DOCSLIB.ORG

Intermediate Filament Assembly: Dynamics to Disease

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Intermediate Filament Assembly: Dynamics to Disease Review Intermediate filament assembly: dynamics to disease Lisa M. Godsel, Ryan P. Hobbs and Kathleen J. Green Department of Pathology, Northwestern University Feinberg School of Medicine, 303 E. Chicago Avenue, Chicago IL 60611, USA Intermediate filament (IF) proteins belong to a large and cytoplasm providing mechanical integrity that is cru- diverse gene family with broad representation in cially important for tissue function. This is highlighted vertebrate tissues. Although considered the ‘toughest’ by a growing list of >75 human genetic diseases caused cytoskeletal fibers, studies in cultured cells have revealed by deficiencies in this network, including skin fragility that IF can be surprisingly dynamic and highly regulated. and epidermolytic disorders, laminopathies, myopathies, This review examines the diversity of IF assembly beha- neuropathies, cataracts and premature aging [6,7] viors, and considers the ideas that IF proteins are co- or (Human Intermediate Filament Mutation Database, post-translationally assembled into oligomeric precur- http://www.interfil.org). Notably, an emerging set of sors, which can be delivered to different subcellular com- mutations in nuclear lamins (reviewed elsewhere) com- partments by microtubules or actomyosin and associated prise a large proportion of human diseases attributable to motor proteins. Their interaction with other cellular IFs [8,9]. This article focuses on cytoplasmic IFs, which elements via IF associated proteins (IFAPs) affects IF are now recognized as players in cell signaling, growth, dynamics and also results in cellular networks with prop- epithelial polarity, wound healing and apoptosis in erties that transcend those of individual components. We addition to providing the cell with resilience to environ- end by discussing how mutations leading to defects in IF mental stress [2,10]. assembly, network formation or IF–IFAP association com- These broad-ranging functions derive from the diversity promise in vivo functions of IF as protectors against of IFs coupled with their unique mechanical and bio- environmental stress. chemical properties. IFs are the most flexible of the bio- logical filaments. Furthermore, unlike MFs and MTs, a Introduction single IF can withstand stretching to more than three Intermediate filaments (IF) are flexible, rod-shaped fibers times its resting length before breaking [11]. Although averaging 10 nm in diameter, a size that is ‘intermediate’ integration with other filament systems is necessary to between microfilaments (MF; 7–8 nm) and microtubules create the final viscoelastic properties of the cytoplasm, it (MT; 25 nm) [1,2]. Of the three non-muscle cytoskeletal is thought that IFs contribute the tensile strength necess- fibers, IFs are the most diverse and are encoded by an ary for maintaining cell integrity (Box 1) [1,11,12]. IFs are estimated 70 IF genes in the human genome (Human also biologically stable structures. However, a recent con- Intermediate Filament Mutation Database; http://www. vergence of in vitro and in vivo explorations has shown the interfil.org). IFs are classified into five major families IF cytoskeleton to be a malleable and dynamic system that expressed in cell-, tissue-, differentiation- and developmen- can be structurally and functionally tailored to suit cells’ tal-specific patterns (Table 1). Families I–IV are localized changing needs. In this review we explore how recent to the cell cytoplasm whereas the type V nuclear lamins are trends have shaped our understanding of IF function, important organizers of the nuclear envelope and karyo- organization and assembly properties in the test tube plasm. IF family members share a common blueprint built and in living cells. We have yet to fully understand how from a central a-helical coiled-coil rod flanked by flexible, these properties are translated into physiologically highly variable N- and C-termini that lead to exceptional relevant in vivo situations. However, the work discussed structural diversity among IFs [3]. This diversity presents here provides insight into how human disease phenotypes many opportunities for tailoring IF networks to cell type- might arise from fundamental defects in IF assembly and specific functions in contrast to the broadly conserved