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Muranova LK, Shatov VM, Gusev NB. Role of Small Heat Shock Proteins in the Remodeling of Actin Microfilaments. BIOCHEMISTRY. BIOKHIMIIA 2022; 87:800-811. [PMID: 36171660 DOI: 10.1134/s0006297922080119] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 04/28/2022] [Accepted: 04/28/2022] [Indexed: 06/16/2023]
Abstract
Small heat shock proteins (sHsps) play an important role in the maintenance of proteome stability and, particularly, in stabilization of the cytoskeleton and cell contractile apparatus. Cell exposure to different types of stress is accompanied by the translocation of sHsps onto actin filaments; therefore, it is commonly believed that the sHsps are true actin-binding proteins. Investigations of last years have shown that this assumption is incorrect. Stress-induced translocation of sHsp to actin filaments is not the result of direct interaction of these proteins with intact actin, but results from the chaperone-like activity of sHsps and their interaction with various actin-binding proteins. HspB1 and HspB5 interact with giant elastic proteins titin and filamin thus providing an integrity of the contractile apparatus and its proper localization in the cell. HspB6 binds to the universal adapter protein 14-3-3 and only indirectly affects the structure of actin filament. HspB7 interacts with filamin C and controls actin filament assembly. HspB8 forms tight complex with the universal regulatory and adapter protein Bag3 and participates in the chaperone-assisted selective autophagy (CASA) of actin-binding proteins (e.g., filamin), as well as in the actin-depending processes taking place in mitoses. Hence, the mechanisms of sHsp participation in the maintenance of the contractile apparatus and cytoskeleton are much more complicated and diverse than it has been postulated earlier and are not limited to direct interactions of sHsps with actin. The old hypothesis on the direct binding of sHsps to intact actin should be revised and further detailed investigation on the sHsp interaction with minor proteins participating in the formation and remodeling of actin filaments is required.
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Affiliation(s)
- Lydia K Muranova
- Faculty of Biology, Lomonosov Moscow State University, Moscow, 119991, Russia
| | - Vladislav M Shatov
- Faculty of Biology, Lomonosov Moscow State University, Moscow, 119991, Russia
| | - Nikolai B Gusev
- Faculty of Biology, Lomonosov Moscow State University, Moscow, 119991, Russia.
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2
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Sajda T, Sinha AA. Autoantibody Signaling in Pemphigus Vulgaris: Development of an Integrated Model. Front Immunol 2018; 9:692. [PMID: 29755451 PMCID: PMC5932349 DOI: 10.3389/fimmu.2018.00692] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 03/21/2018] [Indexed: 01/10/2023] Open
Abstract
Pemphigus vulgaris (PV) is an autoimmune skin blistering disease effecting both cutaneous and mucosal epithelia. Blister formation in PV is known to result from the binding of autoantibodies (autoAbs) to keratinocyte antigens. The primary antigenic targets of pathogenic autoAbs are known to be desmoglein 3, and to a lesser extent, desmoglein 1, cadherin family proteins that partially comprise the desmosome, a protein structure responsible for maintaining cell adhesion, although additional autoAbs, whose role in blister formation is still unclear, are also known to be present in PV patients. Nevertheless, there remain large gaps in knowledge concerning the precise mechanisms through which autoAb binding induces blister formation. Consequently, the primary therapeutic interventions for PV focus on systemic immunosuppression, whose side effects represent a significant health risk to patients. In an effort to identify novel, disease-specific therapeutic targets, a multitude of studies attempting to elucidate the pathogenic mechanisms downstream of autoAb binding, have led to significant advancements in the understanding of autoAb-mediated blister formation. Despite this enhanced characterization of disease processes, a satisfactory explanation of autoAb-induced acantholysis still does not exist. Here, we carefully review the literature investigating the pathogenic disease mechanisms in PV and, taking into account the full scope of results from these studies, provide a novel, comprehensive theory of blister formation in PV.
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Affiliation(s)
- Thomas Sajda
- Department of Dermatology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, United States
| | - Animesh A Sinha
- Department of Dermatology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, United States
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3
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Piri N, Kwong JMK, Gu L, Caprioli J. Heat shock proteins in the retina: Focus on HSP70 and alpha crystallins in ganglion cell survival. Prog Retin Eye Res 2016; 52:22-46. [PMID: 27017896 PMCID: PMC4842330 DOI: 10.1016/j.preteyeres.2016.03.001] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Revised: 03/14/2016] [Accepted: 03/22/2016] [Indexed: 10/22/2022]
Abstract
Heat shock proteins (HSPs) belong to a superfamily of stress proteins that are critical constituents of a complex defense mechanism that enhances cell survival under adverse environmental conditions. Cell protective roles of HSPs are related to their chaperone functions, antiapoptotic and antinecrotic effects. HSPs' anti-apoptotic and cytoprotective characteristics, their ability to protect cells from a variety of stressful stimuli, and the possibility of their pharmacological induction in cells under pathological stress make these proteins an attractive therapeutic target for various neurodegenerative diseases; these include Alzheimer's, Parkinson's, Huntington's, prion disease, and others. This review discusses the possible roles of HSPs, particularly HSP70 and small HSPs (alpha A and alpha B crystallins) in enhancing the survival of retinal ganglion cells (RGCs) in optic neuropathies such as glaucoma, which is characterized by progressive loss of vision caused by degeneration of RGCs and their axons in the optic nerve. Studies in animal models of RGC degeneration induced by ocular hypertension, optic nerve crush and axotomy show that upregulation of HSP70 expression by hyperthermia, zinc, geranyl-geranyl acetone, 17-AAG (a HSP90 inhibitor), or through transfection of retinal cells with AAV2-HSP70 effectively supports the survival of injured RGCs. RGCs survival was also stimulated by overexpression of alpha A and alpha B crystallins. These findings provide support for translating the HSP70- and alpha crystallin-based cell survival strategy into therapy to protect and rescue injured RGCs from degeneration associated with glaucomatous and other optic neuropathies.
