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Huang D, Chen J, Yang C, Wang M. TPX2 silencing mediated by joint action of microvesicles and ultrasonic radiation inhibits the migration and invasion of SKOV3 cells. Mol Med Rep 2018; 17:7627-7635. [PMID: 29620263 PMCID: PMC5983958 DOI: 10.3892/mmr.2018.8810] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 11/13/2017] [Indexed: 01/07/2023] Open
Abstract
Ovarian cancer, with its high morbidity, has one of the highest mortality rates among gynecological malignant tumors. Overexpression of targeting protein for Xklp2 (TPX2) has been identified in numerous malignant tumors. The present study sought to determine whether TPX2 silencing inhibited the growth and metastasis of ovarian cancer cells, and whether microvesicles‑ and ultrasonic radiation‑mediated small interfering (si)RNA‑TPX2 transfection may improve the therapeutic effect. The SKOV3 cell line, derived from papillary serous cytadenocarcinoma of the human ovary, was selected as a cell model. Cells were divided into five groups: Control, siRNA‑TPX2, siRNA‑TPX2 + microvesicle (M), siRNA‑TPX2 + ultrasonic irradiation (UI), and siRNA‑TPX2 + M + UI. Cell viability was evaluated under the aforementioned conditions via the Cell Counting kit 8 (CCK8) assay. Cell migration and invasion were detected using Transwell assays. The expression levels of associated genes, including epithelial cadherin (E‑cadherin), metalloproteinase inhibitor 2 (TIMP‑2), metastasis associated 1 (MTA1) and matrix metallopeptidase 2 (MMP2), were analyzed using reverse transcription‑quantitative polymerase chain reaction analysis and western blotting. MMP2 activity was determined using a gelatin zymography assay. The results suggested that TPX2 serves an important role in the development of SKOV3 cells; it is additionally able to inhibit cell migration and invasion by upregulating E‑cadherin and TIMP2, downregulating MMP2 and MTA1, and inhibiting the phosphorylation of p38 and c‑Jun N‑terminal kinase. The inhibitory effect of siRNA‑TPX2 on SKOV3 cellular metastasis in the presence of microvesicles and ultrasonic radiation was observed to be improved compared with the control. It is proposed that the combination of microvesicles and ultrasonic radiation with TPX2 silencing has the potential to be an effective gene therapy against ovarian cancer.
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Affiliation(s)
- Dong Huang
- Department of Obstetrics and Gynecology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310016, P.R. China
| | - Jianmin Chen
- Department of Obstetrics and Gynecology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310016, P.R. China
| | - Cuiyu Yang
- Department of Obstetrics and Gynecology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310016, P.R. China
| | - Minzhen Wang
- Department of Obstetrics and Gynecology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310016, P.R. China
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Milic B, Chakraborty A, Han K, Bassik MC, Block SM. KIF15 nanomechanics and kinesin inhibitors, with implications for cancer chemotherapeutics. Proc Natl Acad Sci U S A 2018; 115:E4613-E4622. [PMID: 29703754 PMCID: PMC5960320 DOI: 10.1073/pnas.1801242115] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Eg5, a mitotic kinesin, has been a target for anticancer drug development. Clinical trials of small-molecule inhibitors of Eg5 have been stymied by the development of resistance, attributable to mitotic rescue by a different endogenous kinesin, KIF15. Compared with Eg5, relatively little is known about the properties of the KIF15 motor. Here, we employed single-molecule optical-trapping techniques to define the KIF15 mechanochemical cycle. We also studied the inhibitory effects of KIF15-IN-1, an uncharacterized, commercially available, small-molecule inhibitor, on KIF15 motility. To explore the complementary behaviors of KIF15 and Eg5, we also scored the effects of small-molecule inhibitors on admixtures of both motors, using both a microtubule (MT)-gliding assay and an assay for cancer cell viability. We found that (i) KIF15 motility differs significantly from Eg5; (ii) KIF15-IN-1 is a potent inhibitor of KIF15 motility; (iii) MT gliding powered by KIF15 and Eg5 only ceases when both motors are inhibited; and (iv) pairing KIF15-IN-1 with Eg5 inhibitors synergistically reduces cancer cell growth. Taken together, our results lend support to the notion that a combination drug therapy employing both inhibitors may be a viable strategy for overcoming chemotherapeutic resistance.
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Affiliation(s)
- Bojan Milic
- Biophysics Program, Stanford University, Stanford, CA 94305
| | | | - Kyuho Han
- Department of Genetics, Stanford University School of Medicine, Stanford University, Stanford, CA 94305
| | - Michael C Bassik
- Department of Genetics, Stanford University School of Medicine, Stanford University, Stanford, CA 94305
- Chemistry, Engineering, and Medicine for Human Health, Stanford University, Stanford, CA 94305
| | - Steven M Block
- Department of Biology, Stanford University, Stanford, CA 94305;
- Department of Applied Physics, Stanford University, Stanford, CA 94305
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Chen H, Connell M, Mei L, Reid GSD, Maxwell CA. The nonmotor adaptor HMMR dampens Eg5-mediated forces to preserve the kinetics and integrity of chromosome segregation. Mol Biol Cell 2018; 29:786-796. [PMID: 29386294 PMCID: PMC5905292 DOI: 10.1091/mbc.e17-08-0531] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The nonmotor adaptor protein HMMR maintains the kinetics and integrity of chromosome segregation by promoting TPX2-Eg5 complexes that dampen Eg5-mediated forces and support K-fiber stability, kinetochore–microtubule attachments, and inter-kinetochore tension. HMMR is needed to prevent the generation of aneuploid progeny cells. Mitotic spindle assembly and organization require forces generated by motor proteins. The activity of these motors is regulated by nonmotor adaptor proteins. However, there are limited studies reporting the functional importance of adaptors on the balance of motor forces and the promotion of faithful and timely cell division. Here we show that genomic deletion or small interfering RNA silencing of the nonmotor adaptor Hmmr/HMMR disturbs spindle microtubule organization and bipolar chromosome–kinetochore attachments with a consequent elevated occurrence of aneuploidy. Rescue experiments show a conserved motif in HMMR is required to generate interkinetochore tension and promote anaphase entry. This motif bears high homology with the kinesin Kif15 and is known to interact with TPX2, a spindle assembly factor. We find that HMMR is required to dampen kinesin Eg5-mediated forces through localizing TPX2 and promoting the formation of inhibitory TPX2-Eg5 complexes. In HMMR-silenced cells, K-fiber stability is reduced while the frequency of unattached chromosomes and the time needed for chromosome segregation are both increased. These defects can be alleviated in HMMR-silenced cells with chemical inhibition of Eg5 but not through the silencing of Kif15. Together, our findings indicate that HMMR balances Eg5-mediated forces to preserve the kinetics and integrity of chromosome segregation.
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Affiliation(s)
- Helen Chen
- Department of Pediatrics, University of British Columbia, Vancouver, BC V5Z 4H4, Canada
| | - Marisa Connell
- Department of Pediatrics, University of British Columbia, Vancouver, BC V5Z 4H4, Canada
| | - Lin Mei
- Department of Pediatrics, University of British Columbia, Vancouver, BC V5Z 4H4, Canada
| | - Gregor S D Reid
- Department of Pediatrics, University of British Columbia, Vancouver, BC V5Z 4H4, Canada.,Michael Cuccione Childhood Cancer Research Program, BC Children's Hospital, Vancouver, BC V5Z 4H4, Canada
| | - Christopher A Maxwell
- Department of Pediatrics, University of British Columbia, Vancouver, BC V5Z 4H4, Canada.,Michael Cuccione Childhood Cancer Research Program, BC Children's Hospital, Vancouver, BC V5Z 4H4, Canada
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Chen YC, Chen IS, Huang GJ, Kang CH, Wang KC, Tsao MJ, Pan HW. Targeting DTL induces cell cycle arrest and senescence and suppresses cell growth and colony formation through TPX2 inhibition in human hepatocellular carcinoma cells. Onco Targets Ther 2018; 11:1601-1616. [PMID: 29606879 PMCID: PMC5868578 DOI: 10.2147/ott.s147453] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Background Hepatocellular carcinoma (HCC) has an increasing incidence and high mortality. Surgical operation is not a comprehensive strategy for liver cancer. Moreover, tolerating systemic chemotherapy is difficult for patients with HCC because hepatic function is often impaired due to underlying cirrhosis. Therefore, a comprehensive strategy for cancer treatment should be developed. DTL (Cdc10-dependent transcript 2) is a critical regulator of cell cycle progression and genomic stability. In our previous study, the upregulation of DTL expression in aggressive HCC correlated positively with tumor grade and poor patient survival. We hypothesize that targeting DTL may provide a novel therapeutic strategy for liver cancer. DTL small interference RNAs were used to knock down DTL protein expression. Methods A clonogenic assay, immunostaining, double thymidine block, imaging flow cytometry analysis, and a tumor spheroid formation assay were used to analyze the role of DTL in tumor cell growth, cell cycle progression, micronucleation, ploidy, and tumorigenicity. Results Our results demonstrated that targeting DTL reduced cell cycle regulators and chromosome segregation genes, resulting in increased cell micronucleation. DTL depletion inhibited liver cancer cell growth, increased senescence, and reduced tumorigenesis. DTL depletion resulted in the disruption of the mitotic proteins cyclin B, CDK1, securin, seprase, Aurora A, and Aurora B as well as the upregulation of the cell cycle arrest gene p21. A rescue assay indicated that DTL should be targeted through TPX2 downregulation for cancer cell growth inhibition. Moreover, DTL silencing inhibited the growth of patient-derived primary cultured HCC cells. Conclusion Our study results indicate that DTL is a potential novel target gene for treating liver cancer through liver cancer cell senescence induction. Furthermore, our results provide insights into molecular mechanisms for targeting DTL in liver cancer cells. The results also indicate several other starting points for future preclinical and clinical studies on liver cancer treatment.
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Affiliation(s)
- Yu-Chia Chen
- Department of Surgery, Division of General Surgery, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan
| | - I-Shu Chen
- Department of Surgery, Division of General Surgery, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan
| | - Guan-Jin Huang
- Department of Pathology, National Chung Kung University Hospital, Tainan, Taiwan
| | - Chi-Hsiang Kang
- Department of Surgery, Division of General Surgery, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan
| | - Kuo-Chiang Wang
- Department of Surgery, Division of General Surgery, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan
| | - Min-Jen Tsao
- Department of General Surgery, Zuoying Branch of Kaohsiung Armed Forces General Hospital, Kaohsiung, Taiwan
| | - Hung-Wei Pan
- Department of Medical Education and Research, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan.,Department of Applied Chemistry, National Pingtung University, Pingtung, Taiwan
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Dilworth D, Gudavicius G, Xu X, Boyce AKJ, O’Sullivan C, Serpa JJ, Bilenky M, Petrochenko EV, Borchers CH, Hirst M, Swayne LA, Howard P, Nelson CJ. The prolyl isomerase FKBP25 regulates microtubule polymerization impacting cell cycle progression and genomic stability. Nucleic Acids Res 2018; 46:2459-2478. [PMID: 29361176 PMCID: PMC5861405 DOI: 10.1093/nar/gky008] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Revised: 12/14/2017] [Accepted: 01/12/2018] [Indexed: 12/25/2022] Open
Abstract
FK506 binding proteins (FKBPs) catalyze the interconversion of cis-trans proline conformers in proteins. Importantly, FK506 drugs have anti-cancer and neuroprotective properties, but the effectors and mechanisms underpinning these properties are not well understood because the cellular function(s) of most FKBP proteins are unclear. FKBP25 is a nuclear prolyl isomerase that interacts directly with nucleic acids and is associated with several DNA/RNA binding proteins. Here, we show the catalytic FKBP domain binds microtubules (MTs) directly to promote their polymerization and stabilize the MT network. Furthermore, FKBP25 associates with the mitotic spindle and regulates entry into mitosis. This interaction is important for mitotic spindle dynamics, as we observe increased chromosome instability in FKBP25 knockdown cells. Finally, we provide evidence that FKBP25 association with chromatin is cell-cycle regulated by Protein Kinase C phosphorylation. This disrupts FKBP25-DNA contacts during mitosis while maintaining its interaction with the spindle apparatus. Collectively, these data support a model where FKBP25 association with chromatin and MTs is carefully choreographed to ensure faithful genome duplication. Additionally, they highlight that FKBP25 is a MT-associated FK506 receptor and potential therapeutic target in MT-associated diseases.