integration with IF-associated proteins (IFAPs) into func- functions of MT and MF. tionally competent networks. In most vertebrate cells cytoplasmic IFs are tethered to the nucleus and extend into the cytoplasm where they IF structure and in vitro assembly properties provide a scaffold for mitochondria, the Golgi complex, IF proteins exhibit an extended secondary structure built microtubule organizing centers (MTOCs) and other cyto- from a conserved a-helical rod domain of 310–350 amino skeletal elements (Figure 1) [1,2,4,5]. In the periphery acids flanked by divergent non-helical N- and C-termini IFs associate with plasma membrane specializations (Figure 2) [1]. The rod domain drives the formation of such as desmosomes, hemidesmosomes and focal adhe- parallel a-helical coiled-coil dimers through long-range sions. The resulting network integrates and organizes the heptad repeats organized as shown in Figure 2, each with a characteristic pattern of apolar residues in the first (a) Corresponding author: Godsel, L.M. ([email protected]). and fourth (d) positions. These dimers constitute the 28 0962-8924/$ – see front matter ß 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.tcb.2007.11.004 Review TRENDS in Cell Biology Vol.18 No.1 Table 1. Members of the IF superfamily Type Cell types Localization Proteins Disease associations I Epithelia Cytoplasm, hair Acidic keratins (pI < 5.7) K14 – epidermolysis bullosa simplex diseases 17 human epithelial keratins; K9–K28 K10, K16, K14 – keratoderma disorders Hair 11 human hair keratins; K31–40 (Ha1–8) K12 – Meesmann corneal dystrophy K13 – white sponge nevus of cannon K16 – pachyonychia congenita type I K17 – pachyonychia congenita type II II Epithelia Cytoplasm, hair Basic keratins (pI 6.0) K5 – epidermolysis bullosa simplex diseases 20 human epithelial keratins; K1–8, K71–80 K1, K9, K2 – keratoderma disorders 6 human hair keratins: K81–86 (Hb1–6) K3 – Meesmann corneal dystrophy K4 – white sponge nevus of cannon K6a – pachyonychia congenita type I K6b – pachyonychia congenita type II Hair K81 (Hb1), K83 (Hb3), K86 (Hb6) – monilethrix K85 (Hb5) – pure hair-nail type ectodermal dysplasia III Muscle Cytoplasm Desmin Desmin – desmin related myopathy, dilated cardiomyopathy 1I, familial restrictive cardiomyopathy 2 Mesenchymal Vimentin Neurons Peripherin Peripherin – amyotrophic lateral sclerosis Astrocytes and GFAP GFAP – Alexander disease glia IV Neurons Cytoplasm NF-L NF-L, M and H – amyotrophic lateral sclerosis Neurons NF-M NF-L – Charcot-Marie-Tooth diseases Neurons NF-H NF-M – Parkinson disease Neurons a-internexin NF-H – neuronal IF inclusion disease Muscle Synemin a Muscle Synemin b (desmuslin) Muscle Syncoilin Neuroepithelia Nestin V Ubiquitous Nuclear lamina Lamins A/C Lamins – large number of disorders, including lipodystrophies, muscular dystrophies, neurological disorders and premature aging B1 B2 Orphan Eye lens Cytoplasm Phakinin (CP49) CP49 – autosomal dominant cataract disease Filensin (CP115) CP115 – autosomal recessive cataract disease elemental building blocks of IFs and depending on the IF predicted that the head domains of type I and type II type these can be hetero- (e.g. type I and II keratins and epidermal keratins and type III IFs exhibit a flexible type IV neurofilament chains) or homodimeric (e.g. type III structure and could interact with sites in the rod domain. vimentin and desmin). In both cases these N-termini are required for in vitro A hypothetical model based on the in vitro behavior of the filament assembly [13,15–17]. Deletion of the vimentin type III vimentin protein provides a useful platform for C-terminus did not block filament formation, but did result understanding how individual polypeptides might be in an increase in their mass-per-length [3]. However, assembled into an apolar filament (Figure 2). According mutations affecting the K5 tail found in patients with to this model, filament assembly comprises several major epidermolysis bullosa simplex (EBS) dramatically steps starting with the formation of parallel, in-register impaired IF assembly and network formation [18]. Impor- dimers. Dimers then associate into tetramers, thought to tantly, exposure of the N- and C-termini on the filament be organized primarily in a mode termed A11, in which the surface also leaves them free to associate with other fila- 1B subunits of the rods overlap in an anti-parallel manner ments and cellular structures. [13,14]. Tetramers