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Mergelsberg ST, Kim H, Buchko GW, Ginovska B. SAXS of murine amelogenin identifies a persistent dimeric species from pH 5.0 to 8.0. J Struct Biol 2024:108131. [PMID: 39368677 DOI: 10.1016/j.jsb.2024.108131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/07/2024]
Abstract
Amelogenin is an intrinsically disordered protein essential to tooth enamel formation in mammals. Using the latest, advanced small angle X-ray scattering (SAXS) capabilities at synchrotrons and computational models, we revisited measuring the quaternary structure of murine amelogenin as a function of pH and phosphorylation at Ser-16. The SAXS data shows that at the pH extremes, amelogenin exists as an extended monomer at pH 3.0 (Rg = 38.4 Å) and nanospheres at pH 8.0 (Rg = 84.0 Å), consistent with multiple previous observations. At pH 5.0 and above there was no evidence for a significant population of monomeric species. Instead, at pH 5.0 ∼ 80% of the population is a heterogenous dimeric species that increases to ∼ 100% at pH 5.5. The dimer population was observed at all pH > 5 conditions in dynamic equilibrium with a species in the pentamer range at pH < 6.5 and nanospheres at pH 8.0. At pH 8.0 ∼ 40% of the amelogenin remained in the dimeric state. In general, serine-16 phosphorylation of amelogenin appears to modestly stabilize the population of the dimeric species.
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Affiliation(s)
| | - Hoshin Kim
- Pacific Northwest National Laboratory, Richland, WA 99354, USA
| | - Garry W Buchko
- Pacific Northwest National Laboratory, Richland, WA 99354, USA; School of Molecular Biosciences, Washington State University, Pullman, Washington, USA
| | - Bojana Ginovska
- Pacific Northwest National Laboratory, Richland, WA 99354, USA.
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2
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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 PMCID: PMC11363587 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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3
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Zhang Y, Jin T, Zhu W, Pandya M, Gopinathan G, Allen M, Reed D, Keiderling T, Liao X, Diekwisch TGH. Highly acidic pH facilitates enamel protein self-assembly, apatite crystal growth and enamel protein interactions in the early enamel matrix. Front Physiol 2022; 13:1019364. [PMID: 36569763 PMCID: PMC9772882 DOI: 10.3389/fphys.2022.1019364] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Accepted: 11/22/2022] [Indexed: 12/13/2022] Open
Abstract
Tooth enamel develops within a pH sensitive amelogenin-rich protein matrix. The purpose of the present study is to shed light on the intimate relationship between enamel matrix pH, enamel protein self-assembly, and enamel crystal growth during early amelogenesis. Universal indicator dye staining revealed highly acidic pH values (pH 3-4) at the exocytosis site of secretory ameloblasts. When increasing the pH of an amelogenin solution from pH 5 to pH 7, there was a gradual increase in subunit compartment size from 2 nm diameter subunits at pH 5 to a stretched configuration at pH6 and to 20 nm subunits at pH 7. HSQC NMR spectra revealed that the formation of the insoluble amelogenin self-assembly structure at pH6 was critically mediated by at least seven of the 11 histidine residues of the amelogenin coil domain (AA 46-117). Comparing calcium crystal growth on polystyrene plates, crystal length was more than 20-fold elevated at pH 4 when compared to crystals grown at pH 6 or pH 7. To illustrate the effect of pH on enamel protein self-assembly at the site of initial enamel formation, molar teeth were immersed in phosphate buffer at pH4 and pH7, resulting in the formation of intricate berry tree-like assemblies surrounding initial enamel crystal assemblies at pH4 that were not evident at pH7 nor in citrate buffer. Amelogenin and ameloblastin enamel proteins interacted at the secretory ameloblast pole and in the initial enamel layer, and co-immunoprecipitation studies revealed that this amelogenin/ameloblastin interaction preferentially takes place at pH 4-pH 4.5. Together, these studies highlight the highly acidic pH of the very early enamel matrix as an essential contributing factor for enamel protein structure and self-assembly, apatite crystal growth, and enamel protein interactions.
