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Abstract
Cardiac and skeletal striated muscles are intricately designed machines responsible for muscle contraction. Coordination of the basic contractile unit, the sarcomere, and the complex cytoskeletal networks are critical for contractile activity. The sarcomere is comprised of precisely organized individual filament systems that include thin (actin), thick (myosin), titin, and nebulin. Connecting the sarcomere to other organelles (e.g., mitochondria and nucleus) and serving as the scaffold to maintain cellular integrity are the intermediate filaments. The costamere, on the other hand, tethers the sarcomere to the cell membrane. Unique structures like the intercalated disc in cardiac muscle and the myotendinous junction in skeletal muscle help synchronize and transmit force. Intense investigation has been done on many of the proteins that make up these cytoskeletal assemblies. Yet the details of their function and how they interconnect have just started to be elucidated. A vast number of human myopathies are contributed to mutations in muscle proteins; thus understanding their basic function provides a mechanistic understanding of muscle disorders. In this review, we highlight the components of striated muscle with respect to their interactions, signaling pathways, functions, and connections to disease. © 2017 American Physiological Society. Compr Physiol 7:891-944, 2017.
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Affiliation(s)
- Christine A Henderson
- Department of Cellular and Molecular Medicine, The University of Arizona, Tucson, Arizona, USA.,Sarver Molecular Cardiovascular Research Program, The University of Arizona, Tucson, Arizona, USA
| | - Christopher G Gomez
- Department of Cellular and Molecular Medicine, The University of Arizona, Tucson, Arizona, USA.,Sarver Molecular Cardiovascular Research Program, The University of Arizona, Tucson, Arizona, USA
| | - Stefanie M Novak
- Department of Cellular and Molecular Medicine, The University of Arizona, Tucson, Arizona, USA.,Sarver Molecular Cardiovascular Research Program, The University of Arizona, Tucson, Arizona, USA
| | - Lei Mi-Mi
- Department of Cellular and Molecular Medicine, The University of Arizona, Tucson, Arizona, USA.,Sarver Molecular Cardiovascular Research Program, The University of Arizona, Tucson, Arizona, USA
| | - Carol C Gregorio
- Department of Cellular and Molecular Medicine, The University of Arizona, Tucson, Arizona, USA.,Sarver Molecular Cardiovascular Research Program, The University of Arizona, Tucson, Arizona, USA
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2
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Fang KP, Dai W, Ren YH, Xu YC, Zhang SM, Qian YB. Both Talin-1 and Talin-2 correlate with malignancy potential of the human hepatocellular carcinoma MHCC-97 L cell. BMC Cancer 2016; 16:45. [PMID: 26822056 PMCID: PMC4730717 DOI: 10.1186/s12885-016-2076-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Accepted: 01/19/2016] [Indexed: 12/27/2022] Open
Abstract
Background Talin-1 (TLN-1) and TLN-2 are implicated in many cellular processes, but their roles in hepatocellular carcinoma (HCC) remain unclear. This study aimed to assess cell cycle distribution, anoikis, invasion and migration in human HCC MHCC-97 L cells. Methods MHCC-97 L cells, which highly express TLN-1, were transduced with TLN-1 shRNA (experimental group) or scramble shRNA (negative control group); non-transduced MHCC-97 L cells were used as blank controls. TLN-1 and TLN-2 mRNA and protein levels were detected by real-time RT-PCR and western blot, respectively. Then, cell cycle distribution and anoikis were assessed by flow cytometry. In addition, migration and invasion abilities were assessed using Transwell and cell scratch assays. Finally, a xenograft nude mouse model was established to further assess cell tumorigenicity. Results Compared with the blank and negative control groups, TLN-1/2 mRNA and protein levels were significantly reduced in the experiment group. TLN-1/2 knockdown cells showed significantly more cells in the G0/G1 phase (79.24 %) in comparison with both blank (65.36 %) and negative (62.69 %) control groups; conversely, less cells were found in G2/M and S phases in the experimental group compared with controls. Moreover, anoikis was enhanced (P < 0.05), while invasion and migration abilities were reduced (P < 0.05) in TLN-1/2 knockdown cells compared with controls. TLN-1/2 knockdown inhibited MHCC-97 L cell migration (Percentage of wound healing area: experimental group: 32.6 ± 0.7 % vs. negative controls: 50.1 ± 0.6 % and blank controls: 53.6 ± 0.6 %, both P < 0.01). Finally, the tumors obtained with TLN-1/2 knockdown cells were smaller (P < 0.05) compared with controls. Conclusion Both TLN-1 and TLN-2 levels correlate with tumorigenicity in human HCC, indicating that these molecules constitute important molecular targets for the diagnosis and/or treatment of HCC.
