scholarly journals Molecular mechanisms for microtubule length regulation by kinesin-8 and XMAP215 proteins

2014 ◽  
Vol 4 (6) ◽  
pp. 20140031 ◽  
Author(s):  
Louis Reese ◽  
Anna Melbinger ◽  
Erwin Frey
Keyword(s):  
Molecular Motors ◽  
Molecular Mechanisms ◽  
Molecular Motor ◽  
Mutual Exclusion ◽  
High Growth ◽  
Dependent Manner ◽  
Dynamic Regulation ◽  
Filament Dynamics ◽  
Length Regulation ◽  
The Stability

The cytoskeleton is regulated by a plethora of enzymes that influence the stability and dynamics of cytoskeletal filaments. How microtubules (MTs) are controlled is of particular importance for mitosis, during which dynamic MTs are responsible for proper segregation of chromosomes. Molecular motors of the kinesin-8 protein family have been shown to depolymerize MTs in a length-dependent manner, and recent experimental and theoretical evidence suggests a possible role for kinesin-8 in the dynamic regulation of MTs. However, so far the detailed molecular mechanisms of how these molecular motors interact with the growing MT tip remain elusive. Here we show that two distinct scenarios for the interactions of kinesin-8 with the MT tip lead to qualitatively different MT dynamics, including accurate length control as well as intermittent dynamics. We give a comprehensive analysis of the regimes where length regulation is possible and characterize how the stationary length depends on the biochemical rates and the bulk concentrations of the various proteins. For a neutral scenario, where MTs grow irrespective of whether the MT tip is occupied by a molecular motor, length regulation is possible only for a narrow range of biochemical rates, and, in particular, limited to small polymerization rates. By contrast, for an inhibition scenario, where the presence of a motor at the MT tip inhibits MT growth, the regime where length regulation is possible is extremely broad and includes high growth rates. These results also apply to situations where a polymerizing enzyme like XMAP215 and kinesin-8 mutually exclude each other from the MT tip. Moreover, we characterize the differences in the stochastic length dynamics between the two scenarios. While for the neutral scenario length is tightly controlled, length dynamics is intermittent for the inhibition scenario and exhibits extended periods of MT growth and shrinkage. On a broader perspective, the set of models established in this work quite generally suggest that mutual exclusion of molecules at the ends of cytoskeletal filaments is an important factor for filament dynamics and regulation.

scholarly journals The Salmonella effector SifA initiates a kinesin-1 and kinesin-3 recruitment process mirroring that mediated by Arl8a/b

2021 ◽  
Author(s):  
Ziyan Fang ◽  
Mathieu Fallet ◽  
Tomas Moest ◽  
Jean-Pierre Gorvel ◽  
Stéphane Méresse
Keyword(s):  
Host Cell ◽  
Molecular Motors ◽  
Molecular Motor ◽  
Host Protein ◽  
Recruitment Process ◽  
Membrane Compartment ◽  
Infected Cells ◽  
The Stability ◽  
Bacterial Effectors

When intracellular, pathogenic Salmonella reside in a membrane compartment composed of interconnected vacuoles and tubules, the formation of which depends on the translocation of bacterial effectors into the host cell. Cytoskeletons and their molecular motors are prime targets for these effectors. In this study, we show that the microtubule molecular motor KIF1Bß, a member of the kinesin-3 family, is a key element for the establishment of the Salmonella replication niche as its absence is detrimental to the stability of bacterial vacuoles and the formation of associated tubules. Kinesin-3 interacts with the Salmonella effector SifA but also with SKIP, a host protein complexed to SifA. The interaction with SifA is essential for the recruitment of kinesin-3 on Salmonella vacuoles while that with SKIP is incidental. In the non-infectious context, however, the interaction with SKIP is essential for the recruitment and activity of kinesin-3 on a part of lysosomes. Finally, our results show that in infected cells, the presence of SifA establishes a kinesin-1 and kinesin-3 recruitment pathway that is analogous to and functions independently of that mediated by the Arl8a/b GTPases.