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Affiliation(s)
- Youbin Zhang
- Department of Oral Biology, University of Illinois at Chicago, Dallas, Illinois, United States
| | - Tianquan Jin
- Department of Oral Biology, University of Illinois at Chicago, Dallas, Illinois, United States
| | - Weiying Zhu
- Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois, United States
| | - Mirali Pandya
- Center for Craniofacial Research and Diagnosis, Texas A and M College of Dentistry, Dallas, Texas, United States
| | - Gokul Gopinathan
- Center for Craniofacial Research and Diagnosis, Texas A and M College of Dentistry, Dallas, Texas, United States
| | - Michael Allen
- Department of Medicine, University of Chicago, Chicago, Illinois, United States
| | - David Reed
- Department of Oral Biology, University of Illinois at Chicago, Dallas, Illinois, United States
| | - Timothy Keiderling
- Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois, United States,*Correspondence: Timothy Keiderling, ; Xiubei Liao, ; Thomas G. H. Diekwisch,
| | - Xiubei Liao
- Department of Biochemistry, University of Illinois at Chicago, Chicago, Illinois, United States,*Correspondence: Timothy Keiderling, ; Xiubei Liao, ; Thomas G. H. Diekwisch,
| | - Thomas G. H. Diekwisch
- Department of Oral Biology, University of Illinois at Chicago, Dallas, Illinois, United States,Center for Craniofacial Research and Diagnosis, Texas A and M College of Dentistry, Dallas, Texas, United States,*Correspondence: Timothy Keiderling, ; Xiubei Liao, ; Thomas G. H. Diekwisch,
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Amelogenin-Derived Peptides in Bone Regeneration: A Systematic Review. Int J Mol Sci 2021; 22:ijms22179224. [PMID: 34502132 PMCID: PMC8431254 DOI: 10.3390/ijms22179224] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 08/03/2021] [Accepted: 08/11/2021] [Indexed: 11/17/2022] Open
Abstract
Amelogenins are enamel matrix proteins currently used to treat bone defects in periodontal surgery. Recent studies have highlighted the relevance of amelogenin-derived peptides, named LRAP, TRAP, SP, and C11, in bone tissue engineering. Interestingly, these peptides seem to maintain or even improve the biological activity of the full-length protein, which has received attention in the field of bone regeneration. In this article, the authors combined a systematic and a narrative review. The former is focused on the existing scientific evidence on LRAP, TRAP, SP, and C11's ability to induce the production of mineralized extracellular matrix, while the latter is concentrated on the structure and function of amelogenin and amelogenin-derived peptides. Overall, the collected data suggest that LRAP and SP are able to induce stromal stem cell differentiation towards osteoblastic phenotypes; specifically, SP seems to be more reliable in bone regenerative approaches due to its osteoinduction and the absence of immunogenicity. However, even if some evidence is convincing, the limited number of studies and the scarcity of in vivo studies force us to wait for further investigations before drawing a solid final statement on the real potential of amelogenin-derived peptides in bone tissue engineering.
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5
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Geng S, Lei Y, Snead ML. Minimal amelogenin domain for enamel formation. JOM (WARRENDALE, PA. : 1989) 2021; 73:1696-1704. [PMID: 34456537 PMCID: PMC8386916 DOI: 10.1007/s11837-021-04687-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Accepted: 03/31/2021] [Indexed: 06/13/2023]
Abstract
Amelogenin is the most abundant matrix protein guiding hydroxyapatite formation in enamel, the durable bioceramic tissue that covers vertebrate teeth. Here, we sought to refine structure-function for an amelogenin domain based on in vitro data showing a 42 amino acid amelogenin-derived peptide (ADP7) mimicked formation of hydroxyapatite similar to that observed for the full-length mouse 180 amino acid protein. In mice, we used CRISPR-Cas9 to express only ADP7 by the native amelogenin promoter. Analysis revealed ADP7 messenger RNA expression in developing mouse teeth with the formation of a thin layer of enamel. In vivo, ADP7 peptide partially replaced the function of the full-length amelogenin protein and its several protein isoforms. Protein structure-function relationships identified through in vitro assays can be deployed in whole model animals using CRISPR-Cas9 to validate function of a minimal protein domain to be translated for clinical use as an enamel biomimetic.
