DOCSLIB.ORG

Increasing Role of Titin Mutations in Neuromuscular Disorders

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

Journal of Neuromuscular Diseases 3 (2016) 293–308 293 DOI 10.3233/JND-160158 IOS Press Review Increasing Role of Titin Mutations in Neuromuscular Disorders Marco Savaresea, Jaakko Sarparantaa,b, Anna Viholaa, Bjarne Udda,c,d and Peter Hackmana,∗ aFolkh¨alsan Institute of Genetics and Department of Medical Genetics, Haartman Institute, University of Helsinki, Helsinki, Finland bAlbert Einstein College of Medicine, Departments of Medicine–Endocrinology and Molecular Pharmacology, Bronx, NY, USA cNeuromuscular Research Center, University of Tampere and Tampere University Hospital, Tampere, Finland dDepartment of Neurology, Vaasa Central Hospital, Vaasa, Finland Abstract. The TTN gene with 363 coding exons encodes titin, a giant muscle protein spanning from the Z-disk to the M-band within the sarcomere. Mutations in the TTN gene have been associated with different genetic disorders, including hypertrophic and dilated cardiomyopathy and several skeletal muscle diseases. Before the introduction of next generation sequencing (NGS) methods, the molecular analysis of TTN has been laborious, expensive and not widely used, resulting in a limited number of mutations identified. Recent studies however, based on the use of NGS strategies, give evidence of an increasing number of rare and unique TTN variants. The interpretation of these rare variants of uncertain significance (VOUS) represents a challenge for clinicians and researchers. The main aim of this review is to describe the wide spectrum of muscle diseases caused by TTN mutations so far determined, summarizing the molecular findings as well as the clinical data, and to highlight the importance of joint efforts to respond to the challenges arising from the use of NGS. An international collaboration through a clinical and research consortium and the development of a single accessible database listing variants in the TTN gene, identified by high throughput approaches, may be the key to a better assessment of titinopathies and to systematic genotype–phenotype correlation studies. Keywords: TTN, titin, neuromuscular disorders, Limb-girdle muscular dystrophy (LGMD), Hereditary myopathy with early respiratory failure (HMERF), Late-onset autosomal dominant tibial muscular dystrophy (TMD), Congenital centronuclear myopathy (CNM), Early-onset myopathy with fatal cardiomyopathy (EOMFC), Multi-minicore disease with heart disease (MmDHD), Childhood-juvenile onset Emery-Dreifuss-like phenotype without cardiomyopathy INTRODUCTION Titin acts as a scaffold protein aiding in myofibril- lar assembly during myogenesis [2], as a molecular With its 363 coding exons and a full-length spring determining the passive elasticity of the mus- transcript of more than 100 kb [1] TTN gene encodes cle [3, 4], and as a mechanosensor serving various titin, the by far longest known polypeptide in nature. signaling functions [5, 6]. The longest human theoretical isoform of TTN would TTN mutations have to date been reported to cause produce a protein of 3,960 kDa containing 35,991 various cardiomyopathies [7, 8] and a range of skele- amino acids, although this isoform has not been tal muscle diseases and phenotypes listed below: observed [1]. ∗ – Late-onset autosomal dominant tibial muscular Correspondence to: Dr Peter Hackman, Folkhalsan Institute dystrophy (TMD) (MIM #600334); of Genetics and Department of Medical Genetics, Haartman Institute, University of Helsinki, Helsinki, Finland. E-mail: – Young or early adult onset recessive distal peter.hackman@helsinki.fi. titinopathy; ISSN 2214-3599/16/$35.00 © 2016 – IOS Press and the authors. All rights reserved This article is published online with Open Access and distributed under the terms of the Creative Commons Attribution Non-Commercial License (CC BY-NC 4.0). 294 M. Savarese et al. / Increasing Role of Titin Mutations in Neuromuscular Disorders – Limb-girdle muscular dystrophy type 2J in this review. Exon numbering will be according to (LGMD2J; MIM #608807); the HGVS recommendations [10] and to the current – Congenital centronuclear myopathy (CNM; Leiden database (LOVD) numbering (modified on MIM #255200); 11th October 2013, changing exon 47b to exon 48 – Early-onset myopathy with fatal cardiomyopa- and adding +1 to all subsequent exon numbers) [11]. thy, EOMFC (MIM #611705); The titin protein spans from the Z-disk to the M- – Multi-minicore disease with heart disease band [12]. Its modular structure is composed of four (MmDHD) including clinical variations; main parts (Fig. 1): the amino-terminal Z-disc region, – Childhood-juvenile onset Emery-Dreifuss-like the I-band and A-band regions, and the carboxyl- phenotype without cardiomyopathy; terminal part spanning the M-band. Titin is composed – Hereditary myopathy with early respiratory fail- of repeated immunoglobulin-like (Ig) and fibronectin ure (HMERF; MIM #603689); type 3-like (FN3) domains, interspersed by unique – Adult onset recessive proximal muscular dys- sequence regions [1]. It also contains the repetitive trophy. PEVK region, rich in