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Affiliation(s)
- Natik Piri
- Stein Eye Institute, University of California, Los Angeles, CA 90095, USA; Brain Research Institute, University of California, Los Angeles, CA 90095, USA.
| | - Jacky M K Kwong
- Stein Eye Institute, University of California, Los Angeles, CA 90095, USA
| | - Lei Gu
- Stein Eye Institute, University of California, Los Angeles, CA 90095, USA
| | - Joseph Caprioli
- Stein Eye Institute, University of California, Los Angeles, CA 90095, USA; Brain Research Institute, University of California, Los Angeles, CA 90095, USA
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4
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Abstract
Assembly of appropriately oriented actin cables nucleated by formin proteins is necessary for many biological processes in diverse eukaryotes. However, compared with knowledge of how nucleation of dendritic actin filament arrays by the actin-related protein-2/3 complex is regulated, the in vivo regulatory mechanisms for actin cable formation are less clear. To gain insights into mechanisms for regulating actin cable assembly, we reconstituted the assembly process in vitro by introducing microspheres functionalized with the C terminus of the budding yeast formin Bni1 into extracts prepared from yeast cells at different cell-cycle stages. EM studies showed that unbranched actin filament bundles were reconstituted successfully in the yeast extracts. Only extracts enriched in the mitotic cyclin Clb2 were competent for actin cable assembly, and cyclin-dependent kinase 1 activity was indispensible. Cyclin-dependent kinase 1 activity also was found to regulate cable assembly in vivo. Here we present evidence that formin cell-cycle regulation is conserved in vertebrates. The use of the cable-reconstitution system to test roles for the key actin-binding proteins tropomyosin, capping protein, and cofilin provided important insights into assembly regulation. Furthermore, using mass spectrometry, we identified components of the actin cables formed in yeast extracts, providing the basis for comprehensive understanding of cable assembly and regulation.
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Seit-Nebi AS, Datskevich P, Gusev NB. Commentary on paper: Small heat shock proteins and the cytoskeleton: An essential interplay for cell integrity? (Wettstein et al.). Int J Biochem Cell Biol 2013. [DOI: 10.1016/j.biocel.2012.11.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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6
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Phosphorylation-dependent subcellular localization of the small heat shock proteins HspB1/Hsp25 and HspB5/αB-crystallin in cultured hippocampal neurons. Histochem Cell Biol 2012; 138:407-18. [DOI: 10.1007/s00418-012-0964-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/28/2012] [Indexed: 12/26/2022]
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7
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Mymrikov EV, Seit-Nebi AS, Gusev NB. Large potentials of small heat shock proteins. Physiol Rev 2011; 91:1123-59. [PMID: 22013208 DOI: 10.1152/physrev.00023.2010] [Citation(s) in RCA: 316] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Modern classification of the family of human small heat shock proteins (the so-called HSPB) is presented, and the structure and properties of three members of this family are analyzed in detail. Ubiquitously expressed HSPB1 (HSP27) is involved in the control of protein folding and, when mutated, plays a significant role in the development of certain neurodegenerative disorders. HSPB1 directly or indirectly participates in the regulation of apoptosis, protects the cell against oxidative stress, and is involved in the regulation of the cytoskeleton. HSPB6 (HSP20) also possesses chaperone-like activity, is involved in regulation of smooth muscle contraction, has pronounced cardioprotective activity, and seems to participate in insulin-dependent regulation of muscle metabolism. HSPB8 (HSP22) prevents accumulation of aggregated proteins in the cell and participates in the regulation of proteolysis of unfolded proteins. HSPB8 also seems to be directly or indirectly involved in regulation of apoptosis and carcinogenesis, contributes to cardiac cell hypertrophy and survival and, when mutated, might be involved in development of neurodegenerative diseases. All small heat shock proteins play important "housekeeping" roles and regulate many vital processes; therefore, they are considered as attractive therapeutic targets.
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Affiliation(s)
- Evgeny V Mymrikov
- Department of Biochemistry, School of Biology, Moscow State University, Moscow, Russian Federation
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Hu S, Wang Y, Lichtenstein L, Tao Y, Musch MW, Jabri B, Antonopoulos D, Claud EC, Chang EB. Regional differences in colonic mucosa-associated microbiota determine the physiological expression of host heat shock proteins. Am J Physiol Gastrointest Liver Physiol 2010; 299:G1266-75. [PMID: 20864653 PMCID: PMC3006241 DOI: 10.1152/ajpgi.00357.2010] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Cytoprotective heat shock proteins (Hsps) are critical for intestinal homeostasis and are known to be decreased in inflammatory bowel diseases. Signals responsible for maintenance of Hsp expression are incompletely understood. In this study, we find that Hsp25/27 and Hsp70 protein expressions are differentially regulated along the longitudinal length of the large intestine, being highest in the proximal colon and decreasing to the distal colon. This longitudinal gradient was similar in both conventionally colonized mouse colon as well as biopsies of human proximal and distal colon but was abolished in the colon of germ-free mice, suggesting a role of intestinal microbiota in the Hsp regional expression. Correspondingly, analysis of 16S ribosomal RNA genes of bacteria from each colonic segment indicated increased bacterial richness and diversity in the proximal colon. The mechanism of regulation is transcriptional, as Hsp70 mRNA followed a similar pattern to Hsp70 protein expression. Lysates of mucosa-associated bacteria from the proximal colon stimulated greater Hsp25 and Hsp70 mRNA transcription and subsequent protein expression in intestinal epithelial cells than did lysates from distal colon. In addition, transrectal administration of cecal contents stimulated Hsp25 and Hsp70 expression in the distal colon. Thus host-microbial interactions resulting in differential Hsp expression may have significant implications for the maintenance of intestinal homeostasis and possibly for development of inflammatory diseases of the bowel.