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Affiliation(s)
- David Dilworth
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, V8W 3P6, Canada
| | - Geoff Gudavicius
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, V8W 3P6, Canada
| | - Xiaoxue Xu
- Division of Medical Sciences and Island Medical Program, University of Victoria, Victoria V8P 5C2, Canada
| | - Andrew K J Boyce
- Division of Medical Sciences and Island Medical Program, University of Victoria, Victoria V8P 5C2, Canada
| | - Connor O’Sullivan
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, V8W 3P6, Canada
| | - Jason J Serpa
- University of Victoria Genome BC Proteomics Centre, Vancouver Island Technology Park, Victoria, BC, V8Z 7X8, Canada
| | - Misha Bilenky
- BC Cancer Agency Genome Sciences Centre and the Department of Microbiology & Immunology, Michael Smith Laboratories, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada
| | - Evgeniy V Petrochenko
- University of Victoria Genome BC Proteomics Centre, Vancouver Island Technology Park, Victoria, BC, V8Z 7X8, Canada
| | - Christoph H Borchers
- University of Victoria Genome BC Proteomics Centre, Vancouver Island Technology Park, Victoria, BC, V8Z 7X8, Canada
| | - Martin Hirst
- BC Cancer Agency Genome Sciences Centre and the Department of Microbiology & Immunology, Michael Smith Laboratories, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada
| | - Leigh Anne Swayne
- Division of Medical Sciences and Island Medical Program, University of Victoria, Victoria V8P 5C2, Canada
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver V6T 1Z3, Canada
| | - Perry Howard
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, V8W 3P6, Canada
| | - Christopher J Nelson
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, V8W 3P6, Canada
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Abstract
The temporal activation of kinases and timely ubiquitin-mediated degradation is central to faithful mitosis. Here we present evidence that acetylation controlled by Coenzyme A synthase (COASY) and acetyltransferase CBP constitutes a novel mechanism that ensures faithful mitosis. We found that COASY knockdown triggers prolonged mitosis and multinucleation. Acetylome analysis reveals that COASY inactivation leads to hyper-acetylation of proteins associated with mitosis, including CBP and an Aurora A kinase activator, TPX2. During early mitosis, a transient CBP-mediated TPX2 acetylation is associated with TPX2 accumulation and Aurora A activation. The recruitment of COASY inhibits CBP-mediated TPX2 acetylation, promoting TPX2 degradation for mitotic exit. Consistently, we detected a stage-specific COASY-CBP-TPX2 association during mitosis. Remarkably, pharmacological and genetic inactivation of CBP effectively rescued the mitotic defects caused by COASY knockdown. Together, our findings uncover a novel mitotic regulation wherein COASY and CBP coordinate an acetylation network to enforce productive mitosis.
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57
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Inoue D, Wittbrodt J, Gruss OJ. Loss and Rebirth of the Animal Microtubule Organizing Center: How Maternal Expression of Centrosomal Proteins Cooperates with the Sperm Centriole in Zygotic Centrosome Reformation. Bioessays 2018. [PMID: 29522658 DOI: 10.1002/bies.201700135] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Centrosomes are the main microtubule organizing centers in animal cells. In particular during embryogenesis, they ensure faithful spindle formation and proper cell divisions. As metazoan centrosomes are eliminated during oogenesis, they have to be reassembled upon fertilization. Most metazoans use the sperm centrioles as templates for new centrosome biogenesis while the egg's cytoplasm re-prepares all components for on-going centrosome duplication in rapidly dividing embryonic cells. We discuss our knowledge and the experimental challenges to analyze zygotic centrosome reformation, which requires genetic experiments to enable scrutinizing respective male and female contributions. Male and female knockout animals and mRNA injection to mimic maternal expression of centrosomal proteins could point a way to the systematic molecular dissection of the process. The most recent data suggest that timely expression of centrosome components in oocytes is the key to zygotic centrosome reformation that uses male sperm as coordinators for de novo centrosome production.
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Affiliation(s)
- Daigo Inoue
- Dr. D. Inoue, Prof. Dr. J. Wittbrodt, Centre of Organismal Studies, University of Heidelberg, Im Neuenheimer Feld 230, 69120 Heidelberg, Germany
| | - Joachim Wittbrodt
- Dr. D. Inoue, Prof. Dr. J. Wittbrodt, Centre of Organismal Studies, University of Heidelberg, Im Neuenheimer Feld 230, 69120 Heidelberg, Germany
| | - Oliver J Gruss
- Prof. Dr. O. J. Gruss, Institute of Genetics, University of Bonn, Karlrobert-Kreiten-Str.13, 53115 Bonn, Germany
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58
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Wang G, Wang Q, Li Z, Liu C, He X. Clinical value of Xenopus kinesin-like protein 2 as a prognostic marker in patients with digestive system cancers: a systematic review and meta-analysis. Onco Targets Ther 2018; 11:1229-1243. [PMID: 29551902 PMCID: PMC5843138 DOI: 10.2147/ott.s150829] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Xenopus kinesin-like protein 2 (TPX2) is a microtubule-associated protein that plays an important role in spindle assembly and dynamics. However, the clinical and prognostic value of TPX2 in the digestive system cancers remains unclear. The objective of this review was to evaluate the association of TPX2 expression with disease-free survival (DFS), overall survival (OS), and clinicopathological features of digestive system cancers. The software Stata 12.0 was used to analyze the outcomes, including OS, disease-free survival (DFS), and clinicopathological characteristics. A total of 10 eligible studies with 906 patients were included. Elevated TPX2 expression was significantly associated with poor DFS (pooled hazard ratio [HR] =2.48, 95% confidence interval [CI]: 1.96–3.13) and OS (pooled HR =2.66, 95% CI: 2.04–3.48) of digestive system malignancies. Subgroup analyses showed that cancer type, sample size, study quality, and laboratory detection methods did not alter the significant prognostic value of TPX2. Additionally, TPX2 expression was found to be an independent predictive factor for DFS (HR =2.31, 95% CI: 1.78–3.01). TPX2 expression might be associated with TNM stage and pathological grade in digestive system cancer. In conclusion, TPX2 is an independent prognostic factor for survival of patients with digestive system cancer. Furthermore, its overexpression is associated with TNM stage and pathological grade in digestive system cancer.
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Affiliation(s)
- Gang Wang
- Department of General Surgery, Tangdu Hospital, Fourth Military Medical University, Xi'an, China
| | - Qian Wang
- Department of General Surgery, Tangdu Hospital, Fourth Military Medical University, Xi'an, China
| | - Zhengyan Li
- Department of Surgery, Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xi'an, China
| | - Chaoxu Liu
- Department of General Surgery, Huashan Hospital, Fudan University, Shanghai, China
| | - Xianli He
- Department of General Surgery, Tangdu Hospital, Fourth Military Medical University, Xi'an, China
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Mangal S, Sacher J, Kim T, Osório DS, Motegi F, Carvalho AX, Oegema K, Zanin E. TPXL-1 activates Aurora A to clear contractile ring components from the polar cortex during cytokinesis. J Cell Biol 2018; 217:837-848. [PMID: 29311228 PMCID: PMC5839786 DOI: 10.1083/jcb.201706021] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 11/13/2017] [Accepted: 12/01/2017] [Indexed: 02/07/2023] Open
Abstract
During cytokinesis, a signal from the central spindle that forms between the separating anaphase chromosomes promotes the accumulation of contractile ring components at the cell equator, while a signal from the centrosomal microtubule asters inhibits accumulation of contractile ring components at the cell poles. However, the molecular identity of the inhibitory signal has remained unknown. To identify molecular components of the aster-based inhibitory signal, we developed a means to monitor the removal of contractile ring proteins from the polar cortex after anaphase onset. Using this assay, we show that polar clearing is an active process that requires activation of Aurora A kinase by TPXL-1. TPXL-1 concentrates on astral microtubules coincident with polar clearing in anaphase, and its ability to recruit Aurora A and activate its kinase activity are essential for clearing. In summary, our data identify Aurora A kinase as an aster-based inhibitory signal that restricts contractile ring components to the cell equator during cytokinesis.
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Affiliation(s)
- Sriyash Mangal
- Center for Integrated Protein Science, Department Biology II, Ludwig-Maximilians University Munich, Planegg-Martinsried, Germany
| | - Jennifer Sacher
- Center for Integrated Protein Science, Department Biology II, Ludwig-Maximilians University Munich, Planegg-Martinsried, Germany
| | - Taekyung Kim
- Department of Cellular and Molecular Medicine, Ludwig Institute for Cancer Research, University of California, San Diego, La Jolla, CA
| | - Daniel Sampaio Osório
- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
- Instituto de Biologia Molecular e Celular, Porto, Portugal
| | - Fumio Motegi
- Research Link, National University of Singapore, Singapore
| | - Ana Xavier Carvalho
- Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
- Instituto de Biologia Molecular e Celular, Porto, Portugal
| | - Karen Oegema
- Department of Cellular and Molecular Medicine, Ludwig Institute for Cancer Research, University of California, San Diego, La Jolla, CA
| | - Esther Zanin
- Center for Integrated Protein Science, Department Biology II, Ludwig-Maximilians University Munich, Planegg-Martinsried, Germany
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Zhou Z, Cheng Y, Jiang Y, Liu S, Zhang M, Liu J, Zhao Q. Ten hub genes associated with progression and prognosis of pancreatic carcinoma identified by co-expression analysis. Int J Biol Sci 2018; 14:124-136. [PMID: 29483831 PMCID: PMC5821034 DOI: 10.7150/ijbs.22619] [Citation(s) in RCA: 109] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 12/21/2017] [Indexed: 12/16/2022] Open
Abstract
Since the five-year survival rate is less than 5%, pancreatic ductal adenocarcinoma (PDAC) remains the 4th cause of cancer-related death. Although PDAC has been repeatedly researched in recent years, it is still predicted to be the second leading cause of cancer death by year 2030. In our study, the differentially expressed genes in dataset GSE62452 were used to construct a co-expression network by WGCNA. The yellow module related to grade of PDAC was screened. Combined with co-expression network and PPI network, 36 candidates were screened. After survival and regression analysis by using GSE62452 and TCGA dataset, we identified 10 real hub genes (CCNA2, CCNB1, CENPF, DLGAP5, KIF14, KIF23, NEK2, RACGAP1, TPX2 and UBE2C) tightly related to progression of PDAC. According to Oncomine database and The Human Protein Atlas (HPA), we found that all real hub genes were overexpressed in pancreatic carcinoma compared with normal tissues on transcriptional and translational level. ROC curve was plotted and AUC was calculated to distinguish recurrent and non-recurrent PDAC and every AUC of the real hub gene was greater than 0.5. Finally, functional enrichment analysis and gene set enrichment (GSEA) was performed and both of them showed the cell cycle played a vital role in PDAC.
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Affiliation(s)
- Zhou Zhou
- Department of Gastroenterology, Hubei Clinical Center and Key Lab of Intestinal and Colorectal Diseases, Zhongnan Hospital of Wuhan University
| | - Yian Cheng
- Department of Gastroenterology, Renming Hospital of Wuhan University
| | - Yinan Jiang
- Department of Gastrointestinal Surgery, Zhongnan Hospital of Wuhan University
| | - Shi Liu
- Department of Gastroenterology, Hubei Clinical Center and Key Lab of Intestinal and Colorectal Diseases, Zhongnan Hospital of Wuhan University
| | - Meng Zhang
- Department of Gastroenterology, Hubei Clinical Center and Key Lab of Intestinal and Colorectal Diseases, Zhongnan Hospital of Wuhan University
| | - Jing Liu
- Department of Gastroenterology, Hubei Clinical Center and Key Lab of Intestinal and Colorectal Diseases, Zhongnan Hospital of Wuhan University
| | - Qiu Zhao
- Department of Gastroenterology, Hubei Clinical Center and Key Lab of Intestinal and Colorectal Diseases, Zhongnan Hospital of Wuhan University
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Eibes S, Gallisà-Suñé N, Rosas-Salvans M, Martínez-Delgado P, Vernos I, Roig J. Nek9 Phosphorylation Defines a New Role for TPX2 in Eg5-Dependent Centrosome Separation before Nuclear Envelope Breakdown. Curr Biol 2017; 28:121-129.e4. [PMID: 29276125 DOI: 10.1016/j.cub.2017.11.046] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2017] [Revised: 10/31/2017] [Accepted: 11/21/2017] [Indexed: 11/18/2022]
Abstract
Centrosomes [1, 2] play a central role during spindle assembly in most animal cells [3]. In early mitosis, they organize two symmetrical microtubule arrays that upon separation define the two poles of the forming spindle. Centrosome separation is tightly regulated [4, 5], occurring through partially redundant mechanisms that rely on the action of microtubule-based dynein and kinesin motors and the actomyosin system [6]. While centrosomes can separate in prophase or in prometaphase after nuclear envelope breakdown (NEBD), prophase centrosome separation optimizes spindle assembly and minimizes the occurrence of abnormal chromosome attachments that could end in aneuploidy [7, 8]. Prophase centrosome separation relies on the activity of Eg5/KIF11, a mitotic kinesin [9] that accumulates around centrosomes in early mitosis under the control of CDK1 and the Nek9/Nek6/7 kinase module [10-17]. Here, we show that Eg5 localization and centrosome separation in prophase depend on the nuclear microtubule-associated protein TPX2 [18], a pool of which localizes to the centrosomes before NEBD. This localization involves RHAMM/HMMR [19] and the kinase Nek9 [20], which phosphorylates TPX2 nuclear localization signal (NLS) preventing its interaction with importin and nuclear import. The pool of centrosomal TPX2 in prophase has a critical role for both microtubule aster organization and Eg5 localization, and thereby for centrosome separation. Our results uncover an unsuspected role for TPX2 before NEBD and define a novel regulatory mechanism for centrosome separation in prophase. They furthermore suggest NLS phosphorylation as a novel regulatory mechanism for spindle assembly factors controlled by the importin/Ran system.
