Nuclear Morphological Remodeling in Human Granulocytes Is Linked to Prenylation Independently from Cytoskeleton

Nuclear shape modulates cell behavior and function, while aberrant nuclear morphologies correlate with pathological phenotype severity. Nevertheless, functions of specific nuclear morphological features and underlying molecular mechanisms remain poorly understood. Here, we investigate a nucleus-intrinsic mechanism driving nuclear lobulation and segmentation concurrent with granulocyte specification, independently from extracellular forces and cytosolic cytoskeleton contributions. Transcriptomic regulation of cholesterol biosynthesis is equally concurrent with nuclear remodeling. Its putative role as a regulatory element is supported by morphological aberrations observed upon pharmacological impairment of several enzymatic steps of the pathway, most prominently the sterol ∆14-reductase activity of laminB-receptor and protein prenylation. Thus, we support the hypothesis of a nuclear-intrinsic mechanism for nuclear shape control with the putative involvement of the recently discovered GGTase III complex. Such process could be independent from or complementary to the better studied cytoskeleton-based nuclear remodeling essential for cell migration in both physiological and pathological contexts such as immune system function and cancer metastasis.

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The anti-tubercular activity of simvastatin is mediated by cholesterol-driven autophagy via the AMPK-mTORC1-TFEB axis

The Journal of Lipid Research ◽

10.1194/jlr.ra120000895 ◽

2020 ◽

Vol 61 (12) ◽

pp. 1617-1628

Author(s):

Natalie Bruiners ◽

Noton K. Dutta ◽

Valentina Guerrini ◽

Hugh Salamon ◽

Ken D. Yamaguchi ◽

...

Keyword(s):

Molecular Mechanisms ◽

Nuclear Translocation ◽

Mevalonate Pathway ◽

Biological Effects ◽

Cholesterol Biosynthesis ◽

Cholesterol Homeostasis ◽

Infection Model ◽

Protein Prenylation ◽

Macrophage Infection

The rise of drug-resistant tuberculosis poses a major risk to public health. Statins, which inhibit both cholesterol biosynthesis and protein prenylation branches of the mevalonate pathway, increase anti-tubercular antibiotic efficacy in animal models. However, the underlying molecular mechanisms are unknown. In this study, we used an in vitro macrophage infection model to investigate simvastatin’s anti-tubercular activity by systematically inhibiting each branch of the mevalonate pathway and evaluating the effects of the branch-specific inhibitors on mycobacterial growth. The anti-tubercular activity of simvastatin used at clinically relevant doses specifically targeted the cholesterol biosynthetic branch rather than the prenylation branches of the mevalonate pathway. Using Western blot analysis and AMP/ATP measurements, we found that simvastatin treatment blocked activation of mechanistic target of rapamycin complex 1 (mTORC1), activated AMP-activated protein kinase (AMPK) through increased intracellular AMP:ATP ratios, and favored nuclear translocation of transcription factor EB (TFEB). These mechanisms all induce autophagy, which is anti-mycobacterial. The biological effects of simvastatin on the AMPK-mTORC1-TFEB-autophagy axis were reversed by adding exogenous cholesterol to the cells. Our data demonstrate that the anti-tubercular activity of simvastatin requires inhibiting cholesterol biosynthesis, reveal novel links between cholesterol homeostasis, the AMPK-mTORC1-TFEB axis, and Mycobacterium tuberculosis infection control, and uncover new anti-tubercular therapy targets.

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ALS-Causing Protein TDP-43 Impairs SREBP2 Cholesterol Regulation

10.21203/rs.3.rs-608138/v1 ◽

2021 ◽

Author(s):

Naohiro Egawa ◽

Yuishin Izumi ◽

Itaru Tsuge ◽

Koji Fujita ◽

Hitoshi Shimano ◽

...

