNA screen targeting 638 lncRNAs deregulated in cancer entities to analyse their impact on cell division by using time-lapse microscopy. We identified 26 lncRNAs affecting cell morphology and cell cycle including LINC00152. This transcript was ubiquitously expressed in many human cell lines and its RNA levels were significantly upregulated in lung, liver and breast cancer tissues. A comprehensive sequence analysis of LINC00152 revealed a highly similar paralog annotated as MIR4435-2HG and several splice variants of both transcripts. The shortest and most abundant isoform preferentially localized to the cytoplasm. Cells depleted of LINC00152 arrested in prometaphase of mitosis and showed reduced cell viability. In RNA affinity purification (RAP) studies, LINC00152 interacted with a network of proteins that were associated with M phase of the cell cycle. In summary, we provide new insights into the properties and biological function of LINC00152 suggesting that this transcript is crucial for cell cycle progression through mitosis and thus, could act as a non-coding oncogene.

VPAC Receptor Subtypes Tune Purinergic Neuron-to-Glia Communication in the Murine Submucosal Plexus

The enteric nervous system (ENS) situated within the gastrointestinal tract comprises an intricate network of neurons and glia which together regulate intestinal function. The exact neuro-glial circuitry and the signaling molecules involved are yet to be fully elucidated. Vasoactive intestinal peptide (VIP) is one of the main neurotransmitters in the gut, and is important for regulating intestinal secretion and motility. However, the role of VIP and its VPAC receptors within the enteric circuitry is not well understood. We investigated this in the submucosal plexus of mouse jejunum using calcium (Ca²⁺)-imaging. Local VIP application induced Ca²⁺-transients primarily in neurons and these were inhibited by VPAC1- and VPAC2-antagonists (PG 99-269 and PG 99-465 respectively). These VIP-evoked neural Ca²⁺-transients were also inhibited by tetrodotoxin (TTX), indicating that they were secondary to action potential generation. Surprisingly, VIP induced Ca²⁺-transients in glia in the presence of the VPAC2 antagonist. Further, selective VPAC1 receptor activation with the agonist ([K15, R16, L27]VIP(1-7)/GRF(8-27)) predominantly evoked glial responses. However, VPAC1-immunoreactivity did not colocalize with the glial marker glial fibrillary acidic protein (GFAP). Rather, VPAC1 expression was found on cholinergic submucosal neurons and nerve fibers. This suggests that glial responses observed were secondary to neuronal activation. Trains of electrical stimuli were applied to fiber tracts to induce endogenous VIP release. Delayed glial responses were evoked when the VPAC2 antagonist was present. These findings support the presence of an intrinsic VIP/VPAC-initiated neuron-to-glia signaling pathway. VPAC1 agonist-evoked glial responses were inhibited by purinergic antagonists (PPADS and MRS2179), thus demonstrating the involvement of P2Y₁ receptors. Collectively, we showed that neurally-released VIP can activate neurons expressing VPAC1 and/or VPAC2 receptors to modulate purine-release onto glia. Selective VPAC1 activation evokes a glial response, whereas VPAC2 receptors may act to inhibit this response. Thus, we identified a component of an enteric neuron-glia circuit that is fine-tuned by endogenous VIP acting through VPAC1- and VPAC2-mediated pathways.

Disruptions in asymmetric centrosome inheritance and WDR62-Aurora kinase B interactions in primary microcephaly

Recessive mutations in WD repeat domain 62 (WDR62) cause microcephaly and a wide spectrum of severe brain malformations. Disruption of the mouse ortholog results in microcephaly underlain by reduced proliferation of neocortical progenitors during late neurogenesis, abnormalities in asymmetric centrosome inheritance leading to neuronal migration delays, and altered neuronal differentiation. Spindle pole localization of WDR62 and mitotic progression are defective in patient-derived fibroblasts, which, similar to mouse neocortical progenitors, transiently arrest at prometaphase. Expression of WDR62 is closely correlated with components of the chromosome passenger complex (CPC), a key regulator of mitosis. Wild type WDR62, but not disease-associated mutant forms, interacts with the CPC core enzyme Aurora kinase B and staining of CPC components at centromeres is altered in patient-derived fibroblasts. Our findings demonstrate critical and diverse functions of WDR62 in neocortical development and provide insight into the mechanisms by which its disruption leads to a plethora of structural abnormalities.

