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Gabe CM, Bui AT, Lukashova L, Verdelis K, Vasquez B, Beniash E, Margolis HC. Role of amelogenin phosphorylation in regulating dental enamel formation. Matrix Biol 2024; 131:17-29. [PMID: 38759902 DOI: 10.1016/j.matbio.2024.05.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2024] [Revised: 05/08/2024] [Accepted: 05/14/2024] [Indexed: 05/19/2024]
Abstract
Amelogenin (AMELX), the predominant matrix protein in enamel formation, contains a singular phosphorylation site at Serine 16 (S16) that greatly enhances AMELX's capacity to stabilize amorphous calcium phosphate (ACP) and inhibit its transformation to apatitic enamel crystals. To explore the potential role of AMELX phosphorylation in vivo, we developed a knock-in (KI) mouse model in which AMELX phosphorylation is prevented by substituting S16 with Ala (A). As anticipated, AMELXS16A KI mice displayed a severe phenotype characterized by weak hypoplastic enamel, absence of enamel rods, extensive ectopic calcifications, a greater rate of ACP transformation to apatitic crystals, and progressive cell pathology in enamel-forming cells (ameloblasts). In the present investigation, our focus was on understanding the mechanisms of action of phosphorylated AMELX in amelogenesis. We have hypothesized that the absence of AMELX phosphorylation would result in a loss of controlled mineralization during the secretory stage of amelogenesis, leading to an enhanced rate of enamel mineralization that causes enamel acidification due to excessive proton release. To test these hypotheses, we employed microcomputed tomography (µCT), colorimetric pH assessment, and Fourier Transform Infrared (FTIR) microspectroscopy of apical portions of mandibular incisors from 8-week old wildtype (WT) and KI mice. As hypothesized, µCT analyses demonstrated significantly higher rates of enamel mineral densification in KI mice during the secretory stage compared to the WT. Despite a greater rate of enamel densification, maximal KI enamel thickness increased at a significantly lower rate than that of the WT during the secretory stage of amelogenesis, reaching a thickness in mid-maturation that is approximately half that of the WT. pH assessments revealed a lower pH in secretory enamel in KI compared to WT mice, as hypothesized. FTIR findings further demonstrated that KI enamel is comprised of significantly greater amounts of acid phosphate compared to the WT, consistent with our pH assessments. Furthermore, FTIR microspectroscopy indicated a significantly higher mineral-to-organic ratio in KI enamel, as supported by µCT findings. Collectively, our current findings demonstrate that phosphorylated AMELX plays crucial mechanistic roles in regulating the rate of enamel mineral formation, and in maintaining physico-chemical homeostasis and the enamel growth pattern during early stages of amelogenesis.
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Affiliation(s)
- Claire M Gabe
- Department of Oral and Craniofacial Sciences, University of Pittsburgh School of Dental Medicine, 335 Sutherland Drive (UPSDM), Pittsburgh, PA 15260, USA; Center for Craniofacial Regeneration, UPSDM, Pittsburgh, PA, USA
| | - Ai Thu Bui
- Department of Oral and Craniofacial Sciences, University of Pittsburgh School of Dental Medicine, 335 Sutherland Drive (UPSDM), Pittsburgh, PA 15260, USA; Center for Craniofacial Regeneration, UPSDM, Pittsburgh, PA, USA
| | | | - Kostas Verdelis
- Center for Craniofacial Regeneration, UPSDM, Pittsburgh, PA, USA; Department of Endodontics, UPSDM, Pittsburgh, PA, USA
| | - Brent Vasquez
- Department of Oral and Craniofacial Sciences, University of Pittsburgh School of Dental Medicine, 335 Sutherland Drive (UPSDM), Pittsburgh, PA 15260, USA; Center for Craniofacial Regeneration, UPSDM, Pittsburgh, PA, USA
| | - Elia Beniash
- Department of Oral and Craniofacial Sciences, University of Pittsburgh School of Dental Medicine, 335 Sutherland Drive (UPSDM), Pittsburgh, PA 15260, USA; Center for Craniofacial Regeneration, UPSDM, Pittsburgh, PA, USA
| | - Henry C Margolis
- Department of Oral and Craniofacial Sciences, University of Pittsburgh School of Dental Medicine, 335 Sutherland Drive (UPSDM), Pittsburgh, PA 15260, USA; Center for Craniofacial Regeneration, UPSDM, Pittsburgh, PA, USA; Department of Periodontics and Preventive Dentistry, UPSDM, Pittsburgh, PA, USA.
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2
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Zhao H, Zhang Q, Chu J. Effect of phosphate group on remineralization of early enamel caries regulated by amelogenin peptide. PLoS One 2024; 19:e0303147. [PMID: 38771806 PMCID: PMC11108222 DOI: 10.1371/journal.pone.0303147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2022] [Accepted: 04/20/2024] [Indexed: 05/23/2024] Open
Abstract
OBJECTIVE To show the effect of the phosphate group on the remineralization process of early enamel caries mediated by amelogenin peptide. METHODS Freshly extracted, completed, and crack-free bovine teeth were used to create artificial early enamel caries, which were randomly divided into four groups: Group A: fluorination remineralized solution treatment group; Group B: pure remineralized solution treatment group. Group C: 100 g/ml recombinant Amelogenin peptide remineralized solution treatment group (with single phosphate group on N-terminus); Group D: 100 g/ml non-phosphorylated recombinant Amelogenin peptide remineralized solution treatment group (without single phosphate group on N-terminus). For 12 days, fresh remineralized solutions were replaced daily. Transverse microradiography (TMR) was used after remineralization to determine mineral loss and demineralization depth before and after each sample's remineralization. Each sample's depth of remineralization and mineral acquisition were then determined. RESULTS The recombinant amelogenin peptide group significantly outperformed the non-phosphorylated amelogenin peptide group in terms of mineral acquisition and mineralization depth (P<0.05). CONCLUSIONS The recombinant Amelogenin's solitary phosphate group at the N-terminus helps recombinant Amelogenin to encourage the remineralization process of early enamel caries.