PRAMEF2-mediated dynamic regulation of YAP signaling promotes tumorigenesis

2021 ◽  
Vol 118 (40) ◽  
pp. e2105523118
Author(s):  
Madhurima Ghosh ◽  
Sanjeev Das
Keyword(s):  
Molecular Mechanisms ◽  
Nuclear Accumulation ◽  
Dependent Manner ◽  
Transcriptional Coactivator ◽  
Dynamic Regulation ◽  
Cancer Testis Antigens ◽  
Ubiquitin Ligase Complex ◽  
Insight Into ◽  
Cancer Testis

PRAMEF2 is a member of the PRAME multigene family of cancer testis antigens, which serve as prognostic markers for several cancers. However, molecular mechanisms underlying its role in tumorigenesis remain poorly understood. Here, we report that PRAMEF2 is repressed under conditions of altered metabolic homeostasis in a FOXP3-dependent manner. We further demonstrate that PRAMEF2 is a BC-box containing substrate recognition subunit of Cullin 2–based E3 ubiquitin ligase complex. PRAMEF2 mediates polyubiquitylation of LATS1 kinase of the Hippo/YAP pathway, leading to its proteasomal degradation. The site for ubiquitylation was mapped to the conserved Lys860 residue in LATS1. Furthermore, LATS1 degradation promotes enhanced nuclear accumulation of the transcriptional coactivator YAP, resulting in increased expression of proliferative and metastatic genes. Thus, PRAMEF2 promotes malignant phenotype in a YAP-dependent manner. Additionally, elevated PRAMEF2 levels correlate with increased nuclear accumulation of YAP in advanced grades of breast carcinoma. These findings highlight the pivotal role of PRAMEF2 in tumorigenesis and provide mechanistic insight into YAP regulation.

scholarly journals Elevated polar ejection forces stabilize kinetochore–microtubule attachments

2013 ◽  
Vol 200 (2) ◽  
pp. 203-218 ◽  
Author(s):  
Stuart Cane ◽  
Anna A. Ye ◽  
Sasha J. Luks-Morgan ◽  
Thomas J. Maresca
Keyword(s):  
Molecular Motors ◽  
Molecular Mechanisms ◽  
Critical Force ◽  
Aurora B ◽  
Dependent Manner ◽  
Spindle Poles ◽  
Ejection Force ◽  
Chromosome Alignment ◽  
Directed Motility ◽  
Spindle Microtubules

Chromosome biorientation promotes congression and generates tension that stabilizes kinetochore–microtubule (kt-MT) interactions. Forces produced by molecular motors also contribute to chromosome alignment, but their impact on kt-MT attachment stability is unclear. A critical force that acts on chromosomes is the kinesin-10–dependent polar ejection force (PEF). PEFs are proposed to facilitate congression by pushing chromosomes away from spindle poles, although knowledge of the molecular mechanisms underpinning PEF generation is incomplete. Here, we describe a live-cell PEF assay in which tension was applied to chromosomes by manipulating levels of the chromokinesin NOD (no distributive disjunction; Drosophila melanogaster kinesin-10). NOD stabilized syntelic kt-MT attachments in a dose- and motor-dependent manner by overwhelming the ability of Aurora B to mediate error correction. NOD-coated chromatin stretched away from the pole via lateral and end-on interactions with microtubules, and NOD chimeras with either plus end–directed motility or tip-tracking activity produced PEFs. Thus, kt-MT attachment stability is modulated by PEFs, which can be generated by distinct force-producing interactions between chromosomes and dynamic spindle microtubules.

scholarly journals Dynamic Regulation of the Molecular Mechanisms of Regulatory T Cell Migration in Inflamed Skin

2021 ◽  
Vol 12 ◽  
Author(s):  
M. Ursula Norman ◽  
Zachary Chow ◽  
Sarah L. Snelgrove ◽  
Peemapat Prakongtham ◽  
Michael J. Hickey
Keyword(s):  
Inflammatory Response ◽  
Molecular Mechanisms ◽  
Inflammatory Responses ◽  
Hair Follicles ◽  
Dependent Manner ◽  
Dynamic Regulation ◽  
T Cell Migration ◽  
Phosphoinositide 3 Kinase ◽  
Time Point

The presence of regulatory T cells (Tregs) in skin is important in controlling inflammatory responses in this peripheral tissue. Uninflamed skin contains a population of relatively immotile Tregs often located in clusters around hair follicles. Inflammation induces a significant increase both in the abundance of Tregs within the dermis, and in the proportion of Tregs that are highly migratory. The molecular mechanisms underpinning Treg migration in the dermis are unclear. In this study we used multiphoton intravital microscopy to examine the role of RGD-binding integrins and signalling through phosphoinositide 3-kinase P110δ (PI3K p110δ) in intradermal Treg migration in resting and inflamed skin. We found that inflammation induced Treg migration was dependent on RGD-binding integrins in a context-dependent manner. αv integrin was important for Treg migration 24 hours after induction of inflammation, but contributed to Treg retention at 48 hours, while β1 integrin played a role in Treg retention at the later time point but not during the peak of inflammation. In contrast, inhibition of signalling through PI3K p110δ reduced Treg migration throughout the entire inflammatory response, and also in the absence of inflammation. Together these observations demonstrate that the molecular mechanisms controlling intradermal Treg migration vary markedly according to the phase of the inflammatory response.

