Oxysterol-Binding Protein-Related Protein 8 Inhibits Gastric Cancer Growth Through Induction of ER Stress, Inhibition of Wnt Signaling, and Activation of Apoptosis

MKRN1 promotes colorectal cancer metastasis by activating the TGF-β signalling pathway through SNIP1 protein degradation

BACKGROUND

The Makorin ring finger protein 1 (MKRN1) gene, also called RNF61, is located on the long arm of chromosome 7 and is a member of the RING finger protein family. The E3 ubiquitin ligase MKRN1 is closely linked to tumour development, but the exact mechanism needs to be elucidated. In this study, we aimed to investigate the specific mechanism and role of MKRN1 in colorectal cancer (CRC) development.

METHODS

MKRN1 expression in CRC was analysed using the Cancer Cell Line Encyclopaedia and the Cancer Genome Atlas (TCGA) databases. Rectal tumour tissues were frozen to explore the MKRN1 expression in CRC and its clinical significance. The impact of MKRN1 on CRC cell proliferation and migration was observed using CCK8, colony formation, wound healing, and transwell assays. A combination of MKRN1 quantitative proteomics, ubiquitination modification omics analysis, and a string of in vitro and in vivo experiments revealed the potential mechanisms by which MKRN1 regulates CRC metastasis.

RESULTS

MKRN1 expression was significantly elevated in CRC tissues compared to paracancerous tissues and was positively linked with prognosis (P < 0.01). MKRN1 downregulation inhibits CRC cell proliferation, migration, and invasion. Conversely, MKRN1 overexpression promotes the proliferation, migration, and invasion of CRC cells. Mechanistically, MKRN1 induces epithelial-mesenchymal transition (EMT) in CRC cells via ubiquitination and degradation of Smad nuclear-interacting protein 1 (SNIP1). Furthermore, SNIP1 inhibits transforming growth factor-β (TGF-β) signalling, and MKRN1 promotes TGF-β signalling by degrading SNIP1 to induce EMT in CRC cells. Finally, using conditional knockout mice, intestinal lesions and metastatic liver microlesions were greatly reduced in the intestinal knockout MKRN1 group compared to that in the control group.

CONCLUSIONS

High MKRN1 levels promote TGF-β signalling through ubiquitination and degradation of SNIP1, thereby facilitating CRC metastasis, and supporting MKRN1 as a CRC pro-cancer factor. The MKRN1/SNIP1/TGF-β axis may be a potential therapeutic target in CRC.

ORP5 promotes migration and invasion of cervical cancer cells by inhibiting endoplasmic reticulum stress

ORP5 is a transmembrane protein anchored to the endoplasmic reticulum, which mainly functions as a lipid transporter and has reportedly been linked to cancer. However, the specific mechanism of ORP5 action in cervical cancer (CC) is unclear. In this study, we found that ORP5 promotes the migration and invasive ability of CC cells in vitro and in vivo. In addition, ORP5 expression was linked to endoplasmic reticulum stress, and ORP5 encouraged CC metastasis by inhibiting endoplasmic reticulum stress. Mechanistically, ORP5 inhibited endoplasmic reticulum stress in CC cells by stimulating ubiquitination and proteasomal degradation of SREBP1 to reduce its expression. In conclusion, ORP5 promotes the malignant progression of CC by inhibiting endoplasmic reticulum stress, providing a therapeutic target and strategy for CC treatment.

ORP8 inhibits renal cell carcinoma progression by accelerating Stathmin1 degradation and microtubule polymerization

ORP8 has been reported to suppress tumor progression in various malignancies. However, the functions and underlying mechanisms of ORP8 are still unknown in renal cell carcinoma (RCC). Here, decreased expression of ORP8 was detected in RCC tissues and cell lines. Functional assays verified that ORP8 suppressed RCC cell growth, migration, invasion, and metastasis. Mechanistically, ORP8 attenuated Stathmin1 expression by accelerating ubiquitin-mediated proteasomal degradation and led to an increase in microtubule polymerization. Lastly, ORP8 knockdown partly rescued microtubule polymerization, as well as aggressive cell phenotypes induced by paclitaxel. Our findings elucidated that ORP8 suppressed the malignant progression of RCC by increasing Stathmin1 degradation and microtubule polymerization, thus suggesting that ORP8 might be a novel target for the treatment of RCC.