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Affiliation(s)
- Hualei Zhao
- The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
- Zhengzhou Stomatological Hospital, Zhengzhou, China
| | - Qun Zhang
- The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Jinpu Chu
- The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
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3
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Buchko GW, Zhou M, Vesely CH, Tao J, Shaw WJ, Mehl RA, Cooley RB. High-yield recombinant bacterial expression of 13 C-, 15 N-labeled, serine-16 phosphorylated, murine amelogenin using a modified third generation genetic code expansion protocol. Protein Sci 2023; 32:e4560. [PMID: 36585836 PMCID: PMC9850436 DOI: 10.1002/pro.4560] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 12/21/2022] [Accepted: 12/29/2022] [Indexed: 01/01/2023]
Abstract
Amelogenin constitutes ~90% of the enamel matrix in the secretory stage of amelogenesis, a still poorly understood process that results in the formation of the hardest and most mineralized tissue in vertebrates-enamel. Most biophysical research with amelogenin uses recombinant protein expressed in Escherichia coli. In addition to providing copious amounts of protein, recombinant expression allows 13 C- and 15 N-labeling for detailed structural studies using NMR spectroscopy. However, native amelogenin is phosphorylated at one position, Ser-16 in murine amelogenin, and there is mounting evidence that Ser-16 phosphorylation is important. Using a modified genetic code expansion protocol we have expressed and purified uniformly 13 C-, 15 N-labeled murine amelogenin (pS16M179) with ~95% of the protein being correctly phosphorylated. Homogeneous phosphorylation was achieved using commercially available, enriched, 13 C-, 15 N-labeled media, and protein expression was induced with isopropyl β-D-1-thiogalactopyranoside at 310 K. Phosphoserine incorporation was verified from one-dimensional 31 P NMR spectra, comparison of 1 H-15 N HSQC spectra, Phos-tag SDS PAGE, and mass spectrometry. Phosphorus-31 NMR spectra for pS16M179 under conditions known to trigger amelogenin self-assembly into nanospheres confirm nanosphere models with buried N-termini. Lambda phosphatase treatment of these nanospheres results in the dephosphorylation of pS16M179, confirming that smaller oligomers and monomers with exposed N-termini are in equilibrium with nanospheres. Such 13 C-, 15 N-labeling of amelogenin with accurately encoded phosphoserine incorporation will accelerate biomineralization research to understand amelogenesis and stimulate the expanded use of genetic code expansion protocols to introduce phosphorylated amino acids into proteins.
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Affiliation(s)
- Garry W. Buchko
- Earth and Biological Sciences DirectoratePacific Northwest National LaboratoryRichlandWashingtonUSA,School of Molecular BiosciencesWashington State UniversityPullmanWashingtonUSA
| | - Mowei Zhou
- Earth and Biological Sciences DirectoratePacific Northwest National LaboratoryRichlandWashingtonUSA
| | - Cat Hoang Vesely
- Department of Biochemistry and BiophysicsOregon State UniversityCorvallisOregonUSA
| | - Jinhui Tao
- Physical and Computational Sciences DirectoratePacific Northwest National LaboratoryRichlandWashingtonUSA
| | - Wendy J. Shaw
- Physical and Computational Sciences DirectoratePacific Northwest National LaboratoryRichlandWashingtonUSA
| | - Ryan A. Mehl
- Department of Biochemistry and BiophysicsOregon State UniversityCorvallisOregonUSA
| | - Richard B. Cooley
- Department of Biochemistry and BiophysicsOregon State UniversityCorvallisOregonUSA
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4
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Proline-rich protein from S. mutans can perform a competitive mineralization function to enhance bacterial adhesion to teeth. Sci Rep 2022; 12:22250. [PMID: 36564474 PMCID: PMC9789152 DOI: 10.1038/s41598-022-26303-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Accepted: 12/13/2022] [Indexed: 12/25/2022] Open
Abstract
A proline-rich region was found in Streptococcus mutans (S. mutans) surface antigen I/II (Ag I/II). The functions of this region were explored to determine its role in the cariogenic abilities of S. mutans; specifically, the proline-rich region was compared with human amelogenin. The full-length amelogenin genes were cloned from human (AmH) and surface antigen I/II genes from S. mutans. Then, the genes expressed and purified. We analyzed the structure and self-assembly ability of AmH and Ag I/II, compared their capacities to induce mineralization, and assessed the adhesion ability of S. mutans to AmH- and Ag I/II-coated tooth slices. AmH formed ordered chains and net frames in the early stage of protein self-assembly, while Ag I/II formed irregular and overlapping structures. AmH induced mineralization possessed a parallel rosary structure, while Ag I/II-induced mineralization is rougher and more irregular. The S. mutans adhesion assay indicated that the adhesion ability S. mutans on the Ag I/II-induced crystal layer was significantly higher than that on the AmH-induced crystal layer. S. mutans' Ag I/II may have evolved to resemble human amelogenin and form a rougher crystal layer on teeth, which play a competitive mineralization role and promotes better bacterial adhesion and colonization. Thus, the cariogenic ability of S. mutans Ag I/II is increased.
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5
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Buchko GW, Mergelsberg ST, Tarasevich BJ, Shaw WJ. Residue-Specific Insights into the Intermolecular Protein–Protein Interfaces Driving Amelogenin Self-Assembly in Solution. Biochemistry 2022; 61:2909-2921. [DOI: 10.1021/acs.biochem.2c00522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Affiliation(s)
- Garry W. Buchko
- Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164, United States
| | - Sebastian T. Mergelsberg
- Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Barbara J. Tarasevich
- Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Wendy J. Shaw
- Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
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6
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Lei C, Wang YH, Zhuang PX, Li YT, Wan QQ, Ma YX, Tay FR, Niu LN. Applications of Cryogenic Electron Microscopy in Biomineralization Research. J Dent Res 2021; 101:505-514. [PMID: 34918556 DOI: 10.1177/00220345211053814] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Biological mineralization is a natural process manifested by living organisms in which inorganic minerals crystallize under the scrupulous control of biomolecules, producing hierarchical organic-inorganic composite structures with physical properties and design that galvanize even the most ardent structural engineer and architect. Understanding the mechanisms that control the formation of biominerals is challenging in the biomimetic engineering of hard tissues. In this regard, the contribution of cryogenic electron microscopy (cryo-EM) has been nothing short of phenomenal. By preserving materials in their native hydrated status and reducing damage caused by ion beam radiation, cryo-EM outperforms conventional transmission electron microscopy in its ability to directly observe the morphologic evolution of mineral precursor phases at different stages of biomineralization with nanoscale spatial resolution and subsecond temporal resolution in 2 or 3 dimensions. In the present review, the development and applications of cryo-EM are discussed to support the use of this powerful technique in dental research. Because of the rapid development of cryogenic sample preparation techniques, direct electron detection, and image-processing algorithms, the last decade has witnessed an exponential increase in the use of cryo-EM in structural biology and materials research. By amalgamating with other analytic techniques, cryo-EM may be used for qualitative and quantitative analyses of the kinetics and thermodynamic mechanisms in which organic macromolecules participate in the transformation of mineral precursors from their original liquid state to amorphous and ultimately crystalline phases. The present review concentrates on the biomineralization of calcium phosphate mineral phases, while that of calcium carbonate, silica, and magnetite is only briefly mentioned. Bioinspired organic matrix-mediated inorganic crystallization strategies are discussed from the perspective of tissue regeneration engineering.
