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Abstract
Cells use the actin cytoskeleton for many of their functions, including their division, adhesion, mechanosensing, endo- and phagocytosis, migration, and invasion. Actin bundles are the main constituent of actin-rich structures involved in these processes. An ever-increasing number of proteins that crosslink actin into bundles or regulate their morphology is being identified in cells. With recent advances in high-resolution microscopy and imaging techniques, the complex process of bundles formation and the multiple forms of physiological bundles are beginning to be better understood. Here, we review the physiochemical and biological properties of four families of highly conserved and abundant actin-bundling proteins, namely, α-actinin, fimbrin/plastin, fascin, and espin. We describe the similarities and differences between these proteins, their role in the formation of physiological actin bundles, and their properties-both related and unrelated to their bundling abilities. We also review some aspects of the general mechanism of actin bundles formation, which are known from the available information on the activity of the key actin partners involved in this process.
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Affiliation(s)
- Sudeepa Rajan
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
| | - Dmitri S. Kudryashov
- Department of Chemistry and Biochemistry, Ohio State University, Columbus, OH 43210, USA
| | - Emil Reisler
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
- Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
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2
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Odenthal J, Dittrich S, Ludwig V, Merz T, Reitmeier K, Reusch B, Höhne M, Cosgun ZC, Hohenadel M, Putnik J, Göbel H, Rinschen MM, Altmüller J, Koehler S, Schermer B, Benzing T, Beck BB, Brinkkötter PT, Habbig S, Bartram MP. Modeling of ACTN4-Based Podocytopathy Using Drosophila Nephrocytes. Kidney Int Rep 2022; 8:317-329. [PMID: 36815115 PMCID: PMC9939316 DOI: 10.1016/j.ekir.2022.10.024] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 10/17/2022] [Accepted: 10/24/2022] [Indexed: 11/06/2022] Open
Abstract
Introduction Genetic disorders are among the most prevalent causes leading to progressive glomerular disease and, ultimately, end-stage renal disease (ESRD) in children and adolescents. Identification of underlying genetic causes is indispensable for targeted treatment strategies and counseling of affected patients and their families. Methods Here, we report on a boy who presented at 4 years of age with proteinuria and biopsy-proven focal segmental glomerulosclerosis (FSGS) that was temporarily responsive to treatment with ciclosporin A. Molecular genetic testing identified a novel mutation in alpha-actinin-4 (p.M240T). We describe a feasible and efficient experimental approach to test its pathogenicity by combining in silico, in vitro, and in vivo analyses. Results The de novo p.M240T mutation led to decreased alpha-actinin-4 stability as well as protein mislocalization and actin cytoskeleton rearrangements. Transgenic expression of wild-type human alpha-actinin-4 in Drosophila melanogaster nephrocytes was able to ameliorate phenotypes associated with the knockdown of endogenous actinin. In contrast, p.M240T, as well as other established disease variants p.W59R and p.K255E, failed to rescue these phenotypes, underlining the pathogenicity of the novel alpha-actinin-4 variant. Conclusion Our data highlight that the newly identified alpha-actinin-4 mutation indeed encodes for a disease-causing variant of the protein and promote the Drosophila model as a simple and convenient tool to study monogenic kidney disease in vivo.
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Affiliation(s)
- Johanna Odenthal
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, Faculty of Medicine, University of Cologne, University Hospital Cologne, Cologne, Germany
| | - Sebastian Dittrich
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, Faculty of Medicine, University of Cologne, University Hospital Cologne, Cologne, Germany
| | - Vivian Ludwig
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, Faculty of Medicine, University of Cologne, University Hospital Cologne, Cologne, Germany
| | - Tim Merz
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, Faculty of Medicine, University of Cologne, University Hospital Cologne, Cologne, Germany
| | - Katrin Reitmeier
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, Faculty of Medicine, University of Cologne, University Hospital Cologne, Cologne, Germany
| | - Björn Reusch
- Center for Molecular Medicine Cologne, Faculty of Medicine, University of Cologne, University Hospital Cologne, Cologne, Germany,Institute of Human Genetics, Faculty of Medicine, University of Cologne, University Hospital Cologne, Cologne, Germany
| | - Martin Höhne
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, Faculty of Medicine, University of Cologne, University Hospital Cologne, Cologne, Germany
| | - Zülfü C. Cosgun
- Department of Pediatrics, Faculty of Medicine, University of Cologne, University Hospital Cologne, Cologne, Germany
| | - Maximilian Hohenadel
- Department of Pediatrics, Division of Pediatric Nephrology, University of Bonn, Bonn, Germany
| | - Jovana Putnik
- Mother and Child Health Care Institute of Serbia “Dr Vukan Čupić,” Department of Nephrology, Faculty of Medicine, University of Belgrade, Belgrade, Serbia
| | - Heike Göbel
- Institute of Pathology, University Hospital of Cologne, Cologne, Germany
| | - Markus M. Rinschen
- Department of Biomedicine, Aarhus University, Aarhus, Denmark,Aarhus Institute of Advanced Studies, Aarhus University, Aarhus, Denmark,III Medical Clinic, University Hospital Hamburg Eppendorf, Hamburg, Germany
| | - Janine Altmüller
- Berlin Institute of Health at Charité-Universitätsmedizin Berlin, Max Delbrück Center for Molecular Medicine, Berlin, Germany,Cologne Center for Genomics, University of Cologne, Cologne, Germany
| | - Sybille Koehler
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, Faculty of Medicine, University of Cologne, University Hospital Cologne, Cologne, Germany
| | - Bernhard Schermer
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, Faculty of Medicine, University of Cologne, University Hospital Cologne, Cologne, Germany,Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, Faculty of Medicine, University of Cologne, University Hospital Cologne, Cologne, Germany
| | - Thomas Benzing
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, Faculty of Medicine, University of Cologne, University Hospital Cologne, Cologne, Germany,Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, Faculty of Medicine, University of Cologne, University Hospital Cologne, Cologne, Germany
| | - Bodo B. Beck
- Center for Molecular Medicine Cologne, Faculty of Medicine, University of Cologne, University Hospital Cologne, Cologne, Germany,Institute of Human Genetics, Faculty of Medicine, University of Cologne, University Hospital Cologne, Cologne, Germany
| | - Paul T. Brinkkötter
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, Faculty of Medicine, University of Cologne, University Hospital Cologne, Cologne, Germany,Correspondence: Paul T. Brinkkoetter, Department II of Internal Medicine, Faculty of Medicine, University of Cologne, University Hospital Cologne, Kerpener Street 62, Cologne 50935, Germany.