GANT61 exerts anticancer cell and anticancer stem cell capacity in colorectal cancer by blocking the Wnt/β‑catenin and Notch signalling pathways

The present study aimed to assess the anticancer cell and anticancer stem cell (CSC) effects of GANT61, and its regulatory influence on the Wnt/β-catenin and Notch signalling pathways in colorectal cancer (CRC). HT-29 and HCT-116 cells were treated with 0, 2.5, 5, 10, 20 or 40 µM GANT61, after which relative cell viability and the expression of Gli1, β-catenin and Notch1, as well as the percentage of CD133⁺ cells, were detected. Subsequently, HT-29/HCT-116 cells and CSCs were treated with 20 µM GANT61, 10 mM of the Wnt/β-catenin pathway agonist HLY78, and 30 mM of the Notch pathway agonist JAG1 (alone or in combination), which was followed by the assessment of cell viability and apoptosis. In both cell lines, GANT61 reduced relative cell viability in a time- and dose-dependent manner, inhibited Gli1, β-catenin and Notch1 expression, and decreased the percentage of CD133⁺ cells in a dose-dependent manner. Furthermore, HLY78 and JAG1 were both found to improve the relative viability, while downregulating the apoptosis of untreated and GANT61-treated HT-29 and HCT-116 cells. Moreover, Wnt/β-catenin and Notch signalling pathway activity were upregulated in CSCs isolated from HT-29 and HCT-116 cells, compared with the associated control groups. GANT61 also reduced the viability of HT-29 and HCT-116 cells and increased apoptosis, whereas HLY78 and JAG1 treatment resulted in the opposite effect. Moreover, both HLY78 and JAG1 attenuated the effects of GANT61 on cellular viability and apoptosis. In conclusion, GANT61 was found to effectively eliminate cancer cells and CSCs by blocking the Wnt/β-catenin and Notch signalling pathways in CRC.

Natural Compounds for SIRT1-Mediated Oxidative Stress and Neuroinflammation in Stroke: A Potential Therapeutic Target in the Future

Stroke is a fatal cerebral vascular disease with a high mortality rate and substantial economic and social costs. ROS production and neuroinflammation have been implicated in both hemorrhagic and ischemic stroke and have the most critical effects on subsequent brain injury. SIRT1, a member of the sirtuin family, plays a crucial role in modulating a wide range of physiological processes, including apoptosis, DNA repair, inflammatory response, and oxidative stress. Targeting SIRT1 to reduce ROS and neuroinflammation might represent an emerging therapeutic target for stroke. Therefore, we conducted the present review to summarize the mechanisms of SIRT1-mediated oxidative stress and neuroinflammation in stroke. In addition, we provide a comprehensive introduction to the effect of compounds and natural drugs on SIRT1 signaling related to oxidative stress and neuroinflammation in stroke. We believe that our work will be helpful to further understand the critical role of the SIRT1 signaling pathway and will provide novel therapeutic potential for stroke treatment.

Activation of LRP6 with HLY78 Attenuates Oxidative Stress and Neuronal Apoptosis via GSK3β/Sirt1/PGC-1α Pathway after ICH

Background

Oxidative stress and neuronal apoptosis have important roles in the pathogenesis after intracerebral hemorrhage (ICH). Previous studies have reported that low-density lipoprotein receptor-related protein 6 (LRP6) exerts neuroprotection in several neurological diseases. Herein, we investigate the role of LRP6 receptor activation with HLY78 to attenuate oxidative stress and neuronal apoptosis after ICH, as well as the underlying mechanism.