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Affiliation(s)
- C Lei
- State Key Laboratory of Military Stomatology and National Clinical Research Center for Oral Diseases and Shaanxi Key Laboratory of Stomatology, School of Stomatology, the Fourth Military Medical University, Xi'an, China
| | - Y H Wang
- State Key Laboratory of Military Stomatology and National Clinical Research Center for Oral Diseases and Shaanxi Key Laboratory of Stomatology, School of Stomatology, the Fourth Military Medical University, Xi'an, China.,Key Laboratory of Shaanxi Province for Craniofacial Precision Medicine Research, College of Stomatology, Xi'an Jiaotong University, Xi'an, China
| | - P X Zhuang
- State Key Laboratory of Military Stomatology and National Clinical Research Center for Oral Diseases and Shaanxi Key Laboratory of Stomatology, School of Stomatology, the Fourth Military Medical University, Xi'an, China
| | - Y T Li
- State Key Laboratory of Military Stomatology and National Clinical Research Center for Oral Diseases and Shaanxi Key Laboratory of Stomatology, School of Stomatology, the Fourth Military Medical University, Xi'an, China
| | - Q Q Wan
- State Key Laboratory of Military Stomatology and National Clinical Research Center for Oral Diseases and Shaanxi Key Laboratory of Stomatology, School of Stomatology, the Fourth Military Medical University, Xi'an, China
| | - Y X Ma
- State Key Laboratory of Military Stomatology and National Clinical Research Center for Oral Diseases and Shaanxi Key Laboratory of Stomatology, School of Stomatology, the Fourth Military Medical University, Xi'an, China
| | - F R Tay
- The Graduate School, Augusta University, Augusta, GA, USA
| | - L N Niu
- State Key Laboratory of Military Stomatology and National Clinical Research Center for Oral Diseases and Shaanxi Key Laboratory of Stomatology, School of Stomatology, the Fourth Military Medical University, Xi'an, China
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7
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Huang Y, Bai Y, Chang C, Bacino M, Cheng IC, Li L, Habelitz S, Li W, Zhang Y. A N-Terminus Domain Determines Amelogenin's Stability to Guide the Development of Mouse Enamel Matrix. J Bone Miner Res 2021; 36:1781-1795. [PMID: 33957008 PMCID: PMC9307086 DOI: 10.1002/jbmr.4329] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Revised: 04/25/2021] [Accepted: 04/29/2021] [Indexed: 12/16/2022]
Abstract
Amelogenins, the principal proteins in the developing enamel microenvironment, self-assemble into supramolecular structures to govern the remodeling of a proteinaceous organic matrix into longitudinally ordered hydroxyapatite nanocrystal arrays. Extensive in vitro studies using purified native or recombinant proteins have revealed the potential of N-terminal amelogenin on protein self-assembly and its ability to guide the mineral deposition. We have previously identified a 14-aa domain (P2) of N-terminal amelogenin that can self-assemble into amyloid-like fibrils in vitro. Here, we investigated how this domain affects the ability of amelogenin self-assembling and stability of enamel matrix protein scaffolding in an in vivo animal model. Mice harboring mutant amelogenin lacking P2 domain had a hypoplastic, hypomineralized, and aprismatic enamel. In vitro, the mutant recombinant amelogenin without P2 had a reduced tendency to self-assemble and was prone to accelerated hydrolysis by MMP20, the prevailing metalloproteinase in early developing enamel matrix. A reduced amount of amelogenins and a lack of elongated fibrous assemblies in the development enamel matrix of mutant mice were evident compared with that in the wild-type mouse enamel matrix. Our study is the first to demonstrate that a subdomain (P2) at the N-terminus of amelogenin controls amelogenin's assembly into a transient protein scaffold that resists rapid proteolysis during enamel development in an animal model. Understanding the building blocks of fibrous scaffold that guides the longitudinal growth of hydroxyapatites in enamel matrix sheds light on protein-mediated enamel bioengineering. © 2021 American Society for Bone and Mineral Research (ASBMR).
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Affiliation(s)
- Yulei Huang
- Department of Orofacial Sciences, University of California, San Francisco, CA, USA.,Preventive and Restorative Dental Sciences, University of California, San Francisco, CA, USA
| | - Yushi Bai
- Guangdong Provincial Key Laboratory of Stomatology, Guanghua School of Stomatology, Sun-Yat-sen University, Guangzhou, China
| | - Chih Chang
- Department of Orofacial Sciences, University of California, San Francisco, CA, USA
| | - Margot Bacino
- Guangdong Provincial Key Laboratory of Stomatology, Guanghua School of Stomatology, Sun-Yat-sen University, Guangzhou, China
| | - Ieong Cheng Cheng
- Department of Orofacial Sciences, University of California, San Francisco, CA, USA
| | - Li Li
- Department of Orofacial Sciences, University of California, San Francisco, CA, USA
| | - Stefan Habelitz
- Guangdong Provincial Key Laboratory of Stomatology, Guanghua School of Stomatology, Sun-Yat-sen University, Guangzhou, China
| | - Wu Li
- Department of Orofacial Sciences, University of California, San Francisco, CA, USA
| | - Yan Zhang
- Department of Orofacial Sciences, University of California, San Francisco, CA, USA
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8
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Sharma V, Srinivasan A, Nikolajeff F, Kumar S. Biomineralization process in hard tissues: The interaction complexity within protein and inorganic counterparts. Acta Biomater 2021; 120:20-37. [PMID: 32413577 DOI: 10.1016/j.actbio.2020.04.049] [Citation(s) in RCA: 53] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 04/17/2020] [Accepted: 04/26/2020] [Indexed: 02/07/2023]
Abstract
Biomineralization can be considered as nature's strategy to produce and sustain biominerals, primarily via creation of hard tissues for protection and support. This review examines the biomineralization process within the hard tissues of the human body with special emphasis on the mechanisms and principles of bone and teeth mineralization. We describe the detailed role of proteins and inorganic ions in mediating the mineralization process. Furthermore, we highlight the various available models for studying bone physiology and mineralization starting from the historical static cell line-based methods to the most advanced 3D culture systems, elucidating the pros and cons of each one of these methods. With respect to the mineralization process in teeth, enamel and dentin mineralization is discussed in detail. The key role of intrinsically disordered proteins in modulating the process of mineralization in enamel and dentine is given attention. Finally, nanotechnological interventions in the area of bone and teeth mineralization, diseases and tissue regeneration is also discussed. STATEMENT OF SIGNIFICANCE: This article provides an overview of the biomineralization process within hard tissues of the human body, which encompasses the detailed mechanism innvolved in the formation of structures like teeth and bone. Moreover, we have discussed various available models used for studying biomineralization and also explored the nanotechnological applications in the field of bone regeneration and dentistry.
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Affiliation(s)
- Vaibhav Sharma
- Department of Biophysics, All India Institute of Medical Sciences, New Delhi, India.
| | | | | | - Saroj Kumar
- Department of Biophysics, All India Institute of Medical Sciences, New Delhi, India.
