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Holthaus KB, Eckhart L. Development-Associated Genes of the Epidermal Differentiation Complex (EDC). J Dev Biol 2024; 12:4. [PMID: 38248869 PMCID: PMC10801484 DOI: 10.3390/jdb12010004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Revised: 12/28/2023] [Accepted: 01/10/2024] [Indexed: 01/23/2024] Open
Abstract
The epidermal differentiation complex (EDC) is a cluster of genes that encode protein components of the outermost layers of the epidermis in mammals, reptiles and birds. The development of the stratified epidermis from a single-layered ectoderm involves an embryo-specific superficial cell layer, the periderm. An additional layer, the subperiderm, develops in crocodilians and over scutate scales of birds. Here, we review the expression of EDC genes during embryonic development. Several EDC genes are expressed predominantly or exclusively in embryo-specific cell layers, whereas others are confined to the epidermal layers that are maintained in postnatal skin. The S100 fused-type proteins scaffoldin and trichohyalin are expressed in the avian and mammalian periderm, respectively. Scaffoldin forms the so-called periderm granules, which are histological markers of the periderm in birds. Epidermal differentiation cysteine-rich protein (EDCRP) and epidermal differentiation protein containing DPCC motifs (EDDM) are expressed in the avian subperiderm where they are supposed to undergo cross-linking via disulfide bonds. Furthermore, a histidine-rich epidermal differentiation protein and feather-type corneous beta-proteins, also known as beta-keratins, are expressed in the subperiderm. The accumulating evidence for roles of EDC genes in the development of the epidermis has implications on the evolutionary diversification of the skin in amniotes.
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Affiliation(s)
| | - Leopold Eckhart
- Department of Dermatology, Medical University of Vienna, 1090 Vienna, Austria
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2
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Paul AA, Szulc NA, Kobiela A, Brown SJ, Pokrzywa W, Gutowska-Owsiak D. In silico analysis of the profilaggrin sequence indicates alterations in the stability, degradation route, and intracellular protein fate in filaggrin null mutation carriers. Front Mol Biosci 2023; 10:1105678. [PMID: 37200867 PMCID: PMC10185843 DOI: 10.3389/fmolb.2023.1105678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Accepted: 04/19/2023] [Indexed: 05/20/2023] Open
Abstract
Background: Loss of function mutation in FLG is the major genetic risk factor for atopic dermatitis (AD) and other allergic manifestations. Presently, little is known about the cellular turnover and stability of profilaggrin, the protein encoded by FLG. Since ubiquitination directly regulates the cellular fate of numerous proteins, their degradation and trafficking, this process could influence the concentration of filaggrin in the skin. Objective: To determine the elements mediating the interaction of profilaggrin with the ubiquitin-proteasome system (i.e., degron motifs and ubiquitination sites), the features responsible for its stability, and the effect of nonsense and frameshift mutations on profilaggrin turnover. Methods: The effect of inhibition of proteasome and deubiquitinases on the level and modifications of profilaggrin and processed products was assessed by immunoblotting. Wild-type profilaggrin sequence and its mutated variants were analysed in silico using the DEGRONOPEDIA and Clustal Omega tool. Results: Inhibition of proteasome and deubiquitinases stabilizes profilaggrin and its high molecular weight of presumably ubiquitinated derivatives. In silico analysis of the sequence determined that profilaggrin contains 18 known degron motifs as well as multiple canonical and non-canonical ubiquitination-prone residues. FLG mutations generate products with increased stability scores, altered usage of the ubiquitination marks, and the frequent appearance of novel degrons, including those promoting C-terminus-mediated degradation routes. Conclusion: The proteasome is involved in the turnover of profilaggrin, which contains multiple degrons and ubiquitination-prone residues. FLG mutations alter those key elements, affecting the degradation routes and the mutated products' stability.
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Affiliation(s)
- Argho Aninda Paul
- Experimental and Translational Immunology Group, Intercollegiate Faculty of Biotechnology of University of Gdansk and Medical University of Gdansk, University of Gdansk, Gdansk, Poland
| | - Natalia A. Szulc
- Laboratory of Protein Metabolism, International Institute of Molecular and Cell Biology in Warsaw, Warsaw, Poland
| | - Adrian Kobiela
- Experimental and Translational Immunology Group, Intercollegiate Faculty of Biotechnology of University of Gdansk and Medical University of Gdansk, University of Gdansk, Gdansk, Poland
| | - Sara J. Brown
- Centre for Genomic and Experimental Medicine, Institute of Genetics and Cancer, University of Edinburgh, Edinburgh, United Kingdom
| | - Wojciech Pokrzywa
- Laboratory of Protein Metabolism, International Institute of Molecular and Cell Biology in Warsaw, Warsaw, Poland
| | - Danuta Gutowska-Owsiak
- Experimental and Translational Immunology Group, Intercollegiate Faculty of Biotechnology of University of Gdansk and Medical University of Gdansk, University of Gdansk, Gdansk, Poland
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Hori H, Kotani A, Abe J, Matsuguchi S, Hirai Y. Extracellular epimorphin impairs expression and processing of profilaggrin in HaCaT keratinocytes. Cytotechnology 2023; 75:123-133. [PMID: 36969570 PMCID: PMC10030722 DOI: 10.1007/s10616-022-00566-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Accepted: 12/10/2022] [Indexed: 12/23/2022] Open
Abstract
The expression and processing of filaggrin, a filament-associated protein in the skin epidermis, is closely associated with keratinocyte cornification. The large precursor profilaggrin (Pro-FLG) is initially detected at the granular layer in keratohyalin granules, subsequently processed into 10 to 12 filaggrin monomers (mFLGs) for keratin assembly, and ultimately degraded into smaller peptides that behave as natural moisturizing factor (NMF) at the outermost epidermis. We previously reported that epimorphin (EPM) extruded upon external stimuli severely perturbs epidermal terminal differentiation. Using HaCaT keratinocytes with inducible expression and recombinant EPM and FLG, we investigated the effect of extracellular EPM on the expression profile of filaggrin. As expression and processing of Pro-FLG in primary keratinocytes are accompanied with apoptotic cell death, we employed HaCaT keratinocytes that grow and express filaggrin mRNA in standard culture medium. In response to ectopic stimulation with extracellular EPM, Pro-FLG expression decreased with elimination of keratohyalin granules in the cells, with filaggrin mRNA remained constant and profilaggrin processing was not accelerated. Additionally, using a recombinant form of mFLG engineered for intracellular localization, we found that extracellular EPM hindered proteolytic cleavage of mFLG for production of NMF. Taken together, extracellularly extruded EPM, an epidermal cornification blocker, not only decreases Pro-FLG expression but also reduces the production of NMF in HaCaT keratinocytes. Supplementary Information The online version contains supplementary material available at 10.1007/s10616-022-00566-8.