proline (P), glutamate (E), valine (V), and lysine (K) residues, in the I band, and a Mutations in titin will probably prove to be the serine/threonine kinase (TK) domain in the M-band. cause of many additional phenotypes of muscular More than 1 million splice variants could be gen- disorders in the coming years. erated theoretically by the TTN gene [13]. Indeed, Due to its huge size, it has not been possi- extensive alternative splicing results in a remarkable ble to sequence the entire TTN gene routinely in diversity of titin isoforms that can be divided into research and diagnostic laboratories until recently. three main classes based on the presence of the N2A Thus, before implementation of the next generation and N2B elements in the I-band region [1, 14, 15] sequencing (NGS) methods, only a limited amount (Fig. 1). Skeletal muscles express so-called N2A iso- of TTN mutations were identified. NGS sequencing forms, characterized by the inclusion of the N2A has enabled the rapid and thorough investigation of element and exclusion of the cardiac-specific N2B genetic material [9] and has resulted in an explosion element. In the heart, N2BA isoforms include both in the identification of new TTN variants. However, the N2B and N2A elements, while N2B isoforms use their clinical interpretation is a challenge. the N2B element only. The aforementioned isoforms Here, we focus on the current understanding of also differ in the lengths of the proximal tandem-Ig the titin gene and protein from a human disease and PEVK regions, which are longest in the N2A iso- perspective. In particular, we provide an overview forms and shortest in the N2B isoforms. Within each of the different neuromuscular disorders caused by isoform class, the tandem-Ig and PEVK regions also mutations in the TTN gene, reviewing the molecu- show variable expression in different muscles, and lar findings as well as the clinical data. Finally, we across developmental and physiological states. More- highlight the difficulties related to the interpretation over, the second last TTN exon 363 (Mex5), coding of the clinical significance of TTN variations and the for the is7 domain located in the M-band, is dif- need for further functional studies and bioinformatics ferentially spliced, producing is7– and is7+ isoforms tools. [16] The major isoform classes are represented in the THE TITIN GENE, ISOFORMS NCBI RefSeq database by the entries NM 133378 AND PROTEIN (N2A; NP 596869:3,680 kDa and 33,423 aa), NM 001256850.1 (N2BA; NP 001243779:3,780 The titin gene (MIM #188840), is located on the kDa and 34,350 aa), and NM 003319 (N2B; short arm of chromosome 2 (chromosomal band NP 003310:2,960 kDa and 26,926 aa) [1, 14, 15]. q31.2). It contains 363 coding exons and an additional The Novex-1 (NM 133432; NP 597676) and first non-coding exon [1]. The longest theoretical Novex-2 (NM 133437; NP 597681) isoforms are transcript (variant IC, NM 001267550.2), virtually similar to N2B, but they also include further 125 and obtained by the transcription of all the coding exons 192 amino acids encoded by the Novex-1 and Novex- (excluding the alternative C-terminal Novex-3 exon) 2 exons in the I-band. Finally, the much smaller and called “meta isoform”, has been adopted as the Novex-3 isoform (NM 133379; NP 596870:616 kDa gold standard for describing TTN variants, and will be and 5604 aa) only contains the N-terminal part of the used as reference for cDNA and protein numbering protein. This isoform, expressed on a low level in all M. Savarese et al. / Increasing Role of Titin Mutations in Neuromuscular Disorders 295 titin filament ZMZthin filament thick filament Ig domain FN3 domain unique sequence PEVK kinase (TK) Z-disc I-band A-band M-band proximal tandem-Ig distal tandem-Ig N2A / ex102–111 N2A PEVK / ex112–226 N2B / ex49 Z1 (Ig 1) / ex2 Novex-2 / ex46 M10 (Ig 152) / ex364 I106 (FN3 1) / ex253 / ex344 A150 (FN3 119) M1 (Ig 143) / ex359 Z9 (Ig 9) / ex28 / ex270 (FN3 11) I118 kinase (TK) / ex359 M-is7 / ex363 Z repeats / ex 8–14 I1 (Ig 10) / ex28 Novex-1 / ex45 I84 (Ig 80) / ex226 A1 (Ig 97) / ex271 A170 (FN3 132) / ex359 N C telethonin TPM PKA CAPN3 TPM CRYAB MyHC CaM FHL2 α-actinin actin PKG MARPs actin MyBPC NBR1 CAPN3 sAnk1 CAPN1 CRYAB CAPN1 p62 CMYA5 filamin C FHL1 MURF1 α-synemin nebulin FHL2 MURF2 OBSCN OBSL1 MYOM1 N2A (NP_596869) N2BA (NP_001243779) N2B (NP_003310) Novex-1 (NP_597676) Novex-2 (NP_597681) Novex-3 (NP_596870) Novex-3 Fig. 1. Top: A schematic view of the sarcomere, with titin filaments shown in red. One titin molecule, extending from the Z-disc to M- band, is highlighted. Middle: The modular structure of the titin protein (theoretical meta isoform). Titin is mostly comprised of repeated immunoglobulin-like (Ig; red) and fibronectin type 3-like (FN3; white) domains. Selected domains are labeled above the diagram with the classical titin nomenclature (sarcomere region Z/I/A/M+domain number; Bang et al. 2001), followed in parentheses by the alternative numbering scheme (domain type Ig/FN3 + domain number), and with the corresponding exon number.
Recommended publications
  • Dynamin Functions and Ligands: Classical Mechanisms Behind