Keyword(s):

Molecular Mechanisms ◽

Binding Protein ◽

Regulatory Element ◽

Cholesterol Biosynthesis ◽

Transcriptome Profiling ◽

Cholesterol Homeostasis ◽

Neuronal Cultures ◽

Element Binding Protein ◽

Induced Pluripotent ◽

Als Patients

Abstract Dyslipidemia is correlated with the prognosis of amyotrophic lateral sclerosis (ALS), a fatal motor neuron disorder characterized pathologically by TAR DNA binding protein (TDP-43) inclusions. We investigated molecular mechanisms of lipid metabolism regulated by TDP-43 in ALS. Expression microarray and RNA deep sequencing (RNA-Seq) were performed using cell lines expressing doxycycline-inductive TDP-43. Gene expression and transcriptome profiling identified 434 significantly altered genes under high levels of TDP-43 (Tukey’s test, P < 0.05) including sterol regulatory element-binding protein 2 (SREBP2), a master regulator of cholesterol homeostasis and its downstream genes. TDP-43 overexpression impaired SREBP2 transcriptional activity, leading to inhibition of cholesterol biosynthesis via the nutrient- and growth factor-responsive kinase mTOR Complex I (mTORC1). The amount of cholesterol was significantly decreased in motor neuronal cultures derived from ALS-patient induced pluripotent stem cells (iPSCs) as well as in the spinal fluids of ALS patients and in the spinal cord of ALS model mice. Impairment of cholesterol synthesis is caused by an increase in toxic function of TDP-43 in ALS.

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Cyclosporin-induced dyslipoproteinemia is associated with selective activation of SREBP-2

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1999.277.6.e1087 ◽

1999 ◽

Vol 277 (6) ◽

pp. E1087-E1094 ◽

Cited By ~ 3

Author(s):

Jinmei Wu ◽

Yong Hong Zhu ◽

Shailendra B. Patel

Keyword(s):

Cyclosporin A ◽

Molecular Mechanisms ◽

Plasma Cholesterol ◽

Regulatory Element ◽

Cholesterol Biosynthesis ◽

Mrna Level ◽

Northern Analysis ◽

Mrna Levels ◽

Selective Activation ◽

Vldl Triglyceride

The use of cyclosporin A has contributed greatly to the success of organ transplantation. However, cyclosporin-associated side effects of hypertension, nephrotoxicity, and dyslipoproteinemia have tempered these benefits. Cyclosporin-induced dyslipoproteinemia may be an important risk factor for the accelerated atherosclerosis observed posttransplantation. Using a mouse model, we treated Swiss-Webster mice for 6 days with a daily dose of 20 μg/g body wt of cyclosporin and observed significant elevations of plasma cholesterol, triglyceride, and apolipoprotein B (apoB) levels relative to vehicle-alone treated control animals. Measurement of the rate of secretion of very low-density lipoprotein (VLDL) by the liver in vivo showed that cyclosporin treatment led to a significant increase in the rate of hepatic VLDL triglyceride secretion. Total apoB secretion was unaffected. Northern analysis showed that cyclosporin A treatment increased the abundance of hepatic mRNA levels for a number of key genes involved in cholesterol biosynthesis relative to vehicle-alone treated animals. Two key transcriptional factors, sterol regulatory element-binding protein (SREBP)-1 and SREBP-2, also showed differential expression; SREBP-2 expression was increased at the mRNA level, and there was an increase in the active nuclear form, whereas the mRNA and the nuclear form of SREBP-1 were reduced. These results show that the molecular mechanisms by which cyclosporin causes dyslipoproteinemia may, in part, be mediated by selective activation of SREBP-2, leading to enhanced expression of lipid metabolism genes and hepatic secretion of VLDL triglyceride.

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Galectin-3: A factotum in carcinogenesis bestowing an archery for prevention

Tumor Biology ◽

10.3233/tub-200051 ◽

2021 ◽

Vol 43 (1) ◽

pp. 77-96

Author(s):

T. Jeethy Ram ◽

Asha Lekshmi ◽

Thara Somanathan ◽

K. Sujathan

Keyword(s):

Cancer Progression ◽

Molecular Mechanisms ◽

Cancer Metastasis ◽

Epithelial Mesenchymal Transition ◽

Therapy Resistance ◽

Cellular Level ◽

Clinical Samples ◽

Innovative Strategy ◽

Mesenchymal Transition ◽

Galectin 3

Cancer metastasis and therapy resistance are the foremost hurdles in oncology at the moment. This review aims to pinpoint the functional aspects of a unique multifaceted glycosylated molecule in both intracellular and extracellular compartments of a cell namely galectin-3 along with its metastatic potential in different types of cancer. All materials reviewed here were collected through the search engines PubMed, Scopus, and Google scholar. Among the 15 galectins identified, the chimeric gal-3 plays an indispensable role in the differentiation, transformation, and multi-step process of tumor metastasis. It has been implicated in the molecular mechanisms that allow the cancer cells to survive in the intravascular milieu and promote tumor cell extravasation, ultimately leading to metastasis. Gal-3 has also been found to have a pivotal role in immune surveillance and pro-angiogenesis and several studies have pointed out the importance of gal-3 in establishing a resistant phenotype, particularly through the epithelial-mesenchymal transition process. Additionally, some recent findings suggest the use of gal-3 inhibitors in overcoming therapeutic resistance. All these reports suggest that the deregulation of these specific lectins at the cellular level could inhibit cancer progression and metastasis. A more systematic study of glycosylation in clinical samples along with the development of selective gal-3 antagonists inhibiting the activity of these molecules at the cellular level offers an innovative strategy for primary cancer prevention.