| | - Sandra Habbig
- Department of Pediatrics, Faculty of Medicine, University of Cologne, University Hospital Cologne, Cologne, Germany
| | - Malte P. Bartram
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, Faculty of Medicine, University of Cologne, University Hospital Cologne, Cologne, Germany
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3
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Abstract
Alpha-ACTN4, a member of alpha-actinin family is critical for cell motility through its regulated binding of actin filaments. We previously found that EGF exposure of cells triggers the tyrosyl-phosphorylation of ACTN4 in fibroblasts that dramatically downregulates its binding to actin filaments. However, the exact kinase remained uncertain. In the present study, we report that the phosphorylation of ACTN4 occurs within seconds upon EGF treatments and is accomplished via direct interaction of ACTN4 with the EGF receptor. The major binding domain of ACTN4 for EGF receptor is mapped to the N-terminal 32 amino acids. A second domain minimizes the interaction, as truncation of the C-terminal tail enhances ACTN4 binding to EGF receptor. A mimetic phosphorylated ACTN4, Y4/31E, presents low binding to EGF receptor. Overexpression of EGF receptor in melanoma cell lines, also accomplishes the phosphorylation of ACTN4 in the presence of EGF. These findings suggest that the binding of ACTN4 to EGFR enables its direct and rapid phosphorylation resulting in dissociation from EGFR and decreased binding to actin filaments.
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Affiliation(s)
- Hanshuang Shao
- Department of Pathology, University of Pittsburgh, Pittsburgh, PA 15213, United States.,Pittsburgh VA Health System, Pittsburgh, PA 15213, United States
| | - Alan Wells
- Department of Pathology, University of Pittsburgh, Pittsburgh, PA 15213, United States.,Pittsburgh VA Health System, Pittsburgh, PA 15213, United States
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4
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Morita R, Nakano K, Shigeta Y, Harada R. Molecular Mechanism for the Actin-Binding Domain of α-Actinin Ain1 Elucidated by Molecular Dynamics Simulations and Mutagenesis Experiments. J Phys Chem B 2020; 124:8495-8503. [DOI: 10.1021/acs.jpcb.0c04623] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Rikuri Morita
- Department of Biological Sciences, Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennohdai, Tsukuba, Ibaraki 305-8572, Japan
- Center for Computational Sciences, University of Tsukuba, 1-1-1 Tennohdai, Tsukuba, Ibaraki 305-8577, Japan
| | - Kentaro Nakano
- Department of Biological Sciences, Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennohdai, Tsukuba, Ibaraki 305-8572, Japan
| | - Yasuteru Shigeta
- Center for Computational Sciences, University of Tsukuba, 1-1-1 Tennohdai, Tsukuba, Ibaraki 305-8577, Japan
| | - Ryuhei Harada
- Center for Computational Sciences, University of Tsukuba, 1-1-1 Tennohdai, Tsukuba, Ibaraki 305-8577, Japan
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Rai A, Bleimling N, Vetter IR, Goody RS. The mechanism of activation of the actin binding protein EHBP1 by Rab8 family members. Nat Commun 2020; 11:4187. [PMID: 32826901 DOI: 10.1038/s41467-020-17792-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 07/19/2020] [Indexed: 12/18/2022] Open
Abstract
EHBP1 is an adaptor protein that regulates vesicular trafficking by recruiting Rab8 family members and Eps15-homology domain-containing proteins 1/2 (EHD1/2). It also links endosomes to the actin cytoskeleton. However, the underlying molecular mechanism of activation of EHBP1 actin-binding activity is unclear. Here, we show that both termini of EHBP1 have membrane targeting potential. EHBP1 associates with PI(3)P, PI(5)P, and phosphatidylserine via its N-terminal C2 domain. We show that in the absence of Rab8 family members, the C-terminal bivalent Mical/EHBP Rab binding (bMERB) domain forms an intramolecular complex with its central calponin homology (CH) domain and auto-inhibits actin binding. Rab8 binding to the bMERB domain relieves this inhibition. We have analyzed the CH:bMERB auto-inhibited complex and the active bMERB:Rab8 complex biochemically and structurally. Together with structure-based mutational studies, this explains how binding of Rab8 frees the CH domain and allows it to interact with the actin cytoskeleton, leading to membrane tubulation. EHBP1 is an adaptor protein that regulates vesicular trafficking and links endosomes to the actin cytoskeleton. Here, authors show that both termini of EHBP1 have membrane targeting potential and that in the absence of its binding partner Rab8, the bMERB and CH domain of EHBP1 form an intramolecular complex which auto-inhibits actin binding.
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Feng D, Kumar M, Muntel J, Gurley SB, Birrane G, Stillman IE, Ding L, Wang M, Ahmed S, Schlondorff J, Alper SL, Ferrante T, Marquez SL, Ng CF, Novak R, Ingber DE, Steen H, Pollak MR. Phosphorylation of ACTN4 Leads to Podocyte Vulnerability and Proteinuric Glomerulosclerosis. J Am Soc Nephrol 2020; 31:1479-1495. [PMID: 32540856 PMCID: PMC7351002 DOI: 10.1681/asn.2019101032] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Accepted: 03/23/2020] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND Genetic mutations in α-actinin-4 (ACTN4)-an important actin crosslinking cytoskeletal protein that provides structural support for kidney podocytes-have been linked to proteinuric glomerulosclerosis in humans. However, the effect of post-translational modifications of ACTN4 on podocyte integrity and kidney function is not known. METHODS Using mass spectrometry, we found that ACTN4 is phosphorylated at serine (S) 159 in human podocytes. We used phosphomimetic and nonphosphorylatable ACTN4 to comprehensively study the effects of this phosphorylation in vitro and in vivo. We conducted x-ray crystallography, F-actin binding and bundling assays, and immunofluorescence staining to evaluate F-actin alignment. Microfluidic organ-on-a-chip technology was used to assess for detachment of podocytes simultaneously exposed to fluid flow and cyclic strain. We then used CRISPR/Cas9 to generate mouse models and assessed for renal injury by measuring albuminuria and examining kidney histology. We also performed targeted mass spectrometry to determine whether high extracellular glucose or TGF-β levels increase phosphorylation of ACTN4. RESULTS Compared with the wild type ACTN4, phosphomimetic ACTN4 demonstrated increased binding and bundling activity with F-actin in vitro. Phosphomimetic Actn4 mouse podocytes exhibited more spatially correlated F-actin alignment and a higher rate of detachment under mechanical stress. Phosphomimetic Actn4 mice developed proteinuria and glomerulosclerosis after subtotal nephrectomy. Moreover, we found that exposure to high extracellular glucose or TGF-β stimulates phosphorylation of ACTN4 at S159 in podocytes. CONCLUSIONS These findings suggest that increased phosphorylation of ACTN4 at S159 leads to biochemical, cellular, and renal pathology that is similar to pathology resulting from human disease-causing mutations in ACTN4. ACTN4 may mediate podocyte injury as a consequence of both genetic mutations and signaling events that modulate phosphorylation.