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Affiliation(s)
- Shien Hu
- 1The Martin Boyer Laboratories, Department of Medicine, University of Chicago, Chicago, Illinois;
| | - Yunwei Wang
- 1The Martin Boyer Laboratories, Department of Medicine, University of Chicago, Chicago, Illinois;
| | - Lev Lichtenstein
- 2Gastroenterology Institute, Rabin Medical Center, Petach Tiqwa, Israel;
| | - Yun Tao
- 1The Martin Boyer Laboratories, Department of Medicine, University of Chicago, Chicago, Illinois;
| | - Mark W. Musch
- 1The Martin Boyer Laboratories, Department of Medicine, University of Chicago, Chicago, Illinois;
| | - Bana Jabri
- 1The Martin Boyer Laboratories, Department of Medicine, University of Chicago, Chicago, Illinois;
| | | | - Erika C. Claud
- 1The Martin Boyer Laboratories, Department of Medicine, University of Chicago, Chicago, Illinois;
| | - Eugene B. Chang
- 1The Martin Boyer Laboratories, Department of Medicine, University of Chicago, Chicago, Illinois;
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Gliem M, Heupel WM, Spindler V, Harms GS, Waschke J. Actin reorganization contributes to loss of cell adhesion in pemphigus vulgaris. Am J Physiol Cell Physiol 2010; 299:C606-13. [PMID: 20554911 DOI: 10.1152/ajpcell.00075.2010] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the human autoimmune blistering skin disease pemphigus vulgaris autoantibodies (PV-IgG), which are mainly directed against keratinocyte cell adhesion molecules desmoglein (Dsg) 3 and Dsg1, cause keratinocyte cell dissociation (acantholysis). Recent studies reported that loss of keratinocyte cell adhesion was accompanied by profound alterations of the actin cytoskeleton. Nevertheless, the relevance of actin reorganization in this process is unclear at present. In this study, we provide evidence for an important role of actin reorganization in pemphigus pathogenesis. In parallel to loss of cell adhesion and fragmentation of Dsg3 staining along cell borders, PV-IgG treatment resulted in striking changes in actin cytoskeleton organization. Moreover, in experiments using fluorescence recovery after photobleaching (FRAP), PV-IgG were detected to interfere with actin dynamics. Therefore, we investigated whether pharmacological manipulation of actin polymerization modulates pathogenic effects of PV-IgG. Pharmacological stabilization of actin filaments via jasplakinolide significantly blocked cell dissociation and Dsg3 fragmentation, whereas cytochalasin D-induced actin depolymerization strongly enhanced pathogenic effects of PV-IgG. To substantiate these findings, we studied whether the protective effects of Rho GTPases, which are potent regulators of the actin cytoskeleton and were shown to be involved in pemphigus pathogenesis, were dependent on modulation of actin dynamics. Cytotoxic necrotizing factor-1 (CNF-1)-mediated activation of Rho-GTPases enhanced the cortical junction-associated actin belt and blunted PV-IgG-induced cell dissociation. However, when actin polymerization was blocked under these conditions via addition of latrunculin B, the protective effects of CNF-1 were abrogated. Taken together, these experiments indicate that reorganization of cortical actin filaments is a critical step in PV-IgG-induced keratinocyte dissociation.
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Affiliation(s)
- Martin Gliem
- Institute of Anatomy and Cell Biology, Univ. of Würzburg, Würzburg, Germany
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10
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Age-related changes in HSP25 expression in basal ganglia and cortex of F344/BN rats. Neurosci Lett 2010; 472:90-3. [PMID: 20144690 DOI: 10.1016/j.neulet.2010.01.049] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Revised: 01/21/2010] [Accepted: 01/21/2010] [Indexed: 12/12/2022]
Abstract
Normal aging is associated with chronic oxidative stress. In the basal ganglia, oxidative stress may contribute to the increased risk of Parkinson's disease in the elderly. Neurons are thought to actively utilize compensatory defense mechanisms, such as heat shock proteins (HSPs), to protect from persisting stress. Despite their protective role, little is known about HSP expression in the aging basal ganglia. The purpose of this study was to examine HSP expression in striatum, substantia nigra, globus pallidus and cortex in 6-, 18- and 30-month-old Fischer 344/Brown Norway rats. We found robust age-related increases in phosphorylated and total HSP25 in each brain region studied. Conversely, HSP72 (the inducible form of HSP70) was reduced with age, but only in the striatum. p38 MAPK, a protein implicated in activating HSP25, did not change with age, nor did HSC70 (the constitutive form of HSP70), or HSP60. These results suggest that HSP25 is especially responsive to age-related stress in the basal ganglia.
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11
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Bektas M, Rubenstein DS. What's in a name?: Heat shock protein 27 and keratinocyte differentiation. J Invest Dermatol 2010; 130:10-2. [PMID: 20010861 DOI: 10.1038/jid.2009.330] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In this issue of the Journal, Robitaille and colleagues present data supporting a role for the small heat shock protein (HSP) 27 in keratinocyte terminal differentiation. This adds to the growing literature implicating HSP27 as a regulator of biologic function beyond thermal stress response.