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9
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Athanasiadou D, Carneiro KMM. DNA nanostructures as templates for biomineralization. Nat Rev Chem 2021; 5:93-108. [PMID: 37117611 DOI: 10.1038/s41570-020-00242-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/26/2020] [Indexed: 12/22/2022]
Abstract
Nature uses extracellular matrix scaffolds to organize biominerals into hierarchical structures over various length scales. This has inspired the design of biomimetic mineralization scaffolds, with DNA nanostructures being among the most promising. DNA nanotechnology makes use of molecular recognition to controllably give 1D, 2D and 3D nanostructures. The control we have over these structures makes them attractive templates for the synthesis of mineralized tissues, such as bones and teeth. In this Review, we first summarize recent work on the crystallization processes and structural features of biominerals on the nanoscale. We then describe self-assembled DNA nanostructures and come to the intersection of these two themes: recent applications of DNA templates in nanoscale biomineralization, a crucial process to regenerate mineralized tissues.
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10
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Shaw WJ, Tarasevich BJ, Buchko GW, Arachchige RMJ, Burton SD. Controls of nature: Secondary, tertiary, and quaternary structure of the enamel protein amelogenin in solution and on hydroxyapatite. J Struct Biol 2020; 212:107630. [PMID: 32979496 PMCID: PMC7744360 DOI: 10.1016/j.jsb.2020.107630] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Revised: 09/12/2020] [Accepted: 09/17/2020] [Indexed: 10/23/2022]
Abstract
Amelogenin, a protein critical to enamel formation, is presented as a model for understanding how the structure of biomineralization proteins orchestrate biomineral formation. Amelogenin is the predominant biomineralization protein in the early stages of enamel formation and contributes to the controlled formation of hydroxyapatite (HAP) enamel crystals. The resulting enamel mineral is one of the hardest tissues in the human body and one of the hardest biominerals in nature. Structural studies have been hindered by the lack of techniques to evaluate surface adsorbed proteins and by amelogenin's disposition to self-assemble. Recent advancements in solution and solid state nuclear magnetic resonance (NMR) spectroscopy, atomic force microscopy (AFM), and recombinant isotope labeling strategies are now enabling detailed structural studies. These recent studies, coupled with insights from techniques such as CD and IR spectroscopy and computational methodologies, are contributing to important advancements in our structural understanding of amelogenesis. In this review we focus on recent advances in solution and solid state NMR spectroscopy and in situ AFM that reveal new insights into the secondary, tertiary, and quaternary structure of amelogenin by itself and in contact with HAP. These studies have increased our understanding of the interface between amelogenin and HAP and how amelogenin controls enamel formation.
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Affiliation(s)
- Wendy J Shaw
- Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA.
| | - Barbara J Tarasevich
- Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - Garry W Buchko
- Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA; School of Molecular Bioscience, Washington State University, Pullman, WA 99164, USA
| | - Rajith M J Arachchige
- Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - Sarah D Burton
- Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA
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11
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Shin NY, Yamazaki H, Beniash E, Yang X, Margolis SS, Pugach MK, Simmer JP, Margolis HC. Amelogenin phosphorylation regulates tooth enamel formation by stabilizing a transient amorphous mineral precursor. J Biol Chem 2020; 295:1943-1959. [PMID: 31919099 DOI: 10.1074/jbc.ra119.010506] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 12/30/2019] [Indexed: 11/06/2022] Open
Abstract
Dental enamel comprises interwoven arrays of extremely long and narrow crystals of carbonated hydroxyapatite called enamel rods. Amelogenin (AMELX) is the predominant extracellular enamel matrix protein and plays an essential role in enamel formation (amelogenesis). Previously, we have demonstrated that full-length AMELX forms higher-order supramolecular assemblies that regulate ordered mineralization in vitro, as observed in enamel rods. Phosphorylation of the sole AMELX phosphorylation site (Ser-16) in vitro greatly enhances its capacity to stabilize amorphous calcium phosphate (ACP), the first mineral phase formed in developing enamel, and prevents apatitic crystal formation. To test our hypothesis that AMELX phosphorylation is critical for amelogenesis, we generated and characterized a hemizygous knockin (KI) mouse model with a phosphorylation-defective Ser-16 to Ala-16 substitution in AMELX. Using EM analysis, we demonstrate that in the absence of phosphorylated AMELX, KI enamel lacks enamel rods, the hallmark component of mammalian enamel, and, unlike WT enamel, appears to be composed of less organized arrays of shorter crystals oriented normal to the dentinoenamel junction. KI enamel also exhibited hypoplasia and numerous surface defects, whereas heterozygous enamel displayed highly variable mosaic structures with both KI and WT features. Importantly, ACP-to-apatitic crystal transformation occurred significantly faster in KI enamel. Secretory KI ameloblasts also lacked Tomes' processes, consistent with the absence of enamel rods, and underwent progressive cell pathology throughout enamel development. In conclusion, AMELX phosphorylation plays critical mechanistic roles in regulating ACP-phase transformation and enamel crystal growth, and in maintaining ameloblast integrity and function during amelogenesis.
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Affiliation(s)
- Nah-Young Shin
- The Forsyth Institute, Cambridge, Massachusetts 02142; Department of Developmental Biology, Harvard School of Dental Medicine, Boston, Massachusetts 02115
| | - Hajime Yamazaki
- The Forsyth Institute, Cambridge, Massachusetts 02142; Department of Developmental Biology, Harvard School of Dental Medicine, Boston, Massachusetts 02115; Department of Oral Biology, Center for Craniofacial Regeneration, University of Pittsburgh, School of Dental Medicine, Pittsburgh, Pennsylvania 15213
| | - Elia Beniash
- Department of Oral Biology, Center for Craniofacial Regeneration, University of Pittsburgh, School of Dental Medicine, Pittsburgh, Pennsylvania 15213
| | - Xu Yang
- Department of Oral Biology, Center for Craniofacial Regeneration, University of Pittsburgh, School of Dental Medicine, Pittsburgh, Pennsylvania 15213
| | - Seth S Margolis
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Megan K Pugach
- The Forsyth Institute, Cambridge, Massachusetts 02142; Department of Developmental Biology, Harvard School of Dental Medicine, Boston, Massachusetts 02115
| | - James P Simmer
- Department of Biologic and Material Sciences, University of Michigan School of Dentistry, Ann Arbor, Michigan 48108
| | - Henry C Margolis
- The Forsyth Institute, Cambridge, Massachusetts 02142; Department of Developmental Biology, Harvard School of Dental Medicine, Boston, Massachusetts 02115; Department of Periodontics and Preventive Dentistry, Center for Craniofacial Regeneration, University of Pittsburgh, School of Dental Medicine, Pittsburgh, Pennsylvania 15213.