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Affiliation(s)
- Di Feng
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts,Wyss Institute for Biologically Inspired Engineering at Harvard University, Boston, Massachusetts
| | - Mukesh Kumar
- Department of Pathology, Boston Children’s Hospital and Harvard Medical School, Boston, Massachusetts,F.M. Kirby Neurobiology Center, Department of Neurobiology, Boston Children’s Hospital, Boston, Massachusetts
| | | | - Susan B. Gurley
- Division of Nephrology and Hypertension, Oregon Health & Science University, Portland, Oregon
| | - Gabriel Birrane
- Division of Experimental Medicine, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts
| | - Isaac E. Stillman
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts,Department of Pathology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts
| | - Lai Ding
- NeuroTechnology Studio, Program for Interdisciplinary Neuroscience, Brigham and Women’s Hospital, Boston, Massachusetts
| | - Minxian Wang
- Broad Institute of Harvard and Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Saima Ahmed
- Department of Pathology, Boston Children’s Hospital and Harvard Medical School, Boston, Massachusetts
| | - Johannes Schlondorff
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts
| | - Seth L. Alper
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts,Broad Institute of Harvard and Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - Tom Ferrante
- Wyss Institute for Biologically Inspired Engineering at Harvard University, Boston, Massachusetts
| | - Susan L. Marquez
- Wyss Institute for Biologically Inspired Engineering at Harvard University, Boston, Massachusetts
| | - Carlos F. Ng
- Wyss Institute for Biologically Inspired Engineering at Harvard University, Boston, Massachusetts
| | - Richard Novak
- Wyss Institute for Biologically Inspired Engineering at Harvard University, Boston, Massachusetts
| | - Donald E. Ingber
- Wyss Institute for Biologically Inspired Engineering at Harvard University, Boston, Massachusetts,Vascular Biology Program, Boston Children’s Hospital and Harvard Medical School, Boston, Massachusetts,Department of Surgery, Boston Children’s Hospital and Harvard Medical School, Boston, Massachusetts,Harvard John A. Paulson School of Engineering and Applied Sciences, Cambridge, Massachusetts
| | - Hanno Steen
- Department of Pathology, Boston Children’s Hospital and Harvard Medical School, Boston, Massachusetts
| | - Martin R. Pollak
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts,Broad Institute of Harvard and Massachusetts Institute of Technology, Cambridge, Massachusetts
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Harris AR, Belardi B, Jreij P, Wei K, Shams H, Bausch A, Fletcher DA. Steric regulation of tandem calponin homology domain actin-binding affinity. Mol Biol Cell 2019; 30:3112-3122. [PMID: 31693446 PMCID: PMC6938246 DOI: 10.1091/mbc.e19-06-0317] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Revised: 10/03/2019] [Accepted: 10/29/2019] [Indexed: 11/11/2022] Open
Abstract
Tandem calponin homology (CH1-CH2) domains are common actin-binding domains in proteins that interact with and organize the actin cytoskeleton. Despite regions of high sequence similarity, CH1-CH2 domains can have remarkably different actin-binding properties, with disease-associated point mutants known to increase as well as decrease affinity for F-actin. To investigate features that affect CH1-CH2 affinity for F-actin in cells and in vitro, we perturbed the utrophin actin-binding domain by making point mutations at the CH1-CH2 interface, replacing the linker domain, and adding a polyethylene glycol (PEG) polymer to CH2. Consistent with a previous model describing CH2 as a steric negative regulator of actin binding, we find that utrophin CH1-CH2 affinity is both increased and decreased by modifications that change the effective "openness" of CH1 and CH2 in solution. We also identified interface mutations that caused a large increase in affinity without changing solution "openness," suggesting additional influences on affinity. Interestingly, we also observe nonuniform subcellular localization of utrophin CH1-CH2 that depends on the N-terminal flanking region but not on bulk affinity. These observations provide new insights into how small sequence changes, such as those found in diseases, can affect CH1-CH2 binding properties.
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Affiliation(s)
- Andrew R. Harris
- Department of Bioengineering, University of California, Berkeley, Berkeley, CA 94720
| | - Brian Belardi
- Department of Bioengineering, University of California, Berkeley, Berkeley, CA 94720
| | - Pamela Jreij
- Department of Bioengineering, University of California, Berkeley, Berkeley, CA 94720
| | - Kathy Wei
- Department of Bioengineering, University of California, Berkeley, Berkeley, CA 94720
| | - Hengameh Shams
- Department of Mechanical Engineering, University of California, Berkeley, Berkeley, CA 94720
| | - Andreas Bausch
- Lehrstuhl für Biophysik (E27), Technische Universität München, Garching 85748, Germany
| | - Daniel A. Fletcher
- Department of Bioengineering, University of California, Berkeley, Berkeley, CA 94720
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
- Chan Zuckerberg Biohub, San Francisco, CA 94158
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8
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Shao H, Wingert B, Weins A, Pollak MR, Camacho C, Wells A. Focal segmental glomerulosclerosis ACTN4 mutants binding to actin: regulation by phosphomimetic mutations. Sci Rep 2019; 9:15517. [PMID: 31664084 DOI: 10.1038/s41598-019-51825-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Accepted: 10/05/2019] [Indexed: 11/21/2022] Open
Abstract
Natural mutations such as lysine 255 to glutamic acid (K to E), threonine 259 to isoleucine (T to I) and serine 262 to proline (S to P) that occur within the actin binding domain of alpha-actinin-4 (ACTN4) cause an autosomal dominant form of focal segmental glomerulosclerosis (FSGS) in affected humans. This appears due to elevated actin binding propensity in podocytes resulting in a ‘frozen’ cytoskeleton. What is challenging is how this cellular behavior would be compatible with other cell functions that rely on cytoskeleton plasticity. Our previous finding revealed that wild type ACTN4 can be phosphorylated at tyrosine 4 and 31 upon stimulation by epidermal growth factor (EGF) to reduce the binding to actin cytoskeleton. We queried whether the elevated actin binding activity of FSGS mutants can be downregulated by EGF-mediated phosphorylation, to discern a mechanism by which the actin-cytoskeleton can be released in FSGS. In this manuscript, we first constructed variants with Y4/31E to mimic the phosphorylation at tyrosines 4 and 31 based on earlier modeling simulations that predicted that this would bury the actin binding domains and lead to a decrease in actin binding activity. We found that Y4/31E significantly reduced the actin binding activity of K255E, T259I and S262P, dramatically preventing them from aggregating in, and inhibiting motility of, podocytes, fibroblasts and melanoma cells. A putative kinase target site at Y265 in the actin binding domain was also generated as a phosphomimetic ACTN4 Y265E that demonstrated even greater binding to actin filaments than K255E and the other FSGS mutants. That the tyrosine kinase regulation of FSGS mutation binding to actin filaments can occur in cells was shown by phosphorylation on Y4 and Y31 of the K225E after extended exposure of cells to EGF, with a decrease in ACTN4 aggregates in fibroblasts. These findings will provide evidence for targeting the N-termini of FSGS ACTN4 mutants to downregulate their actin binding activities for ameliorating the glomerulosclerotic phenotype of patients.
