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Morel C, Lemerle E, Tsai FC, Obadia T, Srivastava N, Marechal M, Salles A, Albert M, Stefani C, Benito Y, Vandenesch F, Lamaze C, Vassilopoulos S, Piel M, Bassereau P, Gonzalez-Rodriguez D, Leduc C, Lemichez E. Caveolin-1 protects endothelial cells from extensive expansion of transcellular tunnel by stiffening the plasma membrane. eLife 2024; 12:RP92078. [PMID: 38517935 PMCID: PMC10959525 DOI: 10.7554/elife.92078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/24/2024] Open
Abstract
Large transcellular pores elicited by bacterial mono-ADP-ribosyltransferase (mART) exotoxins inhibiting the small RhoA GTPase compromise the endothelial barrier. Recent advances in biophysical modeling point toward membrane tension and bending rigidity as the minimal set of mechanical parameters determining the nucleation and maximal size of transendothelial cell macroaperture (TEM) tunnels induced by bacterial RhoA-targeting mART exotoxins. We report that cellular depletion of caveolin-1, the membrane-embedded building block of caveolae, and depletion of cavin-1, the master regulator of caveolae invaginations, increase the number of TEMs per cell. The enhanced occurrence of TEM nucleation events correlates with a reduction in cell height due to the increase in cell spreading and decrease in cell volume, which, together with the disruption of RhoA-driven F-actin meshwork, favor membrane apposition for TEM nucleation. Strikingly, caveolin-1 specifically controls the opening speed of TEMs, leading to their dramatic 5.4-fold larger widening. Consistent with the increase in TEM density and width in siCAV1 cells, we record a higher lethality in CAV1 KO mice subjected to a catalytically active mART exotoxin targeting RhoA during staphylococcal bloodstream infection. Combined theoretical modeling with independent biophysical measurements of plasma membrane bending rigidity points toward a specific contribution of caveolin-1 to membrane stiffening in addition to the role of cavin-1/caveolin-1-dependent caveolae in the control of membrane tension homeostasis.
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Affiliation(s)
- Camille Morel
- Institut Pasteur, Université Paris Cité, CNRS UMR6047, Inserm U1306, Unité des Toxines Bactériennes, Département de MicrobiologieParisFrance
| | - Eline Lemerle
- Sorbonne Université, INSERM UMR974, Institut de Myologie, Centre de Recherche en MyologieParisFrance
| | - Feng-Ching Tsai
- Institut Curie, PSL Research University, CNRS UMR168, Physics of Cells and Cancer LaboratoryParisFrance
| | - Thomas Obadia
- Institut Pasteur, Université Paris Cité, Bioinformatics and Biostatistics HubParisFrance
- Institut Pasteur, Université Paris Cité, G5 Infectious Diseases Epidemiology and AnalyticsParisFrance
| | - Nishit Srivastava
- Institut Curie and Institut Pierre Gilles de Gennes, PSL Research University, Sorbonne UniversityParisFrance
| | - Maud Marechal
- Institut Pasteur, Université Paris Cité, CNRS UMR6047, Inserm U1306, Unité des Toxines Bactériennes, Département de MicrobiologieParisFrance
| | - Audrey Salles
- Institut Pasteur, Université Paris Cité, Photonic Bio-Imaging, Centre de Ressources et Recherches Technologiques (UTechS-PBI, C2RT)ParisFrance
| | - Marvin Albert
- Institut Pasteur, Université Paris Cité, Image Analysis HubParisFrance
| | - Caroline Stefani
- Benaroya Research Institute at Virginia Mason, Department of ImmunologySeattleUnited States
| | - Yvonne Benito
- Centre National de Référence des Staphylocoques, Hospices Civiles de LyonLyonFrance
| | - François Vandenesch
- CIRI, Centre International de Recherche en Infectiologie, Université de Lyon, Inserm U1111, Université Claude Bernard Lyon 1, CNRS UMR5308, ENS de Lyon, Lyon, FranceLyonFrance
| | - Christophe Lamaze
- Institut Curie, PSL Research University, INSERM U1143, CNRS UMR3666, Membrane Mechanics and Dynamics of Intracellular Signaling LaboratoryParisFrance
| | - Stéphane Vassilopoulos
- Sorbonne Université, INSERM UMR974, Institut de Myologie, Centre de Recherche en MyologieParisFrance
| | - Matthieu Piel
- Institut Curie and Institut Pierre Gilles de Gennes, PSL Research University, Sorbonne UniversityParisFrance
| | - Patricia Bassereau
- Institut Curie, PSL Research University, CNRS UMR168, Physics of Cells and Cancer LaboratoryParisFrance
| | | | - Cecile Leduc
- Université Paris Cité, Institut Jacques Monod, CNRS UMR7592ParisFrance
| | - Emmanuel Lemichez
- Institut Pasteur, Université Paris Cité, CNRS UMR6047, Inserm U1306, Unité des Toxines Bactériennes, Département de MicrobiologieParisFrance
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Sun S, Yang C, Wang K, Huang R, Zhang KN, Liu Y, Cao Z, Zhao Z, Jiang T. Molecular and clinical characterization of PTRF in glioma via 1,022 samples. BMC Cancer 2023; 23:551. [PMID: 37322408 DOI: 10.1186/s12885-023-11001-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 05/24/2023] [Indexed: 06/17/2023] Open
Abstract
Polymerase I and transcript release factor (PTRF) plays a role in the regulation of gene expression and the release of RNA transcripts during transcription, which have been associated with various human diseases. However, the role of PTRF in glioma remains unclear. In this study, RNA sequencing (RNA-seq) data (n = 1022 cases) and whole-exome sequencing (WES) data (n = 286 cases) were used to characterize the PTRF expression features. Gene ontology (GO) functional enrichment analysis was used to assess the biological implication of changes in PTRF expression. As a result, the expression of PTRF was associated with malignant progression in gliomas. Meanwhile, somatic mutational profiles and copy number variations (CNV) revealed the glioma subtypes classified by PTRF expression showed distinct genomic alteration. Furthermore, GO functional enrichment analysis suggested that PTRF expression was associated with cell migration and angiogenesis, particularly during an immune response. Survival analysis confirmed that a high expression of PTRF is associated with a poor prognosis. In summary, PTRF may be a valuable factor for the diagnosis and treatment target of glioma.
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Affiliation(s)
- Si Sun
- Beijing Neurosurgical Institute, Capital Medical University, Beijing, 100070, China
- Department of Neurosurgery, Beijing Tongren Hospital, Capital Medical University, Beijing, 100730, China
| | - Changlin Yang
- Beijing Neurosurgical Institute, Capital Medical University, Beijing, 100070, China
| | - Kuanyu Wang
- Beijing Neurosurgical Institute, Capital Medical University, Beijing, 100070, China
| | - Ruoyu Huang
- Beijing Neurosurgical Institute, Capital Medical University, Beijing, 100070, China
| | - Ke-Nan Zhang
- Beijing Neurosurgical Institute, Capital Medical University, Beijing, 100070, China
| | - Yanwei Liu
- Department of Radiotherapy, Beijing Tiantan Hospital, Capital Medical University, Beijing, 100070, China
| | - Zhi Cao
- Department of Neurosurgery, The Fourth Affiliated Hospital of China Medical University, Shenyang, 110032, China.
| | - Zheng Zhao
- Beijing Neurosurgical Institute, Capital Medical University, Beijing, 100070, China.
- Chinese Glioma Genome Atlas Network and Asian Glioma Genome Atlas Network, Beijing, 100070, China.
| | - Tao Jiang
- Beijing Neurosurgical Institute, Capital Medical University, Beijing, 100070, China.
- Chinese Glioma Genome Atlas Network and Asian Glioma Genome Atlas Network, Beijing, 100070, China.
- Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing, 100070, China.
- Center of Brain Tumor, Beijing Institute for Brain Disorders, Beijing, 100069, China.
- China National Clinical Research Center for Neurological Diseases, Beijing, 100070, China.
- Research Unit of Accurate Diagnosis, Treatment, and Translational Medicine of Brain Tumors, Chinese Academy of Medical Sciences, Beijing, 100070, China.
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Enyong EN, Gurley JM, De Ieso ML, Stamer WD, Elliott MH. Caveolar and non-Caveolar Caveolin-1 in ocular homeostasis and disease. Prog Retin Eye Res 2022; 91:101094. [PMID: 35729002 PMCID: PMC9669151 DOI: 10.1016/j.preteyeres.2022.101094] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 06/03/2022] [Accepted: 06/10/2022] [Indexed: 11/17/2022]
Abstract
Caveolae, specialized plasma membrane invaginations present in most cell types, play important roles in multiple cellular processes including cell signaling, lipid uptake and metabolism, endocytosis and mechanotransduction. They are found in almost all cell types but most abundant in endothelial cells, adipocytes and fibroblasts. Caveolin-1 (Cav1), the signature structural protein of caveolae was the first protein associated with caveolae, and in association with Cavin1/PTRF is required for caveolae formation. Genetic ablation of either Cav1 or Cavin1/PTRF downregulates expression of the other resulting in loss of caveolae. Studies using Cav1-deficient mouse models have implicated caveolae with human diseases such as cardiomyopathies, lipodystrophies, diabetes and muscular dystrophies. While caveolins and caveolae are extensively studied in extra-ocular settings, their contributions to ocular function and disease pathogenesis are just beginning to be appreciated. Several putative caveolin/caveolae functions are relevant to the eye and Cav1 is highly expressed in retinal vascular and choroidal endothelium, Müller glia, the retinal pigment epithelium (RPE), and the Schlemm's canal endothelium and trabecular meshwork cells. Variants at the CAV1/2 gene locus are associated with risk of primary open angle glaucoma and the high risk HTRA1 variant for age-related macular degeneration is thought to exert its effect through regulation of Cav1 expression. Caveolins also play important roles in modulating retinal neuroinflammation and blood retinal barrier permeability. In this article, we describe the current state of caveolin/caveolae research in the context of ocular function and pathophysiology. Finally, we discuss new evidence showing that retinal Cav1 exists and functions outside caveolae.