Methods

A total of 199 CD1 mice were used. ICH was induced via injection of autologous blood into the right basal ganglia. HLY78 was administered via intranasal injection at 1 h after ICH. To explore the underlying mechanism, LRP6 siRNA and selisistat, a Sirt1 selective antagonist, were injected intracerebroventricularly at 48 h before ICH induction. Neurobehavioral tests, Western blot, and immunofluorescence staining were performed.

Results

The expression of endogenous p-LRP6 was gradually increased and expressed on neurons after ICH. HLY78 significantly improved the short- and long-term neurobehavioral deficits after ICH, which was accompanied with decreased oxidative stress and neuronal apoptosis, as well as increased expression of p-GSK3β, Sirt1, and PGC-1α, as well as downregulation of Romo-1 and C-Caspase-3. LRP6 knockdown or Sirt1 inhibition abolished these effects of HLY78 after ICH.

Conclusion

Our results suggest that administration of HLY78 attenuated oxidative stress, neuronal apoptosis, and neurobehavioral impairments through the LRP6/GSK3β/Sirt1/PGC-1α signaling pathway after ICH.

Modulation of lncRNA H19 enhances resveratrol-inhibited cancer cell proliferation and migration by regulating endoplasmic reticulum stress

The phytoalexin resveratrol exhibits anti-tumour activity in many types of cancer. In this study, we showed that resveratrol suppressed the survival of gastric tumour cells both in vivo and in vitro. Resveratrol promoted apoptosis, autophagy and endoplasmic reticulum (ER) stress in a dose-dependent manner. RNA-seq analysis showed that multiple cell death signalling pathways were activated after resveratrol treatment, while the use of ER stress activators (tunicamycin and thapsigargin) in combinatorial with resveratrol led to further inhibition of cancer cell survival. Results also showed that resveratrol altered the expression of several long non-coding RNAs (lncRNAs), including MEG3, PTTG3P, GAS5, BISPR, MALAT1 and H19. Knockdown of H19 in resveratrol-treated cells further enhanced the effects of resveratrol on apoptosis, ER stress and cell cycle S-phase arrest. Furthermore, the migratory ability of resveratrol-treated cells was dramatically decreased after H19 knockdown. In conclusion, resveratrol inhibited cancer cell survival, while knockdown of lncRNA H19 resulted in increased sensitivity to resveratrol therapy.

Coordination of inter-organelle communication and lipid fluxes by OSBP-related proteins

Oxysterol-binding protein (OSBP) and OSBP-related proteins (ORPs) constitute one of the largest families of lipid-binding/transfer proteins (LTPs) in eukaryotes. The current view is that many of them mediate inter-organelle lipid transfer over membrane contact sites (MCS). The transfer occurs in several cases in a 'counter-current' fashion: A lipid such as cholesterol or phosphatidylserine (PS) is transferred against its concentration gradient driven by transport of a phosphoinositide in the opposite direction. In this way ORPs are envisioned to maintain the distinct organelle lipid compositions, with impacts on multiple organelle functions. However, the functions of ORPs extend beyond lipid homeostasis to regulation of processes such as cell survival, proliferation and migration. Important expanding areas of mammalian ORP research include their roles in viral and bacterial infections, cancers, and neuronal function. The yeast OSBP homologue (Osh) proteins execute multifaceted functions in sterol and glycerophospholipid homeostasis, post-Golgi vesicle transport, phosphatidylinositol-4-phosphate, sphingolipid and target of rapamycin (TOR) signalling, and cell cycle control. These observations identify ORPs as lipid transporters and coordinators of signals with an unforeseen variety of cellular processes. Understanding their activities not only enlightens the biology of the living cell but also allows their employment as targets of new therapeutic approaches for disease.