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Abstract
When it comes to crystallization each protein is unique. It can never be predicted beforehand in which condition the particular protein will crystallize or even if it is possible to crystallize. Still, by following some simple checkpoints the chances of obtaining crystals are increased. The primary checkpoints are purity, stability, concentration, and homogeneity. High-quality protein crystals are needed. This protocol will allow an investigator to: clone, express, and crystallize a protein of interest.
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Affiliation(s)
- Karina Persson
- Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden
| | - Lars Backman
- Department of Chemistry, Umeå University, SE-901 87 Umeå, Sweden.
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10
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Fealey ME, Horn B, Coffman C, Miller R, Lin AY, Thompson AR, Schramel J, Groth E, Hinderliter A, Cembran A, Thomas DD. Dynamics of Dystrophin's Actin-Binding Domain. Biophys J 2018; 115:445-454. [PMID: 30007583 DOI: 10.1016/j.bpj.2018.05.039] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 05/25/2018] [Accepted: 05/31/2018] [Indexed: 01/30/2023] Open
Abstract
We have used pulsed electron paramagnetic resonance, calorimetry, and molecular dynamics simulations to examine the structural mechanism of binding for dystrophin's N-terminal actin-binding domain (ABD1) and compare it to utrophin's ABD1. Like other members of the spectrin superfamily, dystrophin's ABD1 consists of two calponin-homology (CH) domains, CH1 and CH2. Several mutations within dystrophin's ABD1 are associated with the development of severe degenerative muscle disorders Duchenne and Becker muscular dystrophies, highlighting the importance of understanding its structural biology. To investigate structural changes within dystrophin ABD1 upon binding to actin, we labeled the protein with spin probes and measured changes in inter-CH domain distance using double-electron electron resonance. Previous studies on the homologous protein utrophin showed that actin binding induces a complete structural opening of the CH domains, resulting in a highly ordered ABD1-actin complex. In this study, double-electron electron resonance shows that dystrophin ABD1 also undergoes a conformational opening upon binding F-actin, but this change is less complete and significantly more structurally disordered than observed for utrophin. Using molecular dynamics simulations, we identified a hinge in the linker region between the two CH domains that grants conformational flexibility to ABD1. The conformational dynamics of both dystrophin's and utrophin's ABD1 showed that compact conformations driven by hydrophobic interactions are preferred and that extended conformations are energetically accessible through a flat free-energy surface. Considering that the binding free energy of ABD1 to actin is on the order of 6-7 kcal/mole, our data are compatible with a mechanism in which binding to actin is largely dictated by specific interactions with CH1, but fine tuning of the binding affinity is achieved by the overlap between conformational ensembles of ABD1 free and bound to actin.
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Affiliation(s)
- Michael E Fealey
- Department of Biochemistry, Molecular Biology & Biophysics, University of Minnesota, Minneapolis, Minnesota
| | - Benjamin Horn
- Department of Chemistry and Biochemistry, University of Minnesota Duluth, Duluth, Minnesota
| | - Christian Coffman
- Department of Chemistry and Biochemistry, University of Minnesota Duluth, Duluth, Minnesota
| | - Robert Miller
- Department of Chemistry and Biochemistry, University of Minnesota Duluth, Duluth, Minnesota
| | - Ava Y Lin
- Department of Biochemistry, Molecular Biology & Biophysics, University of Minnesota, Minneapolis, Minnesota
| | - Andrew R Thompson
- Department of Biochemistry, Molecular Biology & Biophysics, University of Minnesota, Minneapolis, Minnesota
| | - Justine Schramel
- Department of Chemistry and Biochemistry, University of Minnesota Duluth, Duluth, Minnesota
| | - Erin Groth
- Department of Chemistry and Biochemistry, University of Minnesota Duluth, Duluth, Minnesota
| | - Anne Hinderliter
- Department of Chemistry and Biochemistry, University of Minnesota Duluth, Duluth, Minnesota
| | - Alessandro Cembran
- Department of Chemistry and Biochemistry, University of Minnesota Duluth, Duluth, Minnesota
| | - David D Thomas
- Department of Biochemistry, Molecular Biology & Biophysics, University of Minnesota, Minneapolis, Minnesota.
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11
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Abstract
Force transmission through the actin cytoskeleton plays a central role in cell movements, shape change, and internal organization. Dynamic reorganization of actin filaments by an array of specialized binding proteins creates biochemically and architecturally distinct structures, many of which are finely tuned to exert or resist mechanical loads. The molecular complexity of the actin cytoskeleton continues to be revealed by detailed biochemical assays, and the architectural diversity and dynamics of actin structures are being uncovered by advances in super-resolution fluorescence microscopy and electron microscopy. However, our understanding of how mechanical forces feed back on cytoskeletal architecture and actin-binding protein organization is comparatively limited. In this review, we discuss recent work investigating how mechanical forces applied to cytoskeletal proteins are transduced into biochemical signals. We explore multiple mechanisms for mechanical signal transduction, including the mechanosensitive behavior of actin-binding proteins, the effect of mechanical force on actin filament dynamics, and the influence of mechanical forces on the structure of single actin filaments. The emerging picture is one in which the actin cytoskeleton is defined not only by the set of proteins that constitute a network but also by the constant interplay of mechanical forces and biochemistry.
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Affiliation(s)
- Andrew R. Harris
- Department of Bioengineering, and Biophysics Program, University of California, Berkeley, California 94720, USA
| | - Pamela Jreij
- Department of Bioengineering, and Biophysics Program, University of California, Berkeley, California 94720, USA
| | - Daniel A. Fletcher
- Department of Bioengineering, and Biophysics Program, University of California, Berkeley, California 94720, USA
- Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Chan Zuckerberg Biohub, San Francisco, California 94158, USA
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12
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Avery AW, Fealey ME, Wang F, Orlova A, Thompson AR, Thomas DD, Hays TS, Egelman EH. Structural basis for high-affinity actin binding revealed by a β-III-spectrin SCA5 missense mutation. Nat Commun 2017; 8:1350. [PMID: 29116080 DOI: 10.1038/s41467-017-01367-w] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Accepted: 09/08/2017] [Indexed: 12/24/2022] Open
Abstract
Spinocerebellar ataxia type 5 (SCA5) is a neurodegenerative disease caused by mutations in the cytoskeletal protein β-III-spectrin. Previously, a SCA5 mutation resulting in a leucine-to-proline substitution (L253P) in the actin-binding domain (ABD) was shown to cause a 1000-fold increase in actin-binding affinity. However, the structural basis for this increase is unknown. Here, we report a 6.9 Å cryo-EM structure of F-actin complexed with the L253P ABD. This structure, along with co-sedimentation and pulsed-EPR measurements, demonstrates that high-affinity binding caused by the CH2-localized mutation is due to opening of the two CH domains. This enables CH1 to bind actin aided by an unstructured N-terminal region that becomes α-helical upon binding. This helix is required for association with actin as truncation eliminates binding. Collectively, these results shed light on the mechanism by which β-III-spectrin, and likely similar actin-binding proteins, interact with actin, and how this mechanism can be perturbed to cause disease.