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Affiliation(s)
- Haruna Hori
- Department of Biomedical Sciences, Graduate School of Science and Technology, Kwansei Gakuin University, 1, GakuenUegahara, Sanda, 669-1330 Japan
- Present Address: Oppen Cosmetics Co, LTD. 2-17-1 Kisibeminami, Suita, 565-8501 Japan
| | - Ayaka Kotani
- Department of Biomedical Sciences, Graduate School of Science and Technology, Kwansei Gakuin University, 1, GakuenUegahara, Sanda, 669-1330 Japan
| | - Junya Abe
- Department of Biomedical Sciences, Graduate School of Science and Technology, Kwansei Gakuin University, 1, GakuenUegahara, Sanda, 669-1330 Japan
| | - Shuji Matsuguchi
- Department of Biomedical Sciences, Graduate School of Science and Technology, Kwansei Gakuin University, 1, GakuenUegahara, Sanda, 669-1330 Japan
| | - Yohei Hirai
- Department of Biomedical Sciences, Graduate School of Science and Technology, Kwansei Gakuin University, 1, GakuenUegahara, Sanda, 669-1330 Japan
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4
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Hoober JK, Eggink LL. The Discovery and Function of Filaggrin. Int J Mol Sci 2022; 23:ijms23031455. [PMID: 35163390 PMCID: PMC8835998 DOI: 10.3390/ijms23031455] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 01/17/2022] [Accepted: 01/26/2022] [Indexed: 12/11/2022] Open
Abstract
Keratohyalin granules were discovered in the mid-19th century in cells that terminally differentiate to form the outer, cornified layer of the epidermis. The first indications of the composition of these structures emerged in the 1960s from a histochemical stain for histidine, followed by radioautographic evidence of a high incidence of histidine incorporation into newly synthesized proteins in cells containing the granules. Research during the next three decades revealed the structure and function of a major protein in these granules, which was initially called the ‘histidine-rich protein’. Steinert and Dale named the protein ‘filaggrin’ in 1981 because of its ability to aggregate keratin intermediate filaments. The human gene for the precursor, ‘profilaggrin,’ was reported in 1991 to encode 10, 11 or 12 nearly identical repeats. Remarkably, the mouse and rat genes encode up to 20 repeats. The lifetime of filaggrin is the time required for keratinocytes in the granular layer to move into the inner cornified layer. During this transition, filaggrin facilitates the collapse of corneocytes into ‘building blocks’ that become an impermeable surface barrier. The subsequent degradation of filaggrin is as remarkable as its synthesis, and the end-products aid in maintaining moisture in the cornified layer. It was apparent that ichthyosis vulgaris and atopic dermatitis were associated with the absence of this protein. McLean’s team in 2006 identified the cause of these diseases by discovering loss-of-function mutations in the profilaggrin gene, which led to dysfunction of the surface barrier. This story illustrates the complexity in maintaining a healthy, functional epidermis.
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Cracking the Skin Barrier: Liquid-Liquid Phase Separation Shines under the Skin. JID INNOVATIONS 2021; 1:100036. [PMID: 34909733 PMCID: PMC8659386 DOI: 10.1016/j.xjidi.2021.100036] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2021] [Revised: 06/07/2021] [Accepted: 06/18/2021] [Indexed: 12/25/2022] Open
Abstract
Central to forming and sustaining the skin’s barrier, epidermal keratinocytes (KCs) fluxing to the skin surface undergo a rapid and enigmatic transformation into flat, enucleated squames. At the crux of this transformation are intracellular keratohyalin granules (KGs) that suddenly disappear as terminally differentiating KCs transition to the cornified skin surface. Defects in KGs have long been linked to skin barrier disorders. Through the biophysical lens of liquid-liquid phase separation (LLPS), these enigmatic KGs recently emerged as liquid-like membraneless organelles whose assembly and subsequent pH-triggered disassembly drive squame formation. To stimulate future efforts toward cracking the complex process of skin barrier formation, in this review, we integrate the key concepts and foundational work spanning the fields of LLPS and epidermal biology. We review the current progress in the skin and discuss implications in the broader context of membraneless organelles across stratifying epithelia. The discovery of environmentally sensitive LLPS dynamics in the skin points to new avenues for dissecting the skin barrier and for addressing skin barrier disorders. We argue that skin and its appendages offer outstanding models to uncover LLPS-driven mechanisms in tissue biology.
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Key Words
- 3D, three-dimensional
- AD, atopic dermatitis
- CE, cornified envelope
- EDC, epidermal differentiation complex
- ER, endoplasmic reticulum
- IDP, intrinsically-disordered protein
- KC, keratinocyte
- KG, keratohyalin granule
- LCST, lower critical solution temperature
- LLPS, liquid-liquid phase separation
- PTM, post-translational modification
- TG, trichohyalin granule
- UCST, upper critical solution temperature
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6
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Rogerson C, O'Shaughnessy RFL. Protein kinases involved in epidermal barrier formation: The AKT family and other animals. Exp Dermatol 2019; 27:892-900. [PMID: 29845670 DOI: 10.1111/exd.13696] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/24/2018] [Indexed: 12/20/2022]
Abstract
Formation of a stratified epidermis is required for the performance of the essential functions of the skin; to act as an outside-in barrier against the access of microorganisms and other external factors, to prevent loss of water and solutes via inside-out barrier functions and to withstand mechanical stresses. Epidermal barrier function is initiated during embryonic development and is then maintained throughout life and restored after injury. A variety of interrelated processes are required for the formation of a stratified epidermis, and how these processes are both temporally and spatially regulated has long been an aspect of dermatological research. In this review, we describe the roles of multiple protein kinases in the regulation of processes required for epidermal barrier formation.
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Affiliation(s)
- Clare Rogerson
- Centre for Cell Biology and Cutaneous Research, Blizard Institute, Queen Mary University of London, London, UK
| | - Ryan F L O'Shaughnessy
- Centre for Cell Biology and Cutaneous Research, Blizard Institute, Queen Mary University of London, London, UK
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7
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Elkenani M, Nyamsuren G, Raju P, Liakath-Ali K, Hamdaoui A, Kata A, Dressel R, Klonisch T, Watt FM, Engel W, Thliveris JA, Krishna Pantakani DV, Adham IM. Pelota Regulates Epidermal Differentiation by Modulating BMP and PI3K/AKT Signaling Pathways. J Invest Dermatol 2016; 136:1664-1671. [PMID: 27164299 DOI: 10.1016/j.jid.2016.04.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Revised: 04/04/2016] [Accepted: 04/11/2016] [Indexed: 12/25/2022]
Abstract
The depletion of evolutionarily conserved pelota protein causes impaired differentiation of embryonic and spermatogonial stem cells. In this study, we show that temporal deletion of pelota protein before epidermal barrier acquisition leads to neonatal lethality due to perturbations in permeability barrier formation. Further analysis indicated that this phenotype is a result of failed processing of profilaggrin into filaggrin monomers, which promotes the formation of a protective epidermal layer. Molecular analyses showed that pelota protein negatively regulates the activities of bone morphogenetic protein and phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling pathways in the epidermis. To address whether elevated activities of bone morphogenetic protein and PI3K/AKT signaling pathways were the cause for the perturbed epidermal barrier in Pelo-deficient mice, we made use of organotypic cultures of skin explants from control and mutant embryos at embryonic day 15.5. Inhibition of PI3K/AKT signaling did not significantly affect the bone morphogenetic protein activity. However, inhibition of bone morphogenetic protein signaling caused a significant attenuation of PI3K/AKT activity in mutant skin and, more interestingly, the restoration of profilaggrin processing and normal epidermal barrier function. Therefore, increased activity of the PI3K/AKT signaling pathway in Pelo-deficient skin might conflict with the dephosphorylation of profilaggrin and thereby affect its proper processing into filaggrin monomers and ultimately the epidermal differentiation.
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Affiliation(s)
- Manar Elkenani
- Institute of Human Genetics, University of Göttingen, D-37073 Göttingen, Germany; Faculty of Medicine, Mansoura University, Mansoura, Egypt
| | - Gunsmaa Nyamsuren
- Institute of Human Genetics, University of Göttingen, D-37073 Göttingen, Germany
| | - Priyadharsini Raju
- Institute of Human Genetics, University of Göttingen, D-37073 Göttingen, Germany
| | - Kifayathullah Liakath-Ali
- Centre for Stem Cells and Regenerative Medicine, King's College London, Guy's Hospital Campus, London, UK; Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Old Addenbrooke's Site, Cambridge, UK
| | - Aicha Hamdaoui
- Institute of Human Genetics, University of Göttingen, D-37073 Göttingen, Germany
| | - Aleksandra Kata
- Institute of Human Genetics, University of Göttingen, D-37073 Göttingen, Germany
| | - Ralf Dressel
- Institute of Cellular and Molecular Immunology, University Medical Center Göttingen, D-37073 Göttingen, Germany
| | - Thomas Klonisch
- Department of Human Anatomy and Cell Science, College of Medicine, Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Fiona M Watt
- Centre for Stem Cells and Regenerative Medicine, King's College London, Guy's Hospital Campus, London, UK
| | - Wolfgang Engel
- Institute of Human Genetics, University of Göttingen, D-37073 Göttingen, Germany
| | - James A Thliveris
- Department of Human Anatomy and Cell Science, College of Medicine, Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
| | - D V Krishna Pantakani
- Institute of Human Genetics, University of Göttingen, D-37073 Göttingen, Germany; Institute of Clinical Chemistry/UMG-Laboratories, University Medical Center Göttingen, D-37075, Göttingen, Germany
| | - Ibrahim M Adham
- Institute of Human Genetics, University of Göttingen, D-37073 Göttingen, Germany.