aggregate into higher order oligomers to We are far from understanding the specific mechanism of form unit length filaments (ULF) 60 nm long, which assembly for all IF family members, but it is clear that undergo reorganization and elongation by longitudinal differences exist, underscored by the observed rapid kinetics annealing to form immature IF. Within the polymer, other of keratin polymerization and the completely distinct anti-parallel arrangements A12,A22 and ACN can also occur, assembly behavior of nuclear lamins, which form long corresponding to associations between the 1B and 2B sub- head-to-tail arrays that associate laterally [16]. However, domains, between the 2B subdomains, or between the IF family members all share certain attributes that dis- C- and N-termini. The final step is radial compaction of tinguish them from
Load more

Recommended publications
  • ENSG Gene Encodes Effector TCR Pathway Costimulation Inhibitory/Exhaustion Synapse/Adhesion Chemokines/Receptors
    ENSG Gene Encodes Effector TCR pathway Costimulation Inhibitory/exhaustion Synapse/adhesion Chemokines/receptors ENSG00000111537 IFNG IFNg x ENSG00000109471 IL2 IL-2 x ENSG00000232810 TNF TNFa x ENSG00000271503 CCL5 CCL5 x x ENSG00000139187 KLRG1 Klrg1 x ENSG00000117560 FASLG Fas ligand x ENSG00000121858 TNFSF10 TRAIL x ENSG00000134545 KLRC1 Klrc1 / NKG2A x ENSG00000213809 KLRK1 Klrk1 / NKG2D x ENSG00000188389 PDCD1 PD-1 x x ENSG00000117281 CD160 CD160 x x ENSG00000134460 IL2RA IL-2 receptor x subunit alpha ENSG00000110324 IL10RA IL-10 receptor x subunit alpha ENSG00000115604 IL18R1 IL-18 receptor 1 x ENSG00000115607 IL18RAP IL-18 receptor x accessory protein ENSG00000081985 IL12RB2 IL-12 receptor x beta 2 ENSG00000186810 CXCR3 CXCR3 x x ENSG00000005844 ITGAL CD11a x ENSG00000160255 ITGB2 CD18; Integrin x x beta-2 ENSG00000156886 ITGAD CD11d x ENSG00000140678 ITGAX; CD11c x x Integrin alpha-X ENSG00000115232 ITGA4 CD49d; Integrin x x alpha-4 ENSG00000169896 ITGAM CD11b; Integrin x x alpha-M ENSG00000138378 STAT4 Stat4 x ENSG00000115415 STAT1 Stat1 x ENSG00000170581 STAT2 Stat2 x ENSG00000126561 STAT5a Stat5a x ENSG00000162434 JAK1 Jak1 x ENSG00000100453 GZMB Granzyme B x ENSG00000145649 GZMA Granzyme A x ENSG00000180644 PRF1 Perforin 1 x ENSG00000115523 GNLY Granulysin x ENSG00000100450 GZMH Granzyme H x ENSG00000113088 GZMK Granzyme K x ENSG00000057657 PRDM1 Blimp-1 x ENSG00000073861 TBX21 T-bet x ENSG00000115738 ID2 ID2 x ENSG00000176083 ZNF683 Hobit x ENSG00000137265 IRF4 Interferon x regulatory factor 4 ENSG00000140968 IRF8 Interferon
    [Show full text]
  • Large-Scale Opening of Utrophints Tandem Calponin Homology (CH
    Large-scale opening of utrophin’s tandem calponin homology (CH) domains upon actin binding by an induced-fit mechanism Ava Y. Lin, Ewa Prochniewicz, Zachary M. James, Bengt Svensson, and David D. Thomas1 Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455 Edited by James A. Spudich, Stanford University School of Medicine, Stanford, CA, and approved June 20, 2011 (received for review April 21, 2011) We have used site-directed spin labeling and pulsed electron has prevented the development of a reliable structural model for paramagnetic resonance to resolve a controversy concerning the any of these complexes. A major unresolved question concerns structure of the utrophin–actin complex, with implications for the the relative disposition of the tandem CH domains (CH1 and pathophysiology of muscular dystrophy. Utrophin is a homolog of CH2) (9, 10). Crystal structures of the tandem CH domains dystrophin, the defective protein in Duchenne and Becker muscular showed a closed conformation for fimbrin (11) and α-actinin (12), dystrophies, and therapeutic utrophin derivatives are currently but an open conformation for both utrophin (Utr261) (Fig. 1A) being developed. Both proteins have a pair of N-terminal calponin and dystrophin (Dys246) (16). The crystal structure of Utr261 homology (CH) domains that are important for actin binding. suggests that the central helical region connecting CH1 and CH2 Although there is a crystal structure of the utrophin actin-binding is highly flexible. Even for α-actinin, which has a closed crystal domain, electron microscopy of the actin-bound complexes has structure, computational analysis suggests the potential for a high produced two very different structural models, in which the CH do- degree of dynamic flexibility that facilitates actin binding (17).