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Affiliation(s)
- Eric N Enyong
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Ophthalmology, Dean A. McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Jami M Gurley
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Ophthalmology, Dean A. McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Michael L De Ieso
- Department of Ophthalmology, Duke Eye Center, Duke University, Durham, NC, USA
| | - W Daniel Stamer
- Department of Ophthalmology, Duke Eye Center, Duke University, Durham, NC, USA
| | - Michael H Elliott
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Ophthalmology, Dean A. McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
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Huang W, Hong Y, He W, Jiang L, Deng W, Peng B, Tang F, Shen C, Lan Q, Huang H, Zhong H, Lv J, Zeng S, Li M, OuYang Y, Liang J, Mo Z, Chen Q, Cui L, Zhang M, Xu F, Zhou Z. Cavin-1 promotes M2 macrophages/microglia polarization via SOCS3. Inflamm Res 2022; 71:397-407. [PMID: 35275225 DOI: 10.1007/s00011-022-01550-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 02/13/2022] [Accepted: 02/17/2022] [Indexed: 11/27/2022] Open
Abstract
PURPOSE Our study aimed to investigate the function of Cavin-1 and SOCS3 in macrophages/microglia M2 polarization and further explored the relevant mechanism. METHODS Expression levels of Cavin-1 and SOCS3 in macrophages/microglia were measured by western blotting and RT-PCR, respectively. Then, Cavin-1 or SOCS3 was gene silenced by a siRNA approach, and gene silencing efficiency was determined by western blotting. Next, co-immunoprecipitation (Co-IP) was employed to further analyze the interaction between Cavin-1 and SOCS3. Finally, the activation of STAT6/PPAR-γ signaling was evaluated using western blotting, and the M2 macrophages/microglia polarization was validated by measuring the mRNA expression of M2 markers by RT-PCR. RESULTS In the polarization process of macrophages/microglia to M2 phenotype, both Cavin-1 and SOCS3 increased synchronously at protein and mRNA level, reached the peak at the 6 h, and then decreased. After Cavin-1 or SOCS3 silencing, the expression of Cavin-1 and SOCS3 declined. These results suggested that Cavin-1 and SOCS3 were positively correlated in macrophages/microglia, and this conjecture was verified by Co-IP. Besides, Cavin-1 silencing not only suppressed the activation of STAT6/PPAR-γ pathway, but also suppressed the release of anti-inflammatory factors. Finally, we found that SOCS3 overexpression reversed the inhibitory effect of Cavin-1 silencing on the release of anti-inflammatory factors in M2 macrophages/microglia. CONCLUSIONS Cavin-1 and SOCS3 are actively involved in the process of M2 macrophages/microglia polarization. As a SOCS3 interacting protein, Cavin-1 can promote M2 macrophages/microglia polarization via SOCS3.
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Affiliation(s)
- Wei Huang
- Guangxi Health Commission Key Laboratory of Ophthalmology and Related Systemic Diseases Artificial Intelligence Screening Technology & Research Center of Ophthalmology, Guangxi Academy of Medical Sciences & Department of Ophthalmology, The People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, 530021, China
| | - Yiyi Hong
- Guangxi Health Commission Key Laboratory of Ophthalmology and Related Systemic Diseases Artificial Intelligence Screening Technology & Research Center of Ophthalmology, Guangxi Academy of Medical Sciences & Department of Ophthalmology, The People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, 530021, China
| | - Wenjing He
- Guangxi Health Commission Key Laboratory of Ophthalmology and Related Systemic Diseases Artificial Intelligence Screening Technology & Research Center of Ophthalmology, Guangxi Academy of Medical Sciences & Department of Ophthalmology, The People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, 530021, China
| | - Li Jiang
- Guangxi Health Commission Key Laboratory of Ophthalmology and Related Systemic Diseases Artificial Intelligence Screening Technology & Research Center of Ophthalmology, Guangxi Academy of Medical Sciences & Department of Ophthalmology, The People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, 530021, China
| | - Wen Deng
- Guangxi Health Commission Key Laboratory of Ophthalmology and Related Systemic Diseases Artificial Intelligence Screening Technology & Research Center of Ophthalmology, Guangxi Academy of Medical Sciences & Department of Ophthalmology, The People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, 530021, China
| | - Biyan Peng
- Guangxi Health Commission Key Laboratory of Ophthalmology and Related Systemic Diseases Artificial Intelligence Screening Technology & Research Center of Ophthalmology, Guangxi Academy of Medical Sciences & Department of Ophthalmology, The People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, 530021, China
| | - Fen Tang
- Guangxi Health Commission Key Laboratory of Ophthalmology and Related Systemic Diseases Artificial Intelligence Screening Technology & Research Center of Ophthalmology, Guangxi Academy of Medical Sciences & Department of Ophthalmology, The People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, 530021, China
| | - Chaolan Shen
- Guangxi Health Commission Key Laboratory of Ophthalmology and Related Systemic Diseases Artificial Intelligence Screening Technology & Research Center of Ophthalmology, Guangxi Academy of Medical Sciences & Department of Ophthalmology, The People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, 530021, China
| | - Qianqian Lan
- Guangxi Health Commission Key Laboratory of Ophthalmology and Related Systemic Diseases Artificial Intelligence Screening Technology & Research Center of Ophthalmology, Guangxi Academy of Medical Sciences & Department of Ophthalmology, The People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, 530021, China
| | - Hui Huang
- Guangxi Health Commission Key Laboratory of Ophthalmology and Related Systemic Diseases Artificial Intelligence Screening Technology & Research Center of Ophthalmology, Guangxi Academy of Medical Sciences & Department of Ophthalmology, The People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, 530021, China
| | - Haibin Zhong
- Guangxi Health Commission Key Laboratory of Ophthalmology and Related Systemic Diseases Artificial Intelligence Screening Technology & Research Center of Ophthalmology, Guangxi Academy of Medical Sciences & Department of Ophthalmology, The People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, 530021, China
| | - Jian Lv
- Guangxi Health Commission Key Laboratory of Ophthalmology and Related Systemic Diseases Artificial Intelligence Screening Technology & Research Center of Ophthalmology, Guangxi Academy of Medical Sciences & Department of Ophthalmology, The People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, 530021, China
| | - Siming Zeng
- Guangxi Health Commission Key Laboratory of Ophthalmology and Related Systemic Diseases Artificial Intelligence Screening Technology & Research Center of Ophthalmology, Guangxi Academy of Medical Sciences & Department of Ophthalmology, The People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, 530021, China
| | - Min Li
- Guangxi Health Commission Key Laboratory of Ophthalmology and Related Systemic Diseases Artificial Intelligence Screening Technology & Research Center of Ophthalmology, Guangxi Academy of Medical Sciences & Department of Ophthalmology, The People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, 530021, China
| | - Yiqiang OuYang
- Laboratory Animal Center, Guangxi Medical University, Nanning, 530021, China
| | - Jinning Liang
- Laboratory Animal Center, Guangxi Medical University, Nanning, 530021, China
| | - Zhongxiang Mo
- Laboratory Animal Center, Guangxi Medical University, Nanning, 530021, China
| | - Qi Chen
- Guangxi Health Commission Key Laboratory of Ophthalmology and Related Systemic Diseases Artificial Intelligence Screening Technology & Research Center of Ophthalmology, Guangxi Academy of Medical Sciences & Department of Ophthalmology, The People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, 530021, China
| | - Ling Cui
- Guangxi Health Commission Key Laboratory of Ophthalmology and Related Systemic Diseases Artificial Intelligence Screening Technology & Research Center of Ophthalmology, Guangxi Academy of Medical Sciences & Department of Ophthalmology, The People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, 530021, China
| | - Mingyuan Zhang
- Guangxi Health Commission Key Laboratory of Ophthalmology and Related Systemic Diseases Artificial Intelligence Screening Technology & Research Center of Ophthalmology, Guangxi Academy of Medical Sciences & Department of Ophthalmology, The People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, 530021, China
| | - Fan Xu
- Guangxi Health Commission Key Laboratory of Ophthalmology and Related Systemic Diseases Artificial Intelligence Screening Technology & Research Center of Ophthalmology, Guangxi Academy of Medical Sciences & Department of Ophthalmology, The People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, 530021, China.
| | - Zhou Zhou
- Guangxi Health Commission Key Laboratory of Ophthalmology and Related Systemic Diseases Artificial Intelligence Screening Technology & Research Center of Ophthalmology, Guangxi Academy of Medical Sciences & Department of Ophthalmology, The People's Hospital of Guangxi Zhuang Autonomous Region, Nanning, 530021, China.
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Dwyer K, Agarwal N, Pile L, Ansari A. Gene Architecture Facilitates Intron-Mediated Enhancement of Transcription. Front Mol Biosci 2021; 8:669004. [PMID: 33968994 PMCID: PMC8097089 DOI: 10.3389/fmolb.2021.669004] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Accepted: 03/31/2021] [Indexed: 12/28/2022] Open
Abstract
Introns impact several vital aspects of eukaryotic organisms like proteomic plasticity, genomic stability, stress response and gene expression. A role for introns in the regulation of gene expression at the level of transcription has been known for more than thirty years. The molecular basis underlying the phenomenon, however, is still not entirely clear. An important clue came from studies performed in budding yeast that indicate that the presence of an intron within a gene results in formation of a multi-looped gene architecture. When looping is defective, these interactions are abolished, and there is no enhancement of transcription despite normal splicing. In this review, we highlight several potential mechanisms through which looping interactions may enhance transcription. The promoter-5′ splice site interaction can facilitate initiation of transcription, the terminator-3′ splice site interaction can enable efficient termination of transcription, while the promoter-terminator interaction can enhance promoter directionality and expedite reinitiation of transcription. Like yeast, mammalian genes also exhibit an intragenic interaction of the promoter with the gene body, especially exons. Such promoter-exon interactions may be responsible for splicing-dependent transcriptional regulation. Thus, the splicing-facilitated changes in gene architecture may play a critical role in regulation of transcription in yeast as well as in higher eukaryotes.