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12
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Shlaferman J, Paige A, Meserve K, Miech JA, Gerdon AE. Selected DNA Aptamers Influence Kinetics and Morphology in Calcium Phosphate Mineralization. ACS Biomater Sci Eng 2019; 5:3228-3236. [DOI: 10.1021/acsbiomaterials.9b00308] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Jacob Shlaferman
- Department of Chemistry and Physics, Emmanuel College, 400 The Fenway, Boston, Massachusetts 02115, United States
| | - Alexander Paige
- Department of Chemistry and Physics, Emmanuel College, 400 The Fenway, Boston, Massachusetts 02115, United States
| | - Krista Meserve
- Department of Chemistry and Physics, Emmanuel College, 400 The Fenway, Boston, Massachusetts 02115, United States
| | - Jason A. Miech
- Department of Chemistry and Physics, Emmanuel College, 400 The Fenway, Boston, Massachusetts 02115, United States
| | - Aren E. Gerdon
- Department of Chemistry and Physics, Emmanuel College, 400 The Fenway, Boston, Massachusetts 02115, United States
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13
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Su J, Kegulian NC, Arun Bapat R, Moradian-Oldak J. Ameloblastin Binds to Phospholipid Bilayers via a Helix-Forming Motif within the Sequence Encoded by Exon 5. ACS OMEGA 2019; 4:4405-4416. [PMID: 30873509 PMCID: PMC6410667 DOI: 10.1021/acsomega.8b03582] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Accepted: 02/12/2019] [Indexed: 06/09/2023]
Abstract
Ameloblastin (Ambn), the most abundant non-amelogenin enamel protein, is intrinsically disordered and has the potential to interact with other enamel proteins and with cell membranes. Here, through multiple biophysical methods, we investigated the interactions between Ambn and large unilamellar vesicles (LUVs), whose lipid compositions mimicked cell membranes involved in epithelial cell-extracellular matrix adhesion. Using a series of Ambn Trp/Phe variants and Ambn mutants, we further showed that Ambn binds to LUVs through a highly conserved motif within the sequence encoded by exon 5. Synthetic peptides derived from different regions of Ambn confirmed that the sequence encoded by exon 5 is involved in LUV binding. Sequence analysis of Ambn across different species showed that the N-terminus of this sequence contains a highly conserved motif with a propensity to form an amphipathic helix. Mutations in the helix-forming sequence resulted in a loss of peptide binding to LUVs. Our in vitro data suggest that Ambn binds the lipid membrane directly through a conserved helical motif and have implications for biological events such as Ambn-cell interactions, Ambn signaling, and Ambn secretion via secretory vesicles.
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14
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Yamazaki H, Tran B, Beniash E, Kwak SY, Margolis HC. Proteolysis by MMP20 Prevents Aberrant Mineralization in Secretory Enamel. J Dent Res 2019; 98:468-475. [PMID: 30744480 DOI: 10.1177/0022034518823537] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The present study was conducted to investigate the role of proteolysis by matrix metalloproteinase 20 (MMP20) in regulating the initial formation of the enamel mineral structure during the secretory stage of amelogenesis, utilizing Mmp20-null mice that lack this essential protease. Ultrathin sagittal sections of maxillary incisors from 8-wk-old wild-type (WT), Mmp20-null (KO), and heterozygous (HET) littermates were prepared. Secretory-stage enamel ultrastructures from each genotype as a function of development were compared using transmission electron microscopy, selected area electron diffraction, and Raman microspectroscopy. Characteristic rod structures observed in WT enamel exhibited amorphous features in newly deposited enamel, which subsequently transformed into apatite-like crystals in older enamel. Surprisingly, initial mineral formation in KO enamel was found to proceed in the same manner as in the WT. However, soon after a rod structure began to form, large plate-like crystals appeared randomly within the developing KO enamel layer. As development continued, observed plate-like crystals became dominant and obscured the appearance of the enamel rod structure. Upon formation of these plate-like crystals, the KO enamel layer stopped growing in thickness, unlike WT and HET enamel layers that continued to grow at the same rate. Raman results indicated that Mmp20-KO enamel contains a significant portion of octacalcium phosphate, unlike WT enamel. Although normal in all other respects, large, randomly dispersed mineral crystals were observed in secretory HET enamel, although to a lesser extent than that seen in KO enamel, indicating that the level of MMP20 expression has a proportional effect on suppressing aberrant mineral formation. In conclusion, we found that proteolysis of extracellular enamel matrix proteins by MMP20 is not required for the initial development of the enamel rod structure during the early secretory stage of amelogenesis. Proteolysis by MMP20, however, is essential for the prevention of abnormal crystal formation during amelogenesis.
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Affiliation(s)
- H Yamazaki
- 1 The Forsyth Institute, Cambridge, MA, USA.,2 Department of Developmental Biology, Harvard School of Dental Medicine, Boston, MA, USA
| | - B Tran
- 3 Simmons College, Boston, MA, USA
| | - E Beniash
- 4 Center for Craniofacial Regeneration, Department of Oral Biology, University of Pittsburgh School of Dental Medicine, Pittsburgh, PA, USA
| | - S Y Kwak
- 1 The Forsyth Institute, Cambridge, MA, USA.,2 Department of Developmental Biology, Harvard School of Dental Medicine, Boston, MA, USA
| | - H C Margolis
- 1 The Forsyth Institute, Cambridge, MA, USA.,2 Department of Developmental Biology, Harvard School of Dental Medicine, Boston, MA, USA
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15
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Lacruz RS, Habelitz S, Wright JT, Paine ML. DENTAL ENAMEL FORMATION AND IMPLICATIONS FOR ORAL HEALTH AND DISEASE. Physiol Rev 2017; 97:939-993. [PMID: 28468833 DOI: 10.1152/physrev.00030.2016] [Citation(s) in RCA: 223] [Impact Index Per Article: 31.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 01/10/2017] [Accepted: 01/10/2017] [Indexed: 12/16/2022] Open
Abstract
Dental enamel is the hardest and most mineralized tissue in extinct and extant vertebrate species and provides maximum durability that allows teeth to function as weapons and/or tools as well as for food processing. Enamel development and mineralization is an intricate process tightly regulated by cells of the enamel organ called ameloblasts. These heavily polarized cells form a monolayer around the developing enamel tissue and move as a single forming front in specified directions as they lay down a proteinaceous matrix that serves as a template for crystal growth. Ameloblasts maintain intercellular connections creating a semi-permeable barrier that at one end (basal/proximal) receives nutrients and ions from blood vessels, and at the opposite end (secretory/apical/distal) forms extracellular crystals within specified pH conditions. In this unique environment, ameloblasts orchestrate crystal growth via multiple cellular activities including modulating the transport of minerals and ions, pH regulation, proteolysis, and endocytosis. In many vertebrates, the bulk of the enamel tissue volume is first formed and subsequently mineralized by these same cells as they retransform their morphology and function. Cell death by apoptosis and regression are the fates of many ameloblasts following enamel maturation, and what cells remain of the enamel organ are shed during tooth eruption, or are incorporated into the tooth's epithelial attachment to the oral gingiva. In this review, we examine key aspects of dental enamel formation, from its developmental genesis to the ever-increasing wealth of data on the mechanisms mediating ionic transport, as well as the clinical outcomes resulting from abnormal ameloblast function.