Dihydroartemisinin suppresses proliferation, migration, the Wnt/β-catenin pathway and EMT via TNKS in gastric cancer

Gastric cancer is a common malignancy worldwide. However, the molecular mechanisms underlying this malignancy remain unclear and there are a lack of effective drugs. The present study aimed to investigate the antitumor effect of Dihydroartemisinin (DHA) or inhibition of Tankyrases (TNKS), and determine the underlying molecular mechanisms of gastric cancer. Immunohistochemistry and immunofluorescence analyses were performed to detect the expression levels of TNKS, epithelial-to-mesenchymal transition (EMT) and Wnt/β-catenin pathway-related proteins in gastric cancer tissues and adjacent normal tissues. The Cell Counting Kit-8 assay was performed to assess the viability of HGC-27 and AGS cells following treatment with different concentrations of HLY78 (a Wnt activator) or DHA. Following treatment with HLY78, DHA or small interfering (si)-TNKS1/si-TNKS2, colony formation and migratory abilities were assessed via the colony formation, wound healing and Transwell assays. Furthermore, western blot and immunofluorescence analyses were performed to detect the expression levels of TNKS, EMT- and Wnt/β-catenin-related proteins. The results demonstrated that the expression levels of TNKS, AXI2, β-catenin, N-cadherin and Vimentin were upregulated, whereas E-cadherin expression was downregulated in gastric cancer tissues compared with normal tissues. Furthermore, HLY78 and DHA suppressed the viability of HGC-27 and AGS cells, in a concentration-independent manner. Notably, TNKS knockdown or treatment with DHA suppressed colony formation, migration, TNKS expression, EMT and the Wnt/β-catenin pathway. Opposing effects were observed following treatment with HLY78, which were ameliorated following co-treatment with DHA. Taken together, these results suggest that DHA or inhibition of TNKS can suppress the proliferation and migration of gastric cancer cells, which is partly associated with inactivation of the Wnt/β-catenin pathway and EMT process.

Oxysterol-binding protein-like 2 contributes to the developmental progression of preadipocytes by binding to β-catenin

Oxysterol-binding protein-like 2 (OSBPL2), also known as oxysterol-binding protein-related protein (ORP) 2, is a member of lipid transfer protein well-known for its role in regulating cholesterol homeostasis. A recent study reported that OSBPL2/ORP2 localizes to lipid droplets (LDs) and is associated with energy metabolism and obesity. However, the function of OSBPL2/ORP2 in adipocyte differentiation is poorly understood. Here, we report that OSBPL2/ORP2 contributes to the developmental progression of preadipocytes. We found that OSBPL2/ORP2 binds to β-catenin, a key effector in the Wnt signaling pathway that inhibits adipogenesis. This complex plays a role in regulating the protein level of β-catenin only in preadipocytes, not in mature adipocytes. Our data further indicated that OSBPL2/ORP2 mediates the transport of β-catenin into the nucleus and thus regulates target genes related to adipocyte differentiation. Deletion of OSBPL2/ORP2 markedly reduces β-catenin both in the cytoplasm and in the nucleus, promotes preadipocytes maturation, and ultimately leads to obesity-related characteristics. Altogether, we provide novel insight into the function of OSBPL2/ORP2 in the developmental progression of preadipocytes and suggest OSBPL2/ORP2 may be a potential therapeutic target for the treatment of obesity-related diseases.

A Comprehensive Review on Oxysterols and Related Diseases

The present review aims to provide a complete and comprehensive summary of current literature relevant to oxysterols and related diseases. Oxidation of cholesterol leads to the formation of a large number of oxidized products, generally known as oxysterols. They are intermediates in the biosynthesis of bile acids, steroid hormones, and 1,25- dihydroxyvitamin D3. Although oxysterols are considered as metabolic intermediates, there is a growing body of evidence that many of them are bioactive, and their absence or excess may be part of the cause of a disease phenotype. These compounds derive from either enzymatic or non-enzymatic oxidation of cholesterol. This study provides comprehensive information about the structures, formation, and types of oxysterols even when involved in certain disease states, focusing on their effects on metabolism and linkages with these diseases. The role of specific oxysterols as mediators in various disorders, such as degenerative (age-related) and cancer-related disorders, has now become clearer. Oxysterol levels may be employed as suitable markers for the diagnosis of specific diseases or in predicting the incidence rate of diseases, such as diabetes mellitus, Alzheimer's disease, multiple sclerosis, osteoporosis, lung cancer, breast cancer, and infertility. However, further investigations may be required to confirm these mentioned possibilities.