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Affiliation(s)
- Katherine Dwyer
- Department of Biological Science, Wayne State University, Detroit, MI, United States
| | - Neha Agarwal
- Department of Biological Science, Wayne State University, Detroit, MI, United States
| | - Lori Pile
- Department of Biological Science, Wayne State University, Detroit, MI, United States
| | - Athar Ansari
- Department of Biological Science, Wayne State University, Detroit, MI, United States
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Abstract
Caveolae are specialised and dynamic plasma membrane subdomains, involved in many cellular functions including endocytosis, signal transduction, mechanosensing and lipid storage, trafficking, and metabolism. Two protein families are indispensable for caveola formation and function, namely caveolins and cavins. Mutations of genes encoding these caveolar proteins cause serious pathological conditions such as cardiomyopathies, skeletal muscle diseases, and lipodystrophies. Deregulation of caveola-forming protein expression is associated with many types of cancers including prostate cancer. The distinct function of secretion of the prostatic fluid, and the unique metabolic phenotype of prostate cells relying on lipid metabolism as a main bioenergetic pathway further suggest a significant role of caveolae and caveolar proteins in prostate malignancy. Accumulating in vitro, in vivo, and clinical evidence showed the association of caveolin-1 with prostate cancer grade, stage, metastasis, and drug resistance. In contrast, cavin-1 was found to exhibit tumour suppressive roles. Studies on prostate cancer were the first to show the distinct function of the caveolar proteins depending on their localisation within the caveolar compartment or as cytoplasmic or secreted proteins. In this review, we summarise the roles of caveola-forming proteins in prostate cancer and the potential of exploiting them as therapeutic targets or biological markers.
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Hotz PW, Wiesnet M, Tascher G, Braun T, Müller S, Mendler L. Profiling the Murine SUMO Proteome in Response to Cardiac Ischemia and Reperfusion Injury. Molecules 2020; 25:E5571. [PMID: 33260959 PMCID: PMC7731038 DOI: 10.3390/molecules25235571] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Revised: 11/20/2020] [Accepted: 11/24/2020] [Indexed: 01/31/2023] Open
Abstract
SUMOylation is a reversible posttranslational modification pathway catalyzing the conjugation of small ubiquitin-related modifier (SUMO) proteins to lysine residues of distinct target proteins. SUMOylation modifies a wide variety of cellular regulators thereby affecting a multitude of key processes in a highly dynamic manner. The SUMOylation pathway displays a hallmark in cellular stress-adaption, such as heat or redox stress. It has been proposed that enhanced cellular SUMOylation protects the brain during ischemia, however, little is known about the specific regulation of the SUMO system and the potential target proteins during cardiac ischemia and reperfusion injury (I/R). By applying left anterior descending (LAD) coronary artery ligation and reperfusion in mice, we detect dynamic changes in the overall cellular SUMOylation pattern correlating with decreased SUMO deconjugase activity during I/R injury. Further, unbiased system-wide quantitative SUMO-proteomics identified a sub-group of SUMO targets exhibiting significant alterations in response to cardiac I/R. Notably, transcription factors that control hypoxia- and angiogenesis-related gene expression programs, exhibit altered SUMOylation during ischemic stress adaptation. Moreover, several components of the ubiquitin proteasome system undergo dynamic changes in SUMO conjugation during cardiac I/R suggesting an involvement of SUMO signaling in protein quality control and proteostasis in the ischemic heart. Altogether, our study reveals regulated candidate SUMO target proteins in the mouse heart, which might be important in coping with hypoxic/proteotoxic stress during cardiac I/R injury.
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Affiliation(s)
- Paul W. Hotz
- Institute of Biochemistry II, Goethe University Medical School, University Hospital Building 75, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany; (P.W.H.); (G.T.)
| | - Marion Wiesnet
- Department of Cardiac Development and Remodeling, Max Planck Institute for Heart and Lung Research, Ludwigstrasse 43, 61231 Bad Nauheim, Germany; (M.W.); (T.B.)
| | - Georg Tascher
- Institute of Biochemistry II, Goethe University Medical School, University Hospital Building 75, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany; (P.W.H.); (G.T.)
| | - Thomas Braun
- Department of Cardiac Development and Remodeling, Max Planck Institute for Heart and Lung Research, Ludwigstrasse 43, 61231 Bad Nauheim, Germany; (M.W.); (T.B.)
| | - Stefan Müller
- Institute of Biochemistry II, Goethe University Medical School, University Hospital Building 75, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany; (P.W.H.); (G.T.)
| | - Luca Mendler
- Institute of Biochemistry II, Goethe University Medical School, University Hospital Building 75, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany; (P.W.H.); (G.T.)
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8
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Lessons from cavin-1 deficiency. Biochem Soc Trans 2020; 48:147-154. [PMID: 31922193 DOI: 10.1042/bst20190380] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Revised: 12/12/2019] [Accepted: 12/18/2019] [Indexed: 01/19/2023]
Abstract
Caveolae have been implicated in a wide range of critical physiological functions. In the past decade, the dominant role of cavin-1 in caveolae formation has been established, and it has been recognized as another master regulator for caveolae biology. Human patients with cavin-1 mutations develop lipodystrophy and muscular dystrophy and have some major pathological dysfunctions in fat tissue, skeleton muscle, heart, lung and other organs. Cavin-1 deficiency animal models consistently show similar phenotypes. However, the underlying molecular mechanisms remain to be elucidated. Recent studies have suggested many possible pathways, including mechanosensing, stress response, signal transduction, exosome secretion, and potential functions in the nucleus. Many excellent and comprehensive review articles already exist on the topics of caveolae structure formation, caveolins, and their pathophysiological functions. We will focus on recent studies using cavin-1 deficiency models, to summarize the pathophysiological changes in adipose, muscle, and other organs, followed by a summary of mechanistic studies about the roles of cavin-1, which includes caveolae formation, ribosomal RNA transcription, mechanical sensing, stress response, and exosome secretion. Further studies may help to elucidate the exact underlying molecular mechanism to explain the pathological changes observed in cavin-1 deficient human patients and animal models, so potential new therapeutic strategies can be developed.
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Hochreuter MY, Altıntaş A, Garde C, Emanuelli B, Kahn CR, Zierath JR, Vienberg S, Barrès R. Identification of two microRNA nodes as potential cooperative modulators of liver metabolism. Hepatol Res 2019; 49:1451-1465. [PMID: 31408567 PMCID: PMC6972499 DOI: 10.1111/hepr.13419] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 07/03/2019] [Accepted: 07/02/2019] [Indexed: 12/19/2022]
Abstract
AIM Hepatic insulin resistance is a hallmark of type 2 diabetes and non-alcoholic fatty liver disease. Dysregulation of microRNA (miRNA) expression in insulin-resistant livers might coordinate impaired hepatic metabolic function. Here, we aimed to discover miRNAs and their downstream targets involved in hepatic insulin resistance. METHODS We determined miRNA expression profiles by small RNA sequencing of two mouse models of impaired hepatic insulin action: high-fat diet-induced obesity and liver-specific insulin receptor knockout. Conversely, we assessed the hepatic miRNA expression profile after treatment with the antidiabetic hormone, fibroblast growth factor 21 (FGF21). Ontology analysis of predicted miRNA gene targets was performed to identify regulated gene pathways. Target enrichment analysis and miRNA mimic overexpression in vitro were used to identify unified protein targets of nodes of regulated miRNAs. RESULTS We identified an array of miRNA species regulated by impaired liver insulin action or after fibroblast growth factor 21 treatment. Ontology analysis of predicted miRNA gene targets identified pathways controlling hepatic energy metabolism and insulin sensitivity. We identified a node of two miRNAs downregulated in the livers of liver-specific insulin receptor knockout mice, miR-883b and miR-205, which positively regulate the expression of transcription factor zinc finger E-box-binding homeobox 1 (ZBED1). We found another node of two miRNAs upregulated in the livers of fibroblast growth factor 21-treated mice, miR-155-3p and miR-1968-5p, which canonically downregulates the caveola component, polymerase I and transcript release factor (PTRF), a gene previously implicated in hepatic energy metabolism. CONCLUSIONS This study identifies two nodes of coregulated miRNAs that might coordinately control hepatic energy metabolism in states of insulin resistance.
