Comparative analysis of the role of small G proteins in cell migration and cell death: cytoprotective and promigratory effects of RalA

Controlled Plasma Membrane Delivery of FGFR1 and Modulation of Signaling by a Novel Regulated Anterograde RTK Transport Pathway

How human FGFR1 localizes to the PM is unknown. Currently, it is assumed that newly synthesized FGFR1 is continuously delivered to the PM. However, evidence indicates that FGFR1 is mostly sequestered in intracellular post-Golgi vesicles (PGVs) under normal conditions. In this report, live-cell imaging and total internal reflection fluorescence microscopy (TIRFM) were employed to study the dynamics of these FGFR1-positive vesicles. We designed recombinant proteins to target different transport components to and from the FGFR1 vesicles. Mouse embryoid bodies (mEBs) were used as a 3D model system to confirm major findings. Briefly, we found that Rab2a, Rab6a, Rab8a, RalA and caveolins are integral components of FGFR1-positive vesicles, representing a novel compartment. While intracellular sequestration prevented FGFR1 activation, serum starvation and hypoxia stimulated PM localization of FGFR1. Under these conditions, FGFR1 C-terminus acts as a scaffold to assemble proteins to (i) inactivate Rab2a and release sequestration, and (ii) assemble Rab6a for localized activation of Rab8a and RalA-exocyst to deliver the receptor to the PM. This novel pathway is named Regulated Anterograde RTK Transport (RART). This is the first instance of RTK regulated through control of PM delivery.

Ral GTPase is essential for actin dynamics and Golgi apparatus distribution in mouse oocyte maturation

Background

Ral family is a member of Ras-like GTPase superfamily, which includes RalA and RalB. RalA/B play important roles in many cell biological functions, including cytoskeleton dynamics, cell division, membrane transport, gene expression and signal transduction. However, whether RalA/B involve into the mammalian oocyte meiosis is still unclear. This study aimed to explore the roles of RalA/B during mouse oocyte maturation.

Results

Our results showed that RalA/B expressed at all stages of oocyte maturation, and they were enriched at the spindle periphery area after meiosis resumption. The injection of RalA/B siRNAs into the oocytes significantly disturbed the polar body extrusion, indicating the essential roles of RalA/B for oocyte maturation. We observed that in the RalA/B knockdown oocytes the actin filament fluorescence intensity was significantly increased at the both cortex and cytoplasm, and the chromosomes were failed to locate near the cortex, indicating that RalA/B regulate actin dynamics for spindle migration in mouse oocytes. Moreover, we also found that the Golgi apparatus distribution at the spindle periphery was disturbed after RalA/B depletion.

Conclusions

In summary, our results indicated that RalA/B affect actin dynamics for chromosome positioning and Golgi apparatus distribution in mouse oocytes.

Investigation of the molecular mechanisms of hepatic injury upon naphthalene exposure in zebrafish (Danio rerio)

Naphthalene has been used worldwide as a commercial insecticide for decades, which when detected in the environment can have various negative effects on non-target organism, such as hepatotoxicity. However, the molecular mechanisms of how naphthalene acts to affect the liver in zebrafish (Danio rerio) remains unknown. In this study, we evaluated the potential toxic effects of naphthalene on livers in female adult zebrafish over a 21-day subacute exposure. Global hepatic gene expression was examined by microarrays and the results indicated the regulated genes were associated significantly with vital hepatic injury pathways and GO categories upon naphthalene exposure, such as disruptions in lipid metabolism, inflammatory response, and the carcinogenic processes. According to our observations of liver histology, nuclear enlargement as a potential indicator of cancers and hepatic lipometabolic disorder precisely were supported. The 96 h acute naphthalene tests on Tg(lysC:DsRed) and LiPan lines larvae revealed recruitment of neutrophils by the liver, as well as decreased liver size, which further confirmed hepatic inflammation response to naphthalene exposure. Thus, these findings advance the field of ecotoxicology by unveiling a new role of naphthalene as a leading cause of liver damage and provide potential biomarker-genes for environmental naphthalene monitoring.