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Affiliation(s)
- Rodrigo S Lacruz
- Department of Basic Science and Craniofacial Biology, College of Dentistry, New York University, New York, New York; Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, San Francisco, California; Department of Pediatric Dentistry, School of Dentistry, University of North Carolina, Chapel Hill, North Carolina; Herman Ostrow School of Dentistry, Center for Craniofacial Molecular Biology, University of Southern California, Los Angeles, California
| | - Stefan Habelitz
- Department of Basic Science and Craniofacial Biology, College of Dentistry, New York University, New York, New York; Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, San Francisco, California; Department of Pediatric Dentistry, School of Dentistry, University of North Carolina, Chapel Hill, North Carolina; Herman Ostrow School of Dentistry, Center for Craniofacial Molecular Biology, University of Southern California, Los Angeles, California
| | - J Timothy Wright
- Department of Basic Science and Craniofacial Biology, College of Dentistry, New York University, New York, New York; Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, San Francisco, California; Department of Pediatric Dentistry, School of Dentistry, University of North Carolina, Chapel Hill, North Carolina; Herman Ostrow School of Dentistry, Center for Craniofacial Molecular Biology, University of Southern California, Los Angeles, California
| | - Michael L Paine
- Department of Basic Science and Craniofacial Biology, College of Dentistry, New York University, New York, New York; Department of Preventive and Restorative Dental Sciences, University of California, San Francisco, San Francisco, California; Department of Pediatric Dentistry, School of Dentistry, University of North Carolina, Chapel Hill, North Carolina; Herman Ostrow School of Dentistry, Center for Craniofacial Molecular Biology, University of Southern California, Los Angeles, California
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16
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Yamazaki H, Beniash E, Yamakoshi Y, Simmer JP, Margolis HC. Protein Phosphorylation and Mineral Binding Affect the Secondary Structure of the Leucine-Rich Amelogenin Peptide. Front Physiol 2017; 8:450. [PMID: 28706493 PMCID: PMC5489624 DOI: 10.3389/fphys.2017.00450] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Accepted: 06/14/2017] [Indexed: 12/31/2022] Open
Abstract
Previously, we have shown that serine-16 phosphorylation in native full-length porcine amelogenin (P173) and the Leucine-Rich Amelogenin Peptide (LRAP(+P)), an alternative amelogenin splice product, affects protein assembly and mineralization in vitro. Notably, P173 and LRAP(+P) stabilize amorphous calcium phosphate (ACP) and inhibit hydroxyapatite (HA) formation, while non-phosphorylated counterparts (rP172, LRAP(-P)) guide the growth of ordered bundles of HA crystals. Based on these findings, we hypothesize that the phosphorylation of full-length amelogenin and LRAP induces conformational changes that critically affect its capacity to interact with forming calcium phosphate mineral phases. To test this hypothesis, we have utilized Fourier transform infrared spectroscopy (FTIR) to determine the secondary structure of LRAP(-P) and LRAP(+P) in the absence/presence of calcium and selected mineral phases relevant to amelogenesis; i.e., hydroxyapatite (HA: an enamel crystal prototype) and (ACP: an enamel crystal precursor phase). Aqueous solutions of LRAP(-P) or LRAP(+P) were prepared with or without 7.5 mM of CaCl2 at pH 7.4. FTIR spectra of each solution were obtained using attenuated total reflectance, and amide-I peaks were analyzed to provide secondary structure information. Secondary structures of LRAP(+P) and LRAP(-P) were similarly assessed following incubation with suspensions of HA and pyrophosphate-stabilized ACP. Amide I spectra of LRAP(-P) and LRAP(+P) were found to be distinct from each other in all cases. Spectra analyses showed that LRAP(-P) is comprised mostly of random coil and β-sheet, while LRAP(+P) exhibits more β-sheet and α-helix with little random coil. With added Ca, the random coil content increased in LRAP(-P), while LRAP(+P) exhibited a decrease in α-helix components. Incubation of LRAP(-P) with HA or ACP resulted in comparable increases in β-sheet structure. Notably, however, LRAP(+P) secondary structure was more affected by ACP, primarily showing an increase in β-sheet structure, compared to that observed with added HA. These collective findings indicate that phosphorylation induces unique secondary structural changes that may enhance the functional capacity of native phosphorylated amelogenins like LRAP to stabilize an ACP precursor phase during early stages of enamel mineral formation.
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Affiliation(s)
- Hajime Yamazaki
- Center for Biomineralization, The Forsyth InstituteCambridge, MA, United States.,Department of Developmental Biology, Harvard School of Dental MedicineBoston, MA, United States
| | - Elia Beniash
- Department of Oral Biology, Center for Craniofacial Regeneration, McGowan Institute for Regenerative Medicine, University of PittsburghPittsburgh, PA, United States
| | - Yasuo Yamakoshi
- Department of Biochemistry and Molecular Biology, School of Dental Medicine, Tsurumi UniversityYokohama, Japan
| | - James P Simmer
- Department of Biologic and Materials Sciences, University of Michigan School of DentistryAnn Arbor, MI, United States
| | - Henry C Margolis
- Center for Biomineralization, The Forsyth InstituteCambridge, MA, United States.,Department of Developmental Biology, Harvard School of Dental MedicineBoston, MA, United States
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17
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Connelly C, Cicuto T, Leavitt J, Petty A, Litman A, Margolis HC, Gerdon AE. Dynamic interactions of amelogenin with hydroxyapatite surfaces are dependent on protein phosphorylation and solution pH. Colloids Surf B Biointerfaces 2016; 148:377-384. [PMID: 27632699 DOI: 10.1016/j.colsurfb.2016.09.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Revised: 08/03/2016] [Accepted: 09/07/2016] [Indexed: 10/21/2022]
Abstract
Amelogenin, the predominant extracellular matrix protein secreted by ameloblasts, has been shown to be essential for proper tooth enamel formation. In this study, amelogenin adsorption to hydroxyapatite (HAP) surfaces, a prototype for enamel mineral, has been studied using a quartz crystal microbalance (QCM) to interrogate effects of protein phosphorylation and solution pH. Dynamic flow-based experiments were conducted at pH 7.4 and 8.0 using native phosphorylated porcine amelogenin (P173) and recombinant non-phosphorylated porcine amelogenin (rP172). Loading capacities (μmol/m2) on HAP surfaces were calculated under all conditions and adsorption affinities (Kad) were calculated when Langmuir isotherm conditions appeared to be met. At pH 8.0, binding characteristics were remarkably similar for the two proteins. However, at pH 7.4 a higher affinity and lower surface loading for the phosphorylated P173 was found compared to any other set of conditions. This suggests that phosphorylated P173 adopts a more extended conformation than non-phosphorylated full-length amelogenin, occupying a larger footprint on the HAP surface. This surface-induced structural difference may help explain why P173 is a more effective inhibitor of spontaneous HAP formation in vitro than rP172. Differences in the viscoelastic properties of P173 and rP172 in the adsorbed state were also observed, consistent with noted differences in HAP binding. These collective findings provide new insight into the important role of amelogenin phosphorylation in the mechanism by which amelogenin regulates enamel crystal formation.