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Affiliation(s)
- Mette Yde Hochreuter
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Ali Altıntaş
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Christian Garde
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - Brice Emanuelli
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
| | - C. Ronald Kahn
- Section of Integrative Physiology and MetabolismJoslin Diabetes Center and Harvard Medical SchoolBostonMassachusettsUSA
| | - Juleen R. Zierath
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark,Department of Molecular Medicine and SurgeryKarolinska InstitutetStockholmSweden,Department of Physiology and PharmacologyKarolinska InstitutetStockholmSweden
| | | | - Romain Barrès
- Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical SciencesUniversity of CopenhagenCopenhagenDenmark
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10
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Wang H, Pilch PF, Liu L. Cavin-1/PTRF mediates insulin-dependent focal adhesion remodeling and ameliorates high-fat diet-induced inflammatory responses in mice. J Biol Chem 2019; 294:10544-10552. [PMID: 31126986 DOI: 10.1074/jbc.ra119.008824] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Revised: 05/20/2019] [Indexed: 11/06/2022] Open
Abstract
Cavin-1/polymerase I and transcript release factor (PTRF) is a requisite component of caveolae, small plasma membrane invaginations that are highly abundant in adipocytes. Cavin-1 is a dynamic molecule whose dissociation from caveolae plays an important role in mechanoprotection and rRNA synthesis. In the former situation, the acute dissociation of cavin-1 from caveolae allows cell membrane expansion that occurs upon insulin-aided lipid uptake into the fat cells. Cavin-1 dissociation from caveolae and membrane flattening alters the cytoskeleton and the interaction of plasma membrane proteins with the extracellular matrix through interactions with focal adhesion structures. Here, using cavin-1 knockout mice, subcellular fractionation, and immunoblotting methods, we addressed the relationship of cavin-1 with focal adhesion complexes following nutritional stimulation. We found that cavin-1 is acutely translocated to focal complex compartments upon insulin stimulation, where it regulates focal complex formation through an interaction with paxillin. We found that loss of cavin-1 impairs focal complex remodeling and focal adhesion formation and causes a mechanical stress response, concomitant with activation of proinflammatory and senescence/apoptosis pathways. We conclude that cavin-1 plays key roles in dynamic remodeling of focal complexes upon metabolic stimulation. This mechanism also underlies the crucial role of caveolae in the long-term healthy expansion of the adipocyte.
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Affiliation(s)
- Hong Wang
- From the Departments of Biochemistry
| | - Paul F Pilch
- From the Departments of Biochemistry.,Medicine, and
| | - Libin Liu
- From the Departments of Biochemistry, .,Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, Massachusetts 02118
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11
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Abstract
The plasma membrane of eukaryotic cells is not a simple sheet of lipids and proteins but is differentiated into subdomains with crucial functions. Caveolae, small pits in the plasma membrane, are the most abundant surface subdomains of many mammalian cells. The cellular functions of caveolae have long remained obscure, but a new molecular understanding of caveola formation has led to insights into their workings. Caveolae are formed by the coordinated action of a number of lipid-interacting proteins to produce a microdomain with a specific structure and lipid composition. Caveolae can bud from the plasma membrane to form an endocytic vesicle or can flatten into the membrane to help cells withstand mechanical stress. The role of caveolae as mechanoprotective and signal transduction elements is reviewed in the context of disease conditions associated with caveola dysfunction.
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Affiliation(s)
- Robert G. Parton
- Institute for Molecular Bioscience and Centre for Microscopy and Microanalysis, University of Queensland, Brisbane, Queensland 4060, Australia
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12
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Li Q, Bai L, Shi G, Zhang L, Dai Y, Liu P, Cong YS, Wang M. Ptrf
transgenic mice exhibit obesity and fatty liver. Clin Exp Pharmacol Physiol 2018; 45:704-710. [DOI: 10.1111/1440-1681.12920] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Revised: 01/16/2018] [Accepted: 01/18/2018] [Indexed: 12/16/2022]
Affiliation(s)
- Qian Li
- Institute of Aging Research; Hangzhou Normal University School of Medicine; Hangzhou China
| | - Lin Bai
- Key Laboratory of Human Disease Comparative Medicine of the Ministry of Health; Institute of Laboratory Animal Science; Chinese Academy of Medical Sciences and Comparative Medical Center; Peking Union Medical College; Beijing China
| | - Guiying Shi
- Key Laboratory of Human Disease Comparative Medicine of the Ministry of Health; Institute of Laboratory Animal Science; Chinese Academy of Medical Sciences and Comparative Medical Center; Peking Union Medical College; Beijing China
| | - Lianfeng Zhang
- Key Laboratory of Human Disease Comparative Medicine of the Ministry of Health; Institute of Laboratory Animal Science; Chinese Academy of Medical Sciences and Comparative Medical Center; Peking Union Medical College; Beijing China
| | - Yifan Dai
- Center of Metabolic Disease Research; Nanjing Medical University; Nanjing China
| | - Pingsheng Liu
- National Laboratory of Biomacromolecules; Institute of Biophysics; Chinese Academy of Sciences; Beijing China
| | - Yu-Sheng Cong
- Institute of Aging Research; Hangzhou Normal University School of Medicine; Hangzhou China
| | - Miao Wang
- Institute of Aging Research; Hangzhou Normal University School of Medicine; Hangzhou China
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13
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Liu L, Pilch PF. PTRF/Cavin-1 promotes efficient ribosomal RNA transcription in response to metabolic challenges. eLife 2016; 5. [PMID: 27528195 PMCID: PMC4987143 DOI: 10.7554/elife.17508] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 07/18/2016] [Indexed: 01/25/2023] Open
Abstract
Ribosomal RNA transcription mediated by RNA polymerase I represents the rate-limiting step in ribosome biogenesis. In eukaryotic cells, nutrients and growth factors regulate ribosomal RNA transcription through various key factors coupled to cell growth. We show here in mature adipocytes, ribosomal transcription can be acutely regulated in response to metabolic challenges. This acute response is mediated by PTRF (polymerase I transcription and release factor, also known as cavin-1), which has previously been shown to play a critical role in caveolae formation. The caveolae–independent rDNA transcriptional role of PTRF not only explains the lipodystrophy phenotype observed in PTRF deficient mice and humans, but also highlights its crucial physiological role in maintaining adipocyte allostasis. Multiple post-translational modifications of PTRF provide mechanistic bases for its regulation. The role of PTRF in ribosomal transcriptional efficiency is likely relevant to many additional physiological situations of cell growth and organismal metabolism. DOI:http://dx.doi.org/10.7554/eLife.17508.001 Obesity can cause several other health conditions to develop. Type 2 diabetes is one such condition, which arises in part because fat cells become unable to store excess fats. This makes certain tissues in the body less sensitive to the hormone insulin, and so the individual is less able to adapt to changing nutrient levels. Without treatment or a change in lifestyle, this insulin resistance may develop into diabetes. However, “healthy obese” individuals also exist, who can accommodate an overabundance of fat without developing insulin resistance and diabetes. Some forms of rare genetic disorders called lipodystrophies, which result in an almost complete lack of body fat, can also lead to type 2 diabetes. This raises the question of whether lipodystrophy and obesity share some common mechanisms that cause fat cells to trigger insulin resistance. One possible player in such mechanisms is a protein called PTRF. In rare cases, individuals with lipodystrophy lack this protein, and mice that have been engineered to lack PTRF also largely lack body fat and develop insulin resistance. Fat cells can respond rapidly to changes in nutrients during feeding or fasting, and to do so, they must produce new proteins. Structures called ribosomes, which are made up of proteins and ribosomal RNA, build proteins; thus when the cell needs to make new proteins, it also has to produce more ribosomes. PTRF is thought to play a role in ribosome production, but it is not clear how it does so. Liu and Pilch analyzed normal mice as well as those that lacked the PTRF protein. This revealed that in response to cycles of fasting and feeding, PTRF increases the production of ribosomal RNA in fat cells, enabling the cells to produce more proteins. By contrast, the fat cells of mice that lack PTRF have much lower levels of ribosomal RNA and proteins. Liu and Pilch then examined mouse fat cells that were grown in the laboratory. Exposing these cells to insulin caused phosphate groups to be attached to the PTRF proteins inside the cells. This modification caused PTRF to move into the cell’s nucleus, where it increased the production of ribosomal RNA. Overall, the results show that fat cells that lack PTRF are unable to produce the proteins that they need to deal with changing nutrient levels, leading to an increased likelihood of diabetes. The next steps are to investigate the mechanism by which PTRF is modified, and to see whether the mechanisms uncovered in this study also apply to humans. DOI:http://dx.doi.org/10.7554/eLife.17508.002
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Affiliation(s)
- Libin Liu
- Department of Biochemistry, Boston University School of Medicine, Boston, United States
| | - Paul F Pilch
- Department of Biochemistry, Boston University School of Medicine, Boston, United States.,Department of Medicine, Boston University School of Medicine, Boston, United States
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14
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Cavin-1 and Caveolin-1 are both required to support cell proliferation, migration and anchorage-independent cell growth in rhabdomyosarcoma. J Transl Med 2015; 95:585-602. [PMID: 25822667 DOI: 10.1038/labinvest.2015.45] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 01/26/2015] [Accepted: 02/27/2015] [Indexed: 12/17/2022] Open
Abstract
Rhabdomyosarcoma (RMS) is a childhood soft tissue tumor with broad expression of markers that are typically found in skeletal muscle. Cavin-1 is a recently discovered protein actively cooperating with Caveolin-1 (Cav-1) in the morphogenesis of caveolae and whose role in cancer is drawing increasing attention. Using a combined in silico and in vitro analysis here we show that Cavin-1 is expressed in myogenic RMS tumors as well as in human and primary mouse RMS cultures, exhibiting a broad subcellular localization, ranging from nuclei and cytosol to plasma membrane. In particular, the coexpression and plasma membrane interaction between Cavin-1 and Cav-1 characterized the proliferation of human and mouse RMS cell cultures, while a downregulation of their expression levels was observed during the myogenic differentiation. Knockdown of Cavin-1 or Cav-1 in the human RD and RH30 cells led to impairment of cell proliferation and migration. Moreover, loss of Cavin-1 in RD cells impaired the anchorage-independent cell growth in soft agar. While the loss of Cavin-1 did not affect the Cav-1 protein levels in RMS cells, Cav-1 overexpression and knockdown triggered a rise or depletion of Cavin-1 protein levels in RD cells, respectively, in turn reflecting on increased or decreased cell proliferation, migration and anchorage-independent cell growth. Collectively, these data indicate that the interaction between Cavin-1 and Cav-1 underlies the cell growth and migration in myogenic tumors.