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Affiliation(s)
- Meryem Bektas
- Department of Dermatology, University of North Carolina, Chapel Hill, North Carolina, USA
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12
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Stetler RA, Gao Y, Signore AP, Cao G, Chen J. HSP27: mechanisms of cellular protection against neuronal injury. Curr Mol Med 2010; 9:863-72. [PMID: 19860665 DOI: 10.2174/156652409789105561] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The heat shock protein (HSP) family has long been associated with a generalized cellular stress response, particularly in terms of recognizing and chaperoning misfolded proteins. While HSPs in general appear to be protective, HSP27 has recently emerged as a particularly potent neuroprotectant in a number of diverse neurological disorders, ranging from ALS to stroke. Although its robust protective effect on a number of insults has been recognized, the mechanisms and regulation of HSP27's protective actions are still undergoing intense investigation. On the basis of recent studies, HSP27 appears to have a dynamic and diverse range of function in cellular survival. This review provides a forum to compare and contrast recent literature exploring the protective mechanism and regulation of HSP27, focusing on neurological disorders in particular, as they represent a range from protein aggregate-associated diseases to acute stress.
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Affiliation(s)
- R A Stetler
- Department of Neurology, University of Pittsburgh, 507 South Biomedical Science Tower, 200 Lothrop Street, Pittsburgh, PA 15261, USA
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13
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Kazakov AS, Markov DI, Gusev NB, Levitsky DI. Thermally induced structural changes of intrinsically disordered small heat shock protein Hsp22. Biophys Chem 2009; 145:79-85. [DOI: 10.1016/j.bpc.2009.09.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2009] [Revised: 08/31/2009] [Accepted: 09/05/2009] [Indexed: 10/20/2022]
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14
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Stacchiotti A, Bonomini F, Lavazza A, Rodella LF, Rezzani R. Adverse effects of cyclosporine A on HSP25, alpha B-crystallin and myofibrillar cytoskeleton in rat heart. Toxicology 2009; 262:192-8. [DOI: 10.1016/j.tox.2009.06.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2009] [Revised: 06/09/2009] [Accepted: 06/10/2009] [Indexed: 11/27/2022]
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Abstract
The pemphigus family of autoimmune blistering diseases is characterized by an autoantibody response to desmosomal cadherins in epithelia. Autoantibodies against desmogleins, desmosome cell adhesion molecules, induce loss of cell-cell adhesion that is characterized clinically by blister formation. The mechanism by which these autoantibodies induce loss of cell-cell adhesion is under active investigation, but appears to involve a coordinated intracellular response including activation of intracellular signaling and phosphorylation of a number of proteins in the target keratinocyte. Activation of p38 mitogen activated protein kinase may have a critical role in the acantholytic mechanism as inhibitors of p38MAPK block the ability of pemphigus IgG to induce blistering in pemphigus animal models.
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Affiliation(s)
- David S Rubenstein
- Department of Dermatology, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599-7287, USA.
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Pivovarova AV, Chebotareva NA, Gusev NB, Levitsky DI. Some properties of complexes formed by small heat shock proteins with denaturated actin. Biophysics (Nagoya-shi) 2008. [DOI: 10.1134/s0006350908050072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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17
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Levitsky DI, Pivovarova AV, Mikhailova VV, Nikolaeva OP. Thermal unfolding and aggregation of actin. FEBS J 2008; 275:4280-95. [DOI: 10.1111/j.1742-4658.2008.06569.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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18
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Abstract
Desmosomes are patch-like intercellular adhering junctions ("maculae adherentes"), which, in concert with the related adherens junctions, provide the mechanical strength to intercellular adhesion. Therefore, it is not surprising that desmosomes are abundant in tissues subjected to significant mechanical stress such as stratified epithelia and myocardium. Desmosomal adhesion is based on the Ca(2+)-dependent, homo- and heterophilic transinteraction of cadherin-type adhesion molecules. Desmosomal cadherins are anchored to the intermediate filament cytoskeleton by adaptor proteins of the armadillo and plakin families. Desmosomes are dynamic structures subjected to regulation and are therefore targets of signalling pathways, which control their molecular composition and adhesive properties. Moreover, evidence is emerging that desmosomal components themselves take part in outside-in signalling under physiologic and pathologic conditions. Disturbed desmosomal adhesion contributes to the pathogenesis of a number of diseases such as pemphigus, which is caused by autoantibodies against desmosomal cadherins. Beside pemphigus, desmosome-associated diseases are caused by other mechanisms such as genetic defects or bacterial toxins. Because most of these diseases affect the skin, desmosomes are interesting not only for cell biologists who are inspired by their complex structure and molecular composition, but also for clinical physicians who are confronted with patients suffering from severe blistering skin diseases such as pemphigus. To develop disease-specific therapeutic approaches, more insights into the molecular composition and regulation of desmosomes are required.
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Affiliation(s)
- Jens Waschke
- Institute of Anatomy and Cell Biology, University of Würzburg, Koellikerstr. 6, 97070, Würzburg, Germany.