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Affiliation(s)
| | - Thomas Cicuto
- Emmanuel College, Department of Chemistry and Physics, Boston, MA 02115, USA
| | - Jason Leavitt
- Emmanuel College, Department of Chemistry and Physics, Boston, MA 02115, USA
| | - Alexander Petty
- Emmanuel College, Department of Chemistry and Physics, Boston, MA 02115, USA
| | - Amy Litman
- The Forsyth Institute, Center for Biomineralization, Department of Applied Oral Sciences, Cambridge, MA 02142, USA
| | - Henry C Margolis
- The Forsyth Institute, Center for Biomineralization, Department of Applied Oral Sciences, Cambridge, MA 02142, USA
| | - Aren E Gerdon
- Emmanuel College, Department of Chemistry and Physics, Boston, MA 02115, USA.
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18
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Kwak SY, Yamakoshi Y, Simmer JP, Margolis HC. MMP20 Proteolysis of Native Amelogenin Regulates Mineralization In Vitro. J Dent Res 2016; 95:1511-1517. [PMID: 27558264 DOI: 10.1177/0022034516662814] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Recent studies have shown that native phosphorylated full-length porcine amelogenin (P173) and its predominant cleavage product (P148) can inhibit spontaneous calcium phosphate formation in vitro by stabilizing an amorphous calcium phosphate (ACP) precursor phase. Since full-length amelogenin undergoes proteolysis by matrix metalloproteinase 20 (MMP20, enamelysin) soon after secretion, the present study was conducted to assess the effect of amelogenin proteolysis on calcium phosphate formation. Calcium and phosphate were sequentially added to protein solutions without and with added MMP20 (ratio = 200:1) under physiological-like conditions of ionic strength (163 mM) in 50 mM Tris-HCl (pH 7.4) at 37 °C. Protein degradation with time was assessed by gel-electrophoresis, and mineral products formed were characterized by transmission electron microscopy (TEM). MMP20 was found to cleave P173 to primarily generate P148, along with P162, P46-148, and P63/64-148. In sharp contrast, MMP20 did not cleave P148. In addition, the formation of well-aligned bundles of enamel-like hydroxyapatite (HA) crystals was promoted in the presence of P173 with added MMP20, while only ACP particles were seen in the absence of MMP20. Although P148 was found to have a somewhat lower capacity to stabilize ACP and prevent HA formation compared with P173 in the absence of MMP20, essentially no HA formation was observed in the presence of somewhat higher concentrations of P148 regardless of MMP20 addition, due to the lack of observed protein proteolysis. Present findings suggest that ACP transformation to ordered arrays of enamel crystals may be regulated in part by the proteolysis of full-length native amelogenin, while the predominant amelogenin degradation product in developing enamel (e.g., P148) primarily serves to prevent uncontrolled mineral formation during the secretory stage of amelogenesis.
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Affiliation(s)
- S Y Kwak
- Center for Biomineralization, Department of Applied Oral Sciences, The Forsyth Institute, Cambridge, MA, USA.,Department of Developmental Biology, Harvard School of Dental Medicine, Boston, MA, USA
| | - Y Yamakoshi
- Department of Biochemistry and Molecular Biology, School of Dental Medicine, Tsurumi University, Yokohama, Japan
| | - J P Simmer
- Department of Biologic and Materials Science, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - H C Margolis
- Center for Biomineralization, Department of Applied Oral Sciences, The Forsyth Institute, Cambridge, MA, USA .,Department of Developmental Biology, Harvard School of Dental Medicine, Boston, MA, USA
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19
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Boskey AL, Villarreal-Ramirez E. Intrinsically disordered proteins and biomineralization. Matrix Biol 2016; 52-54:43-59. [PMID: 26807759 DOI: 10.1016/j.matbio.2016.01.007] [Citation(s) in RCA: 88] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Revised: 01/19/2016] [Accepted: 01/19/2016] [Indexed: 01/21/2023]
Abstract
In vertebrates and invertebrates, biomineralization is controlled by the cell and the proteins they produce. A large number of these proteins are intrinsically disordered, gaining some secondary structure when they interact with their binding partners. These partners include the component ions of the mineral being deposited, the crystals themselves, the template on which the initial crystals form, and other intrinsically disordered proteins and peptides. This review speculates why intrinsically disordered proteins are so important for biomineralization, providing illustrations from the SIBLING (small integrin binding N-glycosylated) proteins and their peptides. It is concluded that the flexible structure, and the ability of the intrinsically disordered proteins to bind to a multitude of surfaces is crucial, but details on the precise-interactions, energetics and kinetics of binding remain to be determined.
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Affiliation(s)
- Adele L Boskey
- Musculoskeletal Integrity Program, Hospital for Special Surgery, New York, NY 10021, USA.
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20
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Abstract
Mature tooth enamel is acellular and does not regenerate itself. Developing technologies that rebuild tooth enamel and preserve tooth structure is therefore of great interest. Considering the importance of amelogenin protein in dental enamel formation, its ability to control apatite mineralization in vitro, and its potential to be applied in fabrication of future bio-inspired dental material this review focuses on two major subjects: amelogenin and enamel biomimetics. We review the most recent findings on amelogenin secondary and tertiary structural properties with a focus on its interactions with different targets including other enamel proteins, apatite mineral, and phospholipids. Following a brief overview of enamel hierarchical structure and its mechanical properties we will present the state-of-the-art strategies in the biomimetic reconstruction of human enamel.
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Affiliation(s)
- Qichao Ruan
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90033, USA
| | - Janet Moradian-Oldak
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90033, USA
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21
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Hendley CT, Tao J, Kunitake JAMR, De Yoreo JJ, Estroff LA. Microscopy techniques for investigating the control of organic constituents on biomineralization. MRS BULLETIN 2015; 40:480-489. [PMID: 27358507 PMCID: PMC4922639 DOI: 10.1557/mrs.2015.98] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
This article addresses recent advances in the application of microscopy techniques to characterize crystallization processes as they relate to biomineralization and bio-inspired materials synthesis. In particular, we focus on studies aimed at revealing the role organic macromolecules and functionalized surfaces play in modulating the mechanisms of nucleation and growth. In nucleation studies, we explore the use of methods such as in situ transmission electron microscopy, atomic force microscopy, and cryogenic electron microscopy to delineate formation pathways, phase stabilization, and the competing effects of free energy and kinetic barriers. In growth studies, emphasis is placed on understanding the interactions of macromolecular constituents with growing crystals and characterization of the internal structures of the resulting composite crystals using techniques such as electron tomography, atom probe tomography, and vibrational spectromicroscopy. Examples are drawn from both biological and bio-inspired synthetic systems.
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22
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Bonde J, Bülow L. Random mutagenesis of amelogenin for engineering protein nanoparticles. Biotechnol Bioeng 2015; 112:1319-26. [DOI: 10.1002/bit.25556] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Accepted: 01/27/2015] [Indexed: 01/11/2023]
Affiliation(s)
- Johan Bonde
- Division of Pure and Applied Biochemistry; Center for Applied Life Sciences; Lund University; 221 00 Lund Sweden
| | - Leif Bülow
- Division of Pure and Applied Biochemistry; Center for Applied Life Sciences; Lund University; 221 00 Lund Sweden
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23
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Ruan Q, Moradian-Oldak J. Amelogenin and enamel biomimetics. J Mater Chem B 2015. [DOI: 10.1039/c5tb00163c and 21=21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Mature tooth enamel is acellular and does not regenerate itself.