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15
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16
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Emerging role of polymerase-1 and transcript release factor (PTRF/ Cavin-1) in health and disease. Cell Tissue Res 2014; 357:505-13. [PMID: 25107607 DOI: 10.1007/s00441-014-1964-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2014] [Accepted: 07/04/2014] [Indexed: 01/06/2023]
Abstract
Polymerase-1 and release transcript factor (PTRF) was initially reported to be involved in the termination of the transcription process. More recently, it has been implicated in the formation of caveolae, cave-like structures in the plasma membrane. The effects of PTRF related to caveolae suggest that this protein may play important roles in health and disease. PTRF is highly expressed in various cells, including adipocytes, osteoblasts and muscle (cardiac, skeletal and smooth) cells. The role of PTRF in prostate cancer has been recently reviewed but there is growing evidence that PTRF is involved in other physiological processes such as cell repair and the regulation of glucose and lipid metabolism and, furthermore, altered expression of PTRF may be associated with disease. This review discusses the emerging role of PTRF in health and disease.
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17
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Ding SY, Lee MJ, Summer R, Liu L, Fried SK, Pilch PF. Pleiotropic effects of cavin-1 deficiency on lipid metabolism. J Biol Chem 2014; 289:8473-83. [PMID: 24509860 DOI: 10.1074/jbc.m113.546242] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mice and humans lacking caveolae due to gene knock-out or inactivating mutations of cavin-1/PTRF have numerous pathologies including markedly aberrant fuel metabolism, lipodystrophy, and muscular dystrophy. We characterized the physiologic/metabolic profile of cavin-1 knock-out mice and determined that they were lean because of reduced white adipose depots. The knock-out mice were resistant to diet-induced obesity and had abnormal lipid metabolism in the major metabolic organs of white and brown fat and liver. Epididymal white fat cells from cavin-1-null mice were small and insensitive to insulin and β-adrenergic agonists resulting in reduced adipocyte lipid storage and impaired lipid tolerance. At the molecular level, the lipolytic defects in white fat were caused by impaired perilipin phosphorylation, and the reduced triglyceride accumulation was caused by decreased fatty acid uptake and incorporation as well as the virtual absence of insulin-stimulated glucose transport. The livers of cavin-1-null mice were mildly steatotic and did not accumulate more lipid after high-fat feeding. The brown adipose tissues of cavin-1-null mice exhibited decreased mitochondria protein expression, which was restored upon high fat feeding. Taken together, these data suggest that dysfunction in fat, muscle, and liver metabolism in cavin-1-null mice causes a pleiotropic phenotype, one apparently identical to that of humans lacking caveolae in all tissues.
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18
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Nassar ZD, Hill MM, Parton RG, Parat MO. Caveola-forming proteins caveolin-1 and PTRF in prostate cancer. Nat Rev Urol 2013; 10:529-36. [PMID: 23938946 DOI: 10.1038/nrurol.2013.168] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The expression of caveola-forming proteins is dysregulated in prostate cancer. Caveolae are flask-shaped invaginations of the plasma membrane that have roles in membrane trafficking and cell signalling. Members of two families of proteins--caveolins and cavins--are known to be required for the formation and functions of caveolae. Caveolin-1, the major structural protein of caveolae, is overexpresssed in prostate cancer and has been demonstrated to be involved in prostate cancer angiogenesis, growth and metastasis. Polymerase I and transcript release factor (PTRF) is the only cavin family member necessary for caveola formation. When exogenously expressed in prostate cancer cells, PTRF reduces aggressive potential, probably via both caveola-mediated and caveola-independent mechanisms. In addition, stromal PTRF expression decreases with progression of the disease. Evaluation of caveolin-1 antibodies in the clinical setting is underway and it is hoped that future studies will reveal the mechanisms of PTRF action, allowing its targeting for therapeutic purposes.
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Affiliation(s)
- Zeyad D Nassar
- School of Pharmacy, The University of Queensland, 20 Cornwall Street, Woolloongabba, QLD 4102, Australia
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19
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Hamoudane M, Maffioli S, Cordera R, Maggi D, Salani B. Caveolin-1 and polymerase I and transcript release factor: new players in insulin-like growth factor-I receptor signaling. J Endocrinol Invest 2013; 36:204-8. [PMID: 23404184 DOI: 10.3275/8848] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Caveolae are plasma membrane regions enriched in Caveolin proteins which regulate vesicular transport, endocytosis, and cell signaling. IGF-I receptor (IGF-IR) localizes in caveolae and tyrosine phosphorylates Caveolin-1 (Cav-1), the most represented caveolar protein. Cav-1 participates to IGF-IR internalization and signaling directly interacting with IGF-IR and its substrates. Recently, polymerase I and transcript release factor (PTRF) or Cavin-1, has been identified in the caveolar backbone. PTRF does not play a Cav-1 ancillary role and emerging data support a direct role of PTRF in IGF-IR signaling. PTRF and Cav-1 can bind IGF-IR and regulate IGF-IR internalization and plasma membrane replacement, mechanisms frequently deregulated in cancer cells. Although the exact roles of Cav-1 and IGF-IR in human cancer continue to be a matter of some debate, there is a strong evidence for an association between Cav-1 and IGF-IR in cancer development. With the discovery of IGF-IR interaction with PTRF in caveolae, new insight emerged to understand the growing functions of these domains in IGF-I action.
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Affiliation(s)
- M Hamoudane
- Department of Internal Medicine (DiMI) University of Genoa, Genoa, Italy
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20
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Németh A, Perez-Fernandez J, Merkl P, Hamperl S, Gerber J, Griesenbeck J, Tschochner H. RNA polymerase I termination: Where is the end? BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2012; 1829:306-17. [PMID: 23092677 DOI: 10.1016/j.bbagrm.2012.10.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Revised: 10/10/2012] [Accepted: 10/17/2012] [Indexed: 01/01/2023]
Abstract
The synthesis of ribosomal RNA (rRNA) precursor molecules by RNA polymerase I (Pol I) terminates with the dissociation of the protein-DNA-RNA ternary complex. Based on in vitro results the mechanism of Pol I termination appeared initially to be rather conserved and simple until this process was more thoroughly re-investigated in vivo. A picture emerged that Pol I termination seems to be connected to co-transcriptional processing, re-initiation of transcription and, possibly, other processes downstream of Pol I transcription units. In this article, our current understanding of the mechanism of Pol I termination and how this process might be implicated in other biological processes in yeast and mammals is summarized and discussed. This article is part of a Special Issue entitled: Transcription by Odd Pols.
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Affiliation(s)
- Attila Németh
- Universität Regensburg, Biochemie-Zentrum Regensburg (BZR), Lehrstuhl Biochemie III, 93053 Regensburg, Germany.
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21
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Nassoy P, Lamaze C. Stressing caveolae new role in cell mechanics. Trends Cell Biol 2012; 22:381-9. [PMID: 22613354 DOI: 10.1016/j.tcb.2012.04.007] [Citation(s) in RCA: 103] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2012] [Revised: 04/16/2012] [Accepted: 04/18/2012] [Indexed: 01/22/2023]
Abstract
It has been almost 60 years since caveolae were first visualized by Eichi Yamada and George Palade. Nevertheless, these specialized invaginations of the plasma membrane remain without clear and recognized physiological function. The recent identification of new caveolar components and the ability to probe cell mechanics with sophisticated opticophysical devices have shed new light on this fascinating organelle. Early studies from the 1970s suggested that caveolae could participate in the regulation of membrane dynamics. Recent data have established caveolae as mechanosensors that respond immediately to mechanical stress by flattening into the plasma membrane. Here, we focus on the molecular consequences that result from the caveolar disassembly/reassembly cycle induced by membrane tension variations at the surface of the cell under physiological and pathological conditions.
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Affiliation(s)
- Pierre Nassoy
- Université P. et M. Curie/CNRS UMR168, 26 rue d'Ulm, 75248 Paris Cedex 05, France
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22
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Role for gene looping in intron-mediated enhancement of transcription. Proc Natl Acad Sci U S A 2012; 109:8505-10. [PMID: 22586116 DOI: 10.1073/pnas.1112400109] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Intron-containing genes are often transcribed more efficiently than nonintronic genes. The effect of introns on transcription of genes is an evolutionarily conserved feature, being exhibited by such diverse organisms as yeast, plants, flies, and mammals. The mechanism of intron-mediated transcriptional activation, however, is not entirely clear. To address this issue, we inserted an intron in INO1, which is a nonintronic gene, and deleted the intron from ASC1, which contains a natural intron. We then compared transcription of INO1 and ASC1 genes in the presence and absence of an intron. Transcription of both genes was significantly stimulated by the intron. The introns have a direct role in enhancing transcription of INO1 and ASC1 because there was a marked increase in nascent transcripts from these genes in the presence of an intron. Intron-mediated enhancement of transcription required a splicing competent intron. Interestingly, both INO1 and ASC1 were in a looped configuration when their genes contained an intron. Intron-dependent gene looping involved a physical interaction of the promoter and the terminator regions. In addition, the promoter region interacted with the 5' splice site and the terminator with the 3' splice site. Intron-mediated enhancement of transcription was completely abolished in the looping defective sua7-1 strain. No effect on splicing, however, was observed in sua7-1 strain. On the basis of these results, we propose a role for gene looping in intron-mediated transcriptional activation of genes in yeast.