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19
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Markov DI, Pivovarova AV, Chernik IS, Gusev NB, Levitsky DI. Small heat shock protein Hsp27 protects myosin S1 from heat-induced aggregation, but not from thermal denaturation and ATPase inactivation. FEBS Lett 2008; 582:1407-12. [DOI: 10.1016/j.febslet.2008.03.035] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2007] [Revised: 02/11/2008] [Accepted: 03/08/2008] [Indexed: 01/29/2023]
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20
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Induction of p38MAPK and HSP27 Phosphorylation in Pemphigus Patient Skin. J Invest Dermatol 2008; 128:738-40. [DOI: 10.1038/sj.jid.5701080] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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21
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Pivovarova AV, Chebotareva NA, Chernik IS, Gusev NB, Levitsky DI. Small heat shock protein Hsp27 prevents heat-induced aggregation of F-actin by forming soluble complexes with denatured actin. FEBS J 2007; 274:5937-48. [PMID: 17944945 DOI: 10.1111/j.1742-4658.2007.06117.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Previously, we have shown that the small heat shock protein with apparent molecular mass 27 kDa (Hsp27) does not affect the thermal unfolding of F-actin, but effectively prevents aggregation of thermally denatured F-actin [Pivovarova AV, Mikhailova VV, Chernik IS, Chebotareva NA, Levitsky DI & Gusev NB (2005) Biochem Biophys Res Commun331, 1548-1553], and supposed that Hsp27 prevents heat-induced aggregation of F-actin by forming soluble complexes with denatured actin. In the present work, we applied dynamic light scattering, analytical ultracentrifugation and size exclusion chromatography to examine the properties of complexes formed by denatured actin with a recombinant human Hsp27 mutant (Hsp27-3D) mimicking the naturally occurring phosphorylation of this protein at Ser15, Ser78, and Ser82. Our results show that formation of these complexes occurs upon heating and accompanies the F-actin thermal denaturation. All the methods show that the size of actin-Hsp27-3D complexes decreases with increasing Hsp27-3D concentration in the incubation mixture and that saturation occurs at approximately equimolar concentrations of Hsp27-3D and actin. Under these conditions, the complexes exhibit a hydrodynamic radius of approximately 16 nm, a sedimentation coefficient of 17-20 S, and a molecular mass of about 2 MDa. It is supposed that Hsp27-3D binds to denatured actin monomers or short oligomers dissociated from actin filaments upon heating and protects them from aggregation by forming relatively small and highly soluble complexes. This mechanism might explain how small heat shock proteins prevent aggregation of denatured actin and by this means protect the cytoskeleton and the whole cell from damage caused by accumulation of large insoluble aggregates under heat shock conditions.
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Wu Z, Nagano I, Boonmars T, Takahashi Y. Thermally induced and developmentally regulated expression of a small heat shock protein in Trichinella spiralis. Parasitol Res 2007; 101:201-12. [PMID: 17268805 DOI: 10.1007/s00436-007-0462-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2006] [Accepted: 01/09/2007] [Indexed: 12/14/2022]
Abstract
A cDNA encoding a small heat shock protein of Trichinella spiralis, Ts-sHsp, was cloned and expressed and is herein characterized. This cDNA encoded a predicted protein of 165 amino acids, which had a high sequence identity in alpha crystallin domain with various small heat shock proteins of other organisms. A Western blot analysis indicated that anti-Ts-sHsp recombinant antibody recognized the protein of adults and larvae migrating at about 19 kDa. An in situ localization study showed the protein to be abundantly present in the body wall muscle cells, hypodermis, stichocytes, and esophagus of muscle larvae. The Ts-sHsp recombinant protein possessed chaperone activity to suppress the thermally-induced aggregation of citrate synthase. This sHsp was expressed at various developmental stages of T. spiralis, but at different levels. A high level was observed in mature muscle larvae (infective larvae), which was much higher than the levels seen in adults, newborn larvae, or immature muscle larvae. The expression of the sHsp gene was thermal inducible, thus responding to both cold (0 degrees C) and heat shock (43 degrees C) stress; however, at different patterns. The expression of Ts-sHsp increased gradually from 3 to 72 h after cold stress, while the expression was elevated to its highest after 3 h heat stress and then decreased. These results suggest that this small heat shock protein likely plays a role in the tolerance to both chemical and physical stresses, thereby enhancing the survival ability of Trichinella muscle larvae.
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Affiliation(s)
- Z Wu
- Department of Parasitology, Gifu University Graduate School of Medicine, Yanagido 1-1, Gifu 501-1194, Japan.
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Bryantsev AL, Chechenova MB, Shelden EA. Recruitment of phosphorylated small heat shock protein Hsp27 to nuclear speckles without stress. Exp Cell Res 2006; 313:195-209. [PMID: 17123510 PMCID: PMC1893088 DOI: 10.1016/j.yexcr.2006.10.004] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2006] [Revised: 09/09/2006] [Accepted: 10/04/2006] [Indexed: 11/21/2022]
Abstract
During stress, the mammalian small heat shock protein Hsp27 enters cell nuclei. The present study examines the requirements for entry of Hsp27 into nuclei of normal rat kidney (NRK) renal epithelial cells, and for its interactions with specific nuclear structures. We find that phosphorylation of Hsp27 is necessary for the efficient entry into nuclei during heat shock but not sufficient for efficient nuclear entry under control conditions. We further report that Hsp27 is recruited to an RNAse sensitive fraction of SC35 positive nuclear speckles, but not other intranuclear structures, in response to heat shock. Intriguingly, Hsp27 phosphorylation, in the absence of stress, is sufficient for recruitment to speckles found in post-anaphase stage mitotic cells. Additionally, pseudophosphorylated Hsp27 fused to a nuclear localization peptide (NLS) is recruited to nuclear speckles in unstressed interphase cells, but wildtype and nonphosphorylatable Hsp27 NLS fusion proteins are not. The expression of NLS-Hsp27 mutants does not enhance colony forming abilities of cells subjected to severe heat shock, but does regulate nuclear speckle morphology. These data demonstrate that phosphorylation, but not stress, mediates Hsp27 recruitment to an RNAse soluble fraction of nuclear speckles and support a site-specific role for Hsp27 within the nucleus.