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Affiliation(s)
- Kun-Peng Fang
- The People's Hospital, Xuancheng City, Auhui Province, China
| | - Wei Dai
- First Affiliated Hospital of Anhui Medical University, Hefei, 230032, Anhui Province, China
| | - Yan-Hong Ren
- First Affiliated Hospital of Anhui Medical University, Hefei, 230032, Anhui Province, China
| | - Ye-Chuan Xu
- First Affiliated Hospital of Anhui Medical University, Hefei, 230032, Anhui Province, China
| | - She-Min Zhang
- First Affiliated Hospital of Anhui Medical University, Hefei, 230032, Anhui Province, China
| | - Ye-Ben Qian
- The People's Hospital, Xuancheng City, Auhui Province, China. .,First Affiliated Hospital of Anhui Medical University, Hefei, 230032, Anhui Province, China.
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3
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Abstract
Insight into how molecular machines perform their biological functions depends on knowledge of the spatial organization of the components, their connectivity, geometry, and organizational hierarchy. However, these parameters are difficult to determine in multicomponent assemblies such as integrin-based focal adhesions (FAs). We have previously applied 3D superresolution fluorescence microscopy to probe the spatial organization of major FA components, observing a nanoscale stratification of proteins between integrins and the actin cytoskeleton. Here we combine superresolution imaging techniques with a protein engineering approach to investigate how such nanoscale architecture arises. We demonstrate that talin plays a key structural role in regulating the nanoscale architecture of FAs, akin to a molecular ruler. Talin diagonally spans the FA core, with its N terminus at the membrane and C terminus demarcating the FA/stress fiber interface. In contrast, vinculin is found to be dispensable for specification of FA nanoscale architecture. Recombinant analogs of talin with modified lengths recapitulated its polarized orientation but altered the FA/stress fiber interface in a linear manner, consistent with its modular structure, and implicating the integrin-talin-actin complex as the primary mechanical linkage in FAs. Talin was found to be ∼97 nm in length and oriented at ∼15° relative to the plasma membrane. Our results identify talin as the primary determinant of FA nanoscale organization and suggest how multiple cellular forces may be integrated at adhesion sites.
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Kambouris M, Maroun RC, Ben-Omran T, Al-Sarraj Y, Errafii K, Ali R, Boulos H, Curmi PA, El-Shanti H. Mutations in zinc finger 407 [ZNF407] cause a unique autosomal recessive cognitive impairment syndrome. Orphanet J Rare Dis 2014; 9:80. [PMID: 24907849 PMCID: PMC4070100 DOI: 10.1186/1750-1172-9-80] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2013] [Accepted: 05/29/2014] [Indexed: 01/14/2023] Open
Abstract
Background A consanguineous Arab family is affected by an apparently novel autosomal recessive disorder characterized by cognitive impairment, failure-to-thrive, hypotonia and dysmorphic features including bilateral ptosis and epicanthic folds, synophrys, midface hypoplasia, downturned mouth corners, thin upper vermillion border and prominent ears, bilateral 5th finger camptodactyly, bilateral short 4th metatarsal bones, and limited knee mobility bilaterally. Methods The family was studied by homozygosity mapping, candidate gene mutation screening and whole Exome Next Generation Sequencing of a single affected member to identify the offending gene and mutation. The mutated gene product was studied by structural bioinformatics methods. Results A damaging c.C5054G mutation affecting an evolutionary highly conserved amino acid p.S1685W was identified in the ZNF407 gene at 18q23. The Serine to Tryptophane mutation affects two of the three ZNF407 isoforms and is located in the last third of the protein, in a linker peptide adjoining two zinc-finger domains. Structural analyses of this mutation shows disruption of an H-bond that locks the relative spatial position of the two fingers, leading to a higher flexibility of the linker and thus to a decreased probability of binding to the target DNA sequence essentially eliminating the functionality of downstream domains and interfering with the expression of various genes under ZNF407 control during fetal brain development. Conclusions ZNF407 is a transcription factor with an essential role in brain development. When specific and limited in number homozygosity intervals exist that harbor the offending gene in consanguineous families, Whole Exome Sequencing of a single affected individual is an efficient approach to gene mapping and mutation identification.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Hatem El-Shanti
- Qatar Biomedical Research Institute, Medical Genetics Center, 69 Lusail Street, West Bay Area, P,O, Box: 33123, Doha, Qatar.