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8
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Schlage P, Kockmann T, Sabino F, Kizhakkedathu JN, Auf dem Keller U. Matrix Metalloproteinase 10 Degradomics in Keratinocytes and Epidermal Tissue Identifies Bioactive Substrates With Pleiotropic Functions. Mol Cell Proteomics 2015; 14:3234-46. [PMID: 26475864 DOI: 10.1074/mcp.m115.053520] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Indexed: 01/29/2023] Open
Abstract
Matrix metalloproteinases (MMPs) are important players in skin homeostasis, wound repair, and in the pathogenesis of skin cancer. It is now well established that most of their functions are related to processing of bioactive proteins rather than components of the extracellular matrix (ECM). MMP10 is highly expressed in keratinocytes at the wound edge and at the invasive front of tumors, but hardly any non-ECM substrates have been identified and its function in tissue repair and carcinogenesis is unclear. To better understand the role of MMP10 in the epidermis, we employed multiplexed iTRAQ-based Terminal Amine Isotopic Labeling of Substrates (TAILS) and monitored MMP10-dependent proteolysis over time in secretomes from keratinocytes. Time-resolved abundance clustering of neo-N termini classified MMP10-dependent cleavage events by efficiency and refined the MMP10 cleavage site specificity by revealing a so far unknown preference for glutamate in the P1 position. Moreover, we identified and validated the integrin alpha 6 subunit, cysteine-rich angiogenic inducer 61 and dermokine as novel direct MMP10 substrates and provide evidence for MMP10-dependent but indirect processing of phosphatidylethanolamine-binding protein 1. Finally, we sampled the epidermal proteome and degradome in unprecedented depth and confirmed MMP10-dependent processing of dermokine in vivo by TAILS analysis of epidermis from transgenic mice that overexpress a constitutively active mutant of MMP10 in basal keratinocytes. The newly identified substrates are involved in cell adhesion, migration, proliferation, and/or differentiation, indicating a contribution of MMP10 to local modulation of these processes during wound healing and cancer development. Data are available via ProteomeXchange with identifier PXD002474.
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Affiliation(s)
- Pascal Schlage
- From the ‡ETH Zurich, Department of Biology,Institute of Molecular Health Sciences, Otto-Stern-Weg 7, 8093 Zurich, Switzerland
| | - Tobias Kockmann
- From the ‡ETH Zurich, Department of Biology,Institute of Molecular Health Sciences, Otto-Stern-Weg 7, 8093 Zurich, Switzerland
| | - Fabio Sabino
- From the ‡ETH Zurich, Department of Biology,Institute of Molecular Health Sciences, Otto-Stern-Weg 7, 8093 Zurich, Switzerland
| | - Jayachandran N Kizhakkedathu
- §University of British Columbia, Department of Pathology and Laboratory Medicine and Department of Chemistry, Centre for Blood Research, 4.401Life Sciences Institute, 2350 Health Sciences Mall, Vancouver, British Columbia, Canada V6T 1Z3
| | - Ulrich Auf dem Keller
- From the ‡ETH Zurich, Department of Biology,Institute of Molecular Health Sciences, Otto-Stern-Weg 7, 8093 Zurich, Switzerland;
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Abstract
Atopic dermatitis is a very prevalent disease that affects children as well as adults. The disease has a severe impact on quality of life for the patients and their families. The skin in atopic dermatitis patients is a site of both a severe inflammatory reaction dominated by lymphocytes and decreased skin barrier function. The treatment of the disease is mainly aimed at reducing the inflammation in the skin and/or restoring the skin barrier function. However, most of the treatments used today singularly aim at reducing the inflammation in the skin. Depending on the severity of the disease, the anti-inflammatory treatment may be topical or systemic, but basic treatment, no matter the severity, should always be emollients. In addition, new studies have shown good effects of psychosocial interventions, such as eczema schools, for patients and their families. This review covers the latest trends in the treatment of atopic dermatitis.
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10
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Thyssen JP, Kezic S. Causes of epidermal filaggrin reduction and their role in the pathogenesis of atopic dermatitis. J Allergy Clin Immunol 2014; 134:792-9. [PMID: 25065719 DOI: 10.1016/j.jaci.2014.06.014] [Citation(s) in RCA: 248] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Revised: 06/14/2014] [Accepted: 06/14/2014] [Indexed: 02/06/2023]
Abstract
The epidermis protects human subjects from exogenous stressors and helps to maintain internal fluid and electrolyte homeostasis. Filaggrin is a crucial epidermal protein that is important for the formation of the corneocyte, as well as the generation of its intracellular metabolites, which contribute to stratum corneum hydration and pH. The levels of filaggrin and its degradation products are influenced not only by the filaggrin genotype but also by inflammation and exogenous stressors. Pertinently, filaggrin deficiency is observed in patients with atopic dermatitis regardless of filaggrin mutation status, suggesting that the absence of filaggrin is a key factor in the pathogenesis of this skin condition. In this article we review the various causes of low filaggrin levels, centralizing the functional and morphologic role of a deficiency in filaggrin, its metabolites, or both in the etiopathogenesis of atopic dermatitis.
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Affiliation(s)
- Jacob P Thyssen
- National Allergy Research Centre, Department of Dermato-Allergology, Copenhagen University Hospital Gentofte, University of Copenhagen, Hellerup, Denmark.
| | - Sanja Kezic
- Coronel Institute of Occupational Health, Academic Medical Center, Amsterdam, The Netherlands
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Beyond expectations: novel insights into epidermal keratin function and regulation. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2014; 311:265-306. [PMID: 24952920 DOI: 10.1016/b978-0-12-800179-0.00007-6] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The epidermis is a stratified epithelium that relies on its cytoskeleton and cell junctions to protect the body against mechanical injury, dehydration, and infections. Keratin intermediate filament proteins are involved in many of these functions by forming cell-specific cytoskeletal scaffolds crucial for the maintenance of cell and tissue integrity. In response to various stresses, the expression and organization of keratins are altered at transcriptional and posttranslational levels to restore tissue homeostasis. Failure to restore tissue homeostasis in the presence of keratin gene mutations results in acute and chronic skin disorders for which currently no rational therapies are available. Here, we review the recent progress on the role of keratins in cytoarchitecture, adhesion, signaling, and inflammation. By focusing on epidermal keratins, we illustrate the contribution of keratin isotypes to differentiated epithelial functions.
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12
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Yang F, Waters KM, Webb-Robertson BJ, Sowa MB, von Neubeck C, Aldrich JT, Markillie LM, Wirgau RM, Gritsenko MA, Zhao R, Camp DG, Smith RD, Stenoien DL. Quantitative phosphoproteomics identifies filaggrin and other targets of ionizing radiation in a human skin model. Exp Dermatol 2012; 21:352-7. [PMID: 22509832 DOI: 10.1111/j.1600-0625.2012.01470.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Our objective here was to perform a quantitative phosphoproteomic study on a reconstituted human skin tissue to identify low- and high-dose ionizing radiation-dependent signalling in a complex three-dimensional setting. Application of an isobaric labelling strategy using sham and three radiation doses (3, 10, 200 cGy) resulted in the identification of 1052 unique phosphopeptides. Statistical analyses identified 176 phosphopeptides showing significant changes in response to radiation and radiation dose. Proteins responsible for maintaining skin structural integrity including keratins and desmosomal proteins (desmoglein, desmoplakin, plakophilin 1, 2 and 3) had altered phosphorylation levels following exposure to both low and high doses of radiation. Altered phosphorylation of multiple sites in profilaggrin linker domains coincided with altered profilaggrin processing suggesting a role for linker phosphorylation in human profilaggrin regulation. These studies demonstrate that the reconstituted human skin system undergoes a coordinated response to both low and high doses of ionizing radiation involving multiple layers of the stratified epithelium that serve to maintain tissue integrity and mitigate effects of radiation exposure.
