DOCSLIB.ORG

Identification and Extraction of Proteins That Triad Junction Of

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Identification and Extraction of Proteins That Triad Junction Of Identification and Extraction of Proteins That Compose the Triad Junction of Skeletal Muscle ANTHONY H. CASWELL and J.-P. BRUNSCHWIG Department of Pharmacology, University of Miami School of Medicine, Florida 33101 ABSTRACT Treatment of both transverse tubules and terminal cisternae with a combination of Triton X-100 and hypertonic K cacodylate causes dissolution of nonjunctional proteins and selective retention of membrane fragments which are capable of junction formation. Treatment of vesicles with Triton X-100 and either KCI or K gluconate causes complete dissolution of all components. Therefore K cacodylate exerts a specific preservative action on the junctional material. The membrane fragment from treatment of transverse tubules with Triton X-100 + cacodylate contains a protein of Mr = 80,000 in SDS gel electrophoresis as the predominant protein while lipid composition is enriched in cholesterol. The membrane fragment retains in electron microscopy the trilaminar appearance of the intact vesicles. Freeze fracture of transverse tubule fragments reveals a high density of low-profile, intercalated particles, which frequently form strings or occasional small arrays. The fragments from Triton X-100 plus cacodylate treatment of terminal cisternae include the protein of Mr = 80,000 as well as the spanning protein of the triad, calsequestrin, and some minor proteins. The fragments are almost devoid of lipid and display an amorphous morphology suggesting membrane disruption. The ability of the transverse tubular fragment, which contains predominantly the Mr = 80,000 protein, to form junctions with terminal cisternae fragments suggests that it plays a role in anchoring the membrane to the junctional processes of the triad. The junctional proteins may be solubilized in a combination of nonionic detergent and hypertonic NaCI. Subsequent molecular sieve chromatography gives an enriched preparation of the spanning protein. This protein has subunits of Mr = 300,000, 270,000, and 140,000 and migrates in the gel as a protein of Mr = 1.2 x 106 indicating a polymeric structure. The triad junction or dyad junction of muscle is the only tubules to the terminal cisternae (TC) ~ by forming and then known intracellular membrane junction. The morphology of breaking the triad; hence we proposed that the protein this junction has been extensively studied in intact muscle by spanned the gap between the two organelles. The fact that the electron microscopy and has been demonstrated to display a junction could be disrupted without apparent damage to the unique organization very different from such intercellular associated organelles suggested that the spanning protein re- junctions as the gap junction (1). The triad junction almost sided external to the membrane and was associated with it certainly is also the site of message transmission in excitation- through a noncovalent interaction with a recognition site in contraction coupling (2, 3). Our knowledge of the composi- the membrane. Hence it is likely that the junction is composed tion, molecular conformation, and dynamics of the junction not only of a spanning protein, but also of an anchoring is however extremely limited. For these reasons the resolution protein that is attached or embedded in the membrane and of the structure of the junction offers an intriguing challenge. that recognizes and binds the spanning protein. In an earlier article we presented evidence that a protein This article describes a further characterization and extrac- doublet observed in PAGE with molecular weights of Abbreviations used in this paper: HTC, "heavy" terminal cisternae; -325,000 and 300,000 was a constituent of the junction (4). LTC, "light" terminal cisternae; TC, terminal cisternae; T-tubules, This protein could be transferred