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5
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Bouvard D, Pouwels J, De Franceschi N, Ivaska J. Integrin inactivators: balancing cellular functions in vitro and in vivo. Nat Rev Mol Cell Biol 2013; 14:430-42. [DOI: 10.1038/nrm3599] [Citation(s) in RCA: 173] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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6
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Chen NT, Kuwabara Y, Conley C, Liao YC, Hong SY, Chen M, Shih YP, Chen HW, Hsieh F, Lo SH. Phylogenetic analysis, expression patterns, and transcriptional regulation of human CTEN gene. Gene 2013; 520:90-7. [PMID: 23500447 DOI: 10.1016/j.gene.2013.02.041] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Revised: 02/21/2013] [Accepted: 02/23/2013] [Indexed: 10/27/2022]
Abstract
Cten is a focal adhesion molecule and a member of the tensin family. Its expression is highly enriched in the prostate and placenta, suggesting that cten gene might be closely associated with mammalian species. Recent studies have reported that cten expression is frequently up-regulated in a variety of cancers and its levels appear to correlate with tumorigenicity. Here, we have (1) analyzed cten sequences of various species to build a phylogenetic tree, (2) examined cten mRNA levels in human and mouse tissues to establish its expression profiles, and (3) determined the promoter region of human CTEN gene in cell lines and in a mouse model to understand its transcriptional regulation. Our analyses indicate that all currently known cten genes are present in mammals. The prostate and placenta are the two most cten abundant tissues in human and mouse, meanwhile brain and lung also express low levels of cten. Results from cell culture reporter assays demonstrate that a 327-bp fragment is the shortest functional promoter. All functional promoter constructs produce 40- to 160-fold increases in luciferase reporter activities in normal prostate cells, whereas lower activities (<40-fold) are detected in non-prostatic cell lines. To evaluate CTEN promoter activity in mice and develop a new tissue specific Cre recombinase mouse model, we have established pCTEN-Cre:R26R mice by crossing R26R β-galactosidase reporter mice with pCTEN-Cre transgenic mice, in which the 327-bp cten promoter drives the expression of Cre recombinase. X-gal analysis has shown strong β-galactosidase activities in the prostate, brain, and few other tissues in pCTEN-Cre:R26R mice. Altogether, we have identified the promoter region of human cten gene and provided a useful tool for investigating cell lineages and generating tissue-specific knockout or knockin mice.
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Affiliation(s)
- Nien-Tsu Chen
- Department of Biochemistry and Molecular Medicine, University of California-Davis, Sacramento, CA 95817, USA
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7
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Debrand E, Conti FJ, Bate N, Spence L, Mazzeo D, Pritchard CA, Monkley SJ, Critchley DR. Mice carrying a complete deletion of the talin2 coding sequence are viable and fertile. Biochem Biophys Res Commun 2012; 426:190-5. [PMID: 22925892 PMCID: PMC3485561 DOI: 10.1016/j.bbrc.2012.08.061] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2012] [Accepted: 08/13/2012] [Indexed: 12/15/2022]
Abstract
Mice homozygous for several Tln2 gene targeted alleles are viable and fertile. Here we show that although the expression of talin2 protein is drastically reduced in muscle from these mice, other tissues continue to express talin2 albeit at reduced levels. We therefore generated a Tln2 allele lacking the entire coding sequence (Tln2cd). Tln2cd/cd mice were viable and fertile, and the genotypes of Tln2cd/+ intercrosses were at the expected Mendelian ratio. Tln2cd/cd mice showed no major difference in body mass or the weight of the major organs compared to wild-type, although they displayed a mildly dystrophic phenotype. Moreover, Tln2cd/cd mouse embryo fibroblasts showed no obvious defects in cell adhesion, migration or proliferation. However, the number of Tln2cd/cd pups surviving to adulthood was variable suggesting that such mice have an underlying defect.