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Affiliation(s)
- Feng Yang
- Pacific Northwest National Laboratory, Richland, WA 99352, USA
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13
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The matriptase-prostasin proteolytic cascade in epithelial development and pathology. Cell Tissue Res 2012; 351:245-53. [DOI: 10.1007/s00441-012-1348-1] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Accepted: 01/20/2012] [Indexed: 01/05/2023]
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14
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Matsui T, Miyamoto K, Kubo A, Kawasaki H, Ebihara T, Hata K, Tanahashi S, Ichinose S, Imoto I, Inazawa J, Kudoh J, Amagai M. SASPase regulates stratum corneum hydration through profilaggrin-to-filaggrin processing. EMBO Mol Med 2011; 3:320-33. [PMID: 21542132 PMCID: PMC3377080 DOI: 10.1002/emmm.201100140] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2010] [Revised: 03/11/2011] [Accepted: 03/11/2011] [Indexed: 12/23/2022] Open
Abstract
The stratum corneum (SC), the outermost layer of the epidermis, acts as a barrier against the external environment. It is hydrated by endogenous humectants to avoid desiccation. However, the molecular mechanisms of SC hydration remain unclear. We report that skin-specific retroviral-like aspartic protease (SASPase) deficiency in hairless mice resulted in dry skin and a thicker and less hydrated SC with an accumulation of aberrantly processed profilaggrin, a marked decrease of filaggrin, but no alteration in free amino acid composition, compared with control hairless mice. We demonstrated that recombinant SASPase directly cleaved a linker peptide of recombinant profilaggrin. Furthermore, missense mutations were detected in 5 of 196 atopic dermatitis (AD) patients and 2 of 28 normal individuals. Among these, the V243A mutation induced complete absence of protease activity in vitro, while the V187I mutation induced a marked decrease in its activity. These findings indicate that SASPase activity is indispensable for processing profilaggrin and maintaining the texture and hydration of the SC. This provides a novel approach for elucidating the complex pathophysiology of atopic dry skin.
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Affiliation(s)
- Takeshi Matsui
- Medical Top Track (MTT) Program, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan.
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15
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Chatterjea SM, Resing KA, Old W, Nirunsuksiri W, Fleckman P. Optimization of filaggrin expression and processing in cultured rat keratinocytes. J Dermatol Sci 2011; 61:51-9. [PMID: 21146962 PMCID: PMC3031422 DOI: 10.1016/j.jdermsci.2010.11.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Revised: 10/11/2010] [Accepted: 11/06/2010] [Indexed: 12/11/2022]
Abstract
BACKGROUND In normal mammalian epidermis, cell division occurs primarily in the basal layer where cells are attached to the basement membrane. Upon release from the basement membrane, these basal cells stop dividing and begin to differentiate and stratify producing cornified cells expressing differentiation markers, including the keratin bundling protein filaggrin, and cornified envelope proteins. Little is understood about the regulatory mechanisms of these processes. A rat epidermal keratinocyte cell line synthesizing and processing profilaggrin at confluence in a synchronous manner for 4-5 days provides a useful culture model for epidermal differentiation. Profilaggrin expression in this cell line however decreases with passaging, and its processing involves extensive nonspecific proteolysis. OBJECTIVE Our objective was to identify culture conditions that effect the decrease in profilaggrin expression with passaging and nonspecific proteolysis of profilaggrin in order to study epidermal differentiation more closely. METHOD The large amount of nonspecific proteolysis suggested autophagocytosis. To test this, cells were cultured in the presence of 3-methyladenine (3-MA). Two known gradients in epidermis are decreasing serum components and increasing calcium concentrations in the upper cell layers. To determine whether these gradients effected processing, cells were cultured in serum/DMEM or in serum-free KGM and under varying external calcium concentrations. Cells were also cultured in presence of aminoguanidine in an attempt to maintain profilaggrin expression with passaging. RESULTS Profilaggrin expression was enhanced in the presence of 3-MA, with optimum around 6mM. In the absence of aminoguanidine, profilaggrin expression decreased as a function of increasing passage number; in its presence, profilaggrin expression remained high in some, but not in all of the independently maintained cell lines. Thus, culturing in aminoguanidine was necessary, but not sufficient, for sustained ability to express profilaggrin at confluence. Production of filaggrin from profilaggrin was maximized in a serum-free medium with [Ca(2+)] at 5mM. Filaggrin associates with phospholipid vesicles in vitro forming aggregates similar to those seen in vivo, suggesting that filaggrin release induces vesicular aggregation and autophagocytosis. CONCLUSION We have used a keratinocyte cell line that synthesizes and processes profilaggrin after confluence as a culture model to study epidermal differentiation. In this system profilaggrin processing must be preceded by inhibition of autophagosome formation and/or modulation of vesicular trafficking, and these processes are regulated by epidermal calcium and serum factor gradients.
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Affiliation(s)
| | - Katheryn A. Resing
- Dept. of Chemistry & Biochemistry, University of Colorado at Boulder, Boulder CO, 80309
| | - William Old
- Dept. of Chemistry & Biochemistry, University of Colorado at Boulder, Boulder CO, 80309
| | | | - Philip Fleckman
- Division of Dermatology, University of Washington, Seattle WA, 98195
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Sandilands A, Sutherland C, Irvine AD, McLean WHI. Filaggrin in the frontline: role in skin barrier function and disease. J Cell Sci 2009; 122:1285-94. [PMID: 19386895 DOI: 10.1242/jcs.033969] [Citation(s) in RCA: 533] [Impact Index Per Article: 35.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Recently, loss-of-function mutations in FLG, the human gene encoding profilaggrin and filaggrin, have been identified as the cause of the common skin condition ichthyosis vulgaris (which is characterised by dry, scaly skin). These mutations, which are carried by up to 10% of people, also represent a strong genetic predisposing factor for atopic eczema, asthma and allergies. Profilaggrin is the major component of the keratohyalin granules within epidermal granular cells. During epidermal terminal differentiation, the approximately 400 kDa profilaggrin polyprotein is dephosphorylated and rapidly cleaved by serine proteases to form monomeric filaggrin (37 kDa), which binds to and condenses the keratin cytoskeleton and thereby contributes to the cell compaction process that is required for squame biogenesis. Within the squames, filaggrin is citrullinated, which promotes its unfolding and further degradation into hygroscopic amino acids, which constitute one element of natural moisturising factor. Loss of profilaggrin or filaggrin leads to a poorly formed stratum corneum (ichthyosis), which is also prone to water loss (xerosis). Recent human genetic studies strongly suggest that perturbation of skin barrier function as a result of reduction or complete loss of filaggrin expression leads to enhanced percutaneous transfer of allergens. Filaggrin is therefore in the frontline of defence, and protects the body from the entry of foreign environmental substances that can otherwise trigger aberrant immune responses.