scholarly journals Alternative Mechanisms for Coordinating Polymerase α and MCM Helicase

2009 ◽  
Vol 30 (2) ◽  
pp. 423-435 ◽  
Author(s):  
Chanmi Lee ◽  
Ivan Liachko ◽  
Roxane Bouten ◽  
Zvi Kelman ◽  
Bik K. Tye
Keyword(s):  
Dna Replication ◽  
Dna Polymerase ◽  
Molecular Motors ◽  
Replication Fork ◽  
Dna Polymerases ◽  
Physical Stability ◽  
Dependent Manner ◽  
Replication Forks ◽  
Mcm Helicase ◽  
The Stability

ABSTRACT Functional coordination between DNA replication helicases and DNA polymerases at replication forks, achieved through physical linkages, has been demonstrated in prokaryotes but not in eukaryotes. In Saccharomyces cerevisiae, we showed that mutations that compromise the activity of the MCM helicase enhance the physical stability of DNA polymerase α in the absence of their presumed linker, Mcm10. Mcm10 is an essential DNA replication protein implicated in the stable assembly of the replisome by virtue of its interaction with the MCM2-7 helicase and Polα. Dominant mcm2 suppressors of mcm10 mutants restore viability by restoring the stability of Polα without restoring the stability of Mcm10, in a Mec1-dependent manner. In this process, the single-stranded DNA accumulation observed in the mcm10 mutant is suppressed. The activities of key checkpoint regulators known to be important for replication fork stabilization contribute to the efficiency of suppression. These results suggest that Mcm10 plays two important roles as a linker of the MCM helicase and Polα at the elongating replication fork—first, to coordinate the activities of these two molecular motors, and second, to ensure their physical stability and the integrity of the replication fork.

scholarly journals Rpb4 and Puf3 imprint and post-transcriptionally control the stability of a common set of mRNAs in yeast

2020 ◽  
Author(s):  
A.I. Garrido-Godino ◽  
I. Gupta ◽  
F. Gutiérrez-Santiago ◽  
A.B. Martínez-Padilla ◽  
A. Alekseenko ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Mrna Stability ◽  
Molecular Mechanisms ◽  
Rna Binding ◽  
Large Population ◽  
Dependent Manner ◽  
Mrna Synthesis ◽  
Rna Pol Ii ◽  
Pol Ii ◽  
The Stability

ABSTRACTGene expression involving RNA polymerase II is regulated by the concerted interplay between mRNA synthesis and degradation, crosstalk in which mRNA decay machinery and transcription machinery respectively impact transcription and mRNA stability. Rpb4, and likely dimer Rpb4/7, seem the central components of the RNA pol II governing these processes. In this work we unravel the molecular mechanisms participated by Rpb4 that mediate the posttranscriptional events regulating mRNA imprinting and stability. By RIP-Seq, we analyzed genome-wide the association of Rpb4 with mRNAs and demonstrated that it targeted a large population of more than 1400 transcripts. A group of these mRNAs was also the target of the RNA binding protein, Puf3. We demonstrated that Rpb4 and Puf3 physically, genetically, and functionally interact and also affect mRNA stability, and likely the imprinting, of a common group of mRNAs. Furthermore, the Rpb4 and Puf3 association with mRNAs depends on one another. We also demonstrated, for the first time, that Puf3 associates with chromatin in an Rpb4-dependent manner. Our data also suggest that Rpb4 could be a key element of the RNA pol II that coordinates mRNA synthesis, imprinting and stability in cooperation with RBPs.