in part from the transverse transverse tubules. THE JOURNAL OF CELL BIOLOGY . VOLUME 99 SEPTEMBER 1984 929-939 © The Rockefeller University Press • 0021-9525/84/09/0929/11 $1.00 929 tion of proteins that form the triad junction and suggests a glutaraldehyde, 3% sucrose, 50 mM Na cacodylate, pH 7.2. The subsequent molecular structure of the triad. preparation has been described previously (11). For negative staining, a drop of the preparation (-0.05 mg/ml) was placed on top of a 400-mesh parlodion (0.75% in amyl acetate) coated grid and allowed to stand for 1 rain. The drop MATERIALS AND METHODS was then blotted and replaced by a drop of 1% K phosphotungstate, pH 6.7, The preparation of microsomes, TC/triads, ~heavy" terminal cisternae (HTC), allowed to stand for 1 rain, and then gently blotted until almost dry. Specimens were observed under a Philips EM-300 electron microscope (Philips Electronic and transverse tubules (T-tubules) has been described before (5, 6). A brief Instruments, Inc., Mahwah, NJ) operating at 80 kV. description is as follows: TC/triads are prepared from a microsomal fraction from rabbit sacrospinalis muscle by centrifugation on a continuous sucrose- density gradient. The band with isopycnic point ~40% sucrose contains free TC and intact triad junctions consisting of two TC vesicles apposed on each RESULTS side of a T-tubule vesicle. Broken triads are prepared by passing TC/triads Distribution of Proteins between through a French press at 6,000 psi. HTC and T-tubules are prepared by centrifuging the broken triads in a continous sucrose-density gradient on a Subcellular Organelles Sorvall TV850 vertical rotor (DuPont Instruments, Sorvall Biomedical Div., Newtown, CT) for I t/2 h at 130,000 g. Of the three bands formed the lightest is In previous work we have employed specific ligand or T-tubules (22-28% wt/wt sucrose), the intermediate band (30-35% sucrose) is enzyme markers to delineate T-tubules and sarcoplasmic light terminal cisternae (LTC), and the heaviest is HTC (38-42% sucrose). The reticulum subfractions. Several proteins play a role in the organelles were concentrated by centrifugation and resuspended in a medium triad junction which do not exhibit defined enzyme activities. of 250 mM sucrose, 2 mM histidine, pH 7.0. Protein was estimated by the Bradford assay (7) and, where stated, 2 mg of Fig. 1 shows the gel electrophoretic pattern and the densito- Triton X-100/mg of protein was added followed by the salt. The sample was metric assay of some proteins, which are identified as bands layered on a linear continuous sucrose-density gradient between 12.5 and 60% on SDS PAGE. A preparation of TC/triads was passed sucrose in a Beckman SW 41 Ti rotor (Beckman Instruments, Inc., Fullerton, through a French press to break the triad junction and then CA). It was centrifuged for 3 h at 200,000 g. Samples (1.3 ml) were withdrawn sequentially from the top of the gradient for subsequent analysis. centrifuged to equilibrium on a sucrose-density gradient. The samples from the gradient were assayed as follows: protein was assayed Three distinct vesicle bands are discernible with isopycnic by the Folin method. Total lipid phosphorus was assayed by a modified Ames points at 26, 32, and 42% sucrose which we have previously assay (8). Aliquots (50 tzl) were diluted to l ml with water in a small test tube identified as T-tubule, LTC, and HTC, respectively (6). The and lipid was extracted into the organic phase by twice partitioning with l ml first three panels of densitometric analysis show the distribu- of a 2: l ratio of chloroform/methanol. The solvent was removed by passing a stream of air over the sample. H202 (30%, 100 #l) was added and allowed to tion of proteins that are representative markers for the three incubate in an oven at 80"C overnight. To the dry sample was added 0.8 ml of organelles. The 72,000 Mr protein is distributed specifically 0.5 M HC1 and the phosphorus was assayed subsequently by the method of in