    Dynamin Functions and Ligands: Classical Mechanisms Behind

    1521-0111/91/2/123–134$25.00 http://dx.doi.org/10.1124/mol.116.105064 MOLECULAR PHARMACOLOGY Mol Pharmacol 91:123–134, February 2017 Copyright ª 2017 by The American Society for Pharmacology and Experimental Therapeutics MINIREVIEW Dynamin Functions and Ligands: Classical Mechanisms Behind Mahaveer Singh, Hemant R. Jadhav, and Tanya Bhatt Department of Pharmacy, Birla Institute of Technology and Sciences Pilani, Pilani Campus, Rajasthan, India Received May 5, 2016; accepted November 17, 2016 Downloaded from ABSTRACT Dynamin is a GTPase that plays a vital role in clathrin-dependent pathophysiology of various disorders, such as Alzheimer’s disease, endocytosis and other vesicular trafficking processes by acting Parkinson’s disease, Huntington’s disease, Charcot-Marie-Tooth as a pair of molecular scissors for newly formed vesicles originating disease, heart failure, schizophrenia, epilepsy, cancer, dominant ’ from the plasma membrane. Dynamins and related proteins are optic atrophy, osteoporosis, and Down s syndrome. This review is molpharm.aspetjournals.org important components for the cleavage of clathrin-coated vesicles, an attempt to illustrate the dynamin-related mechanisms involved phagosomes, and mitochondria. These proteins help in organelle in the above-mentioned disorders and to help medicinal chemists division, viral resistance, and mitochondrial fusion/fission. Dys- to design novel dynamin ligands, which could be useful in the function and mutations in dynamin have been implicated in the treatment of dynamin-related disorders. Introduction GTP hydrolysis–dependent conformational change of GTPase dynamin assists in membrane fission, leading to the generation Dynamins were originally discovered in the brain and identi- of endocytic vesicles (Praefcke and McMahon, 2004; Ferguson at ASPET Journals on September 23, 2021 fied as microtubule binding partners.
  • How Microtubules Control Focal Adhesion Dynamics