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Shams H, Soheilypour M, Peyro M, Moussavi-Baygi R, Mofrad MRK. Looking "Under the Hood" of Cellular Mechanotransduction with Computational Tools: A Systems Biomechanics Approach across Multiple Scales. ACS Biomater Sci Eng 2017; 3:2712-2726. [PMID: 33418698 DOI: 10.1021/acsbiomaterials.7b00117] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Signal modulation has been developed in living cells throughout evolution to promote utilizing the same machinery for multiple cellular functions. Chemical and mechanical modules of signal transmission and transduction are interconnected and necessary for organ development and growth. However, due to the high complexity of the intercommunication of physical intracellular connections with biochemical pathways, there are many missing details in our overall understanding of mechanotransduction processes, i.e., the process by which mechanical signals are converted to biochemical cascades. Cell-matrix adhesions are mechanically coupled to the nucleus through the cytoskeleton. This modulated and tightly integrated network mediates the transmission of mechanochemical signals from the extracellular matrix to the nucleus. Various experimental and computational techniques have been utilized to understand the basic mechanisms of mechanotransduction, yet many aspects have remained elusive. Recently, in silico experiments have made important contributions to the field of mechanobiology. Herein, computational modeling efforts devoted to understanding integrin-mediated mechanotransduction pathways are reviewed, and an outlook is presented for future directions toward using suitable computational approaches and developing novel techniques for addressing important questions in the field of mechanotransduction.
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Affiliation(s)
- Hengameh Shams
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California 94720-1762, United States
| | - Mohammad Soheilypour
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California 94720-1762, United States
| | - Mohaddeseh Peyro
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California 94720-1762, United States
| | - Ruhollah Moussavi-Baygi
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California 94720-1762, United States
| | - Mohammad R K Mofrad
- Molecular Cell Biomechanics Laboratory, Departments of Bioengineering and Mechanical Engineering, University of California, Berkeley, California 94720-1762, United States
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Haywood NJ, Wolny M, Rogers B, Trinh CH, Shuping Y, Edwards TA, Peckham M. Hypertrophic cardiomyopathy mutations in the calponin-homology domain of ACTN2 affect actin binding and cardiomyocyte Z-disc incorporation. Biochem J 2016; 473:2485-93. [PMID: 27287556 PMCID: PMC4980809 DOI: 10.1042/bcj20160421] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Revised: 06/06/2016] [Accepted: 06/09/2016] [Indexed: 11/17/2022]
Abstract
α-Actinin-2 (ACTN2) is the only muscle isoform of α-actinin expressed in cardiac muscle. Mutations in this protein have been implicated in mild to moderate forms of hypertrophic cardiomyopathy (HCM). We have investigated the effects of two mutations identified from HCM patients, A119T and G111V, on the secondary and tertiary structure of a purified actin binding domain (ABD) of ACTN2 by circular dichroism and X-ray crystallography, and show small but distinct changes for both mutations. We also find that both mutants have reduced F-actin binding affinity, although the differences are not significant. The full length mEos2 tagged protein expressed in adult cardiomyocytes shows that both mutations additionally affect Z-disc localization and dynamic behaviour. Overall, these two mutations have small effects on structure, function and behaviour, which may contribute to a mild phenotype for this disease.
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Affiliation(s)
- Natalie J Haywood
- Astbury Centre for Structural Molecular Biology and the School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, U.K
| | - Marcin Wolny
- Astbury Centre for Structural Molecular Biology and the School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, U.K
| | - Brendan Rogers
- Astbury Centre for Structural Molecular Biology and the School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, U.K
| | - Chi H Trinh
- Astbury Centre for Structural Molecular Biology and the School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, U.K
| | - Yu Shuping
- Astbury Centre for Structural Molecular Biology and the School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, U.K
| | - Thomas A Edwards
- Astbury Centre for Structural Molecular Biology and the School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, U.K
| | - Michelle Peckham
- Astbury Centre for Structural Molecular Biology and the School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, U.K.
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15
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Murphy ACH, Lindsay AJ, McCaffrey MW, Djinović-Carugo K, Young PW. Congenital macrothrombocytopenia-linked mutations in the actin-binding domain of α-actinin-1 enhance F-actin association. FEBS Lett 2016; 590:685-95. [PMID: 26879394 DOI: 10.1002/1873-3468.12101] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 02/09/2016] [Accepted: 02/11/2016] [Indexed: 01/21/2023]
Abstract
Mutations in the actin cross-linking protein actinin-1 were recently linked to dominantly inherited congenital macrothrombocytopenia. Here, we report that several disease-associated mutations that are located within the actinin-1 actin-binding domain cause increased binding of actinin-1 to actin filaments and enhance filament bundling in vitro. These actinin-1 mutants are also more stably associated with the cytoskeleton in cultured cells, as assessed by biochemical fractionation and fluorescence recovery after photobleaching experiments. For two mutations the disruption of contacts between the calponin homology domains within the actinin actin-binding domain may explain increased filament binding--providing mechanistic and structural insights into the basis of actinin-1 dysfunction in congenital macrothrombocytopenia.
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Affiliation(s)
- Anita C H Murphy
- School of Biochemistry and Cell Biology, University College Cork, Ireland
| | - Andrew J Lindsay
- Molecular Cell Biology Laboratory, School of Biochemistry and Cell Biology, Biosciences Institute, University College Cork, Ireland
| | - Mary W McCaffrey
- Molecular Cell Biology Laboratory, School of Biochemistry and Cell Biology, Biosciences Institute, University College Cork, Ireland
| | - Kristina Djinović-Carugo
- Department of Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Austria.,Department of Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Slovenia
| | - Paul W Young
- School of Biochemistry and Cell Biology, University College Cork, Ireland
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16
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Bartram MP, Habbig S, Pahmeyer C, Höhne M, Weber LT, Thiele H, Altmüller J, Kottoor N, Wenzel A, Krueger M, Schermer B, Benzing T, Rinschen MM, Beck BB. Three-layered proteomic characterization of a novel ACTN4 mutation unravels its pathogenic potential in FSGS. Hum Mol Genet 2016; 25:1152-64. [PMID: 26740551 DOI: 10.1093/hmg/ddv638] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2015] [Accepted: 12/31/2015] [Indexed: 01/09/2023] Open
Abstract
Genetic diseases constitute the most important cause for end-stage renal disease in children and adolescents. Mutations in the ACTN4 gene, encoding the actin-binding protein α-actinin-4, are a rare cause of autosomal dominant familial focal segmental glomerulosclerosis (FSGS). Here, we report the identification of a novel, disease-causing ACTN4 mutation (p.G195D, de novo) in a sporadic case of childhood FSGS using next generation sequencing. Proteome analysis by quantitative mass spectrometry (MS) of patient-derived urinary epithelial cells indicated that ACTN4 levels were significantly decreased when compared with healthy controls. By resolving the peptide bearing the mutated residue, we could proof that the mutant protein is less abundant when compared with the wild-type protein. Further analyses revealed that the decreased stability of p.G195D is associated with increased ubiquitylation in the vicinity of the mutation site. We next defined the ACTN4 interactome, which was predominantly composed of cytoskeletal modulators and LIM domain-containing proteins. Interestingly, this entire group of proteins, including several highly specific ACTN4 interactors, was globally decreased in the patient-derived cells. Taken together, these data suggest a mechanistic link between ACTN4 instability and proteome perturbations of the ACTN4 interactome. Our findings advance the understanding of dominant effects exerted by ACTN4 mutations in FSGS. This study illustrates the potential of genomics and complementary, high-resolution proteomics analyses to study the pathogenicity of rare gene variants.