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Affiliation(s)
- Emmanuel Debrand
- Department of Biochemistry, University of Leicester, Lancaster Road, Leicester LE1 9HN, UK
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8
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Praekelt U, Kopp PM, Rehm K, Linder S, Bate N, Patel B, Debrand E, Manso AM, Ross RS, Conti F, Zhang MZ, Harris RC, Zent R, Critchley DR, Monkley SJ. New isoform-specific monoclonal antibodies reveal different sub-cellular localisations for talin1 and talin2. Eur J Cell Biol 2012; 91:180-91. [PMID: 22306379 PMCID: PMC3629562 DOI: 10.1016/j.ejcb.2011.12.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2011] [Revised: 12/13/2011] [Accepted: 12/19/2011] [Indexed: 11/24/2022] Open
Abstract
Talins are adaptor proteins that connect the integrin family of cell adhesion receptors to cytoskeletal actin. Vertebrates express two closely related talins encoded by separate genes, and while it is well established that talin1 plays a key role in cell adhesion and spreading, little is known about the role of talin2. To facilitate such studies, we report the characterisation of 4 new isoform-specific talin mouse monoclonal antibodies that work in Western blotting, immuno-precipitation, immuno-fluorescence and immuno-histochemistry. Using these antibodies, we show that talin1 and talin2 do not form heterodimers, and that they are differentially localised within the cell. Talin1 was concentrated in peripheral focal adhesions while talin2 was observed in both focal and fibrillar adhesions, and knock-down of talin2 compromised fibronectin fibrillogenesis. Although differentiated human macrophages express both isoforms, only talin1 showed discrete staining and was localised to the ring structure of podosomes. However, siRNA-mediated knock-down of macrophage talin2 led to a significant reduction in podosomal matrix degradation. We have also used the antibodies to localise each isoform in tissue sections using both cryostat and paraffin-embedded material. In skeletal muscle talin2 was localised to both myotendinous junctions and costameres while talin1 was restricted to the former structure. In contrast, both isoforms co-localised in kidney with staining of the glomerulus, and the tubular epithelial and interstitial cells of the cortex and medulla. We anticipate that these antibodies will form a valuable resource for future studies on the function of the two major talin isoforms.
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Affiliation(s)
- Uta Praekelt
- Department of Biochemistry, University of Leicester, Lancaster Road, Leicester LE1 9HN, UK
| | - Petra M. Kopp
- Department of Biochemistry, University of Leicester, Lancaster Road, Leicester LE1 9HN, UK
| | - Kerstin Rehm
- University Medical Center Eppendorf, 20246 Hamburg, Germany
| | - Stefan Linder
- University Medical Center Eppendorf, 20246 Hamburg, Germany
| | - Neil Bate
- Department of Biochemistry, University of Leicester, Lancaster Road, Leicester LE1 9HN, UK
| | - Bipin Patel
- Department of Biochemistry, University of Leicester, Lancaster Road, Leicester LE1 9HN, UK
| | - Emmanuel Debrand
- Department of Biochemistry, University of Leicester, Lancaster Road, Leicester LE1 9HN, UK
| | - Ana Maria Manso
- Department of Medicine, University of California at San Diego, School of Medicine, La Jolla, CA, USA
- VA Healthcare San Diego, CA 92161, USA
| | - Robert S. Ross
- Department of Medicine, University of California at San Diego, School of Medicine, La Jolla, CA, USA
- VA Healthcare San Diego, CA 92161, USA
| | - Franceso Conti
- Dubowitz Neuromuscular Centre, Institute of Child Health, University College London, London WC1N 1EH, UK
| | - Ming-Zhi Zhang
- Division of Nephrology, Department of Medicine, Vanderbilt University Medical Center, North Nashville, TN 37232, USA
| | - Raymond C. Harris
- Division of Nephrology, Department of Medicine, Vanderbilt University Medical Center, North Nashville, TN 37232, USA
- Department of Medicine, Veterans Affairs Hospital, Nashville, TN 37212, USA
| | - Roy Zent
- Division of Nephrology, Department of Medicine, Vanderbilt University Medical Center, North Nashville, TN 37232, USA
- Department of Medicine, Veterans Affairs Hospital, Nashville, TN 37212, USA
| | - David R. Critchley
- Department of Biochemistry, University of Leicester, Lancaster Road, Leicester LE1 9HN, UK
| | - Susan J. Monkley
- Department of Biochemistry, University of Leicester, Lancaster Road, Leicester LE1 9HN, UK
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9