Analysis of Microarray Data on Gene Expression and Methylation to Identify Long Non-coding RNAs in Non-small Cell Lung Cancer

To identify what long non-coding RNAs (lncRNAs) are involved in non-small cell lung cancer (NSCLC), we analyzed microarray data on gene expression and methylation. Gene expression chip and HumanMethylation450BeadChip were used to interrogate genome-wide expression and methylation in tumor samples. Differential expression and methylation were analyzed through comparing tumors with adjacent non-tumor tissues. LncRNAs expressed differentially and correlated with coding genes and DNA methylation were validated in additional tumor samples using RT-qPCR and pyrosequencing. In vitro experiments were performed to evaluate lncRNA’s effects on tumor cells. We identified 8,500 lncRNAs expressed differentially between tumor and non-tumor tissues, of which 1,504 were correlated with mRNA expression. Two of the lncRNAs, LOC146880 and ENST00000439577, were positively correlated with expression of two cancer-related genes, KPNA2 and RCC2, respectively. High expression of LOC146880 and ENST00000439577 were also associated with poor survival. Analysis of lncRNA expression in relation to DNA methylation showed that LOC146880 expression was down-regulated by DNA methylation in its promoter. Lowering the expression of LOC146880 or ENST00000439577 in tumor cells could inhibit cell proliferation, invasion and migration. Analysis of microarray data on gene expression and methylation allows us to identify two lncRNAs, LOC146880 and ENST00000439577, which may promote the progression of NSCLC.

A Centromere-Signaling Network Underlies the Coordination among Mitotic Events

There is increasing evidence that regulators of the spindle checkpoint, kinetochore-microtubule attachments, and sister chromatid cohesion are part of an interconnected mitotic regulatory circuit with two positive feedback loops and the chromosome passenger complex (CPC) at its center. If true, this conceptual breakthrough needs to be integrated into models of mitosis. In this review, we describe this circuit and point out how the double feedback loops could provide insights into the self-organization of some mitotic processes and the autonomy of every chromosome on the mitotic spindle. We also provide working models for how mitotic events may be coordinated by this circuit.

The Ran Pathway in Drosophila melanogaster Mitosis

Over the last two decades, the small GTPase Ran has emerged as a central regulator of both mitosis and meiosis, particularly in the generation, maintenance, and regulation of the microtubule (MT)-based bipolar spindle. Ran-regulated pathways in mitosis bear many similarities to the well-characterized functions of Ran in nuclear transport and, as with transport, the majority of these mitotic effects are mediated through affecting the physical interaction between karyopherins and Spindle Assembly Factors (SAFs)—a loose term describing proteins or protein complexes involved in spindle assembly through promoting nucleation, stabilization, and/or depolymerization of MTs, through anchoring MTs to specific structures such as centrosomes, chromatin or kinetochores, or through sliding MTs along each other to generate the force required to achieve bipolarity. As such, the Ran-mediated pathway represents a crucial functional module within the wider spindle assembly landscape. Research into mitosis using the model organism Drosophila melanogaster has contributed substantially to our understanding of centrosome and spindle function. However, in comparison to mammalian systems, very little is known about the contribution of Ran-mediated pathways in Drosophila mitosis. This article sets out to summarize our understanding of the roles of the Ran pathway components in Drosophila mitosis, focusing on the syncytial blastoderm embryo, arguing that it can provide important insights into the conserved functions on Ran during spindle formation.

The Aurora B Kinase in Chromosome Bi-Orientation and Spindle Checkpoint Signaling

Aurora B, a member of the Aurora family of serine/threonine protein kinases, is a key player in chromosome segregation. As part of a macromolecular complex known as the chromosome passenger complex, Aurora B concentrates early during mitosis in the proximity of centromeres and kinetochores, the sites of attachment of chromosomes to spindle microtubules. There, it contributes to a number of processes that impart fidelity to cell division, including kinetochore stabilization, kinetochore–microtubule attachment, and the regulation of a surveillance mechanism named the spindle assembly checkpoint. In the regulation of these processes, Aurora B is the fulcrum of a remarkably complex network of interactions that feed back on its localization and activation state. In this review, we discuss the multiple roles of Aurora B during mitosis, focusing in particular on its role at centromeres and kinetochores. Many details of the network of interactions at these locations remain poorly understood, and we focus here on several crucial outstanding questions.