Knockdown of Ran GTPase expression inhibits the proliferation and migration of breast cancer cells

Breast cancer is the second leading cause of cancer-associated mortality in women worldwide. Strong evidence has suggested that Ran, which is a small GTP binding protein involved in the transport of RNA and protein across the nucleus, may be a key cellular protein involved in the metastatic progression of cancer. The present study investigated Ran gene expression in breast cancer tissue samples obtained from 140 patients who had undergone surgical resection for breast cancer. Western blot analysis of Ran in breast cancer tissues and paired adjacent normal tissues showed that expression of Ran was significantly increased in breast cancer tissues. Immunohistochemistry analyses conducted on formalin-fixed paraffin-embedded breast cancer tissue sections revealed that Ran expression was associated with tumor histological grade, nerve invasion and metastasis, vascular metastasis and Ki-67 expression (a marker of cell proliferation). Kaplan-Meier survival analysis showed that increased Ran expression in patients with breast cancer was positively associated with a poor survival prognosis. Furthermore, in vitro experiments demonstrated that highly migratory MDA-MB-231 cancer cells treated with Ran-si-RNA (si-Ran), which knocked down expression of Ran, exhibited decreased motility in trans-well migration and wound healing assays. Cell cycle analysis of Ran knocked down MDA-MB-231 cells implicated Ran in cell cycle arrest and the inhibition of proliferation. Furthermore, a starvation and re-feeding (CCK-8) assay was performed, which indicated that Ran regulated breast cancer cell proliferation. Taken together, the results provide strong in vitro evidence of the involvement of Ran in the progression of breast cancer and suggest that it could have high potential as a therapeutic target and/or marker of disease.

Role of an imbalanced miRNAs axis in pathogenesis of psoriasis: novel perspectives based on review of the literature

BACKGROUND

Specific profile of microRNAs (miRNAs, miR) expressed in psoriasis has been identified in the past few years, while the studies on roles and molecular mechanisms of these miRNAs are still on the way. In our previous study, four specific miRNAs (miR-31, miR-203, hsa-miR-99a and miR-125b) were found to be specifically altered in psoriatic lesions.We therefore conducted a systematic literature review in this study to reveal the role of these miRNAs in the pathogenesis of psoriasis in order to inform future research.

METHODS

The related articles indexed in PubMed (MEDLINE) database were searched and analyzed. We identified eligible studies related to the mechanism research of miR-31, miR-203, hsa-miR-99a and miR-125b in psoriasis or psoriatic lesional skin from inception up to July 2016. The experts in the field of miRNAs and Psoriasis were involved in analysis process.

RESULT

Both miR-31 and miR-203 are dramatically upregulated in psoriatic lesions. The former plays the pro-proliferative, pro-differentiative and pro-inflammatory roles and the latter holds the potentials for anti-proliferation, pro-inflammation and pro-differentiation in psoriatic keratinocytes. Conversely, both hsa-miR-99a and miR-125b are significantly downregulated in psoriatic skin. These two miRNAs are able to inhibit proliferation while promote differentiation of psoriatic keratinocytes, and miR-125b can also suppress inflammation in psoriatic lesions. By analyzing the contexts related to these miRNAs, we found that each of them does not act alone but rather work in concert with other miRNAs. The imbalance between miR-31/miR-203and hsa-miR-99a/miR-125b may contribute to the intense proliferation and abnormal differentiation of psoriatic keratinocytes, which is a characteristic of pathogenesis of psoriasis.

CONCLUSION

An imbalanced miRNAs axis was for the first time outlined. Apparently, upregulation of miR-31/miR-203 and downregulation of hsa-miR-99a/miR-125b work together in concert to facilitate the development of psoriasis pathogenesis. Further work in this field holds the potentials to open a new way to study psoriasis.