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Affiliation(s)
- Shuhui Geng
- The University of Southern California, Herman Ostrow School of Dentistry of USC, Center for Craniofacial Molecular Biology, Los Angeles, CA 90033
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China, 201210
| | - Yaping Lei
- The University of Southern California, Herman Ostrow School of Dentistry of USC, Center for Craniofacial Molecular Biology, Los Angeles, CA 90033
- Biology and Biologic Engineering, California Institute of Technology, Pasadena, CA 91125
| | - Malcolm L Snead
- The University of Southern California, Herman Ostrow School of Dentistry of USC, Center for Craniofacial Molecular Biology, Los Angeles, CA 90033
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6
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Ali S, Farooq I. A Review of the Role of Amelogenin Protein in Enamel Formation and Novel Experimental Techniques to Study its Function. Protein Pept Lett 2019; 26:880-886. [DOI: 10.2174/0929866526666190731120018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2019] [Revised: 06/06/2019] [Accepted: 06/10/2019] [Indexed: 11/22/2022]
Abstract
:Amelognein protein plays a vital role in the formation and mineralization of enamel matrix. Amelogenin structure is complex in nature and researchers have studied it with different experimental techniques. Considering its important role, there is a need to understand this important protein, which has been discussed in detail in this review. In addition, various experimental techniques to study amelogenin protein used previously have been tackled along with their advantages and disadvantages. A selection of 67 relevant articles/book chapters was included in this study. The review concluded that amelogenins act as nanospheres or spacers for the growth of enamel crystals. Various experimental techniques can be used to study amelogenins, however, their advantages and drawbacks should be kept in mind before performing analysis.
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Affiliation(s)
- Saqib Ali
- Department of Biomedical Dental Sciences, College of Dentistry, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia
| | - Imran Farooq
- Department of Biomedical Dental Sciences, College of Dentistry, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia
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7
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Chen L, Brigstock DR. Cellular or Exosomal microRNAs Associated with CCN Gene Expression in Liver Fibrosis. Methods Mol Biol 2018; 1489:465-480. [PMID: 27734397 DOI: 10.1007/978-1-4939-6430-7_38] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Liver fibrosis occurs during chronic injury and represents, in large part, an exaggerated matrigenic output by hepatic stellate cells (HSCs) which become activated as a result of injury-induced signaling pathways in parenchymal and inflammatory cells (hepatocytes, macrophages, etc.). The molecular components in these pathways (e.g., CCN proteins) are modulated by transcription factors as well as by factors such as microRNAs (miRs) that act posttranscriptionally. MiRs are small (~23 nt) noncoding RNAs that regulate gene expression by specifically interacting with the 3' untranslated region (UTR) of target gene mRNA to repress translation or enhance mRNA cleavage. As well as acting in their cells of production, miRs (and other cellular constituents such as mRNAs and proteins) can be liberated from their cells of origin in nanovesicular membrane exosomes, which traverse the intercellular spaces, and can be delivered to neighboring cells into which they release their molecular payload, causing alterations in gene expression in the target cells. Here we summarize some of the experimental approaches for studying miR action and exosomal trafficking between hepatic cells. Insights into the mechanisms involved will yield new information about how hepatic fibrosis is regulated and, further, may identify new points of therapeutic intervention.
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Affiliation(s)
- Li Chen
- The Research Institute at Nationwide Children's Hospital, Research Building 2, 700 Children's Drive, Columbus, OH, 43205, USA.
| | - David R Brigstock
- The Research Institute at Nationwide Children's Hospital, Research Building 2, 700 Children's Drive, Columbus, OH, 43205, USA.,Molecular, Cellular, and Developmental Biology Program, The Ohio State University, Columbus, OH, 43212, USA.,Department of Surgery, Wexner Medical Center, The Ohio State University, Columbus, OH, 43212, USA
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8
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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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9
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TGF-β1 autocrine signalling and enamel matrix components. Sci Rep 2016; 6:33644. [PMID: 27633089 PMCID: PMC5025654 DOI: 10.1038/srep33644] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Accepted: 08/31/2016] [Indexed: 01/03/2023] Open
Abstract
Transforming growth factor-β1 (TGF-β1) is present in porcine enamel extracts and is critical for proper mineralization of tooth enamel. Here, we show that the mRNA of latent TGF-β1 is expressed throughout amelogenesis. Latent TGF-β1 is activated by matrix metalloproteinase 20 (MMP20), coinciding with amelogenin processing by the same proteinase. Activated TGF-β1 binds to the major amelogenin cleavage products, particularly the neutral-soluble P103 amelogenin, to maintain its activity. The P103 amelogenin-TGF-β1 complex binds to TGFBR1 to induce TGF-β1 signalling. The P103 amelogenin-TGF-β1 complex is slowly cleaved by kallikrein 4 (KLK4), which is secreted into the transition- and maturation-stage enamel matrix, thereby reducing TGF-β1 activity. To exert the multiple biological functions of TGF-β1 for amelogenesis, we propose that TGF-β1 is activated or inactivated by MMP20 or KLK4 and that the amelogenin cleavage product is necessary for the in-solution mobility of TGF-β1, which is necessary for binding to its receptor on ameloblasts and retention of its activity.