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Affiliation(s)
- Malte P Bartram
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Sandra Habbig
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany, Department of Pediatrics
| | - Caroline Pahmeyer
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
| | - Martin Höhne
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD) and Systems Biology of Ageing Cologne, University of Cologne, Cologne, Germany
| | | | | | | | | | | | - Marcus Krueger
- Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD) and
| | - Bernhard Schermer
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD) and Systems Biology of Ageing Cologne, University of Cologne, Cologne, Germany
| | - Thomas Benzing
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD) and Systems Biology of Ageing Cologne, University of Cologne, Cologne, Germany
| | - Markus M Rinschen
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD) and Systems Biology of Ageing Cologne, University of Cologne, Cologne, Germany
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Abstract
Invasion and metastasis are malignant phenotypes in cancer that lead to patient death. Cell motility is involved in these processes. In 1998, we identified overexpression of the actin-bundling protein actinin-4 in several types of cancer. Protein expression of actinin-4 is closely associated with the invasive phenotypes of cancers. Actinin-4 is predominantly expressed in the cellular protrusions that stimulate the invasive phenotype in cancer cells and is essential for formation of cellular protrusions such as filopodia and lamellipodia. ACTN4 (gene name encoding actinin-4 protein) is located on human chromosome 19q. ACTN4 amplification is frequently observed in patients with carcinomas of the pancreas, ovary, lung, and salivary gland, and patients with ACTN4 amplifications have worse outcomes than patients without amplification. In addition, nuclear distribution of actinin-4 is frequently observed in small cell lung, breast, and ovarian cancer. Actinin-4, when expressed in cancer cell nuclei, functions as a transcriptional co-activator. In this review, we summarize recent developments regarding the biological roles of actinin-4 in cancer invasion.
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Affiliation(s)
- Kazufumi Honda
- Department of Chemotherapy and Clinical Research, National Cancer Center Research Institute, 5-1-1 Tsukiji Chuoku, Tokyo, 104-0045 Japan ; AMED-CREST AMED, Japan Agency for Medical Research and Development, 1-7-1 Otemachi, Chiyoda, Tokyo, 100-0004 Japan
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18
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Abstract
Mutations in the Alpha-actinin-4 gene (ACTN4) cause a rare form of familial focal segmental glomerulosclerosis in humans. Individuals with kidney disease-associated ACTN4 mutations tend to have mild to moderate proteinuria, with many developing decreased kidney function progressing to end stage kidney disease. All of the disease-causing ACTN4 mutations identified to date are located within the actin-binding domain of the encoded protein, increasing its binding affinity to F-actin and leading to abnormal actin rich cellular aggregates. The identification of ACTN4 mutations as a cause of human kidney disease demonstrates a key cellular pathway by which alterations in cytoskeletal behavior can mediate kidney disease. Here we review the studies relevant to ACTN4 and its role in mediating kidney disease.
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Affiliation(s)
- Di Feng
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215 USA
| | - Clark DuMontier
- Department of Medicine, Boston University School of Medicine, Boston, MA 02118 USA
| | - Martin R Pollak
- Division of Nephrology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02215 USA
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Shao H, Travers T, Camacho CJ, Wells A. The carboxyl tail of alpha-actinin-4 regulates its susceptibility to m-calpain and thus functions in cell migration and spreading. Int J Biochem Cell Biol 2013; 45:1051-63. [PMID: 23466492 DOI: 10.1016/j.biocel.2013.02.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Revised: 02/08/2013] [Accepted: 02/20/2013] [Indexed: 11/16/2022]
Abstract
Alpha-actinin-4 links the cytoskeleton to sites of adhesion and has been shown to be modulated to enable cell migration. Such focal adhesions must be labile to accomplish migration, with this detachment occurring at least in part via m-calpain activation (Glading et al., 2001, 2002; Xie et al., 1998). In this study, we report that alpha-actinin-4 is initially cleaved by m-calpain between tyrosine 13 and glycine. Removal of the first 13 amino acids does not affect alpha-actinin-4 binding to actin filaments and its localization within fibroblasts but drives cell migration with less persistence. Binding of phosphoinositides PI(4,5)P2, PI(3,4,5)P3 and PI(3,4)P2 to alpha-actinin-4, as well as binding of alpha-actinin-4 to actin filaments all inhibit m-calpain cleavage of ACTN4 between tyrosine 13 and glycine 14. Interestingly, the carboxyl terminus of alpha-actinin-4 including its calcium binding motifs, is inhibitory for a secondary cleavage of alpha-actinin-4 between lysine 283 and valine 284. The minimal length of inhibitory domain is mapped to the last 11 amino acids of alpha-actinin-4. The C-terminal tail of alpha-actinin-4 is essential for maintaining its normal actin binding activity and localization within cytoplasm and also its colocalization with actin in the lamellipodia of locomoting fibroblasts. Live cell imaging reveals that the 1-890 fragment fails to rescue neither the basal or growth factor-stimulated migration nor the revert the spread area of fibroblasts to the level of NR6WT. These findings suggest that the C-terminal tail of alpha-actinin-4 is essential for its function in cell migration and adhesion to substratum.