Acarbose inhibits the proliferation and migration of vascular smooth muscle cells via targeting Ras signaling

Atherosclerosis involves the proliferation and migration of vascular smooth muscle cells (VSMCs). The migration of VSMCs from the media into the intima and their subsequent proliferation are important processes in neointima formation in atherosclerosis and restenosis after percutaneous coronary interventions. Acarbose, an alpha-glucosidase inhibitor, has been demonstrated to not affect serum levels of glucose and decrease the progression of intima-media thickening in rabbits fed with a high cholesterol diet (HCD). We previously showed that increased Ras protein levels enhanced the migration of TNF-α treated A7r5 cells. The aim of this study was to determine the inhibitory effects of acarbose on Ras expression in A7r5 cells. Acarbose also inhibited the phosphorylation of focal adhesion kinase (FAK) and Akt, activities of the matrix metalloproteinases (MMPs) MMP-2 and MMP-9, and protein expressions of small G proteins (Ras, Cdc42, RhoA, and Rac1) in a dose-dependent manner. We also found that acarbose could effectively inhibit the proliferation and migration of Ras^G12V A7r5 cells by blocking small G proteins and phosphoinositide-3-kinase (PI3K)/Akt signaling. These studies demonstrated that acarbose could theoretically decrease atherosclerosis by targeting Ras signaling.

miR-331-3p and Aurora Kinase inhibitor II co-treatment suppresses prostate cancer tumorigenesis and progression

RNA-based therapeutics could represent a new avenue of cancer treatment. miRNA 331-3p (miR-331-3p) is implicated in prostate cancer (PCa) as a putative tumor suppressor, but its functional activity and synergy with other anti-tumor agents is largely unknown. We found miR-331-3p expression in PCa tumors was significantly decreased compared to non-malignant matched tissue. Analysis of publicly available PCa gene expression data sets showed miR-331-3p expression negatively correlated with Gleason Score, tumor stage, lymph node involvement and PSA value, and was significantly down regulated in tumor tissue relative to normal prostate tissue. Overexpression of miR-331-3p reduced PCa cell growth, migration and colony formation, as well as xenograft tumor initiation, proliferation and survival of mice. Microarray analysis identified seven novel targets of miR-331-3p in PCa. The 3’-untranslated regions of PLCγ1 and RALA were confirmed as targets of miR-331-3p, with mutation analyses confirming RALA as a direct target. Expression of miR-331-3p or RALA siRNA in PCa cells reduced RALA expression, proliferation, migration and colony formation in vitro. RALA expression positively correlated with Gleason grade in two separate studies, as well as in a PCa tissue microarray. Co-treatment using siRALA with an Aurora Kinase inhibitor (AKi-II) decreased colony formation of PCa cells while the combination of AKi-II with miR-331-3p resulted in significant reduction of PCa cell proliferation in vitro and PCa xenograft growth in vivo. Thus, miR-331-3p directly targets the RALA pathway and the addition of the AKi-II has a synergistic effect on tumor growth inhibition, suggesting a potential role as combination therapy in PCa.

Control of astrocyte morphology by Rho GTPases

Astrocytes modulate and support neuronal and synapse function via numerous mechanisms that often rely on diffusion of signalling molecules, ions or metabolites through extracellular space. As a consequence, the spatial arrangement and the distance between astrocyte processes and neuronal structures are of functional importance. Likewise, changes of astrocyte structure will affect the ability of astrocytes to interact with neurons. In contrast to neurons, where rapid morphology changes are critically involved in many aspects of physiological brain function, a role of astrocyte restructuring in brain physiology is only beginning to emerge. In neurons, small GTPases of the Rho family are powerful initiators and modulators of structural changes. Less is known about the functional significance of these signalling molecules in astrocytes. Here, we review recent experimental evidence for the role of RhoA, Cdc42 and Rac1 in controlling dynamic astrocyte morphology as well as experimental tools and analytical approaches for studying astrocyte morphology changes.