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Sen S, Ng WP, Kumar S. Contributions of talin-1 to glioma cell-matrix tensional homeostasis. J R Soc Interface 2011; 9:1311-7. [PMID: 22158841 DOI: 10.1098/rsif.2011.0567] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The ability of cells to adapt their mechanical properties to those of the surrounding microenvironment (tensional homeostasis) has been implicated in the progression of a variety of solid tumours, including the brain tumour glioblastoma multiforme (GBM). GBM tumour cells are highly sensitive to extracellular matrix (ECM) stiffness and overexpress a variety of focal adhesion proteins, such as talin. While talin has been shown to play critical early roles in integrin-based force-sensing in non-tumour cells, it remains unclear whether this protein contributes to tensional homeostasis in GBM cells. Here, we investigate the role of the talin isoform talin-1 in enabling human GBM cells to adapt to ECM stiffness. We show that human GBM cells express talin-1, and we use RNA interference to suppress talin-1 expression without affecting levels of talin-2, vinculin or phosphorylated focal adhesion kinase. Knockdown of talin-1 strongly reduces both cell spreading area and random migration speed but does not significantly affect overall focal adhesion size distributions. Most strikingly, atomic force microscopy indentation reveals that talin-1 suppression compromises adaptation of cell stiffness to changes in ECM stiffness. Together, these data support a role for talin-1 in the maintenance of tensional homeostasis in GBM and suggest a functional role for enriched talin expression in this tumour.
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Affiliation(s)
- Shamik Sen
- Department of Bioengineering, University of California, 274A Stanley Hall no. 1762, Berkeley, CA 94720, USA
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10
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Abstract
Cardiomyopathy is a heart muscle disease caused by decreased contractility of the ventricles leading to heart failure and premature death. Multiple conditions like ischemic heart disease (atherosclerosis), hypertension, diabetes, viral infection, alcohol abuse, obesity and genetic mutations can lead to cardiomyopathy. Single gene mutations in sarcomeric proteins, Z-disk-associated proteins, membrane/associated proteins, intermediate filaments, calcium cycle proteins as well as in modifier genes have been linked to cardiomyopathy. Clinical practice guidelines have been formulated by the American Heart Association and the Heart Failure Association of America on how to genetically evaluate patients with cardiomyopathy. To illustrate the concept that alterations in genes cause cardiovascular disease, this review will focus on two membrane-associated proteins, vinculin and talin. We will discuss the general function of vinculin/metavinulin as well as talin1 and talin2, with emphasis on what is understood about their role in the cardiac myocyte and in whole heart.
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11
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Liu J, He X, Qi Y, Tian X, Monkley SJ, Critchley DR, Corbett SA, Lowry SF, Graham AM, Li S. Talin1 regulates integrin turnover to promote embryonic epithelial morphogenesis. Mol Cell Biol 2011; 31:3366-77. [PMID: 21670148 PMCID: PMC3147785 DOI: 10.1128/mcb.01403-10] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Accepted: 05/21/2011] [Indexed: 12/17/2022] Open
Abstract
Talin is a cytoskeletal protein that binds to integrin β cytoplasmic tails and regulates integrin activation. Talin1 ablation in mice disrupts gastrulation and causes embryonic lethality. However, the role of talin in mammalian epithelial morphogenesis is poorly understood. Here we demonstrate that embryoid bodies (EBs) differentiated from talin1-null embryonic stem cells are defective in integrin adhesion complex assembly, epiblast elongation, and lineage differentiation. These defects are accompanied by a significant reduction in integrin β1 protein levels due to accelerated degradation through an MG-132-sensitive proteasomal pathway. Overexpression of integrin β1 or MG-132 treatment in mutant EBs largely rescues the phenotype. In addition, epiblast cells isolated from talin1-null EBs exhibit impaired cell spreading and focal adhesion formation. Transfection of the mutant cells with green fluorescent protein (GFP)-tagged wild-type but not mutant talin1 that is defective in integrin binding normalizes integrin β1 protein levels and restores focal adhesion formation. Significantly, cell adhesion and spreading are also improved by overexpression of integrin β1. All together, these results suggest that talin1 binding to integrin promotes epiblast adhesion and morphogenesis in part by preventing integrin β1 degradation.