    How Microtubules Control Focal Adhesion Dynamics

    JCB: Review Targeting and transport: How microtubules control focal adhesion dynamics Samantha Stehbens and Torsten Wittmann Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, CA 94143 Directional cell migration requires force generation that of integrin-mediated, nascent adhesions near the cell’s leading relies on the coordinated remodeling of interactions with edge, which either rapidly turn over or connect to the actin cytoskeleton (Parsons et al., 2010). Actomyosin-mediated the extracellular matrix (ECM), which is mediated by pulling forces allow a subset of these nascent FAs to grow integrin-based focal adhesions (FAs). Normal FA turn- and mature, and provide forward traction forces. However, in over requires dynamic microtubules, and three members order for cells to productively move forward, FAs also have to of the diverse group of microtubule plus-end-tracking release and disassemble underneath the cell body and in the proteins are principally involved in mediating micro- rear of the cell. Spatial and temporal control of turnover of tubule interactions with FAs. Microtubules also alter these mature FAs is important, as they provide a counterbalance to forward traction forces, and regulated FA disassembly is the assembly state of FAs by modulating Rho GTPase required for forward translocation of the cell body. An important signaling, and recent evidence suggests that microtubule- question that we are only beginning to understand is how FA mediated clathrin-dependent and -independent endo­ turnover is spatially and temporally regulated to allow cells cytosis regulates FA dynamics. In addition, FA-associated to appropriately respond to extracellular signals, allowing for microtubules may provide a polarized microtubule track for coordinated and productive movement.
  • Dynamin Autonomously Regulates Podocyte Focal Adhesion Maturation

    Dynamin Autonomously Regulates Podocyte Focal Adhesion Maturation

    BRIEF COMMUNICATION www.jasn.org Dynamin Autonomously Regulates Podocyte Focal Adhesion Maturation † † † Changkyu Gu,* Ha Won Lee, Garrett Garborcauskas,* Jochen Reiser, Vineet Gupta, and Sanja Sever* *Department of Medicine, Harvard Medical School, Division of Nephrology, Massachusetts General Hospital, Charlestown, Massachusetts; and †Department of Internal Medicine, Rush University Medical Center, Chicago, Illinois ABSTRACT Rho family GTPases, the prototypical members of which are Cdc42, Rac1, and RhoA, in podocytes via a parallel signaling path- are molecular switches best known for regulating the actin cytoskeleton. In addition way to RhoA. to the canonical small GTPases, the large GTPase dynamin has been implicated in To induce actin polymerization, dy- regulating the actin cytoskeleton via direct dynamin-actin interactions. The physio- naminmustformDynOLIGO.12 The logic role of dynamin in regulating the actin cytoskeleton has been linked to the availability of Bis-T-23 (Aberjona Labo- maintenance of the kidney filtration barrier. Additionally, the small molecule Bis-T- ratories, Inc., Woburn, MA) allowed us 23, which promotes actin–dependent dynamin oligomerization and thus, increases to examine whether DynOLIGO–induced actin polymerization, improved renal health in diverse models of CKD, implicating actin polymerization affects the forma- dynamin as a potential therapeutic target for the treatment of CKD. Here, we show tion of FAs and stress fibers in podocytes. that treating cultured mouse podocytes with Bis-T-23 promoted stress fiber forma- The effect of Bis-T-23 on the actin cyto- tion and focal adhesion maturation in a dynamin-dependent manner. Furthermore, skeleton in mouse podocytes (Figure 1A) Bis-T-23 induced the formation of focal adhesions and stress fibers in cells in which was examined using a fully automated the RhoA signaling pathway was downregulated by multiple experimental ap- high–throughput assay that measures proaches.
  • Myosin 1E Interacts with Synaptojanin-1 and Dynamin and Is Involved in Endocytosis

    Myosin 1E Interacts with Synaptojanin-1 and Dynamin and Is Involved in Endocytosis