    [Show full text]
  • The Desmoplakin Carboxyl Terminus Coaligns with and Specifically Disrupts Intermediate Filament Networks When Expressed in Cultured Cells Thaddeus S
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by PubMed Central The Desmoplakin Carboxyl Terminus Coaligns with and Specifically Disrupts Intermediate Filament Networks When Expressed in Cultured Cells Thaddeus S. Stappenbeck and Kathleen J. Green Department of Pathology and the Cancer Center, Northwestern University Medical School, Chicago, Illinois 60611 Abstract. Specific interactions between desmoplakins tides including the 90-kD carboxy-terminal globular I and 11 (DP I and II) and other desmosomal or cyto- domain of DP I specifically colocalized with and ulti- skeletal molecules have been difficult to determine in mately resulted in the complete disruption of IF in part because of the complexity and insolubility of the both cell lines. This effect was specific for IF as micro- desmosome and its constituents . We have used a mo- tubule and microfilament networks were unaltered . lecular genetic approach to investigate the role that This effect was also specific for the carboxyl terminus DP I and 11 may play in the association of the desmo- of DP, as the expression of the 95-kD rod domain of somal plaque with cytoplasmic intermediate filaments DP I did not visibly alter IF networks. Immunogold (IF) . A series of mammalian expression vectors en- localization of COS-7 cells transfected with constructs coding specific predicted domains of DP I were tran- including the carboxyl terminus of DP demonstrated siently expressed in cultured cells that form (COS-7) an accumulation of mutant protein in perinuclear aggre- and do not form (NIH-3T3) desmosomes. Sequence gates within which IF subunits were sequestered.
    [Show full text]
  • Unsheathing WASP's Sting
    news and views required for Swallow-mediated localiza- Cytoplasmic dynein is implicated in Minneapolis 55455, Minnesota, USA tion within the oocyte. many biological processes, including ves- e-mail:[email protected] The interaction between Swallow and icle and organelle transport, mitotic- Roger Karess is at the CNRS Centre de Génétique Dlc is a significant finding and provides spindle function and orientation, and Moléculaire, Ave de la Terrasse, 91198 Gif-sur- the basis for a model in which the dynein- now RNA transport and localization. It is Yvette, France motor complex is responsible for the important to emphasize that a single iso- e-mail: [email protected] anterior localization of bicoid RNA within form of the dynein-motor subunit is 1. St Johnston, D. Cell 81, 167–170 (1995). the oocyte. Interestingly, the transient known to be targeted to several cellular 2. Bashirullah, A., Cooperstock, R. & Lipshitz, H. Annu. Rev. localization of Swallow to the oocyte functions and molecular cargoes within Biochem. 67, 335–394 (1998). anterior occurs at a time when most of the individual cells. Thus it is those molecules 3. Oleynikov, Y. & Singer, R. Trends Cell Biol. 8, 381–383 dynein-motor subunits are concentrated with adaptor functions, such as those pro- (1998). 13 4. Wilhelm, J. & Vale, R. J. Cell Biol. 123, 269–274 (1993). at the posterior of the oocyte . This raises posed here for Swallow, that must 5. Schnorrer, F., Bohmann, K. & Nusslein-Volhard, C. Nature Cell the possibility that at least two distinct account for the functional specificity of Biol.