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Affiliation(s)
- Susana Eibes
- Molecular Biology Institute of Barcelona (IBMB-CSIC) and Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona 08028, Spain
| | - Núria Gallisà-Suñé
- Molecular Biology Institute of Barcelona (IBMB-CSIC) and Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona 08028, Spain
| | - Miquel Rosas-Salvans
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona 08003, Spain; Universitat Pompeu Fabra (UPF), Barcelona 08003, Spain
| | - Paula Martínez-Delgado
- Molecular Biology Institute of Barcelona (IBMB-CSIC) and Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona 08028, Spain
| | - Isabelle Vernos
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Barcelona 08003, Spain; Universitat Pompeu Fabra (UPF), Barcelona 08003, Spain; Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona 08010, Spain
| | - Joan Roig
- Molecular Biology Institute of Barcelona (IBMB-CSIC) and Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona 08028, Spain.
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Robinson NA, Timmerhaus G, Baranski M, Andersen Ø, Takle H, Krasnov A. Training the salmon's genes: influence of aerobic exercise, swimming performance and selection on gene expression in Atlantic salmon. BMC Genomics 2017; 18:971. [PMID: 29246115 PMCID: PMC5731093 DOI: 10.1186/s12864-017-4361-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 12/01/2017] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND Farmed and wild Atlantic salmon are exposed to many infectious and non-infectious challenges that can cause mortality when they enter the sea. Exercise before transfer promotes growth, health and survival in the sea. Swimming performance in juveniles at the freshwater parr stage is positively associated with resistance to some diseases. Genetic variation is likely to affect response to exercise. In this study we map genetic differences associated with aerobic exercise, swimming performance and genetic origin. Eggs from the selectively bred Bolaks salmon and wild Lærdal River salmon strains were reared until parr in a common environment. Swimming performance was assessed by subjecting the fish to either continuous hard exercise or control conditions for 18 days. Heart was sampled for examination of gene expression using RNA-seq (~60 fish/treatment). RESULTS Lower expression of genes affecting immune function was found in domesticated than wild parr. Among wild parr under control exercise the expression of a large number of genes involved in general metabolism, stress and immune response was lower in superior swimmers suggesting that minimisation of energy expenditure during periods of low activity makes parr better able to sustain bursts of swimming for predator avoidance. A similar set of genes were down-regulated with training among wild parr with inferior swimming performance. These parr react to training in a way that their cardiac expression patterns become like the superior performing wild parr under control exercise conditions. Diversifying selection caused by breeding of domesticated stock, and adaptive pressures in wild stock, has affected the expression and frequency of single nucleotide polymorphisms (SNPs) for multiple functional groups of genes affecting diverse processes. SNPs associated with swimming performance in wild parr map to genes involved in energetic processes, coding for contractile filaments in the muscle and controlling cell proliferation. CONCLUSIONS Domesticated parr have less phenotypic plasticity in response to training and lower expression of genes with functions affecting immune response. The genetic response to training is complex and depends on the background of parr and their swimming ability. Exercise should be tailored to the genetics and swimming performance of fish.
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Affiliation(s)
- Nicholas A. Robinson
- Nofima, Osloveien 1, 1430 Ås, Norway
- Sustainable Aquaculture Laboratory - Temperate and Tropical (SALTT), School of BioSciences, The University of Melbourne, Parkville, Vic 3010 Australia
- Nofima, PO Box 210, 1431 Ås, Norway
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63
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Povea-Cabello S, Oropesa-Ávila M, de la Cruz-Ojeda P, Villanueva-Paz M, de la Mata M, Suárez-Rivero JM, Álvarez-Córdoba M, Villalón-García I, Cotán D, Ybot-González P, Sánchez-Alcázar JA. Dynamic Reorganization of the Cytoskeleton during Apoptosis: The Two Coffins Hypothesis. Int J Mol Sci 2017; 18:ijms18112393. [PMID: 29137119 PMCID: PMC5713361 DOI: 10.3390/ijms18112393] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2017] [Revised: 11/09/2017] [Accepted: 11/09/2017] [Indexed: 01/05/2023] Open
Abstract
During apoptosis, cells undergo characteristic morphological changes in which the cytoskeleton plays an active role. The cytoskeleton rearrangements have been mainly attributed to actinomyosin ring contraction, while microtubule and intermediate filaments are depolymerized at early stages of apoptosis. However, recent results have shown that microtubules are reorganized during the execution phase of apoptosis forming an apoptotic microtubule network (AMN). Evidence suggests that AMN is required to maintain plasma membrane integrity and cell morphology during the execution phase of apoptosis. The new “two coffins” hypothesis proposes that both AMN and apoptotic cells can adopt two morphological patterns, round or irregular, which result from different cytoskeleton kinetic reorganization during the execution phase of apoptosis induced by genotoxic agents. In addition, round and irregular-shaped apoptosis showed different biological properties with respect to AMN maintenance, plasma membrane integrity and phagocyte responses. These findings suggest that knowing the type of apoptosis may be important to predict how fast apoptotic cells undergo secondary necrosis and the subsequent immune response. From a pathological point of view, round-shaped apoptosis can be seen as a physiological and controlled type of apoptosis, while irregular-shaped apoptosis can be considered as a pathological type of cell death closer to necrosis.
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Affiliation(s)
- Suleva Povea-Cabello
- Centro Andaluz de Biología del Desarrollo (CABD), and Centro de Investigación Biomédica en Red: Enfermedades Raras, Instituto de Salud Carlos III, Consejo Superior de Investigaciones Científicas, Universidad Pablo de, Carretera de Utrera Km 1, 41013 Sevilla, Spain.
| | - Manuel Oropesa-Ávila
- Centro Andaluz de Biología del Desarrollo (CABD), and Centro de Investigación Biomédica en Red: Enfermedades Raras, Instituto de Salud Carlos III, Consejo Superior de Investigaciones Científicas, Universidad Pablo de, Carretera de Utrera Km 1, 41013 Sevilla, Spain.
| | - Patricia de la Cruz-Ojeda
- Centro Andaluz de Biología del Desarrollo (CABD), and Centro de Investigación Biomédica en Red: Enfermedades Raras, Instituto de Salud Carlos III, Consejo Superior de Investigaciones Científicas, Universidad Pablo de, Carretera de Utrera Km 1, 41013 Sevilla, Spain.
| | - Marina Villanueva-Paz
- Centro Andaluz de Biología del Desarrollo (CABD), and Centro de Investigación Biomédica en Red: Enfermedades Raras, Instituto de Salud Carlos III, Consejo Superior de Investigaciones Científicas, Universidad Pablo de, Carretera de Utrera Km 1, 41013 Sevilla, Spain.
| | - Mario de la Mata
- Centro Andaluz de Biología del Desarrollo (CABD), and Centro de Investigación Biomédica en Red: Enfermedades Raras, Instituto de Salud Carlos III, Consejo Superior de Investigaciones Científicas, Universidad Pablo de, Carretera de Utrera Km 1, 41013 Sevilla, Spain.
| | - Juan Miguel Suárez-Rivero
- Centro Andaluz de Biología del Desarrollo (CABD), and Centro de Investigación Biomédica en Red: Enfermedades Raras, Instituto de Salud Carlos III, Consejo Superior de Investigaciones Científicas, Universidad Pablo de, Carretera de Utrera Km 1, 41013 Sevilla, Spain.
| | - Mónica Álvarez-Córdoba
- Centro Andaluz de Biología del Desarrollo (CABD), and Centro de Investigación Biomédica en Red: Enfermedades Raras, Instituto de Salud Carlos III, Consejo Superior de Investigaciones Científicas, Universidad Pablo de, Carretera de Utrera Km 1, 41013 Sevilla, Spain.
| | - Irene Villalón-García
- Centro Andaluz de Biología del Desarrollo (CABD), and Centro de Investigación Biomédica en Red: Enfermedades Raras, Instituto de Salud Carlos III, Consejo Superior de Investigaciones Científicas, Universidad Pablo de, Carretera de Utrera Km 1, 41013 Sevilla, Spain.
| | - David Cotán
- Centro Andaluz de Biología del Desarrollo (CABD), and Centro de Investigación Biomédica en Red: Enfermedades Raras, Instituto de Salud Carlos III, Consejo Superior de Investigaciones Científicas, Universidad Pablo de, Carretera de Utrera Km 1, 41013 Sevilla, Spain.
| | - Patricia Ybot-González
- Grupo de Neurodesarrollo, Unidad de Gestión de Pediatría, Instituto de Biomedicina de Sevilla (IBIS), Hospital Universitario Virgen del Rocío, 41013 Sevilla, Spain.
| | - José A Sánchez-Alcázar
- Centro Andaluz de Biología del Desarrollo (CABD), and Centro de Investigación Biomédica en Red: Enfermedades Raras, Instituto de Salud Carlos III, Consejo Superior de Investigaciones Científicas, Universidad Pablo de, Carretera de Utrera Km 1, 41013 Sevilla, Spain.
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64
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Zhang R, Roostalu J, Surrey T, Nogales E. Structural insight into TPX2-stimulated microtubule assembly. eLife 2017; 6. [PMID: 29120325 PMCID: PMC5679754 DOI: 10.7554/elife.30959] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 10/29/2017] [Indexed: 11/13/2022] Open
Abstract
During mitosis and meiosis, microtubule (MT) assembly is locally upregulated by the chromatin-dependent Ran-GTP pathway. One of its key targets is the MT-associated spindle assembly factor TPX2. The molecular mechanism of how TPX2 stimulates MT assembly remains unknown because structural information about the interaction of TPX2 with MTs is lacking. Here, we determine the cryo-electron microscopy structure of a central region of TPX2 bound to the MT surface. TPX2 uses two flexibly linked elements ('ridge' and 'wedge') in a novel interaction mode to simultaneously bind across longitudinal and lateral tubulin interfaces. These MT-interacting elements overlap with the binding site of importins on TPX2. Fluorescence microscopy-based in vitro reconstitution assays reveal that this interaction mode is critical for MT binding and facilitates MT nucleation. Together, our results suggest a molecular mechanism of how the Ran-GTP gradient can regulate TPX2-dependent MT formation.
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Affiliation(s)
- Rui Zhang
- Molecular Biophysics and Integrative Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, United States
| | | | | | - Eva Nogales
- Molecular Biophysics and Integrative Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, United States.,Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States.,Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States
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65
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Huang M, Ma X, Shi H, Hu L, Fan Z, Pang L, Zhu F, Yang X, Xu W, Liu B, Zhu Z, Li C. FAM83D, a microtubule-associated protein, promotes tumor growth and progression of human gastric cancer. Oncotarget 2017; 8:74479-74493. [PMID: 29088801 PMCID: PMC5650356 DOI: 10.18632/oncotarget.20157] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 06/02/2017] [Indexed: 01/16/2023] Open
Abstract
FAM83D, a microtubule-associated protein (MAP), is overexpressed in diverse types of human cancer. The expression and critical role of FAM83D in human gastric cancer (GC), however, remains largely unknown. Here, we conducted molecular, cellular and clinical analyses to evaluate the functional link of FAM83D to GC. FAM83D expression was elevated in gastric tumors, and its expression strongly correlated with lymph node metastasis and TNM stage. In addition, over-expression of FAM83D in GC cell lines enhanced cell proliferation, cycle progression, migration, invasion, as well as tumor growth and metastatic dissemination in vivo. Furthermore, FAM83D exhibited a strong cell cycle correlated expression. The knockdown of FAM83D inhibited the regrowth of microtubules in GC cells. FAM83D was co-immunoprecipitated with HMMR, TPX2, and AURKA, a set of drivers of mitosis progression. Taken together, our results demonstrate FAM83D as an important player in the development of human gastric cancer, and as a potential therapeutic target for the treatment of cancer.
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Affiliation(s)
- Minlu Huang
- Shanghai Key Laboratory of Gastric Neoplasms, Department of Surgery, Shanghai Institute of Digestive Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, People’s Republic of China
| | - Xinjie Ma
- Shanghai Key Laboratory of Gastric Neoplasms, Department of Surgery, Shanghai Institute of Digestive Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, People’s Republic of China
| | - Hongpeng Shi
- Shanghai Key Laboratory of Gastric Neoplasms, Department of Surgery, Shanghai Institute of Digestive Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, People’s Republic of China
| | - Lei Hu
- Shanghai Key Laboratory of Gastric Neoplasms, Department of Surgery, Shanghai Institute of Digestive Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, People’s Republic of China
| | - Zhiyuan Fan
- Shanghai Key Laboratory of Gastric Neoplasms, Department of Surgery, Shanghai Institute of Digestive Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, People’s Republic of China
| | - Li Pang
- Shanghai Key Laboratory of Gastric Neoplasms, Department of Surgery, Shanghai Institute of Digestive Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, People’s Republic of China
| | - Fan Zhu
- Shanghai Key Laboratory of Gastric Neoplasms, Department of Surgery, Shanghai Institute of Digestive Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, People’s Republic of China
| | - Xiao Yang
- Shanghai Key Laboratory of Gastric Neoplasms, Department of Surgery, Shanghai Institute of Digestive Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, People’s Republic of China
| | - Wei Xu
- Shanghai Key Laboratory of Gastric Neoplasms, Department of Surgery, Shanghai Institute of Digestive Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, People’s Republic of China
| | - Binya Liu
- Shanghai Key Laboratory of Gastric Neoplasms, Department of Surgery, Shanghai Institute of Digestive Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, People’s Republic of China
| | - Zhenggang Zhu
- Shanghai Key Laboratory of Gastric Neoplasms, Department of Surgery, Shanghai Institute of Digestive Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, People’s Republic of China
| | - Chen Li
- Shanghai Key Laboratory of Gastric Neoplasms, Department of Surgery, Shanghai Institute of Digestive Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, People’s Republic of China
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66
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Programmed Self-Assembly of a Biochemical and Magnetic Scaffold to Trigger and Manipulate Microtubule Structures. Sci Rep 2017; 7:11344. [PMID: 28900114 PMCID: PMC5595911 DOI: 10.1038/s41598-017-10297-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Accepted: 08/07/2017] [Indexed: 11/25/2022] Open
Abstract
Artificial bio-based scaffolds offer broad applications in bioinspired chemistry, nanomedicine, and material science. One current challenge is to understand how the programmed self-assembly of biomolecules at the nanometre level can dictate the emergence of new functional properties at the mesoscopic scale. Here we report a general approach to design genetically encoded protein-based scaffolds with modular biochemical and magnetic functions. By combining chemically induced dimerization strategies and biomineralisation, we engineered ferritin nanocages to nucleate and manipulate microtubule structures upon magnetic actuation. Triggering the self-assembly of engineered ferritins into micrometric scaffolds mimics the function of centrosomes, the microtubule organizing centres of cells, and provides unique magnetic and self-organizing properties. We anticipate that our approach could be transposed to control various biological processes and extend to broader applications in biotechnology or material chemistry.