the T-tubules in accord with our earlier conclusions that Ames (8). Cholesterol and cholesterol ester were estimated from 100-td samples this is a T-tubule specific protein (6). The distribution of this using a SmithKline Instruments reagent cholesterol kit SV/28 (SmithKline protein matches perfectly to that of the [3H]ouabain entrap- Instruments, Inc., Sunnyvale, CA). This assay employs enzymic hydrolysis of cholesterol ester followed by cholesterol oxidase to produce H202 which was ment assay we have employed before (data not shown). The assayed colorimetrically at 500 nm in a l-ml cell in a Zeiss spectrophotometer long tail of activity in the denser region of the gradient reflects, (Carl Zeiss, Inc., New York). All parts of the reaction are present in a single in part, the difficulties in assaying this protein at low concen- reagent sample. A cholesterol standard (0.052 ~tmol) was run simultaneously. tration because it is not a major component of the triad and, PAGE slab gels were those of Laemmli (9). Most gels used 9% acrylamide, 0.24% N,N'-methylene-bis-acrylamide BIS separating phase. The analysis of in part, a possible low extent of T-tubules which were not the spanning protein employed 5% acrylamide, 0.133% N,N-methylene-bis- broken from the triad by French press treatment. The 53,000 acrylamide. Samples were dissolved in an equal volume of sample buffer and Mr protein that has been identified by Michalak et al. (12) as incubated in a boiling water bath for 1 min, and between 100 and 250 ul was an intrinsic glycoprotein shows a preponderant distribution layered in the wells of the gel. Standards are the high-molecular-weight standards towards the LTC although some activity may also exist in the of Bio-Rad Laboratories (Richmond, CA) which contained myosin, B-galacto- sidase, phosphorylase b, BSA, and ovalbumin, whereas calsequestrin and the HTC. Little activity appears to be associated with T-tubules Ca pump protein served as internal standards. Standards for the spanning and the presence of this protein in the T-tubule region prob- protein gel included cross-linked albumin (Sigma Chemical Co., St.
Load more

Recommended publications
  • Stac Adaptor Proteins Regulate Trafficking and Function of Muscle
    Stac adaptor proteins regulate trafficking and function + of muscle and neuronal L-type Ca2 channels Alexander Polster, Stefano Perni, Hicham Bichraoui, and Kurt G. Beam1 Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO 80045 Contributed by Kurt G. Beam, December 5, 2014 (sent for review November 11, 2014; reviewed by Bruce P. Bean and Terry P. Snutch) + Excitation–contraction (EC) coupling in skeletal muscle depends precisely regulated. As for other high-voltage activated Ca2 upon trafficking of CaV1.1, the principal subunit of the dihydropyr- channels, the auxiliary β-subunit is important for membrane traf- + idine receptor (DHPR) (L-type Ca2 channel), to plasma membrane ficking (5, 6). However, it is clear that an additional factor(s) is regions at which the DHPRs interact with type 1 ryanodine recep- also crucial. Specifically, CaV1.1 expresses poorly (7) or not at all tors (RyR1) in the sarcoplasmic reticulum. A distinctive feature of in mammalian cells that are not of muscle origin (e.g., tsA201 2+ this trafficking is that CaV1.1 expresses poorly or not at all in cells), whereas the closely related cardiac/neuronal L-type Ca mammalian cells that are not of muscle origin (e.g., tsA201 cells), channel, CaV1.2, is readily expressed in such cells (8–10). The in which all of the other nine CaV isoforms have been successfully absence of RyR1 seems insufficient to account for the difficulty expressed. Here, we tested whether plasma membrane trafficking of expressing Ca 1.1 in tsA201 cells because Ca 1.1 expresses of Ca 1.1 in tsA201 cells is promoted by the adapter protein Stac3, V V V well in dyspedic myotubes, albeit producing less current per because recent work has shown that genetic deletion of Stac3 in channel (3).