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Affiliation(s)
- Aileen Sandilands
- Epithelial Genetics Group, Division of Molecular Medicine, Colleges of Life Sciences and Medicine, Dentistry and Nursing, University of Dundee, Dundee DD1 5EH, UK
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Netzel-Arnett S, Currie BM, Szabo R, Lin CY, Chen LM, Chai KX, Antalis TM, Bugge TH, List K. Evidence for a matriptase-prostasin proteolytic cascade regulating terminal epidermal differentiation. J Biol Chem 2006; 281:32941-5. [PMID: 16980306 DOI: 10.1074/jbc.c600208200] [Citation(s) in RCA: 153] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Recent gene ablation studies in mice have shown that matriptase, a type II transmembrane serine protease, and prostasin, a glycosylphosphatidylinositol-anchored membrane serine protease, are both required for processing of the epidermis-specific polyprotein, profilaggrin, stratum corneum formation, and acquisition of epidermal barrier function. Here we present evidence that matriptase acts upstream of prostasin in a zymogen activation cascade that regulates terminal epidermal differentiation and is required for prostasin zymogen activation. Enzymatic gene trapping of matriptase combined with prostasin immunohistochemistry revealed that matriptase was co-localized with prostasin in transitional layer cells of the epidermis and that the developmental onset of expression of the two membrane proteases was coordinated and correlated with acquisition of epidermal barrier function. Purified soluble matriptase efficiently converted soluble prostasin zymogen to an active two-chain form that formed SDS-stable complexes with the serpin protease nexin-1. Whereas two forms of prostasin with molecular weights corresponding to the prostasin zymogen and active prostasin were present in wild type epidermis, prostasin was exclusively found in the zymogen form in matriptase-deficient epidermis. These data suggest that matriptase, an autoactivating protease, acts upstream from prostasin to initiate a zymogen cascade that is essential for epidermal differentiation.
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Affiliation(s)
- Sarah Netzel-Arnett
- Center for Vascular and Inflammatory Diseases and Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA
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18
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Delom F, Chevet E. Phosphoprotein analysis: from proteins to proteomes. Proteome Sci 2006; 4:15. [PMID: 16854217 PMCID: PMC1557478 DOI: 10.1186/1477-5956-4-15] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2006] [Accepted: 07/19/2006] [Indexed: 12/16/2022] Open
Abstract
Characterization of protein modification by phosphorylation is one of the major tasks that have to be accomplished in the post-genomic era. Phosphorylation is a key reversible modification occurring mainly on serine, threonine and tyrosine residues that can regulate enzymatic activity, subcellular localization, complex formation and degradation of proteins. The understanding of the regulatory role played by phosphorylation begins with the discovery and identification of phosphoproteins and then by determining how, where and when these phosphorylation events take place. Because phosphorylation is a dynamic process difficult to quantify, we must at first acquire an inventory of phosphoproteins and characterize their phosphorylation sites. Several experimental strategies can be used to explore the phosphorylation status of proteins from individual moieties to phosphoproteomes. In this review, we will examine and catalogue how proteomics techniques can be used to answer specific questions related to protein phosphorylation. Hence, we will discuss the different methods for enrichment of phospho-proteins and -peptides, and then the various technologies for their identification, quantitation and validation.
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Affiliation(s)
- Frédéric Delom
- Dept of Surgery, McGill University, Montreal, Quebec, Canada
- Montreal Proteomics Network, McGill University, Montreal, Quebec, Canada
| | - Eric Chevet
- Dept of Surgery, McGill University, Montreal, Quebec, Canada
- Montreal Proteomics Network, McGill University, Montreal, Quebec, Canada
- Dept of Medicine, McGill University, Montreal, Quebec, Canada
- Dept of Anatomy, McGill University, Montreal, Quebec, Canada
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19
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Candi E, Schmidt R, Melino G. The cornified envelope: a model of cell death in the skin. Nat Rev Mol Cell Biol 2005; 6:328-40. [PMID: 15803139 DOI: 10.1038/nrm1619] [Citation(s) in RCA: 1206] [Impact Index Per Article: 63.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The epidermis functions as a barrier against the environment by means of several layers of terminally differentiated, dead keratinocytes - the cornified layer, which forms the endpoint of epidermal differentiation and death. The cornified envelope replaces the plasma membrane of differentiating keratinocytes and consists of keratins that are enclosed within an insoluble amalgam of proteins, which are crosslinked by transglutaminases and surrounded by a lipid envelope. New insights into the molecular mechanisms and the physiological endpoints of cornification are increasing our understanding of the pathological defects of this unique form of programmed cell death, which is associated with barrier malfunctions and ichthyosis.
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Affiliation(s)
- Eleonora Candi
- Biochemistry Laboratory, IDI-IRCCS, c/o Department of Experimental Medicine, University of Rome Tor Vergata, 00133 Rome, Italy
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20
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Deng FM, Liang FX, Tu L, Resing KA, Hu P, Supino M, Hu CCA, Zhou G, Ding M, Kreibich G, Sun TT. Uroplakin IIIb, a urothelial differentiation marker, dimerizes with uroplakin Ib as an early step of urothelial plaque assembly. J Cell Biol 2002; 159:685-94. [PMID: 12446744 PMCID: PMC2173100 DOI: 10.1083/jcb.200204102] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Urothelial plaques consist of four major uroplakins (Ia, Ib, II, and III) that form two-dimensional crystals covering the apical surface of urothelium, and provide unique opportunities for studying membrane protein assembly. Here, we describe a novel 35-kD urothelial plaque-associated glycoprotein that is closely related to uroplakin III: they have a similar overall type 1 transmembrane topology; their amino acid sequences are 34% identical; they share an extracellular juxtamembrane stretch of 19 amino acids; their exit from the ER requires their forming a heterodimer with uroplakin Ib, but not with any other uroplakins; and UPIII-knockout leads to p35 up-regulation, possibly as a compensatory mechanism. Interestingly, p35 contains a stretch of 80 amino acid residues homologous to a hypothetical human DNA mismatch repair enzyme-related protein. Human p35 gene is mapped to chromosome 7q11.23 near the telomeric duplicated region of Williams-Beuren syndrome, a developmental disorder affecting multiple organs including the urinary tract. These results indicate that p35 (uroplakin IIIb) is a urothelial differentiation product structurally and functionally related to uroplakin III, and that p35-UPIb interaction in the ER is an important early step in urothelial plaque assembly.
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Affiliation(s)
- Fang-Ming Deng
- Epithelial Biology Unit, Ronald O. Perelman Department of Dermatology, New York University School of Medicine, New York, NY 10016, USA
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21
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Pearton DJ, Dale BA, Presland RB. Functional analysis of the profilaggrin N-terminal peptide: identification of domains that regulate nuclear and cytoplasmic distribution. J Invest Dermatol 2002; 119:661-9. [PMID: 12230510 DOI: 10.1046/j.1523-1747.2002.01831.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Profilaggrin is expressed in the differentiating granular layer of epidermis and other stratified epithelia, where it forms a major component of cytoplasmic keratohyalin granules. It consists of two distinct domains, an N-terminal S100-like Ca2+- binding domain containing two EF-hands and multiple filaggrin units that aggregate keratin filaments in the stratum corneum. Here, we report structure-function studies of the N-terminal peptide from mouse, human, and rat profilaggrin. The profilaggrin N- terminal peptides of all species contain two S100-like EF-hands, bipartite nuclear localization sequences, and proprotein convertase cleavage sites. The nuclear localization signals in human and mouse profilaggrin were shown to be functional by transfection of epithelial cells and depended on the absence of filaggrin sequences. The nuclear localization of the processed (free) N-terminal peptide of human profilaggrin is consistent with immunolocalization findings in normal human skin and in parakeratotic skin disorders, which exhibit nuclear staining of granular and/or cornified layers. The mouse profilaggrin N-terminus undergoes proteolytic processing in two steps, first releasing an N-terminal peptide containing some filaggrin sequence and finally the free N-terminus of 28-30 kDa; these peptides have cytoplasmic and nuclear distributions, respectively, when expressed in transfected cells. The N-terminal processing may occur prior to or simultaneously with the proteolytic processing of the polyfilaggrin domain. The nuclear accumulation of the profilaggrin N-terminal peptide in epidermis and in transfected cells strongly suggests a calcium-dependent nuclear function for the profilaggrin N-terminus during epidermal terminal differentia tion when the free N-terminus is released from profilaggrin by specific proteolysis.