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Affiliation(s)
- Hanshuang Shao
- Department of Pathology, University of Pittsburgh, Pittsburgh, PA 15261, United States
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20
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Travers T, Shao H, Wells A, Camacho C. Modeling the assembly of the multiple domains of α-actinin-4 and its role in actin cross-linking. Biophys J 2013; 104:705-15. [PMID: 23442921 PMCID: PMC3566466 DOI: 10.1016/j.bpj.2012.12.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Revised: 12/04/2012] [Accepted: 12/05/2012] [Indexed: 12/30/2022] Open
Abstract
The assembly of proteins into multidomain complexes is critical for their function. In eukaryotic nonmuscle cells, regulation of the homodimeric actin cross-linking protein α-actinin-4 (ACTN4) during cell migration involves signaling receptors with intrinsic tyrosine kinase activity, yet the underlying molecular mechanisms are poorly understood. As a first step to address the latter, we validate here an atomic model for the ACTN4 end region, which corresponds to a ternary complex between the N-terminal actin-binding domain (ABD) and an adjacent helical neck region of one monomer, and the C-terminal calmodulin-like domain of the opposite antiparallel monomer. Mutagenesis experiments designed to disrupt this ternary complex confirm that its formation reduces binding to F-actin. Molecular dynamics simulations show that the phosphomimic mutation Y265E increases actin binding by breaking several interactions that tether the two calponin homology domains into a closed ABD conformation. Simulations also show a disorder-to-order transition in the double phosphomimic mutant Y4E/Y31E of the 45-residue ACTN4 N-terminal region, which can inhibit actin binding by latching both calponin homology domains more tightly. Collectively, these studies provide a starting point for understanding the role of external cues in regulating ACTN4, with different phenotypes resulting from changes in the multidomain assembly of the protein.
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Affiliation(s)
- Timothy Travers
- Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Hanshuang Shao
- Department of Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Alan Wells
- Department of Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Carlos J. Camacho
- Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
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21
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Abstract
Structural analyses of actin binding regions comprising tandem calponin homology domains alone and when bound to F-actin have revealed a number of different conformations with calponin homology domains in ‘open’ and ‘closed’ positions. In an attempt to resolve these issues we have examined the properties of the utrophin actin binding domain in open and closed conformations in order to verify the conformation when bound to F-actin. Locking the actin binding domain in a closed conformation using engineered cysteine residues in each calponin homology domain reduced the affinity for F-actin without affecting the stoichiometry furthermore differential scanning calorimetry experiments revealed a reduction in melting temperature on binding to actin. The data suggest the amino-terminal utrophin actin binding domain is in an open conformation in solution and when bound to F-actin.
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Key Words
- ABD, actin binding domain
- Actin binding domain
- CD, circular dichroism
- CH, calponin homology
- Calponin homology domain
- DSC, differential scanning calorimetry
- Differential scanning calorimetry
- Dystrophin
- EM, electron microscopy
- F-actin, filamentous actin
- NTCB, 2-nitro-5-thiocyanobenzoic acid
- SDS-PAGE, sodium dodecyl sulphate poly-acrylamide electrophoresis
- Spectrin
- Tm, melting temperature
- UTR261, utrophin residues 1-261
- α-Actinin
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Affiliation(s)
- Mike J F Broderick
- Department of Biomedical Science, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK ; IBLS, University of Glasgow, Glasgow G12 8QQ, UK
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Jia Y, Kuroda M. Limited digestion of α-actinin in the presence of F-actin. Biophysics (Nagoya-shi) 2011; 7:29-34. [PMID: 27857590 PMCID: PMC5036780 DOI: 10.2142/biophysics.7.29] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2011] [Accepted: 04/14/2011] [Indexed: 12/01/2022] Open
Abstract
N-terminal actin-binding domain of α-actinin is connected to central rod domain through flexible neck region that is susceptible to proteolysis. It is suggested that the neck region assumes variable orientations by actin binding. In order to examine the effect of actin binding to α-actinin, we carried out limited digestion of α-actinin by chymotrypsin in the presence and absence of F-actin. Although the cleavage process was retarded when bound to F-actin, digestion to 32 kDa-head and 55 kDa-rod domains occurred through the same intermediate products as the digestion in the absence of F-actin. N-terminal sequencing of 55 kDa-fragment showed the neck region was cleaved at 276-Leu. The cleavage site was not affected by binding to F-actin nor ionic strength of the solvent. It was also indicated that α-actinin was cleaved at 15-Tyr by chymotrypsin. Quantitation of the cleavage products by densitometry of the SDS-gels suggested the conformational change of α-actinin at domain-connecting regions by F-actin binding.
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Affiliation(s)
- You Jia
- Department of Biological Science, Faculty of Life and Environmental Sciences, Shimane University, 1060 Nishikawatsu-chou, Matsue 690-0854, Japan
| | - Masaaki Kuroda
- Department of Biological Science, Faculty of Life and Environmental Sciences, Shimane University, 1060 Nishikawatsu-chou, Matsue 690-0854, Japan
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Galkin VE, Orlova A, Salmazo A, Djinovic-Carugo K, Egelman EH. Opening of tandem calponin homology domains regulates their affinity for F-actin. Nat Struct Mol Biol 2010; 17:614-6. [PMID: 20383143 PMCID: PMC2921939 DOI: 10.1038/nsmb.1789] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2009] [Accepted: 02/19/2010] [Indexed: 11/16/2022]
Abstract
Many actin-binding proteins contain calponin homology (CH) domains, but the manner in which these domains interact with F-actin has been controversial. Crystal structures have shown the tandem CH domains of alpha-actinin to be in a compact, closed conformation, but the interpretations of complexes of such tandem CH domains with F-actin have been ambiguous. We show that the tandem CH domains of alpha-actinin bind F-actin in an open conformation, explaining mutations that cause human diseases and suggesting that the opening of these domains may be one of the main regulatory mechanisms for proteins with tandem CH domains.
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Affiliation(s)
- Vitold E. Galkin
- Deaprtment of Biochemistry and Molecular Genetics, University of Virginia Medical Center, Box 800733, Charlottesville, VA 22908-0733, U.S.A
| | - Albina Orlova
- Deaprtment of Biochemistry and Molecular Genetics, University of Virginia Medical Center, Box 800733, Charlottesville, VA 22908-0733, U.S.A
| | - Anita Salmazo
- Department for Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Campus Vienna Biocenter 5, A-1030 Vienna, Austria
| | - Kristina Djinovic-Carugo
- Department for Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Campus Vienna Biocenter 5, A-1030 Vienna, Austria
- Department of Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, 1000 Ljubljana, Slovenia
| | - Edward H. Egelman
- Deaprtment of Biochemistry and Molecular Genetics, University of Virginia Medical Center, Box 800733, Charlottesville, VA 22908-0733, U.S.A
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Abstract
The dynamic remolding of the actin cytoskeleton is a critical part of most cellular activities, and malfunction of cytoskeletal proteins results in various human diseases. The transition between two forms of actin, monomeric or G-actin and filamentous or F-actin, is tightly regulated in time and space by a large number of signaling, scaffolding and actin-binding proteins (ABPs). New ABPs are constantly being discovered in the post-genomic era. Most of these proteins are modular, integrating actin binding, protein-protein interaction, membrane-binding, and signaling domains. In response to extracellular signals, often mediated by Rho family GTPases, ABPs control different steps of actin cytoskeleton assembly, including filament nucleation, elongation, severing, capping, and depolymerization. This review summarizes structure-function relationships among ABPs in the regulation of actin cytoskeleton assembly.