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67
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Roostalu J, Surrey T. Microtubule nucleation: beyond the template. Nat Rev Mol Cell Biol 2017; 18:702-710. [PMID: 28831203 DOI: 10.1038/nrm.2017.75] [Citation(s) in RCA: 115] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Microtubules are cytoskeletal filaments central to a wide range of essential cellular functions in eukaryotic cells. Consequently, cells need to exert tight control over when, where and how many microtubules are being made. Whereas the regulation of microtubule dynamics is well studied, the molecular mechanisms of microtubule nucleation are still poorly understood. Next to the established master template of nucleation, the γ-tubulin ring complex, other microtubule-associated proteins that affect microtubule dynamic properties have recently been found to contribute to nucleation. It has begun to emerge that the nucleation efficiency is controlled not only by template activity but also by, either additionally or alternatively, the stabilization of the nascent microtubule 'nucleus'. This suggests a simple conceptual framework for the mechanisms regulating microtubule nucleation in cells.
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Affiliation(s)
| | - Thomas Surrey
- The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
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68
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Dihydropyrazole and dihydropyrrole structures based design of Kif15 inhibitors as novel therapeutic agents for cancer. Comput Biol Chem 2017; 68:164-174. [DOI: 10.1016/j.compbiolchem.2017.03.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2015] [Accepted: 03/10/2017] [Indexed: 12/15/2022]
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69
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Suzuki K, Itabashi T, Ishiwata S. Mechanical properties of spindle poles are symmetrically balanced. Biophys Physicobiol 2017; 14:1-11. [PMID: 28409085 PMCID: PMC5289413 DOI: 10.2142/biophysico.14.0_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 11/28/2016] [Indexed: 12/01/2022] Open
Abstract
The metaphase spindle is organized for accurate chromosome segregation. One of the fundamental features of the spindle across the species is its symmetrical shape; the spindle consists of two polar arrays of microtubules at both ends. Although it has been suggested that the formation of the bipolar shape requires force balance coordination by molecular motors, i.e., kinesins and dyneins, quantitative analysis for the pole mechanics has not been conducted. Here, we demonstrate that it is not only the shape but also the stiffness and microtubule density of the pairs of pole regions are symmetrically balanced in single spindles self-assembled in Xenopus egg extracts. We found that the inhibition of dynein functions dramatically reduced the stiffness and microtubule density in the pole region. By contrast, the inhibition of one of the kinesins, Eg5, which is the antagonistic motor protein of dynein, increased the value of these parameters. Moreover, the inhibition of both dynein and Eg5 recovered these parameter values to those of non-treated spindle poles. We also found that, when one pole structure was held widened with the use of two glass microneedles, the opposite pole structure spontaneously widened, resulting in the formation of the barrel-like shaped spindle. The values of stiffness and microtubule density in the manipulated pole region decreased, following the spontaneous decrement of those in the paired unmanipulated pole region. These results suggest that the spindle possesses a mechanism to dynamically maintain its symmetry in mechanical properties.
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Affiliation(s)
- Kazuya Suzuki
- Department of Physics, Faculty of Science and Engineering, Waseda University, Shinjuku-ku, Tokyo 169-8555, Japan.,Waseda Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, Singapore 138667, Singapore
| | - Takeshi Itabashi
- Department of Physics, Faculty of Science and Engineering, Waseda University, Shinjuku-ku, Tokyo 169-8555, Japan.,Waseda Bioscience Research Institute in Singapore (WABIOS), 11 Biopolis Way, Singapore 138667, Singapore
| | - Shin'ichi Ishiwata
- Department of Physics, Faculty of Science and Engineering, Waseda University, Shinjuku-ku, Tokyo 169-8555, Japan
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70
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Yoo KW, Maddirevula S, Kumar A, Ro H, Huh TL, Rhee M. Sinup is essential for the integrity of centrosomes and mitotic spindles in zebrafish embryos. Anim Cells Syst (Seoul) 2017; 21:93-99. [PMID: 30460056 PMCID: PMC6138333 DOI: 10.1080/19768354.2017.1308438] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Accepted: 03/13/2017] [Indexed: 11/15/2022] Open
Abstract
Fish lineage-specific gene, sinup [Siaz-interacting nuclear protein], modulates neural plate formation in embryogenesis and shares homology with human TPX2 protein, a member of the vertebrate mitogen-activating protein family. In spite of the presence of the TPX2 domain in Sinup, its cellular function has been unknown. As an initial approach to this question, we expressed Sinup by injecting sinup-EGFP mRNAs into zebrafish embryos at the one- to two-cell stage. First of all, Sinup-EGFP was associated with centrosomes and mitotic spindles. In particular, Sinup was localized to the spindle poles and midbody microtubules during the period between anaphase and cytokinesis. Second, various deleted mutants of Sinup-EGFP failed to be associated with the centrosomes and mitotic spindles. Third, a Sinup mutant, where the 144th Serine residue was converted to alanine, not only disturbed the mitotic spindle organization, such as multipolar spindles, fragmented spindle poles, and flattened spindles, but also arrested the cell cycle at metaphase and cell movement. Finally, Sinup is phosphorylated by Aurora A and the 144th Serine mutant of Sinup is partially phosphorylated by Aurora A kinase. We thus propose that Sinup is an essential element for the integrity of centrosomes and mitotic spindle fibers as well as for the normal process of cell cycle and cellular movement in vertebrate embryos.
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Affiliation(s)
- Kyeong-Won Yoo
- Department of Biological Sciences, College of Biosciences and Biotechnology, Chungnam National University, Daejeon, South Korea
| | - Sateesh Maddirevula
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Ajeet Kumar
- Department of Biological Sciences, College of Biosciences and Biotechnology, Chungnam National University, Daejeon, South Korea
| | - Hyunju Ro
- Department of Biological Sciences, College of Biosciences and Biotechnology, Chungnam National University, Daejeon, South Korea
| | - Tae-Lin Huh
- College of Natural Sciences, School of Life Sciences and Biotechnology, Kyungpook National University, Daegu, South Korea
| | - Myungchull Rhee
- Department of Biological Sciences, College of Biosciences and Biotechnology, Chungnam National University, Daejeon, South Korea
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71
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Alfaro-Aco R, Thawani A, Petry S. Structural analysis of the role of TPX2 in branching microtubule nucleation. J Cell Biol 2017; 216:983-997. [PMID: 28264915 PMCID: PMC5379942 DOI: 10.1083/jcb.201607060] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2016] [Revised: 11/03/2016] [Accepted: 01/09/2017] [Indexed: 12/14/2022] Open
Abstract
TPX2 is required for microtubule nucleation in mitosis, but the mechanism underlying its function is unclear. Alfaro-Aco et al. analyze the domains of TPX2 necessary for its activity and identify the minimal region required for branching microtubule nucleation. The mitotic spindle consists of microtubules (MTs), which are nucleated by the γ-tubulin ring complex (γ-TuRC). How the γ-TuRC gets activated at the right time and location remains elusive. Recently, it was uncovered that MTs nucleate from preexisting MTs within the mitotic spindle, which requires the protein TPX2, but the mechanism basis for TPX2 action is unknown. Here, we investigate the role of TPX2 in branching MT nucleation. We establish the domain organization of Xenopus laevis TPX2 and define the minimal TPX2 version that stimulates branching MT nucleation, which we find is unrelated to TPX2’s ability to nucleate MTs in vitro. Several domains of TPX2 contribute to its MT-binding and bundling activities. However, the property necessary for TPX2 to induce branching MT nucleation is contained within newly identified γ-TuRC nucleation activator motifs. Separation-of-function mutations leave the binding of TPX2 to γ-TuRC intact, whereas branching MT nucleation is abolished, suggesting that TPX2 may activate γ-TuRC to promote branching MT nucleation.
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Affiliation(s)
| | - Akanksha Thawani
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ 08544
| | - Sabine Petry
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544
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72
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Ran-dependent TPX2 activation promotes acentrosomal microtubule nucleation in neurons. Sci Rep 2017; 7:42297. [PMID: 28205572 PMCID: PMC5304320 DOI: 10.1038/srep42297] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Accepted: 01/05/2017] [Indexed: 01/07/2023] Open
Abstract
The microtubule (MT) cytoskeleton is essential for the formation of morphologically appropriate neurons. The existence of the acentrosomal MT organizing center in neurons has been proposed but its identity remained elusive. Here we provide evidence showing that TPX2 is an important component of this acentrosomal MT organizing center. First, neurite elongation is compromised in TPX2-depleted neurons. In addition, TPX2 localizes to the centrosome and along the neurite shaft bound to MTs. Depleting TPX2 decreases MT formation frequency specifically at the tip and the base of the neurite, and these correlate precisely with the regions where active GTP-bound Ran proteins are enriched. Furthermore, overexpressing the downstream effector of Ran, importin, compromises MT formation and neuronal morphogenesis. Finally, applying a Ran-importin signaling interfering compound phenocopies the effect of TPX2 depletion on MT dynamics. Together, these data suggest a model in which Ran-dependent TPX2 activation promotes acentrosomal MT nucleation in neurons.
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73
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Kapoor TM. Metaphase Spindle Assembly. BIOLOGY 2017; 6:biology6010008. [PMID: 28165376 PMCID: PMC5372001 DOI: 10.3390/biology6010008] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 01/17/2017] [Accepted: 01/19/2017] [Indexed: 01/31/2023]
Abstract
A microtubule-based bipolar spindle is required for error-free chromosome segregation during cell division. In this review I discuss the molecular mechanisms required for the assembly of this dynamic micrometer-scale structure in animal cells.
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Affiliation(s)
- Tarun M Kapoor
- Laboratory of Chemistry and Cell Biology, the Rockefeller University, New York, NY 10065, USA.
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74
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Du P, Kumar M, Yao Y, Xie Q, Wang J, Zhang B, Gan S, Wang Y, Wu AM. Genome-wide analysis of the TPX2 family proteins in Eucalyptus grandis. BMC Genomics 2016; 17:967. [PMID: 27881090 PMCID: PMC5122032 DOI: 10.1186/s12864-016-3303-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 11/16/2016] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND The Xklp2 (TPX2) proteins belong to the microtubule-associated (MAP) family of proteins. All members of the family contain the conserved TPX2 motif, which can interact with microtubules, regulate microtubule dynamics or assist with different microtubule functions, for example, maintenance of cell morphology or regulation of cell growth and development. However, the role of members of the TPX family have not been studied in the model tree species Eucalyptus to date. Here, we report the identification of the members of the TPX2 family in Eucalyptus grandis (Eg) and analyse the expression patterns and functions of these genes. RESULTS In present study, a comprehensive analysis of the plant TPX2 family proteins was performed. Phylogenetic analyses indicated that the genes can be classified into 6 distinct subfamilies. A genome-wide survey identified 12 members of the TPX2 family in the sequenced genome of Eucalyptus grandis. The basic genetic properties of the TPX2 family in Eucalyptus were analysed. Our results suggest that the TPX2 family proteins within different sub-groups are relatively conserved but there are important differences between groups. Quantitative real-time PCR (qRT-PCR) was performed to confirm the expression levels of the genes in different tissues. The results showed that in the whole plant, the levels of EgWDL5 transcript are the highest, followed by those of EgWDL4. Compared with other tissues, the level of the EgMAP20 transcript is the highest in the root. Over-expression of EgMAP20 in Arabidopsis resulted in organ twisting. The cotyledon petioles showed left-handed twisting while the hypocotyl epidermal cells produced right-handed helical twisting. Finally, EgMAP20, EgWDL3 and EgWDL3L were all able to decorate microtubules. CONCLUSIONS Plant TPX2 family proteins were systematically analysed using bioinformatics methods. There are 12 TPX2 family proteins in Eucalyptus. We have performed an initial characterization of the functions of several members of the TPX2 family. We found that the gene products are localized to the microtubule cytoskeleton. Our results lay the foundation for future efforts to reveal the biological significance of TPX2 family proteins in Eucalyptus.