    [Show full text]
  • Communications Between Mitochondria and Endoplasmic Reticulum in the Regulation of Metabolic Homeostasis
    cells Review Communications between Mitochondria and Endoplasmic Reticulum in the Regulation of Metabolic Homeostasis Pengcheng Zhang, Daniels Konja, Yiwei Zhang and Yu Wang * The State Key Laboratory of Pharmaceutical Biotechnology, Department of Pharmacology and Pharmacy, The University of Hong Kong, Hong Kong SAR, China; [email protected] (P.Z.); [email protected] (D.K.); [email protected] (Y.Z.) * Correspondence: [email protected] Abstract: Mitochondria associated membranes (MAM), which are the contact sites between en- doplasmic reticulum (ER) and mitochondria, have emerged as an important hub for signaling molecules to integrate the cellular and organelle homeostasis, thus facilitating the adaptation of energy metabolism to nutrient status. This review explores the dynamic structural and functional features of the MAM and summarizes the various abnormalities leading to the impaired insulin sensitivity and metabolic diseases. Keywords: mitochondria; endoplasmic reticulum; MAM; energy metabolism 1. Introduction Citation: Zhang, P.; Konja, D.; Zhang, In mammalian cells, the mitochondrion is the organelle specialized for energy produc- Y.; Wang, Y. Communications tion through the processes of oxidative phosphorylation, tricarboxylic acid (TCA) cycle between Mitochondria and and fatty acid β-oxidation [1]. Approximately 90% of cellular reactive oxygen species Endoplasmic Reticulum in the (ROS) are produced from mitochondria during the reactions of oxidative phosphorylation Regulation of Metabolic Homeostasis. (OXPHOS)
    [Show full text]
  • T-Tubule Biogenesis and Triad Formation in Skeletal Muscle and Implication in Human Diseases
    T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases. Lama Al-Qusairi, Jocelyn Laporte To cite this version: Lama Al-Qusairi, Jocelyn Laporte. T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases.. Skeletal Muscle, BioMed Central, 2011, 1 (1), pp.26. 10.1186/2044- 5040-1-26. inserm-00614419 HAL Id: inserm-00614419 https://www.hal.inserm.fr/inserm-00614419 Submitted on 11 Aug 2011 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Al-Qusairi and Laporte Skeletal Muscle 2011, 1:26 http://www.skeletalmusclejournal.com/content/1/1/26 Skeletal Muscle REVIEW Open Access T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases Lama Al-Qusairi1,2,3,4,5,6 and Jocelyn Laporte1,2,3,4,5* Abstract In skeletal muscle, the excitation-contraction (EC) coupling machinery mediates the translation of the action potential transmitted by the nerve into intracellular calcium release and muscle contraction. EC coupling requires a highly specialized membranous structure, the triad, composed of a central T-tubule surrounded by two terminal cisternae from the sarcoplasmic reticulum.
    [Show full text]
  • Skeletal Muscle Triad Junction Ultrastructure by Focused-Ion-Beam Milling of Muscle and Cryo-Electron Tomography
    Skeletal muscle triad by FIB milling and Cryo-ET Eur J Transl Myol - Basic Appl Myol 2015; 25 (1): 49-56 Skeletal muscle triad junction ultrastructure by Focused-Ion-Beam milling of muscle and Cryo-Electron Tomography Terence Wagenknecht (1,2), Chyongere Hsieh (1), Michael Marko (1) (1) New York State Department of Health, Wadsworth Cente, Empire State Plaza, Albany, NY; (2) Department of Biomedical Sciences, School of Public Health, University at Albany, Albany, NY , USA Abstract Cryo-electron tomography (cryo-ET) has emerged as perhaps the only practical technique for revealing nanometer-level three-dimensional structural details of subcellular macromolecular complexes in their native context, inside the cell. As currently practiced, the specimen should be 0.1- 0.2 microns in thickness to achieve optimal resolution. Thus, application of cryo-ET to intact frozen (vitreous) tissues, such as skeletal muscle, requires that they be sectioned. Cryo- ultramicrotomy is notoriously difficult and artifact-prone when applied to frozen cells and tissue, but a new technique, focused ion beam milling (cryo-FIB), shows great promise for “thinning” frozen biological specimens. Here we describe our initial results in applying cryo- FIB and cryo-ET to triad junctions of skeletal muscle. Key Words: Cryo-electron microscopy, Cryo-electron tomography, Excitation-Contraction Coupling, Focused-Ion-Beam milling, Skeletal muscle Eur J Transl Myol - Basic Appl Myol 2015; 25 (1): 49-56 5,6 Current understanding of the molecular structure of to 2 nm (recently reviewed). Significant the triad junction, the site of excitation-contraction in improvements in resolution are likely forthcoming (see skeletal muscle, is severely limited.