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Affiliation(s)
- Qichao Ruan
- Center for Craniofacial Molecular Biology
- Herman Ostrow School of Dentistry
- University of Southern California
- Los Angeles
- USA
| | - Janet Moradian-Oldak
- Center for Craniofacial Molecular Biology
- Herman Ostrow School of Dentistry
- University of Southern California
- Los Angeles
- USA
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24
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Bidlack FB, Huynh C, Marshman J, Goetze B. Helium ion microscopy of enamel crystallites and extracellular tooth enamel matrix. Front Physiol 2014; 5:395. [PMID: 25346697 PMCID: PMC4193210 DOI: 10.3389/fphys.2014.00395] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Accepted: 09/23/2014] [Indexed: 01/21/2023] Open
Abstract
An unresolved problem in tooth enamel studies has been to analyze simultaneously and with sufficient spatial resolution both mineral and organic phases in their three dimensional (3D) organization in a given specimen. This study aims to address this need using high-resolution imaging to analyze the 3D structural organization of the enamel matrix, especially amelogenin, in relation to forming enamel crystals. Chemically fixed hemi-mandibles from wild type mice were embedded in LR White acrylic resin, polished and briefly etched to expose the organic matrix in developing tooth enamel. Full-length amelogenin was labeled with specific antibodies and 10 nm immuno-gold. This allowed us to use and compare two different high-resolution imaging techniques for the analysis of uncoated samples. Helium ion microscopy (HIM) was applied to study the spatial organization of organic and mineral structures, while field emission scanning electron microscopy (FE-SEM) in various modes, including backscattered electron detection, allowed us to discern the gold-labeled proteins. Wild type enamel in late secretory to early maturation stage reveals adjacent to ameloblasts a lengthwise parallel alignment of the enamel matrix proteins, including full-length amelogenin proteins, which then transitions into a more heterogeneous appearance with increasing distance from the mineralization front. The matrix adjacent to crystal bundles forms a smooth and lacey sheath, whereas between enamel prisms it is organized into spherical components that are interspersed with rod-shaped protein. These findings highlight first, that the heterogeneous organization of the enamel matrix can be visualized in mineralized en bloc samples. Second, our results illustrate that the combination of these techniques is a powerful approach to elucidate the 3D structural organization of organic matrix molecules in mineralizing tissue in nanometer resolution.
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Affiliation(s)
- Felicitas B Bidlack
- Department of Mineralized Tissue Biology, Forsyth Institute Cambridge, MA, USA ; Department of Developmental Biology, Harvard School of Dental Medicine Boston, MA, USA
| | - Chuong Huynh
- Carl Zeiss Microscopy LLC, One Corporation Way Peabody, MA, USA
| | | | - Bernhard Goetze
- Carl Zeiss Microscopy LLC, One Corporation Way Peabody, MA, USA
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25
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Margolis HC, Kwak SY, Yamazaki H. Role of mineralization inhibitors in the regulation of hard tissue biomineralization: relevance to initial enamel formation and maturation. Front Physiol 2014; 5:339. [PMID: 25309443 PMCID: PMC4159985 DOI: 10.3389/fphys.2014.00339] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Accepted: 08/19/2014] [Indexed: 01/09/2023] Open
Abstract
Vertebrate mineralized tissues, i.e., enamel, dentin, cementum, and bone, have unique hierarchical structures and chemical compositions. Although these tissues are similarly comprised of a crystalline calcium apatite mineral phase and a protein component, they differ with respect to crystal size and shape, level and distribution of trace mineral ions, the nature of the proteins present, and their relative proportions of mineral and protein components. Despite apparent differences, mineralized tissues are similarly derived by highly concerted extracellular processes involving matrix proteins, proteases, and mineral ion fluxes that collectively regulate the nucleation, growth and organization of forming mineral crystals. Nature, however, provides multiple ways to control the onset, rate, location, and organization of mineral deposits in developing mineralized tissues. Although our knowledge is quite limited in some of these areas, recent evidence suggests that hard tissue formation is, in part, controlled through the regulation of specific molecules that inhibit the mineralization process. This paper addresses the role of mineralization inhibitors in the regulation of biological mineralization with emphasis on the relevance of current findings to the process of amelogenesis. Mineralization inhibitors can also serve to maintain driving forces for calcium phosphate precipitation and prevent unwanted mineralization. Recent evidence shows that native phosphorylated amelogenins have the capacity to prevent mineralization through the stabilization of an amorphous calcium phosphate precursor phase, as observed in vitro and in developing teeth. Based on present findings, the authors propose that the transformation of initially formed amorphous mineral deposits to enamel crystals is an active process associated with the enzymatic processing of amelogenins. Such processing may serve to control both initial enamel crystal formation and subsequent maturation.
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Affiliation(s)
- Henry C. Margolis
- Department of Applied Oral Sciences, Center for Biomineralization, The Forsyth InstituteCambridge, MA, USA
- Department of Developmental Biology, Harvard School of Dental MedicineBoston, MA, USA
| | - Seo-Young Kwak
- Department of Applied Oral Sciences, Center for Biomineralization, The Forsyth InstituteCambridge, MA, USA
- Department of Developmental Biology, Harvard School of Dental MedicineBoston, MA, USA
| | - Hajime Yamazaki
- Department of Applied Oral Sciences, Center for Biomineralization, The Forsyth InstituteCambridge, MA, USA
- Department of Developmental Biology, Harvard School of Dental MedicineBoston, MA, USA
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26
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Understanding nanocalcification: a role suggested for crystal ghosts. Mar Drugs 2014; 12:4231-46. [PMID: 25056630 PMCID: PMC4113825 DOI: 10.3390/md12074231] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2014] [Revised: 07/07/2014] [Accepted: 07/08/2014] [Indexed: 12/17/2022] Open
Abstract
The present survey deals with the initial stage of the calcification process in bone and other hard tissues, with special reference to the organic-inorganic relationship and the transformation that the early inorganic particles undergo as the process moves towards completion. Electron microscope studies clearly exclude the possibility that these particles might be crystalline structures, as often believed, by showing that they are, instead, organic-inorganic hybrids, each comprising a filamentous organic component (the crystal ghost) made up of acidic proteins. The hypothesis is suggested that the crystal ghosts bind and stabilize amorphous calcium phosphate and that their subsequent degradation allows the calcium phosphate, once released, to acquire a hydroxyapatite, crystal-like organization. A conclusive view of the mechanism of biological calcification cannot yet be proposed; even so, however, the role of crystal ghosts as a template of the structures usually called “crystallites” is a concept that has gathered increasing support and can no longer be disregarded.
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