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Affiliation(s)
- Pingzhou Du
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, South China Agricultural University, Guangzhou, 510642, China.,Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou, 510642, China.,College of Life Sciences, South China Agricultural University, Guangzhou, 510642, China.,Provincial Key Laboratory of Agrobiology, Jiangsu Academy of Agricultural Sciences, Nanjing, 210014, China
| | - Manoj Kumar
- Faculty of Life Science, University of Manchester, Michael Smith Building, Oxford Road, Manchester, M13 9PT, UK
| | - Yuan Yao
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, South China Agricultural University, Guangzhou, 510642, China.,Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou, 510642, China.,College of Life Sciences, South China Agricultural University, Guangzhou, 510642, China
| | - Qiaoli Xie
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, South China Agricultural University, Guangzhou, 510642, China.,Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou, 510642, China
| | - Jinyan Wang
- Provincial Key Laboratory of Agrobiology, Jiangsu Academy of Agricultural Sciences, Nanjing, 210014, China
| | - Baolong Zhang
- Provincial Key Laboratory of Agrobiology, Jiangsu Academy of Agricultural Sciences, Nanjing, 210014, China
| | - Siming Gan
- Research Institute of tropical forestry, Chinese Academy of Forestry, Guangzhou, 510520, China.
| | - Yuqi Wang
- College of Life Sciences, South China Agricultural University, Guangzhou, 510642, China. .,Boyce Thompson Institute for Plant Research, Ithaca, 14853, USA.
| | - Ai-Min Wu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, South China Agricultural University, Guangzhou, 510642, China. .,Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou, 510642, China.
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75
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Bennabi I, Terret ME, Verlhac MH. Meiotic spindle assembly and chromosome segregation in oocytes. J Cell Biol 2016; 215:611-619. [PMID: 27879467 PMCID: PMC5147004 DOI: 10.1083/jcb.201607062] [Citation(s) in RCA: 138] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Revised: 10/10/2016] [Accepted: 11/02/2016] [Indexed: 11/22/2022] Open
Abstract
Centrosomes play a key role in organizing the microtubule spindle that separates chromosomes during mitosis. Bennabi et al. review how microtubule spindle formation and chromosomal segregation also occur in oocytes during cell division by meiosis despite the absence of centrosomes. Oocytes accumulate maternal stores (proteins, mRNAs, metabolites, etc.) during their growth in the ovary to support development after fertilization. To preserve this cytoplasmic maternal inheritance, they accomplish the difficult task of partitioning their cytoplasm unequally while dividing their chromosomes equally. Added to this complexity, most oocytes, for reasons still speculative, lack the major microtubule organizing centers that most cells use to assemble and position their spindles, namely canonical centrosomes. In this review, we will address recent work on the mechanisms of meiotic spindle assembly and chromosome alignment/segregation in female gametes to try to understand the origin of errors of oocyte meiotic divisions. The challenge of oocyte divisions appears indeed not trivial because in both mice and humans oocyte meiotic divisions are prone to chromosome segregation errors, a leading cause of frequent miscarriages and congenital defects.
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Affiliation(s)
- Isma Bennabi
- Centre for Interdisciplinary Research in Biology, Collège de France, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, PSL Research University, Paris 75006, France
| | - Marie-Emilie Terret
- Centre for Interdisciplinary Research in Biology, Collège de France, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, PSL Research University, Paris 75006, France
| | - Marie-Hélène Verlhac
- Centre for Interdisciplinary Research in Biology, Collège de France, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, PSL Research University, Paris 75006, France
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76
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Mann BJ, Balchand SK, Wadsworth P. Regulation of Kif15 localization and motility by the C-terminus of TPX2 and microtubule dynamics. Mol Biol Cell 2016; 28:65-75. [PMID: 27852894 PMCID: PMC5221630 DOI: 10.1091/mbc.e16-06-0476] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 11/04/2016] [Accepted: 11/07/2016] [Indexed: 12/31/2022] Open
Abstract
Mitotic motor proteins generate force to establish and maintain spindle bipolarity, but how they are temporally and spatially regulated in vivo is unclear. Prior work demonstrated that a microtubule-associated protein, TPX2, targets kinesin-5 and kinesin-12 motors to spindle microtubules. The C-terminal domain of TPX2 contributes to the localization and motility of the kinesin-5, Eg5, but it is not known whether this domain regulates kinesin-12, Kif15. We found that the C-terminal domain of TPX2 contributes to the localization of Kif15 to spindle microtubules in cells and suppresses motor walking in vitro. Kif15 and Eg5 are partially redundant motors, and overexpressed Kif15 can drive spindle formation in the absence of Eg5 activity. Kif15-dependent bipolar spindle formation in vivo requires the C-terminal domain of TPX2. In the spindle, fluorescent puncta of GFP-Kif15 move toward the equatorial region at a rate equivalent to microtubule growth. Reduction of microtubule growth with paclitaxel suppresses GFP-Kif15 motility, demonstrating that dynamic microtubules contribute to Kif15 behavior. Our results show that the C-terminal region of TPX2 regulates Kif15 in vitro, contributes to motor localization in cells, and is required for Kif15 force generation in vivo and further reveal that dynamic microtubules contribute to Kif15 behavior in vivo.
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Affiliation(s)
- Barbara J Mann
- Department of Biology and Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA 01003
| | - Sai K Balchand
- Department of Biology and Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA 01003
| | - Patricia Wadsworth
- Department of Biology and Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, MA 01003
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77
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Sanchez-Pulido L, Perez L, Kuhn S, Vernos I, Andrade-Navarro MA. The C-terminal domain of TPX2 is made of alpha-helical tandem repeats. BMC STRUCTURAL BIOLOGY 2016; 16:17. [PMID: 27782824 PMCID: PMC5080731 DOI: 10.1186/s12900-016-0070-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 10/18/2016] [Indexed: 11/19/2022]
Abstract
BACKGROUND TPX2 (Targeting Protein for Xklp2) is essential for spindle assembly, activation of the mitotic kinase Aurora A and for triggering microtubule nucleation. Homologs of TPX2 in Chordata and plants were previously identified. Currently, proteins of the TPX2 family have little structural information and only small parts are covered by defined protein domains. METHODS We have used computational sequence analyses and structural predictions of proteins of the TPX2 family, supported with Circular Dichroism (CD) measurements. RESULTS Here, we report our finding that the C-terminal domain of TPX2, which is responsible of its microtubule nucleation capacity and is conserved in all members of the family, is actually formed by tandem repeats, covering well above 2/3 of the protein. We propose that this region forms a flexible solenoid involved in protein-protein interactions. Structural prediction and molecular modeling, combined with Circular Dichroism (CD) measurements reveal a predominant alpha-helical content. Furthermore, we identify full length homologs in fungi and shorter homologs with a different domain organization in diptera (including a paralogous expansion in Drosophila). CONCLUSIONS Our results, represent the first computational and biophysical analysis of the TPX2 proteins family and help understand the structure and evolution of this conserved protein family to direct future structural studies.
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Affiliation(s)
- Luis Sanchez-Pulido
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, The University of Edinburgh, Western General Hospital, Crewe Road, Edinburgh, EH4 2XU UK
| | - Laurent Perez
- Center for Genomic Regulation, C/ Dr Aiguader 88, 08003 Barcelona, Spain
- Institute for Research in Biomedicine, Università della Svizzera italiana, Via Vincenzo Vela 6, CH-6500 Bellinzona, Switzerland
| | - Steffen Kuhn
- Faculty of Biology, Johannes-Gutenberg University, Gresemundweg 2, 55128 Mainz, Germany
| | - Isabelle Vernos
- Center for Genomic Regulation, C/ Dr Aiguader 88, 08003 Barcelona, Spain
| | - Miguel A. Andrade-Navarro
- Faculty of Biology, Johannes-Gutenberg University, Gresemundweg 2, 55128 Mainz, Germany
- Institute of Molecular Biology, Ackermannweg 4, 55128 Mainz, Germany
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78
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Uematsu K, Okumura F, Tonogai S, Joo-Okumura A, Alemayehu DH, Nishikimi A, Fukui Y, Nakatsukasa K, Kamura T. ASB7 regulates spindle dynamics and genome integrity by targeting DDA3 for proteasomal degradation. J Cell Biol 2016; 215:95-106. [PMID: 27697924 PMCID: PMC5057283 DOI: 10.1083/jcb.201603062] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Accepted: 08/30/2016] [Indexed: 12/31/2022] Open
Abstract
Uematsu et al. show that ASB7 ubiquitinates DDA3, which facilitates Kif2a-mediated depolymerization of microtubules (MTs) for proteasomal degradation. The presence of MTs prevents the ASB7–DDA3 interaction, suggesting a feedback loop to appropriately regulate MT polymerization and spindle dynamics. Proper dynamic regulation of the spindle is essential for successful cell division. However, the molecular mechanisms that regulate spindle dynamics in mitosis are not fully understood. In this study, we show that Cullin 5–interacting suppressor of cytokine signaling box protein ASB7 ubiquitinates DDA3, a regulator of spindle dynamics, thereby targeting it for proteasomal degradation. The presence of microtubules (MTs) prevented the ASB7–DDA3 interaction, thus stabilizing DDA3. Knockdown of ASB7 decreased MT polymerization and increased the proportion of cells with unaligned chromosomes, and this phenotype was rescued by deletion of DDA3. Collectively, these data indicate that ASB7 plays a crucial role in regulating spindle dynamics and genome integrity by controlling the expression of DDA3.
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Affiliation(s)
- Keiji Uematsu
- Division of Biological Science, Graduate School of Science, Nagoya University, Aichi 464-8602, Japan
| | - Fumihiko Okumura
- Division of Biological Science, Graduate School of Science, Nagoya University, Aichi 464-8602, Japan
| | - Syunsuke Tonogai
- Division of Biological Science, Graduate School of Science, Nagoya University, Aichi 464-8602, Japan
| | - Akiko Joo-Okumura
- Division of Biological Science, Graduate School of Science, Nagoya University, Aichi 464-8602, Japan
| | - Dawit Hailu Alemayehu
- Division of Biological Science, Graduate School of Science, Nagoya University, Aichi 464-8602, Japan
| | - Akihiko Nishikimi
- Division of Immunogenetics, Department of Immunobiology and Neuroscience, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, Japan Research Center for Advanced Immunology, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, Japan
| | - Yoshinori Fukui
- Division of Immunogenetics, Department of Immunobiology and Neuroscience, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, Japan Research Center for Advanced Immunology, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, Japan
| | - Kunio Nakatsukasa
- Division of Biological Science, Graduate School of Science, Nagoya University, Aichi 464-8602, Japan
| | - Takumi Kamura
- Division of Biological Science, Graduate School of Science, Nagoya University, Aichi 464-8602, Japan
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79
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Cundell MJ, Hutter LH, Nunes Bastos R, Poser E, Holder J, Mohammed S, Novak B, Barr FA. A PP2A-B55 recognition signal controls substrate dephosphorylation kinetics during mitotic exit. J Cell Biol 2016; 214:539-54. [PMID: 27551054 PMCID: PMC5004449 DOI: 10.1083/jcb.201606033] [Citation(s) in RCA: 122] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 07/13/2016] [Indexed: 11/22/2022] Open
Abstract
PP2A-B55 is one of the major phosphatases regulating cell division. Despite its importance for temporal control during mitotic exit, how B55 substrates are recognized and differentially dephosphorylated is unclear. Using phosphoproteomics combined with kinetic modeling to extract B55-dependent rate constants, we have systematically identified B55 substrates and assigned their temporal order in mitotic exit. These substrates share a bipartite polybasic recognition determinant (BPR) flanking a Cdk1 phosphorylation site. Experiments and modeling show that dephosphorylation rate is encoded into B55 substrates, including its inhibitor ENSA, by cooperative action of basic residues within the BPR. A complementary acidic surface on B55 decodes this signal, supporting a cooperative electrostatic mechanism for substrate selection. A further level of specificity is encoded into B55 substrates because B55 displays selectivity for phosphothreonine. These simple biochemical properties, combined with feedback control of B55 activity by the phosphoserine-containing substrate/inhibitor ENSA, can help explain the temporal sequence of events during exit from mitosis.
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Affiliation(s)
- Michael J Cundell
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, England, UK
| | - Lukas H Hutter
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, England, UK
| | | | - Elena Poser
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, England, UK
| | - James Holder
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, England, UK
| | - Shabaz Mohammed
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, England, UK Department of Chemistry, University of Oxford, Oxford OX1 3TA, England, UK
| | - Bela Novak
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, England, UK
| | - Francis A Barr
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, England, UK
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80
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Wolff ID, Tran MV, Mullen TJ, Villeneuve AM, Wignall SM. Assembly of Caenorhabditis elegans acentrosomal spindles occurs without evident microtubule-organizing centers and requires microtubule sorting by KLP-18/kinesin-12 and MESP-1. Mol Biol Cell 2016; 27:3122-3131. [PMID: 27559133 PMCID: PMC5063619 DOI: 10.1091/mbc.e16-05-0291] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Accepted: 08/19/2016] [Indexed: 01/15/2023] Open
Abstract
Female reproductive cells of most species lack centrosomes, but how spindles form in their absence is poorly understood. Study of oocytes in Caenorhabditis elegans uncovers new steps in this process and reveals mechanisms required for acentrosomal spindle bipolarity via studies of two proteins, KLP-18/kinesin-12 and MESP-1. Although centrosomes contribute to spindle formation in most cell types, oocytes of many species are acentrosomal and must organize spindles in their absence. Here we investigate this process in Caenorhabditis elegans, detailing how acentrosomal spindles form and revealing mechanisms required to establish bipolarity. Using high-resolution imaging, we find that in meiosis I, microtubules initially form a “cage-like” structure inside the disassembling nuclear envelope. This structure reorganizes so that minus ends are sorted to the periphery of the array, forming multiple nascent poles that then coalesce until bipolarity is achieved. In meiosis II, microtubules nucleate in the vicinity of chromosomes but then undergo similar sorting and pole formation events. We further show that KLP-18/kinesin-12 and MESP-1, previously shown to be required for spindle bipolarity, likely contribute to bipolarity by sorting microtubules. After their depletion, minus ends are not sorted outward at the early stages of spindle assembly and instead converge. These proteins colocalize on microtubules, are interdependent for localization, and can interact, suggesting that they work together. We propose that KLP-18/kinesin-12 and MESP-1 form a complex that functions to sort microtubules of mixed polarity into a configuration in which minus ends are away from the chromosomes, enabling formation of nascent poles.