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Affiliation(s)
- David J Pearton
- Department of Oral Biology, University of Washington, Seattle, Washington 98195-7132, USA
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22
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Mann M, Ong SE, Grønborg M, Steen H, Jensen ON, Pandey A. Analysis of protein phosphorylation using mass spectrometry: deciphering the phosphoproteome. Trends Biotechnol 2002; 20:261-8. [PMID: 12007495 DOI: 10.1016/s0167-7799(02)01944-3] [Citation(s) in RCA: 682] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In signal transduction in eukaryotes, protein phosphorylation is a key event. To understand signaling processes, we must first acquire an inventory of phosphoproteins and their phosphorylation sites under different conditions. Because phosphorylation is a dynamic process, elucidation of signaling networks also requires quantitation of these phosphorylation events. In this article, we outline several methods for enrichment of phosphorylated proteins and peptides and discuss various options for their identification and quantitation with special emphasis on mass spectrometry-based techniques.
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Affiliation(s)
- Matthias Mann
- Center for Experimental Bioinformatics, University of Southern Denmark, M, DK-5230, Odense, Denmark.
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23
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Pearton DJ, Nirunsuksiri W, Rehemtulla A, Lewis SP, Presland RB, Dale BA. Proprotein convertase expression and localization in epidermis: evidence for multiple roles and substrates. Exp Dermatol 2001; 10:193-203. [PMID: 11380615 DOI: 10.1034/j.1600-0625.2001.010003193.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Specific proteolysis plays an important role in the terminal differentiation of keratinocytes in the epidermis and several types of proteases have been implicated in this process. The proprotein convertases (PCs) are a family of Ca2+-dependent serine proteases involved in processing and activation of several types of substrates. In this study we examined the expression and some potential substrates of PCs in epidermis. Four PCs are expressed in epidermis: furin, PACE4, PC5/6 and PC7/8. Furin is detected in two forms, either with or without the transmembrane domain, suggesting occurrence of post-translational cleavage to produce a soluble enzyme. In addition the furin active site has differential accessibility in the granular layer of the epidermis relative to the basal layer, whereas antibodies to the transmembrane domain stain both layers. These findings suggest that furin has access to different types of substrates in granular cells as opposed to basal cells. PC7/8, in contrast, is detected throughout the epidermis with antibodies to both the transmembrane and active site and no soluble form observed. A peptide PC inhibitor (dec-RVKR-CMK) inhibits cleavage of Notch-1, a receptor important in cell fate determination that is found throughout the epidermis. Profilaggrin, found in the granular layer, is specifically cleaved by furin and PACE4 in vitro at a site between the amino terminus and the first filaggrin repeat. This work suggests that the PCs play multiple roles during epidermal differentiation.
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Affiliation(s)
- D J Pearton
- Department of Oral Biology, University of Washington, Seattle, WA 98195, USA
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24
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Resing KA, Ahn NG. Applications of mass spectrometry to signal transduction. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 1999; 71:501-23. [PMID: 10354711 DOI: 10.1016/s0079-6107(98)00048-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Advances in mass spectrometry instrumentation, protocols for sample handling, and computational methods provide powerful new approaches to solving problems in analytical biochemistry. This review summarizes recent work illustrating ways in which mass spectrometry has been used to address questions relevant to signal transduction. Rather than encompass all of the instruments or methodologies that might be brought to bear on these problems, we present an overview of commonly used techniques, promising new methodologies, and some applications.
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Affiliation(s)
- K A Resing
- Department of Chemistry and Biochemistry, University of Colorado, Boulder 80309, USA
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25
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Kuechle MK, Thulin CD, Presland RB, Dale BA. Profilaggrin requires both linker and filaggrin peptide sequences to form granules: implications for profilaggrin processing in vivo. J Invest Dermatol 1999; 112:843-52. [PMID: 10383728 DOI: 10.1046/j.1523-1747.1999.00599.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Filaggrin is an intermediate filament associated protein that aids the packing of keratin filaments during terminal differentiation of keratinocytes. Premature aggregation of keratin filaments is prevented by filaggrin expression as the inactive precursor, profilaggrin, which is localized in keratohyalin granules in vivo. Profilaggrin is phosphorylated and contains multiple filaggrin repeats separated by a hydrophobic linker peptide. We have previously shown that filaggrin constructs containing the linker, when transiently transfected into epithelial cells, lead to expression of a protein that resembles keratohyalin (Dale et al. J Invest Dermatol 108:179-187 1997). To characterize further the region(s) of the linker and/or filaggrin that are necessary for granule formation, we generated several mutant constructs from Flag-FG-1, and generated fusions of filaggrin with green fluorescent protein. We also subjected profilaggrin to protein phosphatase 2A treatment and measured its subsequent solubility. We found that granular morphology is not dependent on the linker or conserved phosphorylation sites, nor is solubility affected by protein phosphatase 2A treatment. Granule morphology was abrogated only in a truncated construct, which still contains the linker. A construct consisting of 16 amino acids of filaggrin fused to green fluorescent protein led to rounded and bizarrely shaped transfected cells with compact keratin filaments, suggesting that very little filaggrin sequence is required for keratin filament interaction. Radiolabeled filaggrin-green fluorescent protein constructs specifically bound keratin in overlay assays confirming that the observed cytoskeletal collapse is due to filaggrin-keratin interaction. Our findings indicate that profilaggrin must be extensively processed before it loses both its granule forming ability as well as its insolubility, suggesting that granule formation in vivo correlates with insolubility in vitro. Further, filaggrin retains its ability to bind keratin as it is degraded to smaller peptides.
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Affiliation(s)
- M K Kuechle
- Department of Oral Biology, University of Washington, Seattle 98185-7132, USA
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26
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Scott FL, Paddle-Ledinek JE, Cerruti L, Coughlin PB, Salem HH, Bird PI. Proteinase inhibitor 6 (PI-6) expression in human skin: induction of PI-6 and a PI-6/proteinase complex during keratinocyte differentiation. Exp Cell Res 1998; 245:263-71. [PMID: 9851866 DOI: 10.1006/excr.1998.4241] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Proteinase inhibitor 6 (PI-6) is a 42-kDa intracellular protein present in epithelial cells and endothelial cells. It is capable of inhibiting a number of serine proteinases, including trypsin and chymotrypsin. In this study we examined PI-6 expression in human skin and its primary cell type, the keratinocyte. By immunohistochemical analysis, PI-6 staining is absent from the basal cells, weak in the spinous layer, and strongest in the granulosa layer of human epidermis. Immunoblotting of cultured primary keratinocytes revealed that PI-6 production increases 24-fold on differentiation. Analysis of an immortalized keratinocyte cell line, HaCat, showed a 5-fold increase in PI-6 mRNA and a 7-fold increase in PI-6 protein upon differentiation, and indirect immunofluorescence revealed that this is due to an increase in the number of differentiated cells expressing high levels of PI-6. Of particular interest is the appearance of a preformed complex between PI-6 and an endogenous serine proteinase in differentiating HaCat cells, which was detected by a monoclonal antibody demonstrated to preferentially recognize PI-6 in complex with a proteinase. This identification of a PI-6/proteinase complex is the first example of a serpin bound to a proteinase in keratinocytes. We postulate that a physiological role of PI-6 is to regulate a serine proteinase associated with keratinocyte differentiation.