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In Escherichia coli Ammonia Inhibits Cytochrome bo3 But Activates Cytochrome bd-I

Antioxidants ◽

10.3390/antiox10010013 ◽

2020 ◽

Vol 10 (1) ◽

pp. 13

Author(s):

Elena Forte ◽

Sergey A. Siletsky ◽

Vitaliy B. Borisov

Keyword(s):

Escherichia Coli ◽

Molecular Mechanisms ◽

Dissociation Constants ◽

Reductase Activity ◽

Ammonia Concentration ◽

High Concentration ◽

E Coli ◽

Cytochrome Bd ◽

Cytochrome Bo3 ◽

Oxygen Reductase

Interaction of two redox enzymes of Escherichia coli, cytochrome bo3 and cytochrome bd-I, with ammonium sulfate/ammonia at pH 7.0 and 8.3 was studied using high-resolution respirometry and absorption spectroscopy. At pH 7.0, the oxygen reductase activity of none of the enzymes is affected by the ligand. At pH 8.3, cytochrome bo3 is inhibited by the ligand, with 40% maximum inhibition at 100 mM (NH4)2SO4. In contrast, the activity of cytochrome bd-I at pH 8.3 increases with increasing the ligand concentration, the largest increase (140%) is observed at 100 mM (NH4)2SO4. In both cases, the effector molecule is apparently not NH4+ but NH3. The ligand induces changes in absorption spectra of both oxidized cytochromes at pH 8.3. The magnitude of these changes increases as ammonia concentration is increased, yielding apparent dissociation constants Kdapp of 24.3 ± 2.7 mM (NH4)2SO4 (4.9 ± 0.5 mM NH3) for the Soret region in cytochrome bo3, and 35.9 ± 7.1 and 24.6 ± 12.4 mM (NH4)2SO4 (7.2 ± 1.4 and 4.9 ± 2.5 mM NH3) for the Soret and visible regions, respectively, in cytochrome bd-I. Consistently, addition of (NH4)2SO4 to cells of the E. coli mutant containing cytochrome bd-I as the only terminal oxidase at pH 8.3 accelerates the O2 consumption rate, the highest one (140%) being at 27 mM (NH4)2SO4. We discuss possible molecular mechanisms and physiological significance of modulation of the enzymatic activities by ammonia present at high concentration in the intestines, a niche occupied by E. coli.

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The Association of an SNP in the EXOC4 Gene and Reproductive Traits Suggests Its Use as a Breeding Marker in Pigs

Animals ◽

10.3390/ani11020521 ◽

2021 ◽

Vol 11 (2) ◽

pp. 521

Author(s):

Yingting He ◽

Xiaofeng Zhou ◽

Rongrong Zheng ◽

Yao Jiang ◽

Zhixiang Yao ◽

...

Keyword(s):