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Affiliation(s)
- Ian D Wolff
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208
| | - Michael V Tran
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208
| | - Timothy J Mullen
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208
| | - Anne M Villeneuve
- Departments of Developmental Biology and Genetics, Stanford University, Stanford, CA 94305
| | - Sarah M Wignall
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208
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81
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Abstract
Concentration gradients of soluble proteins are believed to be responsible for control of morphogenesis of subcellular systems, but the mechanisms that generate the spatial organization of these subcellular gradients remain poorly understood. Here, we use a newly developed multipoint fluorescence fluctuation spectroscopy technique to study the ras-related nuclear protein (Ran) pathway, which forms soluble gradients around chromosomes in mitosis and is thought to spatially regulate microtubule behaviors during spindle assembly. We found that the distribution of components of the Ran pathway that influence microtubule behaviors is determined by their interactions with microtubules, resulting in microtubule nucleators being localized by the microtubules whose formation they stimulate. Modeling and perturbation experiments show that this feedback makes the length of the spindle insensitive to the length scale of the Ran gradient, allows the spindle to assemble outside the peak of the Ran gradient, and explains the scaling of the spindle with cell size. Such feedback between soluble signaling pathways and the mechanics of the cytoskeleton may be a general feature of subcellular organization.
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82
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Kahn OI, Baas PW. Microtubules and Growth Cones: Motors Drive the Turn. Trends Neurosci 2016; 39:433-440. [PMID: 27233682 DOI: 10.1016/j.tins.2016.04.009] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Revised: 04/19/2016] [Accepted: 04/21/2016] [Indexed: 01/09/2023]
Abstract
Navigation of the growth cone at the tip of the developing axon is crucial for the proper wiring of the nervous system. Mechanisms of actin-dependent growth cone steering, via signaling cascades, are well documented. Microtubules are also important in growth cone guidance, because their polarized invasion into the peripheral domain on one side of the growth cone is essential for it to turn in that direction. Classically, microtubules have been considered secondary players, invading the peripheral domain only where the actin cytoskeleton permits them to go. Presented here is evidence for an underappreciated mechanism by which signaling cascades can potentially affect growth cone turning, namely through regulatable forces imposed on the microtubules by molecular motor proteins.
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Affiliation(s)
- Olga I Kahn
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, USA
| | - Peter W Baas
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, PA 19129, USA.
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83
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Yan K, Li L, Wang X, Hong R, Zhang Y, Yang H, Lin M, Zhang S, He Q, Zheng D, Tang J, Yin Y, Shao G. The deubiquitinating enzyme complex BRISC is required for proper mitotic spindle assembly in mammalian cells. J Cell Biol 2016. [PMID: 26195665 PMCID: PMC4508884 DOI: 10.1083/jcb.201503039] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The microtubule-associated protein BRISC regulates the interaction of NuMA with dynein and importin-β by removing K63-linked polyubiquitin chains from NuMA, thereby promoting proper bipolar spindle assembly. Deubiquitinating enzymes (DUBs) negatively regulate protein ubiquitination and play an important role in diverse physiological processes, including mitotic division. The BRCC36 isopeptidase complex (BRISC) is a DUB that is specific for lysine 63–linked ubiquitin hydrolysis; however, its biological function remains largely undefined. Here, we identify a critical role for BRISC in the control of mitotic spindle assembly in cultured mammalian cells. BRISC is a microtubule (MT)-associated protein complex that predominantly localizes to the minus ends of K-fibers and spindle poles and directly binds to MTs; importantly, BRISC promotes the assembly of functional bipolar spindle by deubiquitinating the essential spindle assembly factor nuclear mitotic apparatus (NuMA). The deubiquitination of NuMA regulates its interaction with dynein and importin-β, which are required for its function in spindle assembly. Collectively, these results uncover BRISC as an important regulator of the mitotic spindle assembly and cell division, and have important implications for the development of anticancer drugs targeting BRISC.
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Affiliation(s)
- Kaowen Yan
- Department of Cell Biology, School of Basic Medical Sciences, Peking University, Beijing 100191, China Institute of Systems Biomedicine, Beijing Key Laboratory of Tumor Systems Biology, Peking University, Beijing 100191, China
| | - Li Li
- Department of Cell Biology, School of Basic Medical Sciences, Peking University, Beijing 100191, China
| | - Xiaojian Wang
- State Key Laboratory of Agrobiotechnology, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Ruisha Hong
- Department of Cell Biology, School of Basic Medical Sciences, Peking University, Beijing 100191, China School of Medicine, Shenzhen University, Shenzhen, Guangdong 518060, China
| | - Ying Zhang
- Department of Cell Biology, School of Basic Medical Sciences, Peking University, Beijing 100191, China
| | - Hua Yang
- Department of Cell Biology, School of Basic Medical Sciences, Peking University, Beijing 100191, China
| | - Ming Lin
- Department of Cell Biology, School of Basic Medical Sciences, Peking University, Beijing 100191, China
| | - Sha Zhang
- Department of Cell Biology, School of Basic Medical Sciences, Peking University, Beijing 100191, China
| | - Qihua He
- Center of Medical and Health Analysis, Peking University, Beijing 100191, China
| | - Duo Zheng
- School of Medicine, Shenzhen University, Shenzhen, Guangdong 518060, China
| | - Jun Tang
- State Key Laboratory of Agrobiotechnology, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Yuxin Yin
- Institute of Systems Biomedicine, Beijing Key Laboratory of Tumor Systems Biology, Peking University, Beijing 100191, China
| | - Genze Shao
- Department of Cell Biology, School of Basic Medical Sciences, Peking University, Beijing 100191, China Institute of Systems Biomedicine, Beijing Key Laboratory of Tumor Systems Biology, Peking University, Beijing 100191, China
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84
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Ori-McKenney KM, McKenney RJ, Huang HH, Li T, Meltzer S, Jan LY, Vale RD, Wiita AP, Jan YN. Phosphorylation of β-Tubulin by the Down Syndrome Kinase, Minibrain/DYRK1a, Regulates Microtubule Dynamics and Dendrite Morphogenesis. Neuron 2016; 90:551-63. [PMID: 27112495 DOI: 10.1016/j.neuron.2016.03.027] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2015] [Revised: 02/02/2016] [Accepted: 03/16/2016] [Indexed: 12/31/2022]
Abstract
Dendritic arborization patterns are consistent anatomical correlates of genetic disorders such as Down syndrome (DS) and autism spectrum disorders (ASDs). In a screen for abnormal dendrite development, we identified Minibrain (MNB)/DYRK1a, a kinase implicated in DS and ASDs, as a regulator of the microtubule cytoskeleton. We show that MNB is necessary to establish the length and cytoskeletal composition of terminal dendrites by controlling microtubule growth. Altering MNB levels disrupts dendrite morphology and perturbs neuronal electrophysiological activity, resulting in larval mechanosensation defects. Using in vivo and in vitro approaches, we uncover a molecular pathway whereby direct phosphorylation of β-tubulin by MNB inhibits tubulin polymerization, a function that is conserved for mammalian DYRK1a. Our results demonstrate that phosphoregulation of microtubule dynamics by MNB/DYRK1a is critical for dendritic patterning and neuronal function, revealing a previously unidentified mode of posttranslational microtubule regulation in neurons and uncovering a conserved pathway for a DS- and ASD-associated kinase.
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Affiliation(s)
- Kassandra M Ori-McKenney
- Department of Physiology and Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Richard J McKenney
- Department of Cellular and Molecular Pharmacology and Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Hector H Huang
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Tun Li
- Department of Physiology and Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Shan Meltzer
- Department of Physiology and Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Lily Yeh Jan
- Department of Physiology and Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Ronald D Vale
- Department of Cellular and Molecular Pharmacology and Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Arun P Wiita
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Yuh Nung Jan
- Department of Physiology and Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA 94158, USA.
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85
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Abstract
Life depends on cell proliferation and the accurate segregation of chromosomes, which are mediated by the microtubule (MT)-based mitotic spindle and ∼200 essential MT-associated proteins. Yet, a mechanistic understanding of how the mitotic spindle is assembled and achieves chromosome segregation is still missing. This is mostly due to the density of MTs in the spindle, which presumably precludes their direct observation. Recent insight has been gained into the molecular building plan of the metaphase spindle using bulk and single-molecule measurements combined with computational modeling. MT nucleation was uncovered as a key principle of spindle assembly, and mechanistic details about MT nucleation pathways and their coordination are starting to be revealed. Lastly, advances in studying spindle assembly can be applied to address the molecular mechanisms of how the spindle segregates chromosomes.
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Affiliation(s)
- Sabine Petry
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544-1014;
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86
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Abstract
Microtubule dynamics are fundamental for many aspects of cell physiology, but their mechanistic underpinnings remain unclear despite 40 years of intense research. In recent years, the continued union of reconstitution biochemistry, structural biology, and modeling has yielded important discoveries that deepen our understanding of microtubule dynamics. These studies, which we review here, underscore the importance of GTP hydrolysis-induced changes in tubulin structure as microtubules assemble, and highlight the fact that each aspect of microtubule behavior is the output of complex, multi-step processes. Although this body of work moves us closer to appreciating the key features of microtubule biochemistry that drive dynamic instability, the divide between our understanding of microtubules in isolation versus within the cellular milieu remains vast. Bridging this gap will serve as fertile grounds of cytoskeleton-focused research for many years to come.
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Affiliation(s)
- Ryoma Ohi
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Marija Zanic
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA; Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee, USA
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87
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Reid TA, Schuster BM, Mann BJ, Balchand SK, Plooster M, McClellan M, Coombes CE, Wadsworth P, Gardner MK. Suppression of microtubule assembly kinetics by the mitotic protein TPX2. J Cell Sci 2016; 129:1319-28. [PMID: 26869224 DOI: 10.1242/jcs.178806] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2015] [Accepted: 02/05/2016] [Indexed: 01/01/2023] Open
Abstract
TPX2 is a widely conserved microtubule-associated protein that is required for mitotic spindle formation and function. Previous studies have demonstrated that TPX2 is required for the nucleation of microtubules around chromosomes; however, the molecular mechanism by which TPX2 promotes microtubule nucleation remains a mystery. In this study, we found that TPX2 acts to suppress tubulin subunit off-rates during microtubule assembly and disassembly, thus allowing for the support of unprecedentedly slow rates of plus-end microtubule growth, and also leading to a dramatically reduced microtubule shortening rate. These changes in microtubule dynamics can be explained in computational simulations by a moderate increase in tubulin-tubulin bond strength upon TPX2 association with the microtubule lattice, which in turn acts to reduce the departure rate of tubulin subunits from the microtubule ends. Thus, the direct suppression of tubulin subunit off-rates by TPX2 during microtubule growth and shortening could provide a molecular mechanism to explain the nucleation of new microtubules in the presence of TPX2.
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Affiliation(s)
- Taylor A Reid
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | - Breanna M Schuster
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | - Barbara J Mann
- Department of Biology, University of Massachusetts, Amherst, MA 01003, USA
| | | | - Melissa Plooster
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | - Mark McClellan
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | - Courtney E Coombes
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA
| | - Pat Wadsworth
- Department of Biology, University of Massachusetts, Amherst, MA 01003, USA
| | - Melissa K Gardner
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, MN 55455, USA
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88
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Cavazza T, Vernos I. The RanGTP Pathway: From Nucleo-Cytoplasmic Transport to Spindle Assembly and Beyond. Front Cell Dev Biol 2016; 3:82. [PMID: 26793706 PMCID: PMC4707252 DOI: 10.3389/fcell.2015.00082] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Accepted: 12/07/2015] [Indexed: 01/03/2023] Open
Abstract
The small GTPase Ran regulates the interaction of transport receptors with a number of cellular cargo proteins. The high affinity binding of the GTP-bound form of Ran to import receptors promotes cargo release, whereas its binding to export receptors stabilizes their interaction with the cargo. This basic mechanism linked to the asymmetric distribution of the two nucleotide-bound forms of Ran between the nucleus and the cytoplasm generates a switch like mechanism controlling nucleo-cytoplasmic transport. Since 1999, we have known that after nuclear envelope breakdown (NEBD) Ran and the above transport receptors also provide a local control over the activity of factors driving spindle assembly and regulating other aspects of cell division. The identification and functional characterization of RanGTP mitotic targets is providing novel insights into mechanisms essential for cell division. Here we review our current knowledge on the RanGTP system and its regulation and we focus on the recent advances made through the characterization of its mitotic targets. We then briefly review the novel functions of the pathway that were recently described. Altogether, the RanGTP system has moonlighting functions exerting a spatial control over protein interactions that drive specific functions depending on the cellular context.