    [Show full text]
  • Coming of Age Or Midlife Crisis? Erick O
    Hernández-Ochoa and Schneider Skeletal Muscle (2018) 8:22 https://doi.org/10.1186/s13395-018-0167-9 REVIEW Open Access Voltage sensing mechanism in skeletal muscle excitation-contraction coupling: coming of age or midlife crisis? Erick O. Hernández-Ochoa and Martin F. Schneider* Abstract The process by which muscle fiber electrical depolarization is linked to activation of muscle contraction is known as excitation-contraction coupling (ECC). Our understanding of ECC has increased enormously since the early scientific descriptions of the phenomenon of electrical activation of muscle contraction by Galvani that date back to the end of the eighteenth century. Major advances in electrical and optical measurements, including muscle fiber voltage clamp to reveal membrane electrical properties, in conjunction with the development of electron microscopy to unveil structural details provided an elegant view of ECC in skeletal muscle during the last century. This surge of knowledge on structural and biophysical aspects of the skeletal muscle was followed by breakthroughs in biochemistry and molecular biology, which allowed for the isolation, purification, and DNA sequencing of the muscle fiber membrane calcium channel/transverse tubule (TT) membrane voltage sensor (Cav1.1) for ECC and of the muscle ryanodine receptor/sarcoplasmic reticulum Ca2+ release channel (RyR1), two essential players of ECC in skeletal muscle. In regard to the process of voltage sensing for controlling calcium release, numerous studies support the concept that the TT Cav1.1 channel is the voltage sensor for ECC, as well as also being aCa2+ channel in the TT membrane. In this review, we present early and recent findings that support and define the role of Cav1.1 as a voltage sensor for ECC.
    [Show full text]
  • T-Tubule Biogenesis and Triad Formation in Skeletal Muscle and Implication in Human Diseases Lama Al-Qusairi1,2,3,4,5,6 and Jocelyn Laporte1,2,3,4,5*
    Al-Qusairi and Laporte Skeletal Muscle 2011, 1:26 http://www.skeletalmusclejournal.com/content/1/1/26 Skeletal Muscle REVIEW Open Access T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases Lama Al-Qusairi1,2,3,4,5,6 and Jocelyn Laporte1,2,3,4,5* Abstract In skeletal muscle, the excitation-contraction (EC) coupling machinery mediates the translation of the action potential transmitted by the nerve into intracellular calcium release and muscle contraction. EC coupling requires a highly specialized membranous structure, the triad, composed of a central T-tubule surrounded by two terminal cisternae from the sarcoplasmic reticulum. While several proteins located on these structures have been identified, mechanisms governing T-tubule biogenesis and triad formation remain largely unknown. Here, we provide a description of triad structure and plasticity and review the role of proteins that have been linked to T-tubule biogenesis and triad formation and/or maintenance specifically in skeletal muscle: caveolin 3, amphiphysin 2, dysferlin, mitsugumins, junctophilins, myotubularin, ryanodine receptor, and dihydhropyridine Receptor. The importance of these proteins in triad biogenesis and subsequently in muscle contraction is sustained by studies on animal models and by the direct implication of most of these proteins in human myopathies. Introduction tubules). In skeletal muscle, T-tubules tightly associate To trigger skeletal muscle contraction, the action poten- with the sarcoplasmic reticulum (SR), in a region called tial generated by motor neurons is transmitted through terminal cisternae/junctional SR. The close association motor nerves to muscle cells. The excitation-contraction of one T-tubule with two terminal cisternae on both (EC) coupling, i.e.