    [Show full text]
  • Microtubule Plus-End Tracking Proteins in Neuronal Development
    Cell. Mol. Life Sci. (2016) 73:2053–2077 DOI 10.1007/s00018-016-2168-3 Cellular and Molecular Life Sciences REVIEW Microtubule plus-end tracking proteins in neuronal development 1 1 1 Dieudonne´e van de Willige • Casper C. Hoogenraad • Anna Akhmanova Received: 13 December 2015 / Revised: 4 February 2016 / Accepted: 22 February 2016 / Published online: 11 March 2016 Ó The Author(s) 2016. This article is published with open access at Springerlink.com Abstract Regulation of the microtubule cytoskeleton is AIS Axon initial segment of pivotal importance for neuronal development and BDNF Brain-derived neurotrophic factor function. One such regulatory mechanism centers on CAMSAP Calmodulin-regulated spectrin-associated microtubule plus-end tracking proteins (?TIPs): struc- protein turally and functionally diverse regulatory factors, which CAP-Gly Cytoskeletal-associated protein glycine-rich can form complex macromolecular assemblies at the CEP Centrosomal protein growing microtubule plus-ends. ?TIPs modulate important CFEOM1 Congenital fibrosis of the extraocular muscles properties of microtubules including their dynamics and type 1 their ability to control cell polarity, membrane transport CH Calponin homology and signaling. Several neurodevelopmental and neurode- CLASP Cytoplasmic linker protein-associated protein generative diseases are associated with mutations in ?TIPs CLIP Cytoplasmic linker protein or with misregulation of these proteins. In this review, we DRG Dorsal root ganglia focus on the role and regulation of ?TIPs in neuronal EB
    [Show full text]
  • The CAP-Gly and Basic Microtubule Binding Domains of Dynactin Are
    Knockdown of dynactin’s p150Glued subunit abrogates microtubule organization by Jared Todd Roeckner A Thesis Submitted to the Faculty of The Wilkes Honors College In Partial Fulfillment of the Requirements for the Degree of Bachelor of Arts in Liberal Arts and Sciences with a Concentration in Biology Wilkes Honors College of Florida Atlantic University Jupiter, Florida May 2009 Knockdown of dynactin’s p150Glued subunit abrogates microtubule organization by Jared T. Roeckner This thesis was prepared under the direction of the candidate’s thesis advisor, Dr. Nicholas Quintyne, and has been approved by the members of the supervisory committee. It was submitted to the faculty of The Honors College and was accepted in partial fulfillment of the Requirements for the Degree of Bachelor of Arts in Liberal Arts and Sciences. SUPERVISORY COMMITTEE: ________________________ Dr. Nicholas Quintyne ________________________ Dr. Paul Kirchman ________________________ Dean, Wilkes Honors College _________ Date ii ACKNOWLEDGEMENTS First, I would like to thank Dr. Nicholas Quintyne for allowing me to work in his lab for the last three years and overseeing and guiding my thesis research and writing. I would like to acknowledge Dr. Stephen King and Dr. Margret Kincaid at UMKC for providing us with the p150Glued knockdown plasmids. Dr. Paul Kirchman, April Mistrik, and everyone in the Quintyne lab helped me out greatly. Ed Fulton and I worked on many steps of this project together and I thank him for his help. Finally, I would like to thank my family and friends for supporting of my thesis research and my undergraduate studies as a whole. iii ABSTRACT Author: Jared Todd Roeckner Title: Knockdown of dynactin’s p150Glued subunit abrogates microtubule organization Institutions: Harriet L.
    [Show full text]
  • UCSD MOLECULE PAGES Doi:10.6072/H0.MP.A002549.01 Volume 1, Issue 2, 2012 Copyright UC Press, All Rights Reserved
    UCSD MOLECULE PAGES doi:10.6072/H0.MP.A002549.01 Volume 1, Issue 2, 2012 Copyright UC Press, All rights reserved. Review Article Open Access WAVE2 Tadaomi Takenawa1, Shiro Suetsugu2, Daisuke Yamazaki3, Shusaku Kurisu1 WASP family verprolin-homologous protein 2 (WAVE2, also called WASF2) was originally identified by its sequence similarity at the carboxy-terminal VCA (verprolin, cofilin/central, acidic) domain with Wiskott-Aldrich syndrome protein (WASP) and N-WASP (neural WASP). In mammals, WAVE2 is ubiquitously expressed, and its two paralogs, WAVE1 (also called suppressor of cAMP receptor 1, SCAR1) and WAVE3, are predominantly expressed in the brain. The VCA domain of WASP and WAVE family proteins can activate the actin-related protein 2/3 (Arp2/3) complex, a major actin nucleator in cells. Proteins that can activate the Arp2/3 complex are now collectively known as nucleation-promoting factors (NPFs), and the WASP and WAVE families are a founding class of NPFs. The WAVE family has an amino-terminal WAVE homology domain (WHD domain, also called the SCAR homology domain, SHD) followed by the proline-rich region that interacts with various Src-homology 3 (SH3) domain proteins. The VCA domain located at the C-terminus. WAVE2, like WAVE1 and WAVE3, constitutively forms a huge heteropentameric protein complex (the WANP complex), binding through its WHD domain with Abi-1 (or its paralogs, Abi-2 and Abi-3), HSPC300 (also called Brick1), Nap1 (also called Hem-2 and NCKAP1), Sra1 (also called p140Sra1 and CYFIP1; its paralog is PIR121 or CYFIP2). The WANP complex is recruited to the plasma membrane by cooperative action of activated Rac GTPases and acidic phosphoinositides.