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23
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Comprehensive proteomic analysis of influenza virus polymerase complex reveals a novel association with mitochondrial proteins and RNA polymerase accessory factors. J Virol 2011; 85:8569-81. [PMID: 21715506 DOI: 10.1128/jvi.00496-11] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The trimeric RNA polymerase complex (3P, for PA-PB1-PB2) of influenza A virus (IAV) is an important viral determinant of pathogenicity and host range restriction. Specific interactions of the polymerase complex with host proteins may be determining factors in both of these characteristics and play important roles in the viral life cycle. To investigate this question, we performed a comprehensive proteomic analysis of human host proteins associated with the polymerase of the well-characterized H5N1 Vietnam/1203/04 isolate. We identified over 400 proteins by liquid chromatography-tandem mass spectrometry (LC-MS/MS), of which over 300 were found to bind to the PA subunit alone. The most intriguing and novel finding was the large number of mitochondrial proteins (∼20%) that associated with the PA subunit. These proteins mediate molecular transport across the mitochondrial membrane or regulate membrane potential and may in concert with the identified mitochondrion-associated apoptosis inducing factor (AIFM1) have roles in the induction of apoptosis upon association with PA. Additionally, we identified host factors that associated with the PA-PB1 (68 proteins) and/or the 3P complex (34 proteins) including proteins that have roles in innate antiviral signaling (e.g., ZAPS or HaxI) or are cellular RNA polymerase accessory factors (e.g., polymerase I transcript release factor [PTRF] or Supt5H). IAV strain-specific host factor binding to the polymerase was not observed in our analysis. Overall, this study has shed light into the complex contributions of the IAV polymerase to host cell pathogenicity and allows for direct investigations into the biological significance of these newly described interactions.
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Sinha B, Köster D, Ruez R, Gonnord P, Bastiani M, Abankwa D, Stan RV, Butler-Browne G, Vedie B, Johannes L, Morone N, Parton RG, Raposo G, Sens P, Lamaze C, Nassoy P. Cells respond to mechanical stress by rapid disassembly of caveolae. Cell 2011; 144:402-13. [PMID: 21295700 DOI: 10.1016/j.cell.2010.12.031] [Citation(s) in RCA: 645] [Impact Index Per Article: 49.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2010] [Revised: 10/27/2010] [Accepted: 12/23/2010] [Indexed: 12/15/2022]
Abstract
The functions of caveolae, the characteristic plasma membrane invaginations, remain debated. Their abundance in cells experiencing mechanical stress led us to investigate their role in membrane-mediated mechanical response. Acute mechanical stress induced by osmotic swelling or by uniaxial stretching results in a rapid disappearance of caveolae, in a reduced caveolin/Cavin1 interaction, and in an increase of free caveolins at the plasma membrane. Tether-pulling force measurements in cells and in plasma membrane spheres demonstrate that caveola flattening and disassembly is the primary actin- and ATP-independent cell response that buffers membrane tension surges during mechanical stress. Conversely, stress release leads to complete caveola reassembly in an actin- and ATP-dependent process. The absence of a functional caveola reservoir in myotubes from muscular dystrophic patients enhanced membrane fragility under mechanical stress. Our findings support a new role for caveolae as a physiological membrane reservoir that quickly accommodates sudden and acute mechanical stresses.
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25
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26
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Rodríguez-Sánchez L, Rodríguez-López M, García Z, Tenorio-Gómez M, Schvartzman JB, Krimer DB, Hernández P. The fission yeast rDNA-binding protein Reb1 regulates G1 phase under nutritional stress. J Cell Sci 2010; 124:25-34. [PMID: 21118960 DOI: 10.1242/jcs.070987] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Yeast Reb1 and its mammalian ortholog TTF1 are conserved Myb-type DNA-binding proteins that bind to specific sites near the 3'-end of rRNA genes (rDNA). Here, they participate in the termination of transcription driven by RNA polymerase I and block DNA replication forks approaching in the opposite direction. We found that Schizosaccharomyces pombe Reb1 also upregulates transcription of the ste9(+) gene that is required for nitrogen-starvation-induced growth arrest with a G1 DNA content and sexual differentiation. Ste9 activates the anaphase-promoting complex or cyclosome ('APC/C') in G1, targeting B-cyclin for proteasomal degradation in response to nutritional stress. Reb1 binds in vivo and in vitro to a specific DNA sequence at the promoter of ste9(+), similar to the sequence recognized in the rDNA, and this binding is required for ste9(+) transcriptional activation and G1 arrest. This suggests that Reb1 acts as a link between rDNA metabolism and cell cycle control in response to nutritional stress. In agreement with this new role for Reb1 in the regulation of the G1-S transition, reb1Δ and wee1(ts) mutations are synthetically lethal owing to the inability of these cells to lengthen G1 before entering S phase. Similarly, reb1Δ cdc10(ts) cells are unable to arrest in G1 and die at the semi-permissive temperature.
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Affiliation(s)
- Leonor Rodríguez-Sánchez
- Department of Cell Proliferation and Development, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, Ramiro de Maeztu 9, 28040 Madrid, Spain
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27
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Briand N, Dugail I, Le Lay S. Cavin proteins: New players in the caveolae field. Biochimie 2010; 93:71-7. [PMID: 20363285 DOI: 10.1016/j.biochi.2010.03.022] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2010] [Accepted: 03/29/2010] [Indexed: 12/16/2022]
Abstract
Caveolae are specialized lipid microdomains, forming small invaginations in the plasma membrane, known to be implicated in multiple functions including lipid storage, cell signaling and endocytosis. Formation of these wide flask-shaped invaginations is dependent on the expression of a caveolar coat protein, namely caveolin. Until now, the accepted paradigm was that caveolin was the sole and only structural protein of caveolae since its expression was necessary and sufficient to drive caveolae biogenesis. The recent characterizations of PTRF/cavin-1 and subsequently other cavin family members in caveolae formation have highlighted additional levels of complexity in the biogenesis of these plasma membrane invaginations. In this review, recent advances on the role of the different cavin family members in the regulation of caveolae structures as well as potential new functions will be discussed.
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Affiliation(s)
- Nolwenn Briand
- Centre de Recherche des Cordeliers, INSERM, U872, 15 rue de l'école de médecine, Paris F-75006, France
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28
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Hansen CG, Nichols BJ. Exploring the caves: cavins, caveolins and caveolae. Trends Cell Biol 2010; 20:177-86. [PMID: 20153650 DOI: 10.1016/j.tcb.2010.01.005] [Citation(s) in RCA: 222] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2009] [Revised: 01/07/2010] [Accepted: 01/11/2010] [Indexed: 01/29/2023]
Abstract
Caveolae are ampullate (flask-shaped) invaginations that are abundant in the plasma membrane of many mammalian cell types. Although caveolae are implicated in a wide range of processes including endothelial transcytosis, lipid homeostasis and cellular signalling, a detailed molecular picture of many aspects of their function has been elusive. Until recently, the only extensively characterised protein components of caveolae were the caveolins. Recently, data from several laboratories have demonstrated that a family of four related proteins, termed cavins 1-4, plays key roles in caveolar biogenesis and function. Salient properties of the cavin family include their propensity to form complexes with each other and their different but overlapping tissue distribution. This review summarises recent data on the cavins, and sets them in the context of open questions on the construction and function of caveolae. The discovery of cavins implies that caveolae might have unexpectedly diverse structural properties, in accord with the wide range of functions attributed to these 'little caves'.
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El Kaderi B, Medler S, Raghunayakula S, Ansari A. Gene looping is conferred by activator-dependent interaction of transcription initiation and termination machineries. J Biol Chem 2009; 284:25015-25. [PMID: 19602510 DOI: 10.1074/jbc.m109.007948] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Gene looping juxtaposes the promoter and terminator regions of RNA polymerase II-transcribed genes in yeast and mammalian cells. Here we report an activator-dependent interaction of transcription initiation and termination factors during gene looping in budding yeast. Chromatin analysis revealed that MET16, INO1, and GAL1p-BUD3 are in a stable looped configuration during activated transcription. Looping was nearly abolished in the absence of transcription activators Met28, Ino2, and Gal4 of MET16, INO1, and GAL1p-BUD3 genes, respectively. The activator-independent increase in transcription was not accompanied by loop formation, thereby suggesting an essential role for activators in gene looping. The activators did not facilitate loop formation directly because they did not exhibit an interaction with the 3' end of the genes. Instead, activators physically interacted with the general transcription factor TFIIB when the genes were activated and in a looped configuration. TFIIB cross-linked to both the promoter and the terminator regions during the transcriptionally activated state of a gene. The presence of TFIIB on the terminator was dependent on the Rna15 component of CF1 3' end processing complex. Coimmunoprecipitation revealed a physical interaction of Rna15 with TFIIB. We propose that the activators facilitate gene looping through their interaction with TFIIB during transcriptional activation of genes.
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Affiliation(s)
- Belal El Kaderi
- Department of Biological Science, Wayne State University, Detroit, Michigan 48202, USA
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30
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Bastiani M, Liu L, Hill MM, Jedrychowski MP, Nixon SJ, Lo HP, Abankwa D, Luetterforst R, Fernandez-Rojo M, Breen MR, Gygi SP, Vinten J, Walser PJ, North KN, Hancock JF, Pilch PF, Parton RG. MURC/Cavin-4 and cavin family members form tissue-specific caveolar complexes. ACTA ACUST UNITED AC 2009; 185:1259-73. [PMID: 19546242 PMCID: PMC2712963 DOI: 10.1083/jcb.200903053] [Citation(s) in RCA: 211] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Polymerase I and transcript release factor (PTRF)/Cavin is a cytoplasmic protein whose expression is obligatory for caveola formation. Using biochemistry and fluorescence resonance energy transfer–based approaches, we now show that a family of related proteins, PTRF/Cavin-1, serum deprivation response (SDR)/Cavin-2, SDR-related gene product that binds to C kinase (SRBC)/Cavin-3, and muscle-restricted coiled-coil protein (MURC)/Cavin-4, forms a multiprotein complex that associates with caveolae. This complex can constitutively assemble in the cytosol and associate with caveolin at plasma membrane caveolae. Cavin-1, but not other cavins, can induce caveola formation in a heterologous system and is required for the recruitment of the cavin complex to caveolae. The tissue-restricted expression of cavins suggests that caveolae may perform tissue-specific functions regulated by the composition of the cavin complex. Cavin-4 is expressed predominantly in muscle, and its distribution is perturbed in human muscle disease associated with Caveolin-3 dysfunction, identifying Cavin-4 as a novel muscle disease candidate caveolar protein.