The emerging roles of OSBP-related proteins in cancer: Impacts through phosphoinositide metabolism and protein-protein interactions

Oxysterol-binding protein -related proteins (ORPs) form a large family of intracellular lipid binding/transfer proteins. A number of ORPs are implicated in inter-organelle lipid transfer over membrane contacts sites, their mode of action involving in several cases the transfer of two lipids in opposite directions, termed countercurrent lipid transfer. A unifying feature appears to be the capacity to bind phosphatidylinositol polyphosphates (PIPs). These lipids are in some cases transported by ORPs from one organelle to another to drive the transfer of another lipid against its concentration gradient, while they in other cases may act as allosteric regulators of ORPs, or an ORP may introduce a PIP to an enzyme for catalysis. Dysregulation of several ORP family members is implicated in cancers, ORP3, -4, -5 and -8 being thus far the most studied examples. The most likely mechanisms underlying their associations with malignant growth are (i) impacts on PIP-mediated signaling events resulting in altered Ca²⁺ homeostasis, bioenergetics, cell survival, proliferation, and migration, (ii) protein-protein interactions affecting the activity of signaling factors, and (iii) modification of cellular lipid transport in a way that facilitates the proliferation of malignant cells. In this review I discuss the existing functional evidence for the involvement of ORPs in cancerous growth, discuss the findings in the light of the putative mechanisms outlined above and the possibility of employing ORPs as targets of anti-cancer therapy.

Endoplasmic Reticulum-Plasma Membrane Contact Sites: Regulators, Mechanisms, and Physiological Functions

The endoplasmic reticulum (ER) forms direct membrane contact sites with the plasma membrane (PM) in eukaryotic cells. These ER-PM contact sites play essential roles in lipid homeostasis, ion dynamics, and cell signaling, which are carried out by protein-protein or protein-lipid interactions. Distinct tethering factors dynamically control the architecture of ER-PM junctions in response to intracellular signals or external stimuli. The physiological roles of ER-PM contact sites are dependent on a variety of regulators that individually or cooperatively perform functions in diverse cellular processes. This review focuses on proteins functioning at ER-PM contact sites and highlights the recent progress in their mechanisms and physiological roles.

Post-Translational Modification of Cysteines: A Key Determinant of Endoplasmic Reticulum-Mitochondria Contacts (MERCs)

Cells must adjust their redox state to an ever-changing environment that could otherwise result in compromised homeostasis. An obvious way to adapt to changing redox conditions depends on cysteine post-translational modifications (PTMs) to adapt conformation, localization, interactions and catalytic activation of proteins. Such PTMs should occur preferentially in the proximity of oxidative stress sources. A particular concentration of these sources is found near membranes where the endoplasmic reticulum (ER) and the mitochondria interact on domains called MERCs (Mitochondria-Endoplasmic Reticulum Contacts). Here, fine inter-organelle communication controls metabolic homeostasis. MERCs achieve this goal through fluxes of Ca²⁺ ions and inter-organellar lipid exchange. Reactive oxygen species (ROS) that cause PTMs of mitochondria-associated membrane (MAM) proteins determine these intertwined MERC functions. Chronic changes of the pattern of these PTMs not only control physiological processes such as the circadian clock but could also lead to or worsen many human disorders such as cancer and neurodegenerative diseases.