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Affiliation(s)
- Jie Liu
- Department of Surgery, Robert Wood Johnson Medical School-UMDNJ, New Brunswick, New Jersey 08903
| | - Xiaowen He
- Department of Surgery, Robert Wood Johnson Medical School-UMDNJ, New Brunswick, New Jersey 08903
| | - Yanmei Qi
- Department of Surgery, Robert Wood Johnson Medical School-UMDNJ, New Brunswick, New Jersey 08903
| | - Xiaoxiang Tian
- Department of Surgery, Robert Wood Johnson Medical School-UMDNJ, New Brunswick, New Jersey 08903
| | - Susan J. Monkley
- Department of Biochemistry, University of Leicester, Leicester, United Kingdom
| | - David R. Critchley
- Department of Biochemistry, University of Leicester, Leicester, United Kingdom
| | - Siobhan A. Corbett
- Department of Surgery, Robert Wood Johnson Medical School-UMDNJ, New Brunswick, New Jersey 08903
| | - Stephen F. Lowry
- Department of Surgery, Robert Wood Johnson Medical School-UMDNJ, New Brunswick, New Jersey 08903
| | - Alan M. Graham
- Department of Surgery, Robert Wood Johnson Medical School-UMDNJ, New Brunswick, New Jersey 08903
| | - Shaohua Li
- Department of Surgery, Robert Wood Johnson Medical School-UMDNJ, New Brunswick, New Jersey 08903
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Whitman SA, Cover C, Yu L, Nelson DL, Zarnescu DC, Gregorio CC. Desmoplakin and talin2 are novel mRNA targets of fragile X-related protein-1 in cardiac muscle. Circ Res 2011; 109:262-71. [PMID: 21659647 DOI: 10.1161/circresaha.111.244244] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
RATIONALE The proper function of cardiac muscle requires the precise assembly and interactions of numerous cytoskeletal and regulatory proteins into specialized structures that orchestrate contraction and force transmission. Evidence suggests that posttranscriptional regulation is critical for muscle function, but the mechanisms involved remain understudied. OBJECTIVE To investigate the molecular mechanisms and targets of the muscle-specific fragile X mental retardation, autosomal homolog 1 (FXR1), an RNA binding protein whose loss leads to perinatal lethality in mice and cardiomyopathy in zebrafish. METHODS AND RESULTS Using RNA immunoprecipitation approaches we found that desmoplakin and talin2 mRNAs associate with FXR1 in a complex. In vitro assays indicate that FXR1 binds these mRNA targets directly and represses their translation. Fxr1 KO hearts exhibit an up-regulation of desmoplakin and talin2 proteins, which is accompanied by severe disruption of desmosome as well as costamere architecture and composition in the heart, as determined by electron microscopy and deconvolution immunofluorescence analysis. CONCLUSIONS Our findings reveal the first direct mRNA targets of FXR1 in striated muscle and support translational repression as a novel mechanism for regulating heart muscle development and function, in particular the assembly of specialized cytoskeletal structures.