Molecular Mechanisms ◽

Fragment Length Polymorphism ◽

Regulatory Element ◽

Reproductive Traits ◽

Specific Sequence ◽

Litter Weight ◽

Potential Binding ◽

Pcr Rflp ◽

Teat Number ◽

Myeloid Zinc Finger

In mammals, the exocyst complex component 4 (EXOC4) gene has often been reported to be involved in vesicle transport. The SNP rs81471943 (C/T) is located in the intron of porcine EXOC4, while six quantitative trait loci (QTL) within 5–10 Mb around EXOC4 are associated with ovary weight, teat number, total offspring born alive, and corpus luteum number. However, the molecular mechanisms between EXOC4 and the reproductive performance of pigs remains to be elucidated. In this study, rs81471943 was genotyped from a total of 994 Duroc sows, and the genotype and allele frequency of SNP rs81471943 (C/T) were statistically analyzed. Then, the associations between SNP rs81471943 and four reproductive traits, including number of piglets born alive (NBA), litter weight at birth (LWB), number of piglets weaned (NW), and litter weight at weaning (LWW), were determined. Sanger sequencing and PCR restriction fragment length polymorphism (PCR-RFLP) were utilized to identify the rs81471943 genotype. We found that the genotype frequency of CC was significantly higher than that of CT and TT, and CC was the most frequent genotype for NBA, LWB, NW, and LWW. Moreover, 5′-deletion and luciferase assays identified a positive transcription regulatory element in the EXOC4 promoter. After exploring the EXOC4 promoter, SNP −1781G/A linked with SNP rs81471943 (C/T) were identified by analysis of the transcription activity of the haplotypes, and SNP −1781 G/A may influence the potential binding of P53, E26 transformation specific sequence -like 1 transcription factor (ELK1), and myeloid zinc finger 1 (MZF1). These findings provide useful information for identifying a molecular marker of EXOC4-assisted selection in pig breeding.

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The absolute rate of cholesterol biosynthesis in monocyte-macrophages from normal and familial hypercholesterolaemic subjects

Biochemical Journal ◽

10.1042/bj2190461 ◽

1984 ◽

Vol 219 (2) ◽

pp. 461-470 ◽

Cited By ~ 17

Author(s):

D D Patel ◽

C R Pullinger ◽

B L Knight

Keyword(s):

Cholesterol Synthesis ◽

Reductase Activity ◽

Cholesterol Biosynthesis ◽

Specific Radioactivity ◽

Density Lipoprotein ◽

Cellular Protein ◽

True Rate ◽

Hmg Coa Reductase ◽

Coa Reductase ◽

In Cells

The true rate of cholesterogenesis in cultured monocyte-macrophages was determined from the incorporation of [2-14C]acetate into cholesterol, using the desmosterol (cholesta-5,24-dien-3 beta-ol) that accumulated in the presence of the drug triparanol to estimate the specific radioactivity of the newly formed sterols. It was shown that this procedure could be successfully adapted for use with cultured monocytes despite the accumulation of other unidentified biosynthetic intermediates. In cells maintained in 20% (v/v) whole serum approx. 25% of the sterol carbon was derived from exogenous acetate. Cholesterol synthesis was as high in normal cells as in cells from homozygous familial hypercholesterolaemic (FH) subjects and accounted for 50% of the increase in cellular cholesterol. The addition of extra low-density lipoprotein (LDL) reduced cholesterol synthesis, apparently through a decrease in the activity of 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-CoA reductase). When incubated in lipoprotein-deficient serum some cells did not survive, but those that remained showed a normal increase in protein content; the amount of cellular protein and cholesterol in each well did not increase and cholesterol synthesis was reduced by over 80%. HMG-CoA reductase activity fell less dramatically and the proportion of sterol carbon derived from exogenous acetate increased, suggesting that the low rate of cholesterogenesis with lipoprotein-deficient serum was due to a shortage of substrate. The results indicate that under normal conditions monocyte-macrophages obtain cholesterol from endogenous synthesis rather than through receptor-mediated uptake of LDL, and that synthesis together with non-saturable uptake of LDL provides the majority of the cholesterol required to support growth.

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Regulation of the SREBP transcription factors by mTORC1

Biochemical Society Transactions ◽

10.1042/bst0390495 ◽

2011 ◽

Vol 39 (2) ◽

pp. 495-499 ◽

Cited By ~ 42

Author(s):

Caroline A. Lewis ◽

Beatrice Griffiths ◽

Claudio R. Santos ◽

Mario Pende ◽

Almut Schulze

Keyword(s):

Fatty Acid ◽

Fatty Acid Synthase ◽

Target Genes ◽

De Novo ◽

Regulatory Element ◽

Cholesterol Biosynthesis ◽

Mammalian Target Of Rapamycin ◽

Lipid Biosynthesis ◽

De Novo Lipogenesis ◽

Genes Encoding

In recent years several reports have linked mTORC1 (mammalian target of rapamycin complex 1) to lipogenesis via the SREBPs (sterol-regulatory-element-binding proteins). SREBPs regulate the expression of genes encoding enzymes required for fatty acid and cholesterol biosynthesis. Lipid metabolism is perturbed in some diseases and SREBP target genes, such as FASN (fatty acid synthase), have been shown to be up-regulated in some cancers. We have previously shown that mTORC1 plays a role in SREBP activation and Akt/PKB (protein kinase B)-dependent de novo lipogenesis. Our findings suggest that mTORC1 plays a crucial role in the activation of SREBP and that the activation of lipid biosynthesis through the induction of SREBP could be part of a regulatory pathway that co-ordinates protein and lipid biosynthesis during cell growth. In the present paper, we discuss the increasing amount of data supporting the potential mechanisms of mTORC1-dependent activation of SREBP as well as the implications of this signalling pathway in cancer.