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Affiliation(s)
- F L Scott
- Department of Medicine, Monash University, Box Hill Hospital 3128, Melbourne, Australia
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27
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Affiliation(s)
- M Manabe
- Department of Dermatology, Juntendo University School of Medicine, Tokyo, Japan
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28
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Dale BA, Presland RB, Lewis SP, Underwood RA, Fleckman P. Transient expression of epidermal filaggrin in cultured cells causes collapse of intermediate filament networks with alteration of cell shape and nuclear integrity. J Invest Dermatol 1997; 108:179-87. [PMID: 9008231 DOI: 10.1111/1523-1747.ep12334205] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Filaggrin is an intermediate filament-associated protein (IFAP) that aggregates epidermal keratin filaments in vitro and is thought to perform a similar function during terminal differentiation in vivo. To test this function in living cells, we transiently expressed constructs encoding human filaggrin in both simple epithelial cells (COS-7) and rat keratinocytes. Scanning laser confocal microscopy showed that filaggrin-positive cells had collapsed keratin and vimentin intermediate filament (IF) networks, and that filaggrin partially co-localized with the IF networks. Filaggrin was also detected diffusely in the cytoplasm and nucleus. In contrast, when profilaggrin-like constructs, containing five filaggrin domains separated by the linker sequences, were expressed in cultured cells, immunoreactive granules formed. This finding is reminiscent of the insoluble nature of native profilaggrin that accumulates in keratohyalin granules in vivo, suggesting that the linker peptides (present in profilaggrin but not filaggrin) are important for granule formation. Cells expressing filaggrin also displayed disruption of the nucleus and the nuclear envelope; they rounded up and lost attachment to the substratum, in contrast to control cells over-expressing beta-galactosidase. This functional test of filaggrin in living cells supports its role in the reorganization and packing of keratin IF in epidermal differentiation. Moreover, the observed effects on cell morphology and nuclear integrity suggest that filaggrin may contribute to the form of apoptosis associated with terminal differentiation in epidermis.
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Affiliation(s)
- B A Dale
- Department of Oral Biology, University of Washington, Seattle 98195-7132, USA
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Normal Human Epidermal Keratinocytes Express In Vitro Specific Molecular Forms of (Pro)Filaggrin Recognized by Rheumatoid Arthritis-Associated Antifilaggrin Autoantibodies. Mol Med 1997. [DOI: 10.1007/bf03401806] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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30
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Presland RB, Kimball JR, Kautsky MB, Lewis SP, Lo CY, Dale BA. Evidence for specific proteolytic cleavage of the N-terminal domain of human profilaggrin during epidermal differentiation. J Invest Dermatol 1997; 108:170-8. [PMID: 9008230 DOI: 10.1111/1523-1747.ep12333356] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Profilaggrin is a large phosphoprotein that is expressed in the granular cells of epidermis where it is localized in keratohyalin. It consists of multiple copies of single filaggrin units plus N- and C-terminal sequences that differ from filaggrin. Profilaggrin is dephosphorylated and proteolytically processed during terminal differentiation to yield filaggrin, which associates with keratin intermediate filaments to form macrofibrils in the lower layers of the stratum corneum. The N-terminal sequence of human profilaggrin comprises two distinct domains; an acidic A domain of 81 amino acids that binds Ca2+, and a cationic B domain of 212 residues. In this report, we further characterize the N-terminal domain by immunohistochemistry and immunoblot analysis using anti-peptide antibodies raised to the A and B regions. All of these antibodies (n = 4) immunostained keratohyalin in the granular layer of human epidermis and also showed some reaction with the lower stratum corneum. In immunoblot studies, the high molecular weight human profilaggrin reacted with both B domain antibodies whereas it showed a weak and variable reaction with A domain antibodies. In addition to profilaggrin, a cationic 32-kDa protein was detected with all N-terminal antibodies. A similar-sized N-terminal peptide was also produced by in vitro proteolysis of human profilaggrin with endoproteinase 1 (PEP1), a protease involved in processing of mouse profilaggrin, and in cultured rat epidermal keratinocytes transfected with a human profilaggrin cDNA construct. Evidence for at least one additional cleavage within the N-terminal domain is shown by immunoreactivity of smaller (16-20 kDa) acidic and basic proteins with A and B domain antibodies, respectively. These results demonstrate that the N-terminal domain is an integral part of profilaggrin in keratohyalin but is proteolytically cleaved from profilaggrin during the terminal differentiation of keratinocytes to yield a 32-kDa peptide.
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Affiliation(s)
- R B Presland
- Department of Oral Biology, University of Washington, Seattle 98195-7132, USA
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31
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Louie DF, Resing KA, Lewis TS, Ahn NG. Mass spectrometric analysis of 40 S ribosomal proteins from Rat-1 fibroblasts. J Biol Chem 1996; 271:28189-98. [PMID: 8910435 DOI: 10.1074/jbc.271.45.28189] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Although sequences of most mammalian ribosomal proteins are available, little is known about the post-translational processing of ribosomal proteins. To examine their post-translational modifications, 40 S subunit proteins purified from Rat-1 fibroblasts and their peptides were analyzed by liquid chromatography coupled with electrospray mass spectrometry. Of 41 proteins observed, 36 corresponded to the 32 rat 40 S ribosomal proteins with known sequences (S3, S5, S7, and S24 presented in two forms). The observed masses of S4, S6-S8, S13, S15a, S16, S17, S19, S27a, S29, and S30 matched those predicted. Sa, S3a, S5, S11, S15, S18, S20, S21, S24, S26-S28, and an S7 variant showed changes in mass that were consistent with N-terminal demethionylation and/or acetylation (S5 and S27 also appeared to be internally formylated and acetylated, respectively). S23 appeared to be internally hydroxylated or methylated. S2, S3, S9, S10, S12, S14, and S25 showed changes in mass inconsistent with known covalent modifications (+220, -75, +86, +56, -100, -117, and -103 Da, respectively), possibly representing novel post-translational modifications or allelic sequence variation. Five unidentified proteins (12,084, 13,706, 13,741, 13,884, and 34, 987 Da) were observed; for one, a sequence tag (PPGPPP), absent in any known ribosomal proteins, was determined, suggesting that it is a previously undescribed ribosome-associated protein. This study establishes a powerful method to rapidly analyze protein components of large biological complexes and their covalent modifications.
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Affiliation(s)
- D F Louie
- Howard Hughes Medical Institute, University of Colorado, Boulder, Colorado 80309, USA.
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Abstract
The cells of the epidermis and its derivative, the hair follicle, undergo processes of terminal differentiation that involves the synthesis and assembly of classes of protein and enzymes to form the stratum corneum of the epidermis, and the hair fiber and its cuticle. Using genetic linkage and DNA sequencing methods, we now know that mutations in several genes encoding epidermal keratins or a transglutaminase enzyme cause ichthyosis-related diseases. Similar methods have now suggested that mutations in hair keratin genes underlie some cases of monilethrix, and a deficiency in a cuticle lipid metabolizing enzyme causes maple syrup urine disease. It is to be expected that further application of these methods will elucidate the molecular bases of other genetic hair diseases.
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Affiliation(s)
- L N Jones
- Division of Wool Technology, Commonwealth Scientific Industrial Research Organization, Geelong Laboratory, Belmont, Victoria, Australia
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33
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Kelly MA, Vestling MM, Murphy CM, Hua S, Sumpter T, Fenselau C. Primary structure of bovine adenosine deaminase. J Pharm Biomed Anal 1996; 14:1513-9. [PMID: 8877857 DOI: 10.1016/0731-7085(96)01845-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Derivatized bovine adenosine deaminase is used in enzyme replacement therapy and as an adjunct to gene therapy against severe combined immunodeficiency syndrome. Although a gene sequence is known for human adenosine deaminase, the structure of the bovine enzyme has not been characterized. Structure studies using mass spectrometry are reported here that evaluate sequence, processing, post-translational modifications and the extent of homology between the human protein and its therapeutic surrogate.