    FEBS Letters 581 (2007) 644–650 Myosin 1E interacts with synaptojanin-1 and dynamin and is involved in endocytosis Mira Krendela,*, Emily K. Osterweila, Mark S. Moosekera,b,c a Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06511, USA b Department of Cell Biology, Yale University, New Haven, CT 06511, USA c Department of Pathology, Yale University, New Haven, CT 06511, USA Received 21 November 2006; revised 8 January 2007; accepted 11 January 2007 Available online 18 January 2007 Edited by Felix Wieland Myo1 isoforms (Myo3p and Myo5p) leads to defects in endo- Abstract Myosin 1E is one of two ‘‘long-tailed’’ human Class I myosins that contain an SH3 domain within the tail region. SH3 cytosis [3].InAcanthamoeba, various Myo1 isoforms are domains of yeast and amoeboid myosins I interact with activa- found in association with intracellular vesicles [10].InDictyos- tors of the Arp2/3 complex, an important regulator of actin poly- telium, long-tailed Myo1s (myo B, C, and D) are required for merization. No binding partners for the SH3 domains of myosins fluid-phase endocytosis [11]. I have been identified in higher eukaryotes. In the current study, Myo1e, the mouse homolog of the human long-tailed myo- we show that two proteins with prominent functions in endocyto- sin, Myo1E (formerly referred to as Myo1C under the old myo- sis, synaptojanin-1 and dynamin, bind to the SH3 domain of sin nomenclature [12]), has been previously localized to human Myo1E. Myosin 1E co-localizes with clathrin- and dyn- phagocytic structures [13]. In this study, we report that Myo1E amin-containing puncta at the plasma membrane and this co- binds to two proline-rich proteins, synaptojanin-1 and dyn- localization requires an intact SH3 domain.
  • Regulation of Titin-Based Cardiac Stiffness by Unfolded Domain Oxidation (Undox)

    Regulation of Titin-Based Cardiac Stiffness by Unfolded Domain Oxidation (Undox)

    Regulation of titin-based cardiac stiffness by unfolded domain oxidation (UnDOx) Christine M. Loeschera,1, Martin Breitkreuzb,1, Yong Lia, Alexander Nickelc, Andreas Ungera, Alexander Dietld, Andreas Schmidte, Belal A. Mohamedf, Sebastian Kötterg, Joachim P. Schmitth, Marcus Krügere,i, Martina Krügerg, Karl Toischerf, Christoph Maackc, Lars I. Leichertj, Nazha Hamdanib, and Wolfgang A. Linkea,2 aInstitute of Physiology II, University of Munster, 48149 Munster, Germany; bInstitute of Physiology, Ruhr University Bochum, 44801 Bochum, Germany; cComprehensive Heart Failure Center Wuerzburg, University Clinic Wuerzburg, 97078 Wuerzburg, Germany; dDepartment of Internal Medicine II, University Hospital Regensburg, 93053 Regensburg, Germany; eInstitute for Genetics, University of Cologne, 50931 Cologne, Germany; fDepartment of Cardiology and Pneumology, University Medicine Goettingen, 37075 Goettingen, Germany; gDepartment of Cardiovascular Physiology, Heinrich Heine University, 40225 Düsseldorf, Germany; hDepartment of Pharmacology and Clinical Pharmacology, Heinrich Heine University, 40225 Düsseldorf, Germany; iCenter for Molecular Medicine and Excellence Cluster "Cellular Stress Responses in Aging-Associated Diseases" (CECAD), University of Cologne, 50931 Cologne, Germany; and jInstitute for Biochemistry and Pathobiochemistry, Ruhr University Bochum, 44801 Bochum, Germany Edited by Jonathan Seidman, Harvard University, Boston, MA, and approved August 12, 2020 (received for review March 14, 2020) The relationship between oxidative stress and
  • Postmortem Changes in the Myofibrillar and Other Cytoskeletal Proteins in Muscle

    Postmortem Changes in the Myofibrillar and Other Cytoskeletal Proteins in Muscle

    BIOCHEMISTRY - IMPACT ON MEAT TENDERNESS Postmortem Changes in the Myofibrillar and Other C'oskeletal Proteins in Muscle RICHARD M. ROBSON*, ELISABETH HUFF-LONERGAN', FREDERICK C. PARRISH, JR., CHIUNG-YING HO, MARVIN H. STROMER, TED W. HUIATT, ROBERT M. BELLIN and SUZANNE W. SERNETT introduction filaments (titin), and integral Z-line region (a-actinin, Cap Z), as well as proteins of the intermediate filaments (desmin, The cytoskeleton of "typical" vertebrate cells contains paranemin, and synemin), Z-line periphery (filamin) and three protein filament systems, namely the -7-nm diameter costameres underlying the cell membrane (filamin, actin-containing microfilaments, the -1 0-nm diameter in- dystrophin, talin, and vinculin) are listed along with an esti- termediate filaments (IFs), and the -23-nm diameter tubu- mate of their abundance, approximate molecular weights, lin-containing microtubules (Robson, 1989, 1995; Robson and number of subunits per molecule. Because the myofibrils et al., 1991 ).The contractile myofibrils, which are by far the are the overwhelming components of the skeletal muscle cell major components of developed skeletal muscle cells and cytoskeleton, the approximate percentages of the cytoskel- are responsible for most of the desirable qualities of muscle eton listed for the myofibrillar proteins (e.g., myosin, actin, foods (Robson et al., 1981,1984, 1991 1, can be considered tropomyosin, a-actinin, etc.) also would represent their ap- the highly expanded corollary of the microfilament system proximate percentages of total myofibrillar protein. of non-muscle cells. The myofibrils, IFs, cell membrane skel- eton (complex protein-lattice subjacent to the sarcolemma), Some Important Characteristics, Possible and attachment sites connecting these elements will be con- Roles, and Postmortem Changes of Key sidered as comprising the muscle cell cytoskeleton in this Cytoskeletal Proteins review.
  • Α-Actinin/Titin Interaction: a Dynamic and Mechanically Stable Cluster of Bonds in the Muscle Z-Disk