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Affiliation(s)
- A L Bryantsev
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164-4234, USA
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Berkowitz P, Hu P, Warren S, Liu Z, Diaz LA, Rubenstein DS. p38MAPK inhibition prevents disease in pemphigus vulgaris mice. Proc Natl Acad Sci U S A 2006; 103:12855-60. [PMID: 16908851 PMCID: PMC1568937 DOI: 10.1073/pnas.0602973103] [Citation(s) in RCA: 176] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Pemphigus vulgaris (PV) is a life-threatening autoimmune blistering skin disease characterized by detachment of keratinocytes (acantholysis). It has been proposed that PV IgG might trigger signaling and that this process may lead to acantholysis. Indeed, we recently identified a rapid and dose-dependent phosphorylation of p38 mitogen-activated protein kinase (p38MAPK) and heat shock protein (HSP) 27 after binding of PV antibodies to cultured keratinocytes. In human keratinocyte cultures, inhibitors of p38MAPK prevented PV IgG-induced phosphorylation of HSP27 and, more importantly, prevented the early cytoskeletal changes associated with loss of cell-cell adhesion. This study was undertaken to (i) determine whether p38MAPK and HSP25, the murine HSP27 homolog, were similarly phosphorylated in an in vivo model of PV and (ii) investigate the potential therapeutic use of p38MAPK inhibition to block blister formation in an animal model of PV. We now report that p38MAPK inhibitors prevented PV blistering disease in vivo. Targeting the end-organ by inhibiting keratinocyte desmosome signaling may be effective for treating desmosome autoimmune blistering disorders.
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Affiliation(s)
| | | | | | - Zhi Liu
- Departments of *Dermatology and
| | | | - David S. Rubenstein
- Departments of *Dermatology and
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599-7287
- To whom correspondence should be addressed at:
Department of Dermatology, University of North Carolina School of Medicine, Suite 3100 Thurston-Bowles CB 7287, Chapel Hill, NC 27599-7287. E-mail:
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25
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Sun Y, Bojikova-Fournier S, MacRae TH. Structural and functional roles for beta-strand 7 in the alpha-crystallin domain of p26, a polydisperse small heat shock protein from Artemia franciscana. FEBS J 2006; 273:1020-34. [PMID: 16478475 DOI: 10.1111/j.1742-4658.2006.05129.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Oviparous development in the extremophile crustacean, Artemia franciscana, generates encysted embryos which enter a profound state of dormancy, termed diapause. Encystment is marked by the synthesis of p26, a polydisperse small heat shock protein thought to protect embryos from stress. In order to elucidate structural/functional relationships within p26 and other polydisperse small heat shock proteins, and to better define the protein's role during diapause, amino acid substitutions R110G, F112R, R114A and Y116D were generated within the p26 alpha-crystallin domain by site-directed mutagenesis. These residues were chosen because they are highly conserved across species boundaries, and molecular modelling indicates that they are part of a key structural interface between dimers. The F112R mutation, which had the greatest impact on oligomerization, placed two charged residues at the p26 dimer-dimer interface, demonstrating the importance of beta-strand 7 in tetramer formation. All mutated versions of p26 were less able than wild-type p26 to confer thermotolerance on transformed bacteria and they exhibited diminished chaperone action in three in vitro assays; however, all variants retained protective activity. This apparent stability of p26 may, by prolonging effective chaperone life in vivo, enhance embryo stress resistance. All substitutions modified p26 intrinsic fluorescence, surface hydrophobicity and secondary structure, and the pronounced changes in variant R114A, as indicated by these physical measurements, correlated with the greatest loss of function. Although mutation R114A had the greatest effect on p26 chaperoning, it had the least on oligomerization. These results demonstrate that in contrast to many other small heat shock proteins, p26 effectiveness as a chaperone is independent of oligomerization. The results also reinforce the idea, occasioned by modelling, that R114 is removed slightly from dimer-dimer interfaces. Moreover, beta-strand 7 is shown to have an important role in oligomerization of p26, a function first proposed for this structural element upon crystallization of wheat Hsp16.9, a small heat shock protein with different quaternary structure.
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Affiliation(s)
- Yu Sun
- Department of Biology, Dalhousie University, Halifax, NS, Canada
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26
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Keller M, Gerbes AL, Kulhanek-Heinze S, Gerwig T, Grutzner U, van Rooijen N, Vollmar AM, Kiemer AK. Hepatocyte cytoskeleton during ischemia and reperfusion--influence of ANP-mediated p38 MAPK activation. World J Gastroenterol 2006; 11:7418-29. [PMID: 16437711 PMCID: PMC4725179 DOI: 10.3748/wjg.v11.i47.7418] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM To determine functional consequences of this activation, whereby we focused on a potential regulation of the hepatocyte cytoskeleton during ischemia and reperfusion. METHODS For in vivo experiments, animals received ANP (5 microg/kg) intravenously. In a different experimental setting, isolated rat livers were perfused with KH-buffer+/-ANP (200 nmol/L) +/-SB203580 (2 micromol/L). Livers were then kept under ischemic conditions for 24 h, and either transplanted or reperfused. Actin, Hsp27, and phosphorylated Hsp27 were determined by Western blotting, p38 MAPK activity by in vitro phosphorylation assay. F-actin distribution was determined by confocal microscopy. RESULTS We first confirmed that ANP preconditioning leads to an activation of p38 MAPK and observed alterations of the cytoskeleton in hepatocytes of ANP-preconditioned organs. ANP induced an increase of hepatic F-actin after ischemia, which could be prevented by the p38 MAPK inhibitor SB203580 but had no effect on bile flow. After ischemia untreated livers showed a translocation of Hsp27 towards the cytoskeleton and an increase in total Hsp27, whereas ANP preconditioning prohibited translocation but caused an augmentation of Hsp27 phosphorylation. This effect is also mediated via p38 MAPK, since it was abrogated by the p38 MAPK inhibitor SB203580. CONCLUSION This study reveals that ANP-mediated p38 MAPK activation leads to changes in hepatocyte cytoskeleton involving an elevation of phosphorylated Hsp27 and thereby for the first time shows functional consequences of ANP-induced hepatic p38 MAPK activation.