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Microenvironment-mediated cancer dormancy: Insights from metastability theory

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2111046118 ◽

2021 ◽

Vol 119 (1) ◽

pp. e2111046118

Author(s):

Sadra Bakhshandeh ◽

Carsten Werner ◽

Peter Fratzl ◽

Amaia Cipitria

Keyword(s):

Cancer Cells ◽

Molecular Mechanisms ◽

Cancer Metastasis ◽

Droplet Growth ◽

Protective Mechanism ◽

Dormant State ◽

Strong Focus ◽

Tumor Tissues ◽

Cancer Dormancy ◽

Thermodynamic Phase

Dormancy is an evolutionarily conserved protective mechanism widely observed in nature. A pathological example is found during cancer metastasis, where cancer cells disseminate from the primary tumor, home to secondary organs, and enter a growth-arrested state, which could last for decades. Recent studies have pointed toward the microenvironment being heavily involved in inducing, preserving, or ceasing this dormant state, with a strong focus on identifying specific molecular mechanisms and signaling pathways. Increasing evidence now suggests the existence of an interplay between intracellular as well as extracellular biochemical and mechanical cues in guiding such processes. Despite the inherent complexities associated with dormancy, proliferation, and growth of cancer cells and tumor tissues, viewing these phenomena from a physical perspective allows for a more global description, independent from many details of the systems. Building on the analogies between tissues and fluids and thermodynamic phase separation concepts, we classify a number of proposed mechanisms in terms of a thermodynamic metastability of the tumor with respect to growth. This can be governed by interaction with the microenvironment in the form of adherence (wetting) to a substrate or by mechanical confinement of the surrounding extracellular matrix. By drawing parallels with clinical and experimental data, we advance the notion that the local energy minima, or metastable states, emerging in the tissue droplet growth kinetics can be associated with a dormant state. Despite its simplicity, the provided framework captures several aspects associated with cancer dormancy and tumor growth.

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SPNS2 Downregulation Induces EMT and Promotes Colorectal Cancer Metastasis via Activating AKT Signaling Pathway

Frontiers in Oncology ◽

10.3389/fonc.2021.682773 ◽

2021 ◽

Vol 11 ◽

Author(s):

Lei Lv ◽

Qiyi Yi ◽

Ying Yan ◽

Fengmei Chao ◽

Ming Li

Keyword(s):

Colorectal Cancer ◽

Molecular Mechanisms ◽

Cancer Metastasis ◽

Epithelial Mesenchymal Transition ◽

Ectopic Expression ◽

Migration And Invasion ◽

Akt Inhibitor ◽

Colon Adenoma ◽

Mesenchymal Transition

Spinster homologue 2 (SPNS2), a transporter of S1P (sphingosine-1-phosphate), has been reported to mediate immune response, vascular development, and pathologic processes of diseases such as cancer via S1P signaling pathways. However, its biological functions and expression profile in colorectal cancer (CRC) is elusive. In this study, we disclosed that SPNS2 expression, which was regulated by copy number variation and DNA methylation of its promoter, was dramatically upregulated in colon adenoma and CRC compared to normal tissues. However, its expression was lower in CRC than in colon adenoma, and low expression of SPN2 correlated with advanced T/M/N stage and poor prognosis in CRC. Ectopic expression of SPNS2 inhibited cell proliferation, migration, epithelial–mesenchymal transition (EMT), invasion, and metastasis in CRC cell lines, while silencing SPNS2 had the opposite effects. Meanwhile, measuring the intracellular and extracellular level of S1P after overexpression of SPNS2 pinpointed a S1P-independent model of SPNS2. Mechanically, SPNS2 led to PTEN upregulation and inactivation of Akt. Moreover, AKT inhibitor (MK2206) abrogated SPNS2 knockdown-induced promoting effects on the migration and invasion, while AKT activator (SC79) reversed the repression of migration and invasion by SPNS2 overexpression in CRC cells, confirming the pivotal role of AKT for SPNS2’s function. Collectively, our study demonstrated the suppressor role of SPNS2 during CRC metastasis, providing new insights into the pathology and molecular mechanisms of CRC progression.

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