    Α-Actinin/Titin Interaction: a Dynamic and Mechanically Stable Cluster of Bonds in the Muscle Z-Disk

    α-Actinin/titin interaction: A dynamic and mechanically stable cluster of bonds in the muscle Z-disk Marco Grisona, Ulrich Merkela, Julius Kostanb, Kristina Djinovic-Carugob,c, and Matthias Riefa,d,1 aPhysik Department E22, Technische Universität München, 85748 Garching, Germany; bDepartment of Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, A-1030 Vienna, Austria; cDepartment of Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, SI-1000 Ljubljana, Slovenia; and dMunich Center for Integrated Protein Science, 81377 Munich, Germany Edited by James A. Spudich, Stanford University School of Medicine, Stanford, CA, and approved December 16, 2016 (received for review August 2, 2016) Stable anchoring of titin within the muscle Z-disk is essential for In humans, the isoforms of titin exhibit four to seven Z-repeats preserving muscle integrity during passive stretching. One of the (15, 16, 20). The structure of the EF3-4 hands complex with titin main candidates for anchoring titin in the Z-disk is the actin cross- Z-repeat 7 shows the bound Z-repeat in an α-helical confor- linker α-actinin. The calmodulin-like domain of α-actinin binds to mation (21). In solution assays, binding affinities of various the Z-repeats of titin. However, the mechanical and kinetic prop- Z-repeats to EF3-4 were determined to lie in the micromolar erties of this important interaction are still unknown. Here, we use range (22). Micromolar affinity points only to a moderately a dual-beam optical tweezers assay to study the mechanics of this stable interaction, the kinetics of which are unknown.
  • Table 1 Top 100 Phosphorylated Substrates and Their Corresponding Kinases in Chondrosarcoma Cultures As Used for IPA Analysis

    Table 1 Top 100 Phosphorylated Substrates and Their Corresponding Kinases in Chondrosarcoma Cultures As Used for IPA Analysis

    Table 1 Top 100 phosphorylated substrates and their corresponding kinases in chondrosarcoma cultures as used for IPA analysis. Average Fold Adj intensity in Change p- chondrosarcoma Corresponding MSC value cultures Substrate Protein Psite kinase (log2) MSC 1043.42 RKKKVSSTKRH Cytohesin-1 S394 PKC 1.83 0.001 746.95 RKGYRSQRGHS Vitronectin S381 PKC 1.00 0.056 709.03 RARSTSLNERP Tuberin S939 AKT1 1.64 0.008 559.42 SPPRSSLRRSS Transcription elongation factor A-like1 S37 PKC; GSK3 0.18 0.684 515.29 LRRSLSRSMSQ Telethonin S157 Titin 0.77 0.082 510.00 MQPDNSSDSDY CD5 T434 PKA -0.35 0.671 476.27 GGRGGSRARNL Heterogeneous nuclear ribonucleoprotein K S302 PKCdelta 1.03 0.028 455.97 LKPGSSHRKTK Bruton's tyrosine kinase S180 PKCbeta 1.55 0.001 444.65 RRRMASMQRTG E1A binding protein p300 S1834 AKT; p70S6 kinase; pp90Rsk 0.53 0.195 Guanine nucleotide binding protein, alpha Z 440.26 HLRSESQRQRR polypeptide S27 PKC 0.88 0.199 6-phosphofructo-2-kinase/fructose-2,6- 424.12 RPRNYSVGSRP biphosphatase 2 S483 AKT 1.32 0.003 419.61 KKKIATRKPRF Metabotropic glutamate receptor 1 T695 PKC 1.75 0.001 391.21 DNSSDSDYDLH CD5 T453 Lck; Fyn -2.09 0.001 377.39 LRQLRSPRRAQ Ras associated protein Rab4 S204 CDC2 0.63 0.091 376.28 SSQRVSSYRRT Desmin S12 Aurora kinase B 0.56 0.255 369.05 ARIGGSRRERS EP4 receptor S354 PKC 0.29 0.543 RPS6 kinase alpha 3; PKA; 367.99 EPKRRSARLSA HMG14 S7 PKC -0.01 0.996 Peptidylglycine alpha amidating 349.08 SRKGYSRKGFD monooxygenase S930 PKC 0.21 0.678 347.92 RRRLSSLRAST Ribosomal protein S6 S236 PAK2 0.02 0.985 346.84 RSNPPSRKGSG Connexin
  • Association of Titin and Myosin Heavy Chain in Developing Skeletal Muscle (Myogenesis/Cytoskeleton/Assembly in Vvo) W