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Affiliation(s)
- Sung Haeng Lee
- Chosun University School of Medicine, Department of Cellular and Molecular Medicine, Gwangju 501-759, Korea.
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25
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Lek M, Quinlan KGR, North KN. The evolution of skeletal muscle performance: gene duplication and divergence of human sarcomeric alpha-actinins. Bioessays 2010; 32:17-25. [PMID: 19967710 DOI: 10.1002/bies.200900110] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
In humans, there are two skeletal muscle alpha-actinins, encoded by ACTN2 and ACTN3, and the ACTN3 genotype is associated with human athletic performance. Remarkably, approximately 1 billion people worldwide are deficient in alpha-actinin-3 due to the common ACTN3 R577X polymorphism. The alpha-actinins are an ancient family of actin-binding proteins with structural, signalling and metabolic functions. The skeletal muscle alpha-actinins diverged approximately 250-300 million years ago, and ACTN3 has since developed restricted expression in fast muscle fibres. Despite ACTN2 and ACTN3 retaining considerable sequence similarity, it is likely that following duplication there was a divergence in function explaining why alpha-actinin-2 cannot completely compensate for the absence of alpha-actinin-3. This paper focuses on the role of skeletal muscle alpha-actinins, and how possible changes in functions between these duplicates fit in the context of gene duplication paradigms.
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Affiliation(s)
- Monkol Lek
- Institute for Neuroscience and Muscle Research, The Children's Hospital at Westmead, Sydney, NSW, Australia
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Shao H, Wu C, Wells A. Phosphorylation of alpha-actinin 4 upon epidermal growth factor exposure regulates its interaction with actin. J Biol Chem 2009; 285:2591-600. [PMID: 19920151 DOI: 10.1074/jbc.m109.035790] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The ubiquitously expressed family of alpha-actinins bridges actin filaments to stabilize adhesions, a process disrupted during growth factor-induced migration of cells. During the dissolution of the actin cytoskeleton, actinins are phosphorylated on tyrosines, although the consequences of this are unknown. We expressed the two isoforms of human alpha-actinin in murine fibroblasts that express human epidermal growth factor receptor (EGFR) and found that both alpha-actinin 1 (ACTN1) and alpha-actinin 4 (ACTN4) were phosphorylated on tyrosine residues after stimulation with EGF, although ACTN4 was phosphorylated to the greater extent. This required the activation of Src protein-tyrosine kinase and p38-MAPK (and phosphoinositide trisphosphate kinase in part) but not MEK/ERK or Rac1, as determined by inhibitors. The EGF-induced phosphorylation sites of ACTN4 were mapped to tyrosine 4, the major site, and tyrosine 31, the minor one. Truncation mutagenesis showed that the C-terminal domains of ACTN4 (amino acids 300-911), which cross-link the actin binding head domains, act as an inhibitory domain for both actin binding and EGF-mediated phosphorylation. These two properties were mutually exclusive; removal of the C terminus enhanced actin binding of ACTN4 mutants while limiting EGF-induced phosphorylation, and conversely EGF-stimulated phosphorylation of ACTN4 decreased its affinity to actin. Interestingly, a phosphomimetic of tyrosine 265 (which can be found in carcinoma cells and lies near the K255E mutation that causes focal segmental glomerulosclerosis) demonstrated increased actin binding activity and susceptibility of ACTN4 to calpain-mediated cleavage; this variant also retarded cell spreading. Remarkably, either treatment of cells with low concentrations of latrunculin A, which has been shown to depolymerize F-actin, or the deletion of the actin binding domain (100-252 amino acids) of ACTN4Y265E restored EGF-induced phosphorylation. An F-actin binding assay in vitro showed that Y4E/Y31E, a mimetic of diphosphorylated ACTN4, bound F-actin slightly compared with wild type (WT). Importantly, the EGF-mediated phosphorylation of ACTN4 at tyrosine 4 and 31 significantly inhibited multinucleation of proliferating NR6WT fibroblasts that overexpress ACTN4. These results suggest that EGF regulates the actin binding activity of ACTN4 by inducing tyrosyl-directed phosphorylation.
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Affiliation(s)
- Hanshuang Shao
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA
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27
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Clark AR, Sawyer GM, Robertson SP, Sutherland-Smith AJ. Skeletal dysplasias due to filamin A mutations result from a gain-of-function mechanism distinct from allelic neurological disorders†. Hum Mol Genet 2009; 18:4791-800. [DOI: 10.1093/hmg/ddp442] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Sawyer GM, Clark AR, Robertson SP, Sutherland-Smith AJ. Disease-associated substitutions in the filamin B actin binding domain confer enhanced actin binding affinity in the absence of major structural disturbance: Insights from the crystal structures of filamin B actin binding domains. J Mol Biol 2009; 390:1030-47. [PMID: 19505475 DOI: 10.1016/j.jmb.2009.06.009] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Revised: 05/29/2009] [Accepted: 06/03/2009] [Indexed: 10/20/2022]
Abstract
Missense mutations in filamin B (FLNB) are associated with the autosomal dominant atelosteogenesis (AO) and the Larsen group of skeletal malformation disorders. These mutations cluster in particular FLNB protein domains and act in a presumptive gain-of-function mechanism. In contrast the loss-of-function disorder, spondylocarpotarsal synostosis syndrome, is characterised by the complete absence of FLNB. One cluster of AO missense mutations is found within the second of two calponin homology (CH) domains that create a functional actin-binding domain (ABD). This N-terminal ABD is required for filamin F-actin crosslinking activity, a crucial aspect of filamin's role of integrating cell-signalling events with cellular scaffolding and mechanoprotection. This study characterises the wild type FLNB ABD and investigates the effects of two disease-associated mutations on the structure and function of the FLNB ABD that could explain a gain-of-function mechanism for the AO diseases. We have determined high-resolution X-ray crystal structures of the human filamin B wild type ABD, plus W148R and M202V mutants. All three structures display the classic compact monomeric conformation for the ABD with the CH1 and CH2 domains in close contact. The conservation of tertiary structure in the presence of these mutations shows that the compact ABD conformation is stable to the sequence substitutions. In solution the mutant ABDs display reduced melting temperatures (by 6-7 degrees C) as determined by differential scanning fluorimetry. Characterisation of the wild type and mutant ABD F-actin binding activities via co-sedimentation assays shows that the mutant FLNB ABDs have increased F-actin binding affinities, with dissociation constants of 2.0 microM (W148R) and 0.56 microM (M202V), compared to the wild type ABD K(d) of 7.0 microM. The increased F-actin binding affinity of the mutants presents a biochemical mechanism that differentiates the autosomal dominant gain-of-function FLNB disorders from those that arise through the complete loss of FLNB protein.
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Affiliation(s)
- Gregory M Sawyer
- Institute of Molecular BioSciences, Massey University, Palmerston North, New Zealand
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