Small GTPase and regulation of inflammation response in atherogenesis

Small GTPases are key signal transducers from extracellular stimuli to the nucleus that regulate a variety of cellular responses, including changes in gene expression and cell adhesion and migration. Accumulating data have demonstrated that abnormal activation of these small GTPases plays a critical role in the atherosclerosis characterized by vascular abnormalities, especially endothelial dysfunction and inflammation. Here, we discuss the linkage between small GTPases, inflammation, and atherogenesis. First, small GTPases affect gene expression of inflammatory cytokines through proinflammatory signaling pathways, such as nuclear factor-κB, vascular cell adhesion molecule-1, intercellular adhesion molecule-1, interlukin-8, and monocyte chemoattractant protein-1. Then, these molecules regulate the vascular inflammation through cell adhesion and migration. In turn, small GTPases are also regulated by extracellular stimuli, such as L-selectin, thrombin, oxidized phospholipids, and interleukins. Thus, these inflammatory cytokines generate a vicious cycle for small GTPases and inflammatory responses in the atherogenesis.

Discovery of potent HDAC inhibitors based on chlamydocin with inhibitory effects on cell migration

The histone deacetylase (HDAC) family is a promising drug target class owing to the importance of these enzymes in a variety of cellular processes. Docking studies were conducted to identify novel HDAC inhibitors. Subtle modifications in the recognition domain were introduced into a series of chlamydocin analogues, and the resulting scaffolds were combined with various zinc binding domains. Remarkably, cyclo(L-Asu(NHOH)-L-A3mc6c-L-Phe-D-Pro, compound 1 b), with a methyl group at positions 3 or 5 on the aliphatic ring, exhibited better antiproliferative effects than trichostatin A (TSA) against MCF-7 and K562 cell lines. In addition to cell-cycle arrest and apoptosis, cell migration inhibition was observed in cells treated with compound 1 b. Subsequent western blot analysis revealed that the balance between matrix metalloproteinase 2 (MMP2) and tissue inhibitors of metalloproteinase 1 (TIMP1) determines the degree of metalloproteinase activity in MCF-7 cells, thereby regulating cell migration. The improved inhibitory activity imparted by altering the hydrophobic substitution pattern at the bulky cap group is a valuable approach in the development of novel HDAC inhibitors.

MicroRNA-203 contributes to skin re-epithelialization

Keratinocyte proliferation and migration are crucial steps for the rapid closure of the epidermis during wound healing, but the molecular mechanisms involved in this cellular response remain to be completely elucidated. Here, by in situ hybridization we characterize the expression pattern of miR-203 after the induction of wound in mouse epidermis, showing that its expression is downregulated in the highly proliferating keratinocytes of the 'migrating tongue', whereas it is strongly expressed in the differentiating cells of the skin outside the wound. Furthermore, subcutaneous injections of antagomiR-203 in new born mice dorsal skin strengthened, in vivo, the inverse correlation between miR-203 expression and two new target mRNAs: RAN and RAPH1. Our data suggest that miR-203, by controlling the expression of target proteins that are responsible for both keratinocyte proliferation and migration, exerts a specific role in wound re-epithelialization and epidermal homeostasis re-establishment of injured skin.

Stress- and Rho-activated ZO-1-associated nucleic acid binding protein binding to p21 mRNA mediates stabilization, translation, and cell survival

A central component of the cellular stress response is p21(WAF1/CIP1), which regulates cell proliferation, survival, and differentiation. Inflammation and cell stress often up-regulate p21 posttranscriptionally by regulatory mechanisms that are poorly understood. ZO-1-associated nucleic acid binding protein (ZONAB)/DbpA is a Y-box transcription factor that is regulated by components of intercellular junctions that are affected by cytokines and tissue damage. We therefore asked whether ZONAB activation is part of the cellular stress response. Here, we demonstrate that ZONAB promotes cell survival in response to proinflammatory, hyperosmotic, and cytotoxic stress and that stress-induced ZONAB activation involves the Rho regulator GEF-H1. Unexpectedly, stress-induced ZONAB activation does not stimulate ZONAB's activity as a transcription factor but leads to the posttranscriptional up-regulation of p21 protein and mRNA. Up-regulation is mediated by ZONAB binding to specific sites in the 3'-untranslated region of the p21 mRNA, resulting in mRNA stabilization and enhanced translation. Binding of ZONAB to mRNA is activated by GEF-H1 via Rho stimulation and also mediates Ras-induced p21 expression. We thus identify a unique type of stress and Rho signaling activated pathway that drives mRNA stabilization and translation and links the cellular stress response to p21 expression and cell survival.