HLY78 Attenuates Neuronal Apoptosis via the LRP6/GSK3β/β-Catenin Signaling Pathway After Subarachnoid Hemorrhage in Rats

Neuronal apoptosis is one of the essential mechanisms of early brain injury after subarachnoid hemorrhage (SAH). Recently, HLY78 has been shown to inhibit apoptosis in tumor cells and embryonic cells caused by carbon ion radiation through activation of the Wnt/β-catenin pathway. This study was designed to explore the anti-apoptotic role of HLY78 in experimental SAH. The results demonstrated that HLY78 attenuated neuronal apoptosis and the neurological deficits after SAH through the activation of low-density lipoprotein receptor-related protein 6 (LRP6), which subsequently increased the level of phosphorylated glycogen synthesis kinase 3 beta (p-GSK3β) (Ser9), β-catenin, and Bcl-2, accompanied by a decrease of p-β-catenin, Bax, and cleaved caspase 3. An LRP6 small-interfering ribonucleic acid reversed the effects of HLY78. In conclusion, HLY78 attenuates neuronal apoptosis and improves neurological deficits through the LRP6/GSK3β/β-catenin signaling pathway after SAH in rats. HLY78 is a promising therapeutic agent to attenuate early brain injury after SAH.

ORP5 and ORP8: Sterol Sensors and Phospholipid Transfer Proteins at Membrane Contact Sites?

Oxysterol binding related proteins 5 and 8 (ORP5 and ORP8) are two close homologs of the larger oxysterol binding protein (OSBP) family of sterol sensors and lipid transfer proteins (LTP). Early studies indicated these transmembrane proteins, anchored to the endoplasmic reticulum (ER), bound and sensed cholesterol and oxysterols. They were identified as important for diverse cellular functions including sterol homeostasis, vesicular trafficking, proliferation and migration. In addition, they were implicated in lipid-related diseases such as atherosclerosis and diabetes, but also cancer, although their mechanisms of action remained poorly understood. Then, alongside the increasing recognition that membrane contact sites (MCS) serve as hubs for non-vesicular lipid transfer, added to their structural similarity to other LTPs, came discoveries showing that ORP5 and 8 were in fact phospholipid transfer proteins that rather sense and exchange phosphatidylserine (PS) for phosphoinositides, including phosphatidylinositol-4-phosphate (PI(4)P) and potentially phosphatidylinositol-(4,5)-bisphosphate (PI(4,5)P2). Evidence now points to their action at MCS between the ER and various organelles including the plasma membrane, lysosomes, mitochondria, and lipid droplets. Dissecting exactly how this unexpected phospholipid transfer function connects with sterol regulation in health or disease remains a challenge for future studies.

ORP8 induces apoptosis by releasing cytochrome c from mitochondria in non‑small cell lung cancer

Non‑small cell lung cancer (NSCLC) is the most common type of lung cancer, and numerous oncogenes are associated with this disease. Oxysterol‑binding protein‑related protein 8 (ORP8) is essential for cell growth, migration and the modulation of mitochondrial respiration and morphology. However, the underlying role of ORP8 in NSCLC remains unclear. In the present study, it was reported that the expression of ORP8 was low in NSCLC cells and tissues. The ORP8 expression levels were analyzed by immunohistochemistry (IHC), quantitative real‑time PCR (qPCR) and western blot analysis. ORP8 overexpression inhibited cell growth and induced apoptosis in NSCLC cells with MTS, anchorage‑independent growth and Hoechst 33342 staining assay. Further experiments demonstrated that ORP8 overexpression induced the apoptosis of NSCLC cells via the release of cytochrome c from mitochondria into the cytoplasm with western blot analysis and confocal microscopy results. In addition, qPCR analysis showed that miR‑421 was upregulated in NSCLC cell lines, with the bioinformatics analysis, western blot analysis and Dual‑Luciferase reporter assay, it was determined that miR‑421 could target ORP8. The inhibition of cell proliferation via ORP8 overexpression was rescued by a miR‑421 mimic, which aided in maintaining the proliferative potential of the cells. Overall, the present study revealed that ORP8 may be a candidate target in the prevention and treatment of NSCLC.