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Affiliation(s)
- Melanie Keller
- Department of Pharmacy, Centre of Drug Research, University of Munich, Germany
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27
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Villeneuve TS, Ma X, Sun Y, Oulton MM, Oliver AE, MacRae TH. Inhibition of apoptosis by p26: implications for small heat shock protein function during Artemia development. Cell Stress Chaperones 2006; 11:71-80. [PMID: 16572731 PMCID: PMC1400614 DOI: 10.1379/csc-154r.1] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2005] [Revised: 10/12/2005] [Accepted: 10/26/2005] [Indexed: 11/24/2022] Open
Abstract
p26, an abundantly expressed small heat shock protein, is thought to establish stress resistance in oviparously developing embryos of the crustacean Artemia franciscana by preventing irreversible protein denaturation, but it might also promote survival by inhibiting apoptosis. To test this possibility, stably transfected mammalian cells producing p26 were generated and their ability to resist apoptosis induction determined. Examination of immunofluorescently stained transfected 293H cells by confocal microscopy demonstrated p26 is diffusely distributed in the cytoplasm with a minor amount of the protein in nuclei. As shown by immunoprobing of Western blots, p26 constituted approximately 0.6% of soluble cell protein. p26 localization and quantity were unchanged during prolonged culture, and the protein had no apparent ill effects on transfected cells. Molecular sieve chromatography in Sepharose 6B revealed p26 oligomers of about 20 monomers, with a second fraction occurring as larger aggregates. A similar pattern was observed in sucrose gradients, but overall oligomer size was smaller. Mammalian cells containing p26 were more thermotolerant than cells transfected with the expression vector only, and as measured by annexin V labeling, Hoescht 33342 nuclear staining and procaspase-3 activation, transfected cells effectively resisted apoptosis induction by heat and staurosporine. The ability to confer thermotolerance and limit heat-induced apoptosis is important because Artemia embryos are frequently exposed to high temperature in their natural habitat. p26 also blocked apoptosis in transfected cells during drying and rehydration, findings with direct relevance to Artemia life history characteristics because desiccation terminates cyst diapause. Thus, in addition to functioning as a molecular chaperone, p26 inhibits apoptosis, an activity shared by other small heat shock proteins and with the potential to play an important role during Artemia embryo development.
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28
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Bukach OV, Marston SB, Gusev NB. Small heat shock protein with apparent molecular mass 20 kDa (Hsp20, HspB6) is not a genuine actin-binding protein. J Muscle Res Cell Motil 2005; 26:175-81. [PMID: 16205842 DOI: 10.1007/s10974-005-9008-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2005] [Accepted: 07/13/2005] [Indexed: 11/29/2022]
Abstract
The interaction of recombinant human small heat shock protein with apparent molecular mass 20 kDa (Hsp20, HspB6) with actin was investigated. Wild type Hsp20 and its S16D mutant mimicking phosphorylation of Hsp20 by cyclic nucleotide-dependent protein kinases do not affect the rate and extent of actin polymerization. Ultracentrifugation of the mixture of Hsp20 (or its S16D mutant) with isolated F-actin or F-actin containing tropomyosin, calponin or alpha-actinin resulted in co-sedimentation of less than 0.04 mol of Hsp20 monomer per mol of actin. Myofibrils of skeletal, cardiac or smooth muscle bound less than 0.04 mol of Hsp20 monomer per mol of actin and this stoichiometry was independent of phosphorylation or mutation of Ser16 of Hsp20. Since Hsp20 is not a genuine actin-binding protein, the earlier described correlation between Hsp20 phosphorylation and smooth muscle relaxation cannot be explained by direct interaction of Hsp20 with actin.
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Affiliation(s)
- Olesya V Bukach
- Department of Biochemistry, School of Biology, Moscow State University, 119992 Moscow, Russia
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29
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Sun Y, MacRae TH. Characterization of novel sequence motifs within N- and C-terminal extensions of p26, a small heat shock protein from Artemia franciscana. FEBS J 2005; 272:5230-43. [PMID: 16218954 DOI: 10.1111/j.1742-4658.2005.04920.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The small heat shock proteins function as molecular chaperones, an activity often requiring reversible oligomerization and which protects against irreversible protein denaturation. An abundantly produced small heat shock protein termed p26 is thought to contribute to the remarkable stress resistance exhibited by encysted embryos of the crustacean, Artemia franciscana. Three novel sequence motifs termed G, R and TS were individually deleted from p26 by site-directed mutagenesis. G encompasses residues G8-G29, a glycine-enriched region, and R includes residues R36-R45, an arginine-enhanced sequence, both in the amino terminus. TS, composed of residues T169-T186, resides in the carboxy-extension and is augmented in threonine and serine. Deletion of R had more influence than removal of G on p26 oligomerization and chaperoning, the latter determined by thermotolerance induction in Escherichia coli, protection of insulin and citrate synthase from dithiothreitol- and heat-induced aggregation, respectively, and preservation of citrate synthase activity upon heating. Oligomerization of the TS and R variants was similar, but the TS deletion was slightly more effective than R as a chaperone. The extent of p26 structural perturbation introduced by internal deletions, including modification of intrinsic fluorescence, 1-anilino-8-naphthalene-sulphonate binding and secondary structure, paralleled reductions in oligomerization and chaperoning. Three-dimensional modeling of p26 based on wheat Hsp16.9 crystal structure indicated many similarities between the two proteins, including peptide loops associated with secondary structure elements. Loop 1 of p26 was deleted in the G variant with minimal effect on oligomerization and chaperoning, whereas loop 3, containing beta-strand 6 was smaller than the corresponding loop in Hsp16.9, which may influence p26 function.