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Affiliation(s)
- Michele Bastiani
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
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31
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McMahon KA, Zajicek H, Li WP, Peyton MJ, Minna JD, Hernandez VJ, Luby-Phelps K, Anderson RGW. SRBC/cavin-3 is a caveolin adapter protein that regulates caveolae function. EMBO J 2009; 28:1001-15. [PMID: 19262564 DOI: 10.1038/emboj.2009.46] [Citation(s) in RCA: 159] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2008] [Accepted: 01/21/2009] [Indexed: 11/09/2022] Open
Abstract
Caveolae are a major membrane domain common to most cells. One of the defining features of this domain is the protein caveolin. The exact function of caveolin, however, is not clear. One possible function is to attract adapter molecules to caveolae in a manner similar to how clathrin attracts molecules to coated pits. Here, we characterize a candidate adapter molecule called SRBC. SRBC binds PKCdelta and is a member of the STICK (substrates that interact with C-kinase) superfamily of PKC-binding proteins. We also show it co-immunoprecipitates with caveolin-1. A leucine zipper in SRBC is essential for both co-precipitation with caveolin and localization to caveolae. SRBC remains associated with caveolin when caveolae bud to form vesicles (cavicles) that travel on microtubules to different regions of the cell. In the absence of SRBC, intracellular cavicle traffic is markedly impaired. We conclude that SRBC (sdr-related gene product that binds to c-kinase) and two other family members [PTRF (Pol I and transcription release factor) and SDPR] function as caveolin adapter molecules that regulate caveolae function.
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Affiliation(s)
- Kerrie-Ann McMahon
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9039, USA
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32
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Abstract
Ribosomal RNA transcription was one of the first model systems for molecular characterization of a transcription regulatory mechanism and certainly one of the best studied in the widest range of organisms. In multicellular organisms, however, the issue of cell-type-specific regulation of rRNA transcription has not been well addressed. Here I propose that a systematic study of cell-type-specific regulation of rRNA transcription may reveal new regulatory mechanisms that have not been previously realized. Specifically, issues concerning the cell-type-specific requirement for rRNA production, the universality of Pol I transcription complex and the division of rDNA into regulatory subdomains are discussed.
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Affiliation(s)
- Hung Tseng
- Department of Dermatology, Department of Cell and Developmental Biology, Center for Research on Reproduction and Women's Health, University of Pennsylvania, CRB Room 242B, 415 Curie Boulevard, Philadelphia, PA 19104, USA.
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33
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Aboulaich N, Ortegren U, Vener AV, Strålfors P. Association and insulin regulated translocation of hormone-sensitive lipase with PTRF. Biochem Biophys Res Commun 2006; 350:657-61. [PMID: 17026959 DOI: 10.1016/j.bbrc.2006.09.094] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2006] [Accepted: 09/20/2006] [Indexed: 11/22/2022]
Abstract
Polymerase I and transcript release factor (PTRF) is in human adipocytes mainly localized at the plasma membrane. This localization was under control of insulin, which translocated PTRF to the cytosol and nucleus, indicating a novel role for PTRF in insulin transcriptional control. In the plasma membrane PTRF was specifically bound to a triacylglycerol-metabolizing subclass of caveolae containing hormone-sensitive lipase (HSL). In response to insulin PTRF was translocated to the cytosol in parallel with HSL. PTRF and HSL were quantitatively immunoprecipitated from the cytosol by antibodies against either PTRF or HSL. The findings indicate also a novel extranuclear function for PTRF in the control of lipolysis.
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Affiliation(s)
- Nabila Aboulaich
- Department of Cell Biology and Diabetes Research Centre, Linköping University, SE58185 Linköping, Sweden
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34
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Vinten J, Johnsen AH, Roepstorff P, Harpøth J, Tranum-Jensen J. Identification of a major protein on the cytosolic face of caveolae. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2005; 1717:34-40. [PMID: 16236245 DOI: 10.1016/j.bbamem.2005.09.013] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2005] [Revised: 09/01/2005] [Accepted: 09/06/2005] [Indexed: 11/24/2022]
Abstract
Cav-p60, a specific and ubiquitous caveolar protein, was immunoprecipitated from solubilized rat adipocyte plasma membranes and identified as similar to a GeneBank entry annotated mouse polymerase transcript release factor (PTRF) by MALDI-TOF and MS-MS of major fragments. Cloning and virtual translation of the corresponding rat adipocyte cDNA sequence revealed 98.7% identity with mouse PTRF. In vitro translation of this sequence produced a protein, which was recognized by antibodies to both cav-p60 and PTRF. EM gold labeling studies showed that a rabbit antiserum against murine PTRF immunolabeled caveolae specifically in adipocytes from both mouse and rat. In view of the reported function of the protein, which is exerted in the cell nucleus, its subcellular localization was investigated. We found that the protein could be purified by differential solubilization of a plasma membrane fraction followed by SDS-PAGE, and that the protein was as abundant as caveolin in this fraction. We were unable to detect the protein in cell nuclei by subcellular fractionation or fluorescence microscopy. The results show that in a large number of cell types, PTRF is essentially located to caveolae, and that each caveola harbors many copies of the protein. Consequently, we suggest the name Cavin for this protein.
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Affiliation(s)
- J Vinten
- Department of Medical Physiology, Panum Institute, University of Copenhagen, Denmark.
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35
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Abstract
The mitochondrial ribomotor model has been proposed to explain how the balance between rRNA and mRNA in mammalian mitochondria is regulated. In this model, the interaction of the mitochondrial transcription termination factor (mTERF) with some unknown component(s), causes a loop to form in the mtDNA chain that brings the initiation and termination regions together at its base. By bringing these sites into closer proximity, the mtRNA polymerase molecules can be directly transferred from the termination site to the IH1 initiation site of the H-strand once transcription terminates. This process occurs when mTERF is phosphorylated. When unphosphorylated, transcription is initiated from the IH2 site and the polymerase reads through the mTERF-dependent termination site, resulting in the transcription of almost the entire H-strand.
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36
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Abstract
Vectorial proteomics is a methodology for the differential identification and characterization of proteins and their domains exposed to the opposite sides of biological membranes. Proteomics of membrane vesicles from defined isolated membranes automatically determine cellular localization of the identified proteins and reduce complexity of protein characterizations. The enzymatic shaving of naturally-oriented, or specifically-inverted sealed membrane vesicles, release the surface-exposed peptides from membrane proteins. These soluble peptides are amenable to various chromatographic separations and to sequencing by mass spectrometry, which provides information on the topology of membrane proteins and on their posttranslational modifications. The membrane shaving techniques have made a breakthrough in the identification of in vivo protein phosphorylation sites in membrane proteins form plant photosynthetic and plasma membranes, and from caveolae membrane vesicles of human fat cells. This approach has also allowed investigation of dynamics for in vivo protein phosphorylation in membranes from cells exposed to different conditions. Vectorial proteomics of membrane vesicles with retained peripheral proteins identify extrinsic proteins associated with distinct membrane surfaces, as well as a variety of posttranslational modifications in these proteins. The rapid integration of versatile vectorial proteomics techniques in the functional characterization of biological membranes is anticipated to bring significant insights in cell biology.
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Affiliation(s)
- Alexander V Vener
- Division of Cell Biology and Diabetes Research Center, Linköping University, Linköping, Sweden.
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37
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Abstract
In the extensive network of interdependent biochemical processes required for cell growth and division, there is mounting evidence that ribosomal DNA transcription by RNA polymerase I (pol I) not only drives cell growth via its direct role in production of the ribosomal RNA (rRNA) component of the protein-synthesis machinery, but that it is also crucial in determining the fate of the cell. Considerable progress has been made in recent years towards understanding both the function of components of the pol I transcription machinery and how cells accomplish the tight control of pol I transcription, balancing the supply of rRNA with demand under different growth conditions.
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Affiliation(s)
- Jackie Russell
- Division of Gene Regulation and Expression, Wellcome Trust Biocentre, University of Dundee, Dundee DD1 5EH, Scotland, UK
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38
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Aboulaich N, Vainonen J, Strålfors P, Vener A. Vectorial proteomics reveal targeting, phosphorylation and specific fragmentation of polymerase I and transcript release factor (PTRF) at the surface of caveolae in human adipocytes. Biochem J 2004; 383:237-48. [PMID: 15242332 PMCID: PMC1134064 DOI: 10.1042/bj20040647] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2004] [Revised: 07/02/2004] [Accepted: 07/09/2004] [Indexed: 02/06/2023]
Abstract
Caveolae, the specialized invaginations of plasma membranes, formed sealed vesicles with outwards-orientated cytosolic surface after isolation from primary human adipocytes. This morphology allowed differential, vectorial identification of proteins at the opposite membrane surfaces by proteolysis and MS. Extracellular-exposed caveolae-specific proteins CD36 and copper-containing amine oxidase were concealed inside the vesicles and resisted trypsin treatment. The cytosol-orientated caveolins were efficiently digested by trypsin, producing peptides amenable to direct MS sequencing. Isolation of peripheral proteins associated with the cytosolic surface of caveolae revealed a set of proteins that contained nuclear localization signals, leucine-zipper domains and PEST (amino acid sequence enriched in proline, glutamic acid, serine and threonine) domains implicated in regulation by proteolysis. In particular, PTRF (polymerase I and transcript release factor) was found as a major caveolae-associated protein and its co-localization with caveolin was confirmed by immunofluorescence confocal microscopy. PTRF was present at the surface of caveolae in the intact form and in five different truncated forms. Peptides (44 and 45 amino acids long) comprising both the PEST domains were sequenced by nanospray-quadrupole-time-of-flight MS from the full-length PTRF, but were not found in the truncated forms of the protein. Two endogenous cleavage sites corresponding to calpain specificity were identified in PTRF; one of them was in a PEST domain. Both cleavage sites were flanked by mono- or diphosphorylated sequences. The phosphorylation sites were localized to Ser-36, Ser-40, Ser-365 and Ser-366 in PTRF. Caveolae of human adipocytes are proposed to function in targeting, relocation and proteolytic control of PTRF and other PEST-domain-containing signalling proteins.