    Association of Titin and Myosin Heavy Chain in Developing Skeletal Muscle (Myogenesis/Cytoskeleton/Assembly in Vvo) W

    Proc. Natl. Acad. Sci. USA Vol. 89, pp. 74%-7500, August 1992 Cell Biology Association of titin and myosin heavy chain in developing skeletal muscle (myogenesis/cytoskeleton/assembly in vvo) W. B. ISAACS*, I. S. KIM, A. STRUVE, AND A. B. FULTONt Department of Biochemistry, University of Iowa, Iowa City, IA 52242 Communicated by Sheldon Penman, May 22, 1992 ABSTRACT To understand molecular interactions that deficient medium (10). After labeling, cultures either were organize developing myoflbrils, we examined the biosynthesis extracted immediately or were chased by adding complete and interaction of titin and myosin heavy chain in cultures of medium supplemented with 2 mM unlabeled methionine and developing muscle. Use of pulse-labeling, immunoprecipita- incubating at 370C for various times before extraction. Ex- tion, and a reversible cross-linking procedure demonstrates tractions used 0.5% Triton X-100 in extraction buffer (100 that within minutes of synthesis, titin and myosin heavy chain mM KCI/10 mM Pipes, pH 6.8/300 mM sucrose/2 mM can be chemically cross-linked into very large, detergent- MgCI2/1 mM EGTA) containing protease inhibitors (1 mM resistant complexes retaining many features of intact myo- phenylmethylsulfonyl fluoride and 100 mM leupeptin; ref. tubes. These complexes, predominantly of titin and myosin, 11). occur very early in myofibrillogenesis as well as later. These Immunoprecipitation. Titin was precipitated by using a data suggest that synthesis and assembly oftitin and myosin are mouse monoclonal antibody (mAb), AMF-1, as described temporally and spatially coordinated in nascent myofibrils and (10). Muscle-specific myosin heavy chain (hereafter myosin) support the hypothesis that titin molecules help to organize was precipitated with mAb MF-20 (12), a gift ofD.
  • Titin N2A Domain and Its Interactions at the Sarcomere

    Titin N2A Domain and Its Interactions at the Sarcomere

    International Journal of Molecular Sciences Review Titin N2A Domain and Its Interactions at the Sarcomere Adeleye O. Adewale and Young-Hoon Ahn * Department of Chemistry, Wayne State University, Detroit, MI 48202, USA; [email protected] * Correspondence: [email protected]; Tel.: +1-(313)-577-1384 Abstract: Titin is a giant protein in the sarcomere that plays an essential role in muscle contraction with actin and myosin filaments. However, its utility goes beyond mechanical functions, extending to versatile and complex roles in sarcomere organization and maintenance, passive force, mechanosens- ing, and signaling. Titin’s multiple functions are in part attributed to its large size and modular structures that interact with a myriad of protein partners. Among titin’s domains, the N2A element is one of titin’s unique segments that contributes to titin’s functions in compliance, contraction, structural stability, and signaling via protein–protein interactions with actin filament, chaperones, stress-sensing proteins, and proteases. Considering the significance of N2A, this review highlights structural conformations of N2A, its predisposition for protein–protein interactions, and its multiple interacting protein partners that allow the modulation of titin’s biological effects. Lastly, the nature of N2A for interactions with chaperones and proteases is included, presenting it as an important node that impacts titin’s structural and functional integrity. Keywords: titin; N2A domain; protein–protein interaction 1. Introduction Citation: Adewale, A.O.; Ahn, Y.-H. The complexity of striated muscle is defined by the intricate organization of its com- Titin N2A Domain and Its ponents [1]. The involuntary cardiac and voluntary skeletal muscles are the primary types Interactions at the Sarcomere.
  • B3GALNT2 Is a Gene Associated with Congenital Muscular Dystrophy with Brain Malformations