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Affiliation(s)
- M A Kelly
- Department of Chemistry and Biochemistry, University of Maryland Baltimore County 21228, USA
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Thulin CD, Taylor JA, Walsh KA. Microheterogeneity of human filaggrin: analysis of a complex peptide mixture using mass spectrometry. Protein Sci 1996; 5:1157-64. [PMID: 8762147 PMCID: PMC2143439 DOI: 10.1002/pro.5560050618] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Filaggrin is the product of posttranslational processing of the large, epidermal protein profilaggrin, which consists of 10 or more tandem filaggrin domains plus an amino and a carboxyl domain. According to fragmentary cDNA sequences, the filaggrin domains in the human protein vary at 40% of the amino acid positions; hence, mature filaggrin is a population of homologous but heterogeneous proteins, even within one individual. Available gene sequences give only a limited picture of the heterogeneity of human filaggrin protein because no complete human profilaggrin gene has been sequenced. Questions about the extent of heterogeneity of filaggrin within and between individuals have not been answered, nor have questions concerning the limited proteolytic cleavage of human profilaggrin that generates filaggrin in vivo. In order to address these questions and to provide an analysis of the primary structure of human filaggrins, we employed various methods of mass spectrometry. The intact protein and a tryptic digest of the mixture of human filaggrins were examined by matrix-assisted laser desorption time-of-flight mass spectrometry. Tryptic digests of human filaggrin from single individuals were also separated and analyzed by liquid chromatography/mass spectrometry (LC/MS) (using electrospray mass spectrometry), and specific peptides were identified by tandem mass spectrometry (MS/MS). A robust data analysis program, Sherpa, was developed to facilitate the interpretation of both LC/MS and MS/MS. These experiments show that human filaggrin includes heterogeneity not yet seen in cDNA sequences, but that much structure is highly conserved. Interestingly, we found that the heterogeneity is conserved among individuals. An approximation of the regions linking filaggrins in human profilaggrin is developed. These investigations provide a unique test of the limits of tryptic mapping of complex mixtures using mass spectrometry.
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Affiliation(s)
- C D Thulin
- Department of Biochemistry, University of Washington, Seattle 98195, USA.
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35
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Resing KA, Thulin C, Whiting K, al-Alawi N, Mostad S. Characterization of profilaggrin endoproteinase 1. A regulated cytoplasmic endoproteinase of epidermis. J Biol Chem 1995; 270:28193-8. [PMID: 7499312 DOI: 10.1074/jbc.270.47.28193] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Profilaggrin, an insoluble precursor of the intermediate filament-associated protein filaggrin, contains multiple internal repeats (PIRs). At terminal differentiation of epidermis, proteolytic processing within a "linker" region of each PIR releases soluble filaggrin in a two-stage process. The first stage endoproteinase (PEP1, profilaggrin endoproteinase 1) cleaves mouse profilaggrin at a subset of the linkers, yielding processing intermediates consisting of several filaggrin repeats. An epidermal endoproteinase that cleaves the requisite linker subset has been purified 4,966-fold from mouse epidermal extracts. SDS-polyacrylamide gel electrophoresis demonstrated a band of molecular mass of 29.5 kDa that correlated with the activity. Labeling with [3H]diisopropylfluorophosphate identified PEP1 as a serine protease; inhibitor studies suggest that it is similar to chymotrypsin, as expected from previous in vivo studies. The purified PEP1 cleaved a peptide derived from profilaggrin (P1) at three residues within and adjacent to a multiple tyrosine sequence, consistent with the in vivo processing sites. No exopeptidase activity was detected. PEP1 is only active toward insoluble profilaggrin, resulting in partial solubilization, consistent with a role in dispersal of profilaggrin during terminal differentiation. In contrast to the specific cleavage of mouse profilaggrin, PEP1 cleaved all linker regions of rat profilaggrin. Studies with phosphorylated P1 suggest that PEP1 specificity may be partly regulated by profilaggrin phosphorylation.
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Affiliation(s)
- K A Resing
- Department of Chemistry and Biochemistry, University of Colorado, Boulder 80309, USA
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36
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Resing KA, Johnson RS, Walsh KA. Mass spectrometric analysis of 21 phosphorylation sites in the internal repeat of rat profilaggrin, precursor of an intermediate filament associated protein. Biochemistry 1995; 34:9477-87. [PMID: 7626618 DOI: 10.1021/bi00029a024] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Profilaggrin, a highly phosphorylated protein synthesized in mammalian cornified epithelia, is the precursor of filaggrin, a protein that is involved in aggregation of keratin during terminal differentiation. Possible functions for the phosphorylation include preventing premature aggregation of keratin, packing profilaggrin into a storage granule, association of other proteins with the granule, and/or regulating proteolytic processing of profilaggrin. As a first step in characterizing the phosphorylation of rat profilaggrin, tryptic peptides of filaggrin and profilaggrin were fractionated by reverse-phase HPLC and analyzed by ionspray mass spectrometry. Nine putative phosphopeptides were identified as those with masses 80 Da (or multiples of 80 Da) greater than the predicted unphosphorylated masses. The six that were phosphorylated to a high stoichiometry were analyzed further. Several multiply phosphorylated peptides underwent neutral loss of H3PO4 during collisional activation, complicating interpretation of the MS/MS spectra. In order to circumvent this problem, an alternative strategy was applied in which peptide mixtures were treated with Ba(OH)2, resulting in beta-elimination of H3PO4 and generation of dehydrated serine or threonine at the site of phosphorylation. Peptides containing dehydrated serine or threonine fragmented well, providing unequivocal identification of multiple phosphorylation sites in peptides as long as 39 amino acids. The phosphopeptides (with phosphorylated residues underlined) were GQQHSGHPQVYYYGVEETEDESDAQQGHHQQQQQQR, GGQAGSHSESEASGGQAGR, HTSRPEQSPDTAGR, GESPAGQQSPDR, EASASQSSDSEGHSGAHAGIGQGQTSTTHR, and GSSESQASDSEGHSDYSEAHTQGAHGGIQTSSQR.
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Affiliation(s)
- K A Resing
- Department of Chemistry and Biochemistry, University of Colorado, Boulder 80303, USA
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Heath RL, Barton PA, Simpson RJ, Reid GE, Lim G, Anderson MA. Characterization of the protease processing sites in a multidomain proteinase inhibitor precursor from Nicotiana alata. EUROPEAN JOURNAL OF BIOCHEMISTRY 1995; 230:250-7. [PMID: 7601108 DOI: 10.1111/j.1432-1033.1995.tb20558.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
A gene encoding a 40.3-kDa serine proteinase inhibitor (PI) precursor is expressed at high levels in the stigma of the ornamental tobacco, Nicotiana alata. The precursor is processed proteolytically in vivo to release five homologous proteinase inhibitors of approximately 6 kDa, as well as two flanking peptides. The five PIs have been purified from stigmas and identified by N-terminal sequencing, electrospray mass spectrometry and inhibition activity against chymotrypsin or trypsin. One of the PIs inhibits chymotrypsin and the other four are most active on trypsin. Cleavage occurs in a linker region (EEKKND) that is repeated six times in the precursor molecule. In the plant, the initial cleavage probably occurs between asparagine and the aspartate residues and ragged ends are formed by subsequent trimming. In vitro, the protease-sensitive linker region is selectively cleaved by the endoproteinases Asp-N, Glu-C and Lys-C to release fully active approximately 6-kDa PIs that are resistant to further proteolytic digestion. The precursor, produced by a recombinant baculovirus, inhibits chymotrypsin more effectively than trypsin. The stoichiometry of 2.6 trypsin molecules/1 precursor molecule indicates that processing is required to activate or expose all of the four trypsin inhibitory sites.
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Affiliation(s)
- R L Heath
- Plant Cell Biology Research Centre, School of Botany, University of Melbourne, Victoria, Australia
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38
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Heath RL, Barton PA, Simpson RJ, Reid GE, Lim G, Anderson MA. Characterization of the Protease Processing Sites in a Multidomain Proteinase Inhibitor Precursor from Nicotiana Alata. ACTA ACUST UNITED AC 1995. [DOI: 10.1111/j.1432-1033.1995.0250i.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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