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Affiliation(s)
- Yu Sun
- Department of Biology, Dalhousie University, Halifax, Canada
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Pivovarova AV, Mikhailova VV, Chernik IS, Chebotareva NA, Levitsky DI, Gusev NB. Effects of small heat shock proteins on the thermal denaturation and aggregation of F-actin. Biochem Biophys Res Commun 2005; 331:1548-53. [PMID: 15883049 DOI: 10.1016/j.bbrc.2005.04.077] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2005] [Indexed: 10/25/2022]
Abstract
Effect of recombinant chicken small heat shock protein with molecular mass 24 kDa (Hsp24) and recombinant human small heat shock protein with molecular mass 27 kDa (Hsp27) on the heat-induced denaturation and aggregation of skeletal F-actin was analyzed by means of differential scanning calorimetry and light scattering. All small heat shock proteins did not affect thermal unfolding of F-actin measured by differential scanning calorimetry, but effectively prevented aggregation of thermally denatured actin. Small heat shock protein formed stable complexes with denatured (but not with intact) F-actin. The size of these highly soluble complexes was smaller than the size of intact F-actin filaments. It is supposed that protective effect of small heat shock proteins on the cytoskeleton is at least partly due to prevention of aggregation of denatured actin.
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Abstract
In the human autoimmune blistering disease pemphigus vulgaris (PV) pathogenic antibodies bind the desmosomal cadherin desmoglein-3 (dsg3), causing epidermal cell-cell detachment (acantholysis). Pathogenic PV dsg3 autoantibodies were used to initiate desmosome signaling in human keratinocyte cell cultures. Heat shock protein 27 (HSP27) and p38MAPK were identified as proteins rapidly phosphorylated in response to PV IgG. Inhibition of p38MAPK activity prevented PV IgG-induced HSP27 phosphorylation, keratin filament retraction, and actin reorganization. These observations suggest that PV IgG binding to dsg3 activates desmosomal signal transduction cascades leading to (i) p38MAPK and HSP27 phosphorylation and (ii) cytoskeletal reorganization, supporting a mechanistic role for signaling in PV IgG-induced acantholysis. Targeting desmosome signaling via inhibition of p38MAPK and HSP27 phosphorylation may provide novel treatments for PV and other desmosome-associated blistering diseases.
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Affiliation(s)
- Paula Berkowitz
- Department of Dermatology, University of North Carolina-Chapel Hill School of Medicine, 27599, USA
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Williams KL, Rahimtula M, Mearow KM. Hsp27 and axonal growth in adult sensory neurons in vitro. BMC Neurosci 2005; 6:24. [PMID: 15819993 PMCID: PMC1087488 DOI: 10.1186/1471-2202-6-24] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2004] [Accepted: 04/08/2005] [Indexed: 11/10/2022] Open
Abstract
Background Neurite growth can be elicited by growth factors and interactions with extracellular matrix molecules like laminin. Among the targets of the signalling pathways activated by these stimuli are cytoskeletal elements, such as actin, tubulin and neurofilaments. The cytoskeleton can also be modulated by other proteins, such as the small heat shock protein Hsp27. Hsp27 interacts with actin and tubulin in non-neuronal cells and while it has been suggested to play a role in the response of some neurons to injury, there have been no direct studies of its contribution to axonal regeneration. Results We have investigated neurite initiation and process extension using cultures of adult dorsal root ganglion (DRG) sensory neurons and a laminin stimulation paradigm. Employing confocal microscopy and biochemical analyses we have examined localization of Hsp27 at early and later stages of neurite growth. Our results show that Hsp27 is colocalized with actin and tubulin in lamellopodia, filopodia, focal contacts and mature neurites and growth cones. Disruption of the actin cytoskeleton with cytochalasin D results in aberrant neurite initiation and extension, effects which may be attributable to alterations in actin polymerization states. Inhibition of Hsp27 phosphorylation in our cultures results in an atypical growth pattern that may be attributable to an effect of pHsp27 on the stability of the actin cytoskeleton. Conclusion We observed colocalization of the phosphorylated and non-phosphorylated forms of Hsp27 with actin and tubulin in both very early and later stages of neurite growth from cultured adult DRG neurons. The colocalization of Hsp27 and pHsp27 with actin in lamellopodia and focal contacts at early stages of neurite growth, and in processes, branch points and growth cones at later stages, suggests that Hsp27 may play a role in neuritogenesis and subsequent neurite extension, and potentially in the patterning of this growth. Hsp27 has been reported to play a key role in modulating actin cytoskeletal dynamics as an actin-capping protein in non-neuronal cells. Our results suggest that this may also be the case in neurons and support a role for Hsp27 in neurite outgrowth via its phosphorylation state-dependent interactions with actin.
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Affiliation(s)
- Kristy L Williams
- Division of Basic Medical Sciences, Memorial University of Newfoundland, St. John's, NL, A1B 3V6, Canada
| | - Masuma Rahimtula
- Division of Basic Medical Sciences, Memorial University of Newfoundland, St. John's, NL, A1B 3V6, Canada
| | - Karen M Mearow
- Division of Basic Medical Sciences, Memorial University of Newfoundland, St. John's, NL, A1B 3V6, Canada
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