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Affiliation(s)
- Nabila Aboulaich
- Division of Cell Biology and Diabetes Research Centre, Faculty of Health Sciences, Linköping University, SE58185 Linköping, Sweden
| | - Julia P. Vainonen
- Division of Cell Biology and Diabetes Research Centre, Faculty of Health Sciences, Linköping University, SE58185 Linköping, Sweden
| | - Peter Strålfors
- Division of Cell Biology and Diabetes Research Centre, Faculty of Health Sciences, Linköping University, SE58185 Linköping, Sweden
| | - Alexander V. Vener
- Division of Cell Biology and Diabetes Research Centre, Faculty of Health Sciences, Linköping University, SE58185 Linköping, Sweden
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Prieto-Martín A, Montoya J, Martínez-Azorín F. Phosphorylation of rat mitochondrial transcription termination factor (mTERF) is required for transcription termination but not for binding to DNA. Nucleic Acids Res 2004; 32:2059-68. [PMID: 15087485 PMCID: PMC407814 DOI: 10.1093/nar/gkh528] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Despite the crucial importance of mitochondrial transcription, knowledge of its regulation is poor. Therefore, characterization of mammalian mitochondrial transcription termination factor (mTERF) functionality and regulation is of fundamental biological interest in order to understand the regulation of mitochondrial transcription. Here we report that mTERF is the first protein having a role in mammalian mitochondrial gene expression that appears to be controlled by phosphorylation. Recombinant mature rat mTERF protein has specific DNA-binding capacity for the sequence required for transcription termination. Furthermore, unlike recombinant human mTERF, the rat protein bound to its mitochondrial DNA binding site promotes the termination of transcription initiated with heterologous RNA polymerase. Interestingly, mTERF is a phosphoprotein with four phosphate groups, and while the DNA-binding activity of mTERF is unaffected by the phosphorylation/dephosphorylation state, only the phosphorylated form of the protein is active for termination activity. Moreover, natural human mTERF is also a phosphoprotein and its termination activity is inhibited by dephosphorylation. These data suggest that mTERF functioning in vivo is regulated by phosphorylation.
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Affiliation(s)
- Ascensión Prieto-Martín
- Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, Miguel Servet 177, E-50013 Zaragoza, Spain
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40
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Ibarrola N, Molina H, Iwahori A, Pandey A. A Novel Proteomic Approach for Specific Identification of Tyrosine Kinase Substrates Using [13C]Tyrosine. J Biol Chem 2004; 279:15805-13. [PMID: 14739304 DOI: 10.1074/jbc.m311714200] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Proteomic studies to find substrates of tyrosine kinases generally rely on identification of protein bands that are "pulled down" by antiphosphotyrosine antibodies from ligand-stimulated samples. One can obtain erroneous results from such experiments because of two major reasons. First, some proteins might be basally phosphorylated on tyrosine residues in the absence of ligand stimulation. Second, proteins can bind non-specifically to the antibodies or the affinity matrix. Induction of phosphorylation of proteins by ligand must therefore be confirmed by a different approach, which is not always feasible. We have developed a novel proteomic approach to identify substrates of tyrosine kinases in signaling pathways studies based on in vivo labeling of proteins with "light" (12C-labeled) or "heavy" (13C-labeled) tyrosine. This stable isotope labeling in cell culture method enables the unequivocal identification of tyrosine kinase substrates, as peptides derived from true substrates give rise to a unique signature in a mass spectrometry experiment. By using this approach, from a single experiment, we have successfully identified several known substrates of insulin signaling pathway and a novel substrate, polymerase I and transcript release factor, a protein that is implicated in the control of RNA metabolism and regulation of type I collagen promoters. This approach is amenable to high throughput global studies as it simplifies the specific identification of substrates of tyrosine kinases as well as serine/threonine kinases using mass spectrometry.
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Affiliation(s)
- Nieves Ibarrola
- McKusick-Nathans Institute for Genetic Medicine and the Department of Biological Chemistry, The Johns Hopkins University, Baltimore, Maryland 21205, USA
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41
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Asin-Cayuela J, Helm M, Attardi G. A Monomer-to-Trimer Transition of the Human Mitochondrial Transcription Termination Factor (mTERF) Is Associated with a Loss of in Vitro Activity. J Biol Chem 2004; 279:15670-7. [PMID: 14744862 DOI: 10.1074/jbc.m312537200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The human mitochondrial transcription termination factor (mTERF) is a nuclear-encoded 39-kDa protein that recognizes a mtDNA segment within the mitochondrial tRNA(Leu(UUR)) gene immediately adjacent to and downstream of the 16 S rRNA gene. Binding of mTERF to this site promotes termination of rDNA transcription. Despite the fact that mTERF binds DNA as a monomer, the presence in its sequence of three leucine-zipper motifs suggested the possibility of mTERF establishing intermolecular interactions with proteins of the same or different type. When a mitochondrial lysate from HeLa cells was submitted to gel filtration chromatography, mTERF was eluted in two peaks, as detected by immunoblotting. The first peak, which varied in proportion between 30 and 50%, appeared at the position expected from the molecular mass of the monomer (41 +/- 2 kDa), and the gel filtration fractions that contained it exhibited DNA binding activity. Most interestingly, the material in this peak had a strong stimulating activity on in vitro transcription of the mitochondrial rDNA. The second peak eluted at a position corresponding to an estimated molecular mass of 111 +/- 5 kDa. No mTERF DNA binding activity could be detected in the corresponding gel filtration fractions. Therefore, we propose that mTERF exists in mitochondria in two forms, an active monomer and an inactive large size complex. The estimated molecular weight of this complex and the fact that purified mTERF can be eluted from a gel filtration column as a complex of the same molecular weight strongly suggest that this inactive complex is a homotrimer of mTERF.
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Affiliation(s)
- Jordi Asin-Cayuela
- Division of Biology, California Institute of Technology, Pasadena, California 91125, USA.
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42
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Abstract
Gene transcription is repetitive, enabling the synthesis of multiple copies of identical RNA molecules from the same template. The cyclic process of RNA synthesis from active genes, referred to as transcription reinitiation, contributes significantly to the level of RNAs in living cells. Contrary to the perception that multiple transcription cycles are a mere iteration of mechanistically identical steps, a large body of evidence indicates that, in most transcription systems, reinitiation involves highly specific and regulated pathways. These pathways influence the availability for reinitiation of template DNA and/or transcription proteins, and represent an important yet poorly characterized aspect of gene regulation.
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Affiliation(s)
- Giorgio Dieci
- Dipartimento di Biochimica e Biologia Molecolare, Università di Parma, Italy.
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43
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Valerius O, Brendel C, Düvel K, Braus GH. Multiple factors prevent transcriptional interference at the yeast ARO4-HIS7 locus. J Biol Chem 2002; 277:21440-5. [PMID: 11937506 DOI: 10.1074/jbc.m201841200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Increased transcriptional activity may cause transcriptional interference in organisms with compact genomes such as the yeast Saccharomyces cerevisiae. Replacement of the yeast ARO4 promoter by the stronger ACT1 promoter increases ARO4 transcription and simultaneously reduces the basal transcription of the downstream HIS7 gene. The open reading frames of ARO4 and HIS7 are tandemly transcribed and are separated by 416 bp. In wild-type cells, a nuclease-resistant site suggests that the two genes are separated by a single positioned nucleosome. Transcriptional interference correlates with Micrococcus nuclease accessibility of this otherwise nuclease-resistant site. Deletion analyses of the region between the two open reading frames revealed that transcriptional interference increases upon removal of either parts of the ARO4 3' end or HIS7 promoter sequences. The abolishment of the Abf1p-binding site within the HIS7 promoter significantly enhances transcriptional interference, resulting in a histidine auxotrophic strain. Our data suggest that the yeast cell prevents transcriptional interference by the combined action of efficient ARO4 transcription termination, the positioning of a fixed nucleosome, and transcription factor binding to the HIS7 promoter.
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Affiliation(s)
- Oliver Valerius
- Institute of Microbiology and Genetics, Georg-August-University, Grisebachstrasse 8, D-37077 Göttingen, Germany
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44
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Smith ER, Allis CD, Lucchesi JC. Linking global histone acetylation to the transcription enhancement of X-chromosomal genes in Drosophila males. J Biol Chem 2001; 276:31483-6. [PMID: 11445559 DOI: 10.1074/jbc.c100351200] [Citation(s) in RCA: 139] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
It has become well established for several genes that targeting of histone acetylation to promoters is required for the activation of transcription. In contrast, global patterns of acetylation have not been ascribed to any particular regulatory function. In Drosophila, a specific modification of H4, acetylation at lysine 16, is enriched at hundreds of sites on the male X chromosome due to the activity of the male-specific lethal (MSL) dosage compensation complex. Utilizing chromatin immunoprecipitation, we have determined that H4Ac16 is present along the entire length of X-linked genes targeted by the MSL complex with relatively modest levels of acetylation at the promoter regions and high levels in the middle and/or 3' end of the transcription units. We propose that global acetylation by the MSL complex increases the expression of X-linked genes by facilitating transcription elongation rather than by enhancing promoter accessibility. We have also determined that H4Ac16 is absent from a region of the X chromosome that includes a gene known to be dosage-compensated by a MSL-independent mechanism. This study represents the first biochemical interpretation of the very large body of cytological observations on the chromosomal distribution of the MSL complex.
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Affiliation(s)
- E R Smith
- Department of Biology, Emory University, Atlanta, Georgia 30322, USA
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