    [Show full text]
  • Overview of the Cytoskeleton from an Evolutionary Perspective
    Downloaded from http://cshperspectives.cshlp.org/ on October 1, 2021 - Published by Cold Spring Harbor Laboratory Press Overview of the Cytoskeleton from an Evolutionary Perspective Thomas D. Pollard1 and Robert D. Goldman2 1Departments of Molecular Cellular and Developmental Biology, Molecular Biophysics and Biochemistry, and Cell Biology ,Yale University, New Haven, Connecticut 06520-8103 2Department of Cell and Molecular Biology, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611 Correspondence: [email protected] SUMMARY Organisms in the three domains of life depend on protein polymers to form a cytoskeleton that helps to establish their shapes, maintain their mechanical integrity, divide, and, in many cases, move. Eukaryotes have the most complex cytoskeletons, comprising three cytoskeletal poly- mers—actin filaments, intermediate filaments, and microtubules—acted on by three families of motor proteins (myosin, kinesin, and dynein). Prokaryotes have polymers of proteins ho- mologous to actin and tubulin but no motors, and a few bacteria have a protein related to intermediate filament proteins. Outline 1 Introduction—Overview of cellular 4 Overview of the evolution of the cytoskeleton functions 5 Conclusion 2 Structures of the cytoskeletal polymers References 3 Assembly of cytoskeletal polymers Editors: Thomas D. Pollard and Robert D. Goldman Additional Perspectives on The Cytoskeleton available at www.cshperspectives.org Copyright # 2018 Cold Spring Harbor Laboratory Press; all rights reserved; doi: 10.1101/cshperspect.a030288 Cite this article as Cold Spring Harb Perspect Biol 2018;10:a030288 1 Downloaded from http://cshperspectives.cshlp.org/ on October 1, 2021 - Published by Cold Spring Harbor Laboratory Press T.D. Pollard and R.D. Goldman 1 INTRODUCTION—OVERVIEW OF CELLULAR contrast, intermediate filaments do not serve as tracks for FUNCTIONS molecular motors (reviewed by Herrmann and Aebi 2016) but, rather, are transported by these motors.
    [Show full text]
  • 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.
    [Show full text]
  • Keratins and Plakin Family Cytolinker Proteins Control the Length Of
    RESEARCH ARTICLE Keratins and plakin family cytolinker proteins control the length of epithelial microridge protrusions Yasuko Inaba*, Vasudha Chauhan, Aaron Paul van Loon, Lamia Saiyara Choudhury, Alvaro Sagasti* Molecular, Cell and Developmental Biology Department and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, United States Abstract Actin filaments and microtubules create diverse cellular protrusions, but intermediate filaments, the strongest and most stable cytoskeletal elements, are not known to directly participate in the formation of protrusions. Here we show that keratin intermediate filaments directly regulate the morphogenesis of microridges, elongated protrusions arranged in elaborate maze-like patterns on the surface of mucosal epithelial cells. We found that microridges on zebrafish skin cells contained both actin and keratin filaments. Keratin filaments stabilized microridges, and overexpressing keratins lengthened them. Envoplakin and periplakin, plakin family cytolinkers that bind F-actin and keratins, localized to microridges, and were required for their morphogenesis. Strikingly, plakin protein levels directly dictate microridge length. An actin-binding domain of periplakin was required to initiate microridge morphogenesis, whereas periplakin-keratin binding was required to elongate microridges. These findings separate microridge morphogenesis into distinct steps, expand our understanding of intermediate filament functions, and identify microridges as protrusions that integrate actin and intermediate filaments. *For correspondence: [email protected] (YI); Introduction [email protected] (AS) Cytoskeletal filaments are scaffolds for membrane protrusions that create a vast diversity of cell shapes. The three major classes of cytoskeletal elements—microtubules, actin filaments, and inter- Competing interests: The mediate filaments (IFs)—each have distinct mechanical and biochemical properties and associate authors declare that no with different regulatory proteins, suiting them to different functions.