    [Show full text]
  • Structural Insights Into Binding of STAC Proteins to Voltage-Gated
    Structural insights into binding of STAC proteins to PNAS PLUS voltage-gated calcium channels Siobhan M. Wong King Yuena,b, Marta Campiglioc, Ching-Chieh Tunga,b, Bernhard E. Flucherc, and Filip Van Petegema,b,1 aDepartment of Biochemistry and Molecular Biology, University of British Columbia, V6T 1Z3 Vancouver, BC, Canada; bThe Life Sciences Centre, University of British Columbia, V6T 1Z3 Vancouver, BC, Canada; and cDepartment of Physiology and Medical Physics, Medical University of Innsbruck, 6020 Innsbruck, Austria Edited by Kurt G. Beam, University of Colorado, Denver, Aurora, CO, and approved September 28, 2017 (received for review June 1, 2017) Excitation–contraction (EC) coupling in skeletal muscle requires degree of CaV1.1 expression, have a drastically reduced EC functional and mechanical coupling between L-type voltage- coupling. In addition, zebrafish embryos that are null for gated calcium channels (CaV1.1) and the ryanodine receptor STAC3 still have normal levels of CaV1.1, but display a highly (RyR1). Recently, STAC3 was identified as an essential protein reduced EC coupling (14). Finally, STAC2 and STAC3 have for EC coupling and is part of a group of three proteins that beenshowntoslowdowninactivationofCaV1.2 (15), an iso- can bind and modulate L-type voltage-gated calcium channels. form expressed in both the heart and the brain. This suggests a Here, we report crystal structures of tandem-SH3 domains of dif- possible role for STAC proteins in CaV regulation outside of ferent STAC isoforms up to 1.2-Å resolution. These form a rigid skeletal muscle. interaction through a conserved interdomain interface. We iden- STAC3 is the target for a disease mutation (W284S) linked to tify the linker connecting transmembrane repeats II and III in two Native American myopathy (NAM).
    [Show full text]
  • Muscle Tissue[PDF]
    Muscle Tissue BY Dr Navneet Kumar Professor Anatomy KGMU LKO Dr Navneet Kumar Professor Anatomy KGMU LKO Muscle Tissue A muscle tissue is made of contractile cells Dr Navneet Kumar Professor Anatomy KGMU LKO Muscle Tissue • Types- • 1.Muscle tissue -Skeletal muscle -Smooth muscle -Cardiac muscle 2.Single cell unite -myoepithelial cells -myofibroblast cells Dr Navneet Kumar Professor Anatomy KGMU LKO Muscle Tissue Plasma membrane -Sarcolema Cytoplasm -Sarcoplasm Endoplasmic reticulum-Sarcoplasmic reticulum Mitochondria- -Sarcosome Dr Navneet Kumar Professor Anatomy KGMU LKO Skeletal muscle…. • Epi mysium • Peri mysium • Endo mysium Dr Navneet Kumar Professor Anatomy KGMU LKO SKELETAL MUSCLE Dr Navneet Kumar Professor Anatomy KGMU LKO Skeletal muscle • features • Skeletal muscle composed of muscle fibres • Each muscle fibre is an elongated unbranched cell, voluntary • Nuclei present at periphery • Striations, Alternative dark and light bands Dr Navneet Kumar Professor Anatomy KGMU LKO Skeletal muscle….. E.M. Structure • Muscle fibre or Muscle cell A muscle fibre (muscle cell) contains bundle of myofibril Myofibril • myofibrils are made of myofilaments Myofilament -Thick myofilaments- myosin protein -Thin myofilaments- actin protein Cross striations are the result of overlapping of myosin protein& actin protein - Transvers tubule system - triad Dr Navneet Kumar Professor Anatomy KGMU LKO Arrangement of myofibril Dr Navneet Kumar Professor Anatomy KGMU LKO Dr Navneet Kumar Professor Anatomy KGMU LKO Arrangement of Myofilament -Dark band-’A’
    [Show full text]
  • 13Dd01ec2bff68c5aae29489c98