The Anti-Atherogenic Properties of Sesamin are Mediated via Improved Macrophage Cholesterol Efflux Through PPARγ1-LXRα and MAPK Signaling

2014 ◽  
Vol 84 (1-2) ◽  
pp. 79-91 ◽  
Author(s):  
Amin F. Majdalawieh ◽  
Hyo-Sung Ro
Keyword(s):  
Cholesterol Efflux ◽  
Transcriptional Activity ◽  
Molecular Mechanisms ◽  
Foam Cell ◽  
Mapk Signaling ◽  
Luciferase Reporter ◽  
Foam Cell Formation ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Macrophage Cholesterol Efflux

Background: Foam cell formation resulting from disrupted macrophage cholesterol efflux, which is triggered by PPARγ1 and LXRα, is a hallmark of atherosclerosis. Sesamin and sesame oil exert anti-atherogenic effects in vivo. However, the exact molecular mechanisms underlying such effects are not fully understood. Aim: This study examines the potential effects of sesamin (0, 25, 50, 75, 100 μM) on PPARγ1 and LXRα expression and transcriptional activity as well as macrophage cholesterol efflux. Methods: PPARγ1 and LXRα expression and transcriptional activity are assessed by luciferase reporter assays. Macrophage cholesterol efflux is evaluated by ApoAI-specific cholesterol efflux assays. Results: The 50 μM, 75 μM, and 100 μM concentrations of sesamin up-regulated the expression of PPARγ1 (p< 0.001, p < 0.001, p < 0.001, respectively) and LXRα (p = 0.002, p < 0.001, p < 0.001, respectively) in a concentration-dependent manner. Moreover, 75 μM and 100 μM concentrations of sesamin led to 5.2-fold (p < 0.001) and 6.0-fold (p<0.001) increases in PPAR transcriptional activity and 3.9-fold (p< 0.001) and 4.2-fold (p < 0.001) increases in LXR transcriptional activity, respectively, in a concentration- and time-dependent manner via MAPK signaling. Consistently, 50 μM, 75 μM, and 100 μM concentrations of sesamin improved macrophage cholesterol efflux by 2.7-fold (p < 0.001), 4.2-fold (p < 0.001), and 4.2-fold (p < 0.001), respectively, via MAPK signaling. Conclusion: Our findings shed light on the molecular mechanism(s) underlying sesamin’s anti-atherogenic effects, which seem to be due, at least in part, to its ability to up-regulate PPARγ1 and LXRα expression and transcriptional activity, improving macrophage cholesterol efflux. We anticipate that sesamin may be used as a therapeutic agent for treating atherosclerosis.

Neuroblastoma: An Updated Review on Biology and Treatment

2020 ◽  
Vol 20 (13) ◽  
pp. 1014-1022 ◽  
Author(s):  
Suresh Mallepalli ◽  
Manoj Kumar Gupta ◽  
Ramakrishna Vadde
Keyword(s):  
Survival Rate ◽  
High Risk ◽  
Molecular Mechanisms ◽  
Definitive Treatment ◽  
Therapeutic Drug ◽  
Mycn Amplification ◽  
Dependent Manner ◽  
High Risk Patients ◽  
Treatment And Prevention ◽  
Risk Patients

Background: Neuroblastoma (NB) is the second leading extracranial solid tumors of early childhood and clinically characterized by the presence of round, small, monomorphic cells with excess nuclear pigmentation (hyperchromasia).Owing to a lack of definitive treatment against NB and less survival rate in high-risk patients, there is an urgent requirement to understand molecular mechanisms associated with NB in a better way, which in turn can be utilized for developing drugs towards the treatment of NB in human. Objectives: In this review, an approach was adopted to understand major risk factors, pathophysiology, the molecular mechanism associated with NB, and various therapeutic agents that can serve as drugs towards the treatment of NB in humans. Conclusions: Numerous genetic (e.g., MYCN amplification), perinatal, and gestational factors are responsible for developing NB. However, no definite environmental or parental exposures responsible for causing NB have been confirmed to date. Though intensive multimodal treatment approaches, namely, chemotherapy, surgery &radiation, may help in improving the survival rate in children, these approaches have several side effects and do not work efficiently in high-risk patients. However, recent studies suggested that numerous phytochemicals, namely, vincristine, and matrine have a minimal side effect in the human body and may serve as a therapeutic drug during the treatment of NB. Most of these phytochemicals work in a dose-dependent manner and hence must be prescribed very cautiously. The information discussed in the present review will be useful in the drug discovery process as well as treatment and prevention on NB in humans.