Endoplasmic reticulum proteostasis control and gastric cancer

The endoplasmic reticulum (ER) is the primary organelle responsible for the synthesis, modification, folding and secretion of proteins, especially in specialized secretory cells. It also contributes to the maintenance of cellular functions, such as Ca²⁺ storage, lipogenesis, gluconeogenesis, and organelle biogenesis. Cellular stress conditions, such as glucose deprivation, hypoxia and disturbance of Ca²⁺ homeostasis, may increase the risk of protein misfolding and perturb proteostasis. This activates ER stress and triggers the unfolded protein response (UPR), leading to either the restoration of homeostasis or cell death. ER stress and UPR have been shown to play crucial roles in the pathogenesis, progression and treatment response of various cancers. In gastric cancer (GC), one of the most aggressive cancer types, critical functions of ER stress signaling have also started to emerge. Herein, we summarize the current knowledge linking ER stress and UPR to GC; we also discuss the possible nodes of therapeutic intervention and propose directions of future research.

PGC-1α/SNAI1 axis regulates tumor growth and metastasis by targeting miR-128b in gastric cancer

Peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) is a transcriptional coactivator that has been characterized as master regulators of mitochondrial biogenesis. It has been reported that aberrant regulation of PGC-1α is involved in a variety of human cancers. However, whether PGC-1α is involved in the regulation of tumor growth and metastasis in gastric cancer (GC) remains unknown. In the present study, we found that the expression of PGC-1α was upregulated in GC tissues and GC cell lines. Inhibition of PGC-1α inhibited cell viability, migration, and invasion, and promoted cell apoptosis of GC cells. Furthermore, inhibition of PGC-1α downregulated the SNAI1 expression, whereas upregulated microRNA (miR)-128b expression. The expression of SNAI1 was upregulated and the expression of miR-128b was downregulated in GC tissues. We further found that there was a positive correlation between PGC-1α and SNAI1 expression, and a negative correlation between PGC-1α and miR-128b expression or between SNAI1 and miR-128b expression in GC tissues. Moreover, PGC-1α inhibition-induced increased miR-128b expression, and PGC-1α overexpression-induced decreased miR-128b expression were both markedly suppressed by SNAI1 overexpression. In addition, SNAI1 overexpression or miR-128b inhibition partly reversed the effects of PGC-1α inhibition in GC cells. Furthermore, inhibition of PGC-1α suppressed the tumor growth in a nude mouse model, which may be related with the dysregulation of SNAI1 and miR-128b. In conclusion, these data indicate that the PGC-1α/SNAI1/miR-128b axis plays a vital role in GC via regulating cell viability, migration, invasion, and apoptosis.

Radial glia fibers translate Fgf8 morphogenetic signals to generate a thalamic nuclear complex protomap in the mantle layer

Thalamic neurons are distributed between different nuclear groups of the thalamic multinuclear complex; they develop topologically ordered specific projections that convey information on voluntary motor programs and sensory modalities to functional areas in the cerebral cortex. Since thalamic neurons present a homogeneous morphology, their functional specificity is derived from their afferent and efferent connectivity. Adequate development of thalamic afferent and efferent connections depends on guide signals that bind receptors in nuclear neuropils and axonal growth cones, respectively. These are finally regulated by regionalization processes in the thalamic neurons, codifying topological information. In this work, we studied the role of Fgf8 morphogenetic signaling in establishing the molecular thalamic protomap, which was revealed by Igsf21, Pde10a and Btbd3 gene expression in the thalamic mantle layer. Fgf8 signaling activity was evidenced by pERK expression in radial glia cells and fibers, which may represent a scaffold that translates neuroepithelial positional information to the mantle layer. In this work, we describe the fact that Fgf8-hypomorphic mice did not express pERK in radial glia cells and fibers and presented disorganized thalamic regionalization, increasing neuronal death in the ventro-lateral thalamus and strong disruption of thalamocortical projections. In conclusion, Fgf8 encodes the positional information required for thalamic nuclear regionalization and the development of thalamocortical projections.