    Triad Formation: Organization and Function of the Sarcoplasmic Reticulum Calcium Release Channel and Triadin in Normal and Dysgenic Muscle In Vitro Bernhard E. Flucher, S. Brian Andrews, Sidney Fleischer,* Andrew R. Marks,* Anthony Caswell,§ and Jeanne A. Powelll[ Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892; * Department of Molecular Biology, Vanderbilt University, Nashville, Tennessee 37235; *Molecular Medicine Program and Brookdale Center for Molecular Biology, Mount Sinai School of Medicine, New York, 10029; §Department of Molecular and Cellular Pharmacology, University of Miami, Florida 33101; and 11Department of Biological Sciences, Smith College, Northampton, Massachusetts 01060 Abstract. Excitation-contraction (E-C) coupling is molecular organization of the RyR and triadin in the thought to involve close interactions between the cal- terminal cisternae of SR as well as its association with cium release channel (ryanodine receptor; RyR) of the the T-tubules are independent of interactions with the sarcoplasmic reticulum (SR) and the dihydrophyridine DHPR c~ subunit. Analysis of calcium transients in receptor (DHPR) or1 subunit in the T-tubule mem- dysgenic myotubes with fluorescent calcium indicators brane. Triadin, a 95-kD protein isolated from heavy reveals spontaneous and caffeine-induced calcium re- SR, binds both the RyR and DHPR and may thus par- lease from intracellular stores similar to those of nor- ticipate in E-C coupling or in interactions responsible mal muscle; however, depolarization-induced calcium for the formation of SR/T-tubule junctions. Im- release is absent. Thus, characteristic calcium release munofluorescence labeling of normal mouse myotubes properties of the RyR do not require interactions with shows that the RyR and triadin co-aggregate with the the DHPR; neither do they require the normal organi- DHPR in punctate clusters upon formation of func- zation of the RyR in the terminal SR cisternae.
    [Show full text]
  • Muscles and Muscle Tissue 279
    278 UNIT 2 Covering, Support, and Movement of the Body Muscles and WHY THIS 9 Muscle Tissue MATTERS In this chapter, you will learn that Muscles use actin and myosin molecules to convert the energy of ATP into force beginning with 9.1 Overview of muscle types, special characteristics, next exploring and functions then exploring Skeletal muscle Smooth muscle and investigating then asking and asking 9.2 Gross and 9.4 How does a nerve 9.9 How does smooth muscle microscopic anatomy impulse cause a muscle fiber differ from skeletal muscle? to contract? and and finally, exploring and 9.3 Intracellular structures and sliding 9.5 What are the properties of Developmental Aspects filament model whole muscle contraction? of Muscles and 9.6 How do muscles generate ATP? and 9.7 What determines the force, velocity, and duration of contraction? and 9.8 How does skeletal muscle respond to exercise? Electron micrograph of a bundle of skeletal muscle fibers wrapped in connective tissue. < 278 Chapter 9 Muscles and Muscle Tissue 279 ecause flexing muscles look like mice scurrying beneath the by the nervous system. Most of us have no conscious control B skin, some scientist long ago dubbed them muscles, from over how fast our heart beats. the Latin mus meaning “little mouse.” Indeed, we tend to ● Key words to remember for cardiac muscle are cardiac, stri- think of the rippling muscles of professional boxers or weight lift- ated, and involuntary. ers when we hear the word muscle. But muscle is also the domi- nant tissue in the heart and in the walls of other hollow organs.