RPS24c Isoform Facilitates Tumor Angiogenesis Via Promoting the Stability of MVIH in Colorectal Cancer

2020 ◽  
Vol 20 (5) ◽  
pp. 388-395 ◽  
Author(s):  
Yue Wang ◽  
Youjun Wu ◽  
Kun Xiao ◽  
Yingjie Zhao ◽  
Gang Lv ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Ribosomal Protein ◽  
Real Time ◽  
Tumor Angiogenesis ◽  
Real Time Pcr ◽  
Molecular Mechanisms ◽  
Migration And Invasion ◽  
Binding Interaction ◽  
Tubule Formation ◽  
The Stability

Background: Colorectal cancer (CRC) is the second leading cause of death worldwide, and distant metastasis is responsible for the poor prognosis in patients with advanced-stage CRC. RPS24 (ribosomal protein S24) as a ribosomal protein, multiple transcript variant encoding different isoforms have been found for this gene. Our previous studies have demonstrated that RPS24 is overexpressed in CRC. However, the mechanisms underlying the role of RPS24 in tumor development have not been fully defined. Methods: Expression of RPS24 isoforms and lncRNA MVIH in CRC tissues and cell lines were quantified by real-time PCR or western blotting assay. Endothelial tube formation assay was performed to determine the effect of RPS24 on tumor angiogenesis. The cell viability of HUVEC was determined by MTT assay, and the migration and invasion ability of HUVEC were detected by transwell assay. PGK1 secretion was tested with a specific ELISA kit. Results: Here, we found that RPS24c isoform was a major contributor to tumor angiogenesis, a vital process in tumor growth and metastasis. Real-time PCR revealed that RPS24c isoform was highly expressed in CRC tissues, while other isoforms are present in both normal and CRC tissues with no statistical difference. Moreover the change of RPS24 protein level is mainly due to the fluctuation of RPS24c. Furthermore, we observed that silencing RPS24c could decrease angiogenesis by inhibiting tubule formation, HUVEC cell proliferation and migration. Additionally, we investigated the molecular mechanisms and demonstrated that RPS24c mRNA interacted with lncRNA MVIH, the binding-interaction enhanced the stability of each other, thereby activated angiogenesis by inhibiting the secretion of PGK1. Conclusion: RPS24c facilitates tumor angiogenesis via the RPS24c/MVIH/PGK1 pathway in CRC. RPS24c inhibition may be a novel option for anti-vascular treatment in CRC.

Pisosterol Induces G2/M Cell Cycle Arrest and Apoptosis via the ATM/ATR Signaling Pathway in Human Glioma Cells

2020 ◽  
Vol 20 (6) ◽  
pp. 734-750
Author(s):  
Wallax A.S. Ferreira ◽  
Rommel R. Burbano ◽  
Claudia do Ó. Pessoa ◽  
Maria L. Harada ◽  
Bárbara do Nascimento Borges ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Signaling Pathway ◽  
Glioma Cell ◽  
Molecular Mechanisms ◽  
Glioma Cells ◽  
Dependent Manner ◽  
M Cell ◽  
Trypan Blue Exclusion ◽  
Cycle Arrest

Background: Pisosterol, a triterpene derived from Pisolithus tinctorius, exhibits potential antitumor activity in various malignancies. However, the molecular mechanisms that mediate the pisosterol-specific effects on glioma cells remain unknown. Objective: This study aimed to evaluate the antitumoral effects of pisosterol on glioma cell lines. Methods: The 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) and trypan blue exclusion assays were used to evaluate the effect of pisosterol on cell proliferation and viability in glioma cells. The effect of pisosterol on the distribution of the cells in the cell cycle was performed by flow cytometry. The expression and methylation pattern of the promoter region of MYC, ATM, BCL2, BMI1, CASP3, CDK1, CDKN1A, CDKN2A, CDKN2B, CHEK1, MDM2, p14ARF and TP53 was analyzed by RT-qPCR, western blotting and bisulfite sequencing PCR (BSP-PCR). Results: Here, it has been reported that pisosterol markedly induced G2/M arrest and apoptosis and decreased the cell viability and proliferation potential of glioma cells in a dose-dependent manner by increasing the expression of ATM, CASP3, CDK1, CDKN1A, CDKN2A, CDKN2B, CHEK1, p14ARF and TP53 and decreasing the expression of MYC, BCL2, BMI1 and MDM2. Pisosterol also triggered both caspase-independent and caspase-dependent apoptotic pathways by regulating the expression of Bcl-2 and activating caspase-3 and p53. Conclusions: It has been, for the first time, confirmed that the ATM/ATR signaling pathway is a critical mechanism for G2/M arrest in pisosterol-induced glioma cell cycle arrest and suggests that this compound might be a promising anticancer candidate for further investigation.

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