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Affiliation(s)
- Samantha A Whitman
- Department of Cellular and Molecular Medicine, University of Arizona, 1656 East Mabel, Tucson, AZ 85724, USA
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13
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Monkley SJ, Kostourou V, Spence L, Petrich B, Coleman S, Ginsberg MH, Pritchard CA, Critchley DR. Endothelial cell talin1 is essential for embryonic angiogenesis. Dev Biol 2011; 349:494-502. [PMID: 21081121 PMCID: PMC3025397 DOI: 10.1016/j.ydbio.2010.11.010] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Revised: 11/04/2010] [Accepted: 11/05/2010] [Indexed: 11/30/2022]
Abstract
Using Tln1(fl/fl);CreER mice, we show that tamoxifen-induced inactivation of the talin1 gene throughout the embryo produces an angiogenesis phenotype that is restricted to newly forming blood vessels. The phenotype has a rapid onset in early embryos, resulting in vessel defects by 48 h and death of the embryo within 72 h. Very similar vascular defects were obtained using a Tie2-Cre endothelial cell-specific Tln1 knockout, a phenotype that was rescued by expression of a Tln1 mini-gene in endothelial cells. We show that endothelial cells, unlike most other cell types, do not express talin2, which can compensate for loss of talin1, and demonstrate for the first time that endothelial cells in vivo lacking talin1 are unable to undergo the cell spreading and flattening required to form vessels.
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Affiliation(s)
- Susan J Monkley
- Department of Biochemistry, University of Leicester, Lancaster Road, Leicester, LE1 9HN, UK.
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14
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Kopp PM, Bate N, Hansen TM, Brindle NPJ, Praekelt U, Debrand E, Coleman S, Mazzeo D, Goult BT, Gingras AR, Pritchard CA, Critchley DR, Monkley SJ. Studies on the morphology and spreading of human endothelial cells define key inter- and intramolecular interactions for talin1. Eur J Cell Biol 2010; 89:661-73. [PMID: 20605055 PMCID: PMC2958305 DOI: 10.1016/j.ejcb.2010.05.003] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2010] [Revised: 05/14/2010] [Accepted: 05/17/2010] [Indexed: 01/07/2023] Open
Abstract
Talin binds to and activates integrins and is thought to couple them to cytoskeletal actin. However, functional studies on talin have been restricted by the fact that most cells express two talin isoforms. Here we show that human umbilical vein endothelial cells (HUVEC) express only talin1, and that talin1 knockdown inhibited focal adhesion (FA) assembly preventing the cells from maintaining a spread morphology, a phenotype that was rescued by GFP-mouse talin1. Thus HUVEC offer an ideal model system in which to conduct talin structure/function studies. Talin contains an N-terminal FERM domain (comprised of F1, F2 and F3 domains) and a C-terminal flexible rod. The F3 FERM domain binds β-integrin tails, and mutations in F3 that inhibited integrin binding (W359A) or activation (L325R) severely compromised the ability of GFP-talin1 to rescue the talin1 knockdown phenotype despite the presence of a second integrin-binding site in the talin rod. The talin rod contains several actin-binding sites (ABS), and mutations in the C-terminal ABS that reduced actin-binding impaired talin1 function, whereas those that increased binding resulted in more stable FAs. The results show that both the N-terminal integrin and C-terminal actin-binding functions of talin are essential to cell spreading and FA assembly. Finally, mutations that relieve talin auto-inhibition resulted in the rapid and excessive production of FA, highlighting the importance of talin regulation within the cell.
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Affiliation(s)
- Petra M Kopp
- Department of Biochemistry, University of Leicester, Leicester, UK
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15
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Critchley DR. Biochemical and structural properties of the integrin-associated cytoskeletal protein talin. Annu Rev Biophys 2009; 38:235-54. [PMID: 19416068 DOI: 10.1146/annurev.biophys.050708.133744] [Citation(s) in RCA: 201] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Interaction of cells with the extracellular matrix is fundamental to a wide variety of biological processes, such as cell proliferation, cell migration, embryogenesis, and organization of cells into tissues, and defects in cell-matrix interactions are an important element in many diseases. Cell-matrix interactions are frequently mediated by the integrin family of cell adhesion molecules, transmembrane alphabeta-heterodimers that are typically linked to the actin cytoskeleton by one of a number of adaptor proteins including talin, alpha-actinin, filamin, tensin, integrin-linked kinase, melusin, and skelemin. The focus of this review is talin, which appears unique among these proteins in that it also induces a conformational change in integrins that is propagated across the membrane, and increases the affinity of the extracellular domain for ligand. Particular emphasis is given to recent progress on the structure of talin, its interaction with binding partners, and its mode of regulation.