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Affiliation(s)
- Tommaso Cavazza
- Cell and Developmental Biology, Centre for Genomic Regulation, The Barcelona Institute of Science and TechnologyBarcelona, Spain; Universitat Pompeu FabraBarcelona, Spain
| | - Isabelle Vernos
- Cell and Developmental Biology, Centre for Genomic Regulation, The Barcelona Institute of Science and TechnologyBarcelona, Spain; Universitat Pompeu FabraBarcelona, Spain; Institució Catalana de Recerca I Estudis AvançatsBarcelona, Spain
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89
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Roostalu J, Cade NI, Surrey T. Complementary activities of TPX2 and chTOG constitute an efficient importin-regulated microtubule nucleation module. Nat Cell Biol 2015; 17:1422-34. [PMID: 26414402 PMCID: PMC4826748 DOI: 10.1038/ncb3241] [Citation(s) in RCA: 112] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 08/21/2015] [Indexed: 01/28/2023]
Abstract
Spindle assembly and function require precise control of microtubule nucleation and dynamics. The chromatin-driven spindle assembly pathway exerts such control locally in the vicinity of chromosomes. One of the key targets of this pathway is TPX2. The molecular mechanism of how TPX2 stimulates microtubule nucleation is not understood. Using microscopy-based dynamic in vitro reconstitution assays with purified proteins, we find that human TPX2 directly stabilizes growing microtubule ends and stimulates microtubule nucleation by stabilizing early microtubule nucleation intermediates. Human microtubule polymerase chTOG (XMAP215/Msps/Stu2p/Dis1/Alp14 homologue) only weakly promotes nucleation, but acts synergistically with TPX2. Hence, a combination of distinct and complementary activities is sufficient for efficient microtubule formation in vitro. Importins control the efficiency of the microtubule nucleation by selectively blocking the interaction of TPX2 with microtubule nucleation intermediates. This in vitro reconstitution reveals the molecular mechanism of regulated microtubule formation by a minimal nucleation module essential for chromatin-dependent microtubule nucleation in cells.
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Affiliation(s)
- Johanna Roostalu
- The Francis Crick Institute, 44 Lincoln’s Inn Fields, London WC2A 3LY, United Kingdom
| | - Nicholas I. Cade
- The Francis Crick Institute, 44 Lincoln’s Inn Fields, London WC2A 3LY, United Kingdom
| | - Thomas Surrey
- The Francis Crick Institute, 44 Lincoln’s Inn Fields, London WC2A 3LY, United Kingdom
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90
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The γ-tubulin-specific inhibitor gatastatin reveals temporal requirements of microtubule nucleation during the cell cycle. Nat Commun 2015; 6:8722. [PMID: 26503935 PMCID: PMC4640066 DOI: 10.1038/ncomms9722] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Accepted: 09/24/2015] [Indexed: 11/26/2022] Open
Abstract
Inhibitors of microtubule (MT) assembly or dynamics that target α/β-tubulin are widely exploited in cancer therapy and biological research. However, specific inhibitors of the MT nucleator γ-tubulin that would allow testing temporal functions of γ-tubulin during the cell cycle are yet to be identified. By evolving β-tubulin-binding drugs we now find that the glaziovianin A derivative gatastatin is a γ-tubulin-specific inhibitor. Gatastatin decreased interphase MT dynamics of human cells without affecting MT number. Gatastatin inhibited assembly of the mitotic spindle in prometaphase. Addition of gatastatin to preformed metaphase spindles altered MT dynamics, reduced the number of growing MTs and shortened spindle length. Furthermore, gatastatin prolonged anaphase duration by affecting anaphase spindle structure, indicating the continuous requirement of MT nucleation during mitosis. Thus, gatastatin facilitates the dissection of the role of γ-tubulin during the cell cycle and reveals the sustained role of γ-tubulin. Current microtubule inhibitors target α/β-tubulin, but no specific inhibitor of γ-tubulin has been developed. Here the authors present gatastatin as a γ-tubulin inhibitor and use it to probe the role of γ-tubulin during the cell cycle.
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91
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Meunier S, Vernos I. Acentrosomal Microtubule Assembly in Mitosis: The Where, When, and How. Trends Cell Biol 2015; 26:80-87. [PMID: 26475655 DOI: 10.1016/j.tcb.2015.09.001] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Revised: 08/31/2015] [Accepted: 09/01/2015] [Indexed: 01/08/2023]
Abstract
In mitosis the cell assembles the bipolar spindle, a microtubule (MT)-based apparatus that segregates the duplicated chromosomes into two daughter cells. Most animal cells enter mitosis with duplicated centrosomes that provide an active source of dynamic MTs. However, it is now established that spindle assembly relies on the nucleation of acentrosomal MTs occurring around the chromosomes after nuclear envelope breakdown, and on pre-existing microtubules. Where chromosome-dependent MT nucleation occurs, when MT amplification takes place and how the two pathways function are still key questions that generate some controversies. We reconcile the data and present an integrated model accounting for acentrosomal microtubule assembly in the dividing cell.
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Affiliation(s)
- Sylvain Meunier
- Cell and Developmental Biology Programme, Centre for Genomic Regulation (CRG), Doctor Aiguader 88, 08003 Barcelona, Spain; Universitat Pompeu Fabra (UPF), Doctor Aiguader 88, 08003 Barcelona, Spain
| | - Isabelle Vernos
- Cell and Developmental Biology Programme, Centre for Genomic Regulation (CRG), Doctor Aiguader 88, 08003 Barcelona, Spain; Universitat Pompeu Fabra (UPF), Doctor Aiguader 88, 08003 Barcelona, Spain; Institució Catalana de Recerca I Estudis Avançats (ICREA), Passeig de Lluis Companys 23, 08010 Barcelona, Spain.
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92
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Oropesa Ávila M, Fernández Vega A, Garrido Maraver J, Villanueva Paz M, De Lavera I, De La Mata M, Cordero MD, Alcocer Gómez E, Delgado Pavón A, Álvarez Córdoba M, Cotán D, Sánchez-Alcázar JA. Emerging roles of apoptotic microtubules during the execution phase of apoptosis. Cytoskeleton (Hoboken) 2015; 72:435-46. [PMID: 26382917 DOI: 10.1002/cm.21254] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Revised: 09/01/2015] [Accepted: 09/09/2015] [Indexed: 12/14/2022]
Abstract
Apoptosis is a genetically programmed energy-dependent process of cell demise, characterized by specific morphological and biochemical events in which the activation of caspases has an essential role. During apoptosis the cytoskeleton participates actively in characteristic morphological rearrangements of the dying cell. This reorganisation has been assigned mainly to actinomyosin ring contraction, while microtubule and intermediate filaments are depolymerized at early stages of apoptosis. However, recent reports have showed that microtubules are reformed during the execution phase of apoptosis organizing an apoptotic microtubule network (AMN). AMN is organized behind plasma membrane, forming a cortical structure. Apoptotic microtubules repolymerization takes place in many cell types and under different apoptotic inducers. It has been hypothesized that AMN is critical for maintaining plasma membrane integrity and cell morphology during the execution phase of apoptosis. AMN disorganization leads apoptotic cells to secondary necrosis and the release of potential toxic molecules which can damage neighbor cells and promotes inflammation. Therefore, AMN formation during physiological apoptosis or in pathological apoptosis induced by anti-cancer treatments is essential for tissue homeostasis and the prevention of additional cell damage and inflammation.
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Affiliation(s)
- Manuel Oropesa Ávila
- Centro Andaluz De Biología Del Desarrollo (CABD), and Centro De Investigación Biomédica En Red: Enfermedades Raras, Instituto De Salud Carlos III, Universidad Pablo De Olavide-Consejo Superior De Investigaciones Científicas, Sevilla, 41013, Spain
| | - Alejandro Fernández Vega
- Centro Andaluz De Biología Del Desarrollo (CABD), and Centro De Investigación Biomédica En Red: Enfermedades Raras, Instituto De Salud Carlos III, Universidad Pablo De Olavide-Consejo Superior De Investigaciones Científicas, Sevilla, 41013, Spain
| | - Juan Garrido Maraver
- Centro Andaluz De Biología Del Desarrollo (CABD), and Centro De Investigación Biomédica En Red: Enfermedades Raras, Instituto De Salud Carlos III, Universidad Pablo De Olavide-Consejo Superior De Investigaciones Científicas, Sevilla, 41013, Spain
| | - Marina Villanueva Paz
- Centro Andaluz De Biología Del Desarrollo (CABD), and Centro De Investigación Biomédica En Red: Enfermedades Raras, Instituto De Salud Carlos III, Universidad Pablo De Olavide-Consejo Superior De Investigaciones Científicas, Sevilla, 41013, Spain
| | - Isabel De Lavera
- Centro Andaluz De Biología Del Desarrollo (CABD), and Centro De Investigación Biomédica En Red: Enfermedades Raras, Instituto De Salud Carlos III, Universidad Pablo De Olavide-Consejo Superior De Investigaciones Científicas, Sevilla, 41013, Spain
| | - Mario De La Mata
- Centro Andaluz De Biología Del Desarrollo (CABD), and Centro De Investigación Biomédica En Red: Enfermedades Raras, Instituto De Salud Carlos III, Universidad Pablo De Olavide-Consejo Superior De Investigaciones Científicas, Sevilla, 41013, Spain
| | - Mario D Cordero
- Facultad De Odontología. Universidad De Sevilla, Sevilla, 41009, Spain
| | - Elizabet Alcocer Gómez
- Centro Andaluz De Biología Del Desarrollo (CABD), and Centro De Investigación Biomédica En Red: Enfermedades Raras, Instituto De Salud Carlos III, Universidad Pablo De Olavide-Consejo Superior De Investigaciones Científicas, Sevilla, 41013, Spain
| | - Ana Delgado Pavón
- Centro Andaluz De Biología Del Desarrollo (CABD), and Centro De Investigación Biomédica En Red: Enfermedades Raras, Instituto De Salud Carlos III, Universidad Pablo De Olavide-Consejo Superior De Investigaciones Científicas, Sevilla, 41013, Spain
| | - Mónica Álvarez Córdoba
- Centro Andaluz De Biología Del Desarrollo (CABD), and Centro De Investigación Biomédica En Red: Enfermedades Raras, Instituto De Salud Carlos III, Universidad Pablo De Olavide-Consejo Superior De Investigaciones Científicas, Sevilla, 41013, Spain
| | - David Cotán
- Centro Andaluz De Biología Del Desarrollo (CABD), and Centro De Investigación Biomédica En Red: Enfermedades Raras, Instituto De Salud Carlos III, Universidad Pablo De Olavide-Consejo Superior De Investigaciones Científicas, Sevilla, 41013, Spain
| | - José Antonio Sánchez-Alcázar
- Centro Andaluz De Biología Del Desarrollo (CABD), and Centro De Investigación Biomédica En Red: Enfermedades Raras, Instituto De Salud Carlos III, Universidad Pablo De Olavide-Consejo Superior De Investigaciones Científicas, Sevilla, 41013, Spain
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93
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Kahn OI, Ha N, Baird MA, Davidson MW, Baas PW. TPX2 regulates neuronal morphology through kinesin-5 interaction. Cytoskeleton (Hoboken) 2015; 72:340-8. [PMID: 26257190 DOI: 10.1002/cm.21234] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2015] [Revised: 08/05/2015] [Accepted: 08/06/2015] [Indexed: 01/19/2023]
Abstract
TPX2 (targeting protein for Xklp2) is a multifunctional mitotic spindle assembly factor that in mammalian cells localizes and regulates mitotic motor protein kinesin-5 (also called Eg5 or kif11). We previously showed that upon depletion or inhibition of kinesin-5 in cultured neurons, microtubule movements increase, resulting in faster growing axons and thinner dendrites. Here, we show that depletion of TPX2 from cultured neurons speeds their rate of process outgrowth, similarly to kinesin-5 inhibition. The phenotype is rescued by TPX2 re-expression, but not if TPX2's kinesin-5-interacting domain is deleted. These results, together with studies showing a spike in TPX2 expression during dendritic differentiation, suggest that the levels and distribution of TPX2 are likely to be determinants of when and where kinesin-5 acts in neurons.