Bridging the molecular and biological functions of the oxysterol-binding protein family

Oxysterol-binding protein (OSBP) and OSBP-related proteins (ORPs) constitute a large eukaryotic gene family that transports and regulates the metabolism of sterols and phospholipids. The original classification of the family based on oxysterol-binding activity belies the complex dual lipid-binding specificity of the conserved OSBP homology domain (OHD). Additional protein- and membrane-interacting modules mediate the targeting of select OSBP/ORPs to membrane contact sites between organelles, thus positioning the OHD between opposing membranes for lipid transfer and metabolic regulation. This unique subcellular location, coupled with diverse ligand preferences and tissue distribution, has identified OSBP/ORPs as key arbiters of membrane composition and function. Here, we will review how molecular models of OSBP/ORP-mediated intracellular lipid transport and regulation at membrane contact sites relate to their emerging roles in cellular and organismal functions.

Oxysterol-binding protein-related protein 5 (ORP5) promotes cell proliferation by activation of mTORC1 signaling

Oxysterol-binding protein (OSBP) and OSBP-related proteins (ORPs) constitute a large family of proteins that mainly function in lipid transport and sensing. ORP5 is an endoplasmic reticulum (ER)-anchored protein implicated in lipid transfer at the contact sites between the ER and other membranes. Recent studies indicate that ORP5 is also involved in cancer cell invasion and tumor progression. However, the molecular mechanism underlying ORP5's involvement in cancer is unclear. Here, we report that ORP5 promotes cell proliferation and motility of HeLa cells, an effect that depends on its functional OSBP-related domain (ORD). We also found that ORP5 depletion or substitutions of key residues located within ORP5-ORD and responsible for interactions with lipids interfered with cell proliferation, migration, and invasion. ORP5 interacted with the protein mechanistic target of rapamycin (mTOR), and this interaction also required ORP5-ORD. Of note, whereas ORP5 overexpression induced mTOR complex 1 (mTORC1) activity, ORP5 down-regulation had the opposite effect. Finally, ORP5-depleted cells exhibited impaired mTOR localization to lysosomes, which may have accounted for the blunted mTORC1 activation. Together, our results suggest that ORP5 expression is positively correlated with mTORC1 signaling and that ORP5 stimulates cell proliferation, at least in part, by activating mTORC1.

The Overexpression of CARM1 Promotes Human Osteosarcoma Cell Proliferation through the pGSK3β/β-Catenin/cyclinD1 Signaling Pathway

Osteosarcoma (OS) is a kind of malignant bone tumor that occurs frequently in the region surrounding the knee joint and poses a threat to the health of teenagers. Since the application of chemotherapy to treat OS, 5-year survival rate in patients has improved from 10% to 70%, but patient survival has not changed over the past four decades. Coactivator-associated arginine methyltransferase 1 (CARM1) is a member of the PRMT protein family; it acts as an oncogene in many cancers, but its function in OS is still unknown. In this study, we found that CARM1 is overexpressed in OS and its expression is correlated with the Enneking stage. CCK-8 and colony forming assays showed that proliferation in OS cell lines was downregulated when siRNA was used to knockdown CARM1 expression. The cell cycle was inhibited in S phase after si-CARM1 transfection in OS cell lines. An antibody array indicated that Erk1/2 (Thr202/Tyr204), PARS40 (Thr246), and GSK3β (Ser9) expression are affected by CARM1, and western blotting verified that CARM1 promotes OS cell proliferation via pGSK3β/β-catenin/cyclinD1 signaling. Accordingly, CARM1 is a crucial gene in OS and is a potential new treatment target.

The Role of Oxysterols in Human Cancer

Oxysterols are oxygenated derivatives of cholesterol formed in the human body or ingested in the diet. By modulating the activity of many proteins [e.g., liver X receptors (LXRs), oxysterol-binding proteins (OSBPs), some ATP-binding cassette (ABC) transporters], oxysterols can affect many cellular functions and influence various physiological processes (e.g., cholesterol metabolism, membrane fluidity regulation, intracellular signaling pathways). Therefore, the role of oxysterols is also important in pathological conditions (e.g., atherosclerosis, diabetes mellitus type 2, neurodegenerative disorders). Finally, current evidence suggests that oxysterols play a role in malignancies such as breast, prostate, colon, and bile duct cancer. This review summarizes the physiological importance of oxysterols in the human body with a special emphasis on their roles in various tumors.