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Affiliation(s)
- David R Critchley
- Department of Biochemistry, University of Leicester, Leicester LE1 9HN, UK.
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Goult BT, Bate N, Anthis NJ, Wegener KL, Gingras AR, Patel B, Barsukov IL, Campbell ID, Roberts GCK, Critchley DR. The structure of an interdomain complex that regulates talin activity. J Biol Chem 2009; 284:15097-106. [PMID: 19297334 PMCID: PMC2685691 DOI: 10.1074/jbc.m900078200] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2009] [Revised: 02/27/2009] [Indexed: 11/16/2022] Open
Abstract
Talin is a large flexible rod-shaped protein that activates the integrin family of cell adhesion molecules and couples them to cytoskeletal actin. It exists in both globular and extended conformations, and an intramolecular interaction between the N-terminal F3 FERM subdomain and the C-terminal part of the talin rod contributes to an autoinhibited form of the molecule. Here, we report the solution structure of the primary F3 binding domain within the C-terminal region of the talin rod and use intermolecular nuclear Overhauser effects to determine the structure of the complex. The rod domain (residues 1655-1822) is an amphipathic five-helix bundle; Tyr-377 of F3 docks into a hydrophobic pocket at one end of the bundle, whereas a basic loop in F3 (residues 316-326) interacts with a cluster of acidic residues in the middle of helix 4. Mutation of Glu-1770 abolishes binding. The rod domain competes with beta3-integrin tails for binding to F3, and the structure of the complex suggests that the rod is also likely to sterically inhibit binding of the FERM domain to the membrane.
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Affiliation(s)
- Benjamin T Goult
- Department of Biochemistry, University of Leicester, Lancaster Road, Leicester LE1 9HN, UK
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Debrand E, El Jai Y, Spence L, Bate N, Praekelt U, Pritchard CA, Monkley SJ, Critchley DR. Talin 2 is a large and complex gene encoding multiple transcripts and protein isoforms. FEBS J 2009; 276:1610-28. [PMID: 19220457 PMCID: PMC2702505 DOI: 10.1111/j.1742-4658.2009.06893.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Talins are large adaptor proteins that link the integrin family of adhesion molecules to F-actin. In vertebrates, there are two talin genes. Talin 1 is essential for integrin-mediated cell adhesion; the role of talin 2 is unclear. Here we report a detailed analysis of mammalian talin 2. This reveals the existence of a previously unrecognized promoter associated with a CpG island, and separated from the first coding exon by numerous alternatively spliced noncoding exons spanning > 200 kb. Analysis of a mouse gene trap line shows that this promoter accounts for most of the talin 2 expression in adult tissues. We also demonstrate that testis and kidney express truncated talin 2 isoforms that lack the N-terminal half of the protein, and provide evidence for the developmentally regulated expression of the short testis-specific talin 2 isoform in elongating spermatids. Finally, we identify four tissue-specific alternative splicing events within the coding region of talin 2.
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Affiliation(s)
- Emmanuel Debrand
- Department of Biochemistry, University of Leicester, Leicester, UK
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Lo SH. Focal adhesions: what's new inside. Dev Biol 2006; 294:280-91. [PMID: 16650401 DOI: 10.1016/j.ydbio.2006.03.029] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2005] [Revised: 03/22/2006] [Accepted: 03/27/2006] [Indexed: 01/15/2023]
Abstract
The cytoplasmic side of focal adhesions is comprised of large molecular complexes that link transmembrane receptors, such as integrins, to the actin cytoskeleton and mediate signals modulating cell attachment, migration, proliferation, differentiation, and gene expression. These complexes are heterogeneous and dynamic structures that are apparent targets of regulatory signals that control the function of focal adhesions. Recent studies using genetic approaches in invertebrate and vertebrate systems have begun to reveal the structure and function of these complexes in vivo.
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Affiliation(s)
- Su Hao Lo
- Center for Tissue Regeneration and Repair, Department of Orthopaedic Surgery and Cancer Center, University of California-Davis, Davis, Sacramento, CA 95817, USA.
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