    B3GALNT2 Is a Gene Associated with Congenital Muscular Dystrophy with Brain Malformations

    European Journal of Human Genetics (2014) 22, 707–710 & 2014 Macmillan Publishers Limited All rights reserved 1018-4813/14 www.nature.com/ejhg SHORT REPORT B3GALNT2 is a gene associated with congenital muscular dystrophy with brain malformations Carola Hedberg*,1, Anders Oldfors1 and Niklas Darin2 Congenital muscular dystrophies associated with brain malformations are a group of disorders frequently associated with aberrant glycosylation of a-dystroglycan. They include disease entities such a Walker–Warburg syndrome, muscle–eye–brain disease and various other clinical phenotypes. Different genes involved in glycosylation of a-dystroglycan are associated with these dystroglycanopathies. We describe a 5-year-old girl with psychomotor retardation, ataxia, spasticity, muscle weakness and increased serum creatine kinase levels. Immunhistochemistry of skeletal muscle revealed reduced glycosylated a-dystroglycan. Magnetic resonance imaging of the brain at 3.5 years of age showed increased T2 signal from supratentorial and infratentorial white matter, a hypoplastic pons and subcortical cerebellar cysts. By whole exome sequencing, the patient was identified to be compound heterozygous for a one-base duplication and a missense mutation in the gene B3GALNT2 (b-1,3-N-acetylgalactos- aminyltransferase 2; B3GalNAc-T2). This patient showed a milder phenotype than previously described patients with mutations in the B3GALNT2 gene. European Journal of Human Genetics (2014) 22, 707–710; doi:10.1038/ejhg.2013.223; published online 2 October 2013 Keywords:
  • Drebrin Restricts Rotavirus Entry by Inhibiting Dynamin-Mediated Endocytosis

    Drebrin Restricts Rotavirus Entry by Inhibiting Dynamin-Mediated Endocytosis

    Drebrin restricts rotavirus entry by inhibiting dynamin-mediated endocytosis Bin Lia,b,c,d,1, Siyuan Dinga,b,c,1,2, Ningguo Fenga,b,c, Nancie Mooneya,e, Yaw Shin Ooia, Lili Renf, Jonathan Diepa, Marcus R. Kellya,e, Linda L. Yasukawaa,b,c, John T. Pattong, Hiroyuki Yamazakih, Tomoaki Shiraoh, Peter K. Jacksona,e, and Harry B. Greenberga,b,c,2 aDepartment of Microbiology and Immunology, Stanford University, Stanford, CA 94305; bDepartment of Medicine, Division of Gastroenterology and Hepatology, Stanford University, Stanford, CA 94305; cPalo Alto Veterans Institute of Research, VA Palo Alto Health Care System, Palo Alto, CA 94304; dInstitute of Veterinary Medicine, Jiangsu Academy of Agricultural Sciences, Nanjing, 210014, China; eBaxter Laboratory for Stem Cell Biology, Stanford University, Stanford, CA 94305; fSchool of Pharmaceutical Sciences, Nanjing Tech University, Nanjing, 211816, China; gDepartment of Veterinary Medicine, University of Maryland, College Park, MD 20740; and hDepartment of Neurobiology and Behavior, Gunma University, Maebashi, Gunma 371-8511, Japan Edited by Peter Palese, Icahn School of Medicine at Mount Sinai, New York, New York, and approved March 28, 2017 (received for review November 22, 2016) Despite the wide administration of several effective vaccines, cells relies primarily on the viral outer capsid spike protein VP4 (8, rotavirus (RV) remains the single most important etiological agent 9). After VP4 binds to its cognate receptors on cellular surfaces, it of severe diarrhea in infants and young children worldwide, with undergoes a marked conformational change that allows the RV an annual mortality of over 200,000 people. RV attachment and particles to be taken up by the host cells via endocytosis.