    [Show full text]
  • Molecular Organization of Transverse Tubule/ Sarcoplasmic Reticulum Junctions During Development of Excitation-Contraction Coupling in Skeletal Muscle Bernard E
    Molecular Biology of the Cell Vol. 5, 1105-1118, October 1994 Molecular Organization of Transverse Tubule/ Sarcoplasmic Reticulum Junctions During Development of Excitation-Contraction Coupling in Skeletal Muscle Bernard E. Flucher,*t S. Brian Andrews,* and Mathew P. Daniels* *Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke; and tLaboratory of Biochemical Genetics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892 Submitted June 10, 1994; Accepted August 15, 1994 Monitoring Editor: Roger Y. Tsien The relationship between the molecular composition and organization of the triad junction and the development of excitation-contraction (E-C) coupling was investigated in cultured skeletal muscle. Action potential-induced calcium transients develop concomitantly with the first expression of the dihydropyridine receptor (DHPR) and the ryanodine receptor (RyR), which are colocalized in clusters from the time of their earliest appearance. These DHPR/RyR clusters correspond to junctional domains of the transverse tubules (T-tubules) and sarcoplasmic reticulum (SR), respectively. Thus, at first contact T-tubules and SR form molecularly and structurally specialized membrane domains that support E-C coupling. The earliest T-tubule/SR junctions show structural characteristics of mature triads but are diverse in conformation and typically are formed before the extensive development of myofibrils. Whereas the initial formation of T-tubule/SR junctions is independent of as- sociation with myofibrils, the reorganization into proper triads occurs as junctions become associated with the border between the A band and the I band of the sarcomere. This final step in triad formation manifests itself in an increased density and uniformity of junctions in the cytoplasm, which in turn results in increased calcium release and reuptake rates.
    [Show full text]
  • KRAUSE's ESSENTIAL HUMAN HISTOLOGY for MEDICAL STUDENTS Third Edition
    KRAUSE’S ESSENTIAL HUMAN HISTOLOGY FOR MEDICAL STUDENTS Third Edition William J. Krause, Ph.D. Professor of Anatomy Department of Pathology and Anatomical Sciences University of Missouri School of Medicine Columbia, Missouri 1 Table of Contents 1. The Cell 5 7. Special Connective Tissue: Protoplasm 5 Hemopoietic Tissue 79 Cytoplasmic Organelles 6 Embryonic and Fetal Hemopoiesis 79 Cytoskeleton 18 Bone Marrow 80 Cytoplasmic Inclusions 20 Development of Erythrocytes 83 Nucleus 21 Development of Granular Summary 23 Leukocytes 84 Development of Platelets 86 2. Mitosis 29 Development of Monocytes 87 Summary 31 Marrow Lymphocytes 87 Interrelationships of 3. Epithelium 32 Hemopoietic Cells 88 Sheet/Barrier Epithelium 32 Summary 88 Classification of Epithelia 32 Cell Attachments 34 8. Muscle 89 Junctional Complexes 34 Classification 89 Specializations of Epithelial Skeletal Muscle 89 Membranes 37 Cardiac Muscle 97 Glandular Epithelium 39 Smooth Muscle 99 Histogenesis 41 Histogenesis 101 Summary 42 Summary 102 4. General Connective Tissue 43 9. Nervous Tissue 105 Organization 43 Neurons 105 Classification 43 Neuroglia 113 Subtypes of Loose Connective Spinal Cord 115 Tissue 49 Cerebellar and Cerebral Dense Connective Tissue 50 Hemispheres 115 Special Connective Tissue 50 Meninges 117 Histogenesis 51 Autonomic Nervous System 117 Summary 51 Histogenesis 118 Summary 118 5. Special Connective Tissue: Cartilage, Bone, and Joints 52 10. Cardiovascular and Lymph Vascular Cartilage 52 Systems 120 Bone 53 Heart 120 Joints 56 Blood Vessels 123 Histogenesis 59 Arteries 124 Repair of Cartilage and Bone 63 Capillaries 126 Summary 64 Veins 128 Special Circulations 130 6. Special Connective Tissue: Blood 67 Lymph Vascular System 130 Components of Blood 67 Organogenesis 132 Erythrocytes 68 Summary 132 Platelets 70 Leukocytes 71 Blood in Children 77 Summary 77 2 11.
    [Show full text]