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Affiliation(s)
- Olga I Kahn
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania
| | - Ngoc Ha
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania
| | - Michelle A Baird
- National High Magnetic Field Laboratory and Department of Biological Science, Florida State University, Tallahassee, Florida
| | - Michael W Davidson
- National High Magnetic Field Laboratory and Department of Biological Science, Florida State University, Tallahassee, Florida
| | - Peter W Baas
- Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania
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94
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Liu Q, Tu K, Zhang H, Zheng X, Yao Y, Liu Q. TPX2 as a novel prognostic biomarker for hepatocellular carcinoma. Hepatol Res 2015; 45:906-18. [PMID: 25263743 DOI: 10.1111/hepr.12428] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Revised: 09/02/2014] [Accepted: 09/24/2014] [Indexed: 12/24/2022]
Abstract
AIM Targeting protein for Xenopus kinesin-like protein 2 (TPX2) is a microtubule-associated protein that impacts spindle assembly in human cells. Several studies have shown that the overexpression of TPX2 is correlated with multiple tumor types. However, the role of TPX2 in hepatocellular carcinoma (HCC) remains undetermined. METHODS TPX2 expression was detected by quantitative reverse transcription polymerase chain reaction and immunoblotting in six cell lines and 130 pairs of HCC and adjacent non-cancerous liver tissues. Matrix metalloproteinase (MMP)2 and MMP9 expression was detected by immunohistochemistry to evaluate their correlations with TXP2. TPX2 siRNA was used to knock down TPX2 expression, and cell migration and invasion were determined. Moreover, clinical significance of TPX2 in HCC was analyzed. RESULTS TPX2 expression was found to be obviously higher in HCC tissues than that in non-tumor tissues. Elevated TPX2 expression was observed in HCC cell lines as compared with that in a non-transformed hepatic cell line. Clinical analysis indicated that TPX2 expression in the HCC tissues was evidently correlated with the tumor-node-metastasis stage, tumor number and tumor differentiation. TPX2 is a novel prognostic marker for predicting 5-year overall survival and disease-free survival of HCC patients. TPX2 expression was positively correlated with MMP2 and MMP9. In vitro studies found that TPX2 knockdown prominently reduced cell invasion and migration and decreased phosphorylated AKT, MMP2 and MMP9 expression in MHCC-97H cells. CONCLUSION Overexpression of TPX2 was associated with clinicopathological characteristics and poor patient outcomes. TPX2 may serve as a novel prognostic marker for HCC.
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Affiliation(s)
- Qingquan Liu
- Department of Hepatobiliary Surgery, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Kangsheng Tu
- Department of Hepatobiliary Surgery, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Hongyong Zhang
- Department of Hepatobiliary Surgery, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Xin Zheng
- Department of Hepatobiliary Surgery, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Yingmin Yao
- Department of Hepatobiliary Surgery, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
| | - Qingguang Liu
- Department of Hepatobiliary Surgery, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, China
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95
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Abstract
A metaphase spindle is a complex structure consisting of microtubules and a myriad of different proteins that modulate microtubule dynamics together with chromatin and kinetochores. A decade ago, a full description of spindle formation and function seemed a lofty goal. Here, we describe how work in the last 10 years combining cataloging of spindle components, the characterization of their biochemical activities using single-molecule techniques, and theory have advanced our knowledge. Taken together, these advances suggest that a full understanding of spindle assembly and function may soon be possible.
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Affiliation(s)
- Simone Reber
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany Integrative Research Institute (IRI) for the Life Sciences, Humboldt-Universität zu Berlin, 10115 Berlin, Germany
| | - Anthony A Hyman
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
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96
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Balchand SK, Mann BJ, Titus J, Ross JL, Wadsworth P. TPX2 Inhibits Eg5 by Interactions with Both Motor and Microtubule. J Biol Chem 2015; 290:17367-79. [PMID: 26018074 DOI: 10.1074/jbc.m114.612903] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Indexed: 12/27/2022] Open
Abstract
The microtubule-associated protein, TPX2, regulates the activity of the mitotic kinesin, Eg5, but the mechanism of regulation is not established. Using total internal reflection fluorescence microscopy, we observed that Eg5, in extracts of mammalian cells expressing Eg5-EGFP, moved processively toward the microtubule plus-end at an average velocity of 14 nm/s. TPX2 bound to microtubules with an apparent dissociation constant of ∼ 200 nm, and microtubule binding was not dependent on the C-terminal tails of tubulin. Using single molecule assays, we found that full-length TPX2 dramatically reduced Eg5 velocity, whereas truncated TPX2, which lacks the domain that is required for the interaction with Eg5, was a less effective inhibitor at the same concentration. To determine the region(s) of Eg5 that is required for interaction with TPX2, we performed microtubule gliding assays. Dimeric, but not monomeric, Eg5 was differentially inhibited by full-length and truncated TPX2, demonstrating that dimerization or residues in the neck region are important for the interaction of TPX2 with Eg5. These results show that both microtubule binding and interaction with Eg5 contribute to motor inhibition by TPX2 and demonstrate the utility of mammalian cell extracts for biophysical assays.
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Affiliation(s)
- Sai K Balchand
- the Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, Massachusetts 01003
| | - Barbara J Mann
- the Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, Massachusetts 01003
| | - Janel Titus
- the Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, Massachusetts 01003
| | - Jennifer L Ross
- the Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, Massachusetts 01003 Physics and
| | - Patricia Wadsworth
- the Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, Massachusetts 01003 From the Departments of Biology and
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97
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Weaver LN, Ems-McClung SC, Chen SHR, Yang G, Shaw SL, Walczak CE. The Ran-GTP gradient spatially regulates XCTK2 in the spindle. Curr Biol 2015; 25:1509-14. [PMID: 25981788 DOI: 10.1016/j.cub.2015.04.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Revised: 02/11/2015] [Accepted: 04/09/2015] [Indexed: 11/18/2022]
Abstract
Ran is a small GTP binding protein that was originally identified as a regulator of nucleocytoplasmic transport [1] and subsequently found to be important for spindle formation [2-5]. In mitosis, a gradient of Ran-GTP emanates from chromatin and diminishes toward spindle poles [6]. Ran-GTP promotes spindle self-organization through the release of importin-bound spindle assembly factors (SAFs), which stimulate microtubule (MT) nucleation and organization and regulate MT dynamics [7-9]. Although many SAFs are non-motile MT-associated proteins, such as NuMA, TPX2, and HURP [7, 10-12], Ran also controls motor proteins, including Kid and HSET/XCTK2 [13, 14]. The Kinesin-14 XCKT2 is important for spindle assembly and pole organization [15-20], and Ran-GTP is proposed to promote XCKT2 MT crosslinking activity by releasing importin α/β from a bipartite nuclear localization signal (NLS) located in the tail domain [14]. Here, we show that the Ran-GTP gradient spatially regulates XCTK2 within the spindle. A flattened Ran-GTP gradient blocked the ability of excess XCTK2 to stimulate bipolar spindle assembly and resulted in XCTK2-mediated bundling of free MTs. These effects required the XCTK2 tail, which promoted the motility of XCTK2 within the spindle independent of the Ran-GTP gradient. In addition, the turnover kinetics of XCTK2 were spatially controlled: they were faster near the poles relative to the chromatin, but not with a mutant XCTK2 that cannot bind to importin α/β. Our results support a model in which the Ran-GTP gradient spatially coordinates motor localization with motility to ensure efficient spindle formation.
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Affiliation(s)
- Lesley N Weaver
- Department of Biology, Indiana University, 915 E. 3(rd) Street, Bloomington, IN 47405, USA
| | | | - Sez-Hon R Chen
- Department of Biomedical Engineering and Computational Biology, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213, USA
| | - Ge Yang
- Department of Biomedical Engineering and Computational Biology, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213, USA
| | - Sidney L Shaw
- Department of Biology, Indiana University, 915 E. 3(rd) Street, Bloomington, IN 47405, USA
| | - Claire E Walczak
- Medical Sciences, Indiana University, 915 E. 3(rd) Street, Bloomington, IN 47405, USA.
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98
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Holvey RS, Valkov E, Neal D, Stewart M, Abell C. Selective Targeting of the TPX2 Site of Importin-α Using Fragment-Based Ligand Design. ChemMedChem 2015; 10:1232-9. [PMID: 25899172 PMCID: PMC4515083 DOI: 10.1002/cmdc.201500014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Indexed: 01/05/2023]
Abstract
Protein-protein interactions are difficult therapeutic targets, and inhibiting pathologically relevant interactions without disrupting other essential ones presents an additional challenge. Herein we report how this might be achieved for the potential anticancer target, the TPX2-importin-α interaction. Importin-α is a nuclear transport protein that regulates the spindle assembly protein TPX2. It has two binding sites--major and minor-to which partners bind. Most nuclear transport cargoes use the major site, whereas TPX2 binds principally to the minor site. Fragment-based approaches were used to identify small molecules that bind importin-α, and crystallographic studies identified a lead series that was observed to bind specifically to the minor site, representing the first ligands specific for this site. Structure-guided synthesis informed the elaboration of these fragments to explore the source of ligand selectivity between the minor and major sites. These ligands are starting points for the development of inhibitors of this protein-protein interaction.
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Affiliation(s)
- Rhian S Holvey
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW (UK)
| | - Eugene Valkov
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH (UK)
| | - David Neal
- University of Cambridge, Department of Oncology, Box 279, Addenbrooke's Hospital, Hills Road, Cambridge, CB2 0QQ (UK)
| | - Murray Stewart
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH (UK)
| | - Chris Abell
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW (UK).
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99
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Chen A, Akhshi TK, Lavoie BD, Wilde A. Importin β2 Mediates the Spatio-temporal Regulation of Anillin through a Noncanonical Nuclear Localization Signal. J Biol Chem 2015; 290:13500-9. [PMID: 25829492 DOI: 10.1074/jbc.m115.649160] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Indexed: 11/06/2022] Open
Abstract
The compartmentalization of cell cycle regulators is a common mechanism to ensure the precise temporal control of key cell cycle events. For instance, many mitotic spindle assembly factors are known to be sequestered in the nucleus prior to mitotic onset. Similarly, the essential cytokinetic factor anillin, which functions at the cell membrane to promote the physical separation of daughter cells at the end of mitosis, is sequestered in the nucleus during interphase. To address the mechanism and role of anillin targeting to the nucleus in interphase, we identified the nuclear targeting motif. Here, we show that anillin is targeted to the nucleus by importin β2 in a Ran-dependent manner through an atypical basic patch PY nuclear localization signal motif. We show that although importin β2 binding does not regulate anillin's function in mitosis, it is required to prevent the cytosolic accumulation of anillin, which disrupts cellular architecture during interphase. The nuclear sequestration of anillin during interphase serves to restrict anillin's function at the cell membrane to mitosis and allows anillin to be rapidly available when the nuclear envelope breaks down to remodel the cellular architecture necessary for successful cell division.
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Affiliation(s)
- Anan Chen
- From the Departments of Biochemistry and
| | | | - Brigitte D Lavoie
- Molecular Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Andrew Wilde
- From the Departments of Biochemistry and Molecular Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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100
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Shim SY, Perez de Castro I, Neumayer G, Wang J, Park SK, Sanada K, Nguyen MD. Phosphorylation of targeting protein for Xenopus kinesin-like protein 2 (TPX2) at threonine 72 in spindle assembly. J Biol Chem 2015; 290:9122-34. [PMID: 25688093 DOI: 10.1074/jbc.m114.591545] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Indexed: 12/23/2022] Open
Abstract
The human ortholog of the targeting protein for Xenopus kinesin-like protein 2 (TPX2) is a cytoskeletal protein that plays a major role in spindle assembly and is required for mitosis. During spindle morphogenesis, TPX2 cooperates with Aurora A kinase and Eg5 kinesin to regulate microtubule organization. TPX2 displays over 40 putative phosphorylation sites identified from various high-throughput proteomic screenings. In this study, we characterize the phosphorylation of threonine 72 (Thr(72)) in human TPX2, a residue highly conserved across species. We find that Cdk1/2 phosphorylate TPX2 in vitro and in vivo. Using homemade antibodies specific for TPX2 phosphorylated at Thr(72), we show that this phosphorylation is cell cycle-dependent and peaks at M phase. Endogenous TPX2 phosphorylated at Thr(72) does not associate with the mitotic spindle. Furthermore, ectopic GFP-TPX2 T72A preferentially concentrates on the spindle, whereas GFP-TPX2 WT distributes to both spindle and cytosol. The T72A mutant also increases the proportion of cells with multipolar spindles phenotype. This effect is associated with increased Aurora A activity and abnormally elongated spindles, indicative of higher Eg5 activity. In summary, we propose that phosphorylation of Thr(72) regulates TPX2 localization and impacts spindle assembly via Aurora A and Eg5.
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Affiliation(s)
- Su Yeon Shim
- From the Departments of Clinical Neurosciences, Cell Biology & Anatomy, and Biochemistry & Molecular Biology and Hotchkiss Brain Institute, University of Calgary, Calgary, Canada T2N4N1
| | - Ignacio Perez de Castro
- the Cell Division and Cancer Group, Centro Nacional de Investigaciones Oncológicas (CNIO), Madrid 28029, Spain
| | - Gernot Neumayer
- From the Departments of Clinical Neurosciences, Cell Biology & Anatomy, and Biochemistry & Molecular Biology and Hotchkiss Brain Institute, University of Calgary, Calgary, Canada T2N4N1
| | - Jian Wang
- From the Departments of Clinical Neurosciences, Cell Biology & Anatomy, and Biochemistry & Molecular Biology and Hotchkiss Brain Institute, University of Calgary, Calgary, Canada T2N4N1
| | - Sang Ki Park
- the Department of Life Sciences, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea
| | - Kamon Sanada
- the Molecular Genetics Research Laboratory, Graduate School of Science, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan, and
| | - Minh Dang Nguyen
- From the Departments of Clinical Neurosciences, Cell Biology & Anatomy, and Biochemistry & Molecular Biology and Hotchkiss Brain Institute, University of Calgary, Calgary, Canada T2N4N1,
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