    [Show full text]
  • Genetic Background Effects of Keratin 8 and 18 in a DDC-Induced Hepatotoxicity and Mallory-Denk Body Formation Mouse Model
    Laboratory Investigation (2012) 92, 857–867 & 2012 USCAP, Inc All rights reserved 0023-6837/12 $32.00 Genetic background effects of keratin 8 and 18 in a DDC-induced hepatotoxicity and Mallory-Denk body formation mouse model Johannes Haybaeck1, Cornelia Stumptner1, Andrea Thueringer1, Thomas Kolbe2, Thomas M Magin3, Michael Hesse4, Peter Fickert5, Oleksiy Tsybrovskyy1, Heimo Mu¨ller1, Michael Trauner5,6, Kurt Zatloukal1 and Helmut Denk1 Keratin 8 (K8) and keratin 18 (K18) form the major hepatocyte cytoskeleton. We investigated the impact of genetic loss of either K8 or K18 on liver homeostasis under toxic stress with the hypothesis that K8 and K18 exert different functions. krt8À/À and krt18À/À mice crossed into the same 129-ola genetic background were treated by acute and chronic ad- ministration of 3,5-diethoxy-carbonyl-1,4-dihydrocollidine (DDC). In acutely DDC-intoxicated mice, macrovesicular steatosis was more pronounced in krt8À/À and krt18À/À compared with wild-type (wt) animals. Mallory-Denk bodies (MDBs) appeared in krt18À/À mice already at an early stage of intoxication in contrast to krt8À/À mice that did not display MDB formation when fed with DDC. Keratin-deficient mice displayed significantly lower numbers of apoptotic hepatocytes than wt animals. krt8À/À, krt18À/À and control mice displayed comparable cell proliferation rates. Chronically DDC-intoxicated krt18À/À and wt mice showed a similarly increased degree of steatohepatitis with hepatocyte ballooning and MDB formation. In krt8À/À mice, steatosis was less, ballooning, and MDBs were absent. krt18À/À mice developed MDBs whereas krt8À/À mice on the same genetic background did not, highlighting the significance of different structural properties of keratins.
    [Show full text]
  • Tracking Melanosomes Inside a Cell to Study Molecular Motors and Their Interaction
    Tracking melanosomes inside a cell to study molecular motors and their interaction Comert Kural*, Anna S. Serpinskaya†, Ying-Hao Chou†, Robert D. Goldman†, Vladimir I. Gelfand†‡, and Paul R. Selvin*§¶ *Center for Biophysics and Computational Biology and §Department of Physics, University of Illinois at Urbana–Champaign, Urbana, IL 61801; and †Department of Cell and Molecular Biology, Northwestern University School of Medicine, Chicago, IL 60611 Communicated by Gordon A. Baym, University of Illinois at Urbana–Champaign, Urbana, IL, January 9, 2007 (received for review June 4, 2006) Cells known as melanophores contain melanosomes, which are membrane organelles filled with melanin, a dark, nonfluorescent pigment. Melanophores aggregate or disperse their melanosomes when the host needs to change its color in response to the environment (e.g., camouflage or social interactions). Melanosome transport in cultured Xenopus melanophores is mediated by my- osin V, heterotrimeric kinesin-2, and cytoplasmic dynein. Here, we describe a technique for tracking individual motors of each type, both individually and in their interaction, with high spatial (Ϸ2 nm) and temporal (Ϸ1 msec) localization accuracy. This method enabled us to observe (i) stepwise movement of kinesin-2 with an average step size of 8 nm; (ii) smoother melanosome transport (with fewer pauses), in the absence of intermediate filaments (IFs); and (iii) motors of actin filaments and microtubules working on the same cargo nearly simultaneously, indicating that a diffusive step is not needed between the two systems of transport. In concert with our previous report, our results also show that dynein-driven retro- grade movement occurs in 8-nm steps. Furthermore, previous studies have shown that melanosomes carried by myosin V move 35 nm in a stepwise fashion in which the step rise-times can be as long as 80 msec.
    [Show full text]