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10
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Patel A, Sant S. Hypoxic tumor microenvironment: Opportunities to develop targeted therapies. Biotechnol Adv 2016; 34:803-812. [PMID: 27143654 PMCID: PMC4947437 DOI: 10.1016/j.biotechadv.2016.04.005] [Citation(s) in RCA: 143] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 04/13/2016] [Accepted: 04/28/2016] [Indexed: 01/18/2023]
Abstract
In recent years, there has been great progress in the understanding of tumor biology and its surrounding microenvironment. Solid tumors create regions with low oxygen levels, generally termed as hypoxic regions. These hypoxic areas offer a tremendous opportunity to develop targeted therapies. Hypoxia is not a random by-product of the cellular milieu due to uncontrolled tumor growth; rather it is a constantly evolving participant in overall tumor growth and fate. This article reviews current trends and recent advances in drug therapies and delivery systems targeting hypoxia in the tumor microenvironment. In the first part, we give an account of important physicochemical changes and signaling pathways activated in the hypoxic microenvironment. This is then followed by various treatment strategies including hypoxia-sensitive signaling pathways and approaches to develop hypoxia-targeted drug delivery systems.
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Affiliation(s)
- Akhil Patel
- Department of Pharmaceutical Sciences, University of Pittsburgh School of Pharmacy, United States
| | - Shilpa Sant
- Department of Pharmaceutical Sciences, University of Pittsburgh School of Pharmacy, United States; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15261, United States; McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, PA 15261, United States.
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11
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Apicella A, Heunemann P, Bolisetty S, Marascio M, Gemperli Graf A, Garamszegi L, Mezzenga R, Fischer P, Plummer CJ, Månson JA. The Influence of Arginine on the Response of Enamel Matrix Derivative (EMD) Proteins to Thermal Stress: Towards Improving the Stability of EMD-Based Products. PLoS One 2015; 10:e0144641. [PMID: 26670810 PMCID: PMC4699454 DOI: 10.1371/journal.pone.0144641] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Accepted: 10/07/2015] [Indexed: 11/19/2022] Open
Abstract
In a current procedure for periodontal tissue regeneration, enamel matrix derivative (EMD), which is the active component, is mixed with a propylene glycol alginate (PGA) gel carrier and applied directly to the periodontal defect. Exposure of EMD to physiological conditions then causes it to precipitate. However, environmental changes during manufacture and storage may result in modifications to the conformation of the EMD proteins, and eventually premature phase separation of the gel and a loss in therapeutic effectiveness. The present work relates to efforts to improve the stability of EMD-based formulations such as Emdogain™ through the incorporation of arginine, a well-known protein stabilizer, but one that to our knowledge has not so far been considered for this purpose. Representative EMD-buffer solutions with and without arginine were analyzed by 3D-dynamic light scattering, UV-Vis spectroscopy, transmission electron microscopy and Fourier transform infrared spectroscopy at different acidic pH and temperatures, T, in order to simulate the effect of pH variations and thermal stress during manufacture and storage. The results provided evidence that arginine may indeed stabilize EMD against irreversible aggregation with respect to variations in pH and T under these conditions. Moreover, stopped-flow transmittance measurements indicated arginine addition not to suppress precipitation of EMD from either the buffers or the PGA gel carrier when the pH was raised to 7, a fundamental requirement for dental applications.
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Affiliation(s)
- Alessandra Apicella
- Laboratoire des Technologie des Composites et Polymères (LTC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Peggy Heunemann
- Food Process Engineering, Institute of Food, Nutrition and Health, ETH Zurich, 8092 Zurich, Switzerland
| | - Sreenath Bolisetty
- Food and Soft Materials Science, Institute of Food, Nutrition and Health, ETH Zurich, 8092 Zurich, Switzerland
| | - Matteo Marascio
- Laboratoire des Technologie des Composites et Polymères (LTC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | | | | | - Raffaele Mezzenga
- Food and Soft Materials Science, Institute of Food, Nutrition and Health, ETH Zurich, 8092 Zurich, Switzerland
| | - Peter Fischer
- Food Process Engineering, Institute of Food, Nutrition and Health, ETH Zurich, 8092 Zurich, Switzerland
- * E-mail: (PF); (CJP)
| | - Christopher J. Plummer
- Laboratoire des Technologie des Composites et Polymères (LTC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
- * E-mail: (PF); (CJP)
| | - Jan-Anders Månson
- Laboratoire des Technologie des Composites et Polymères (LTC), Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
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12
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CryoTEM study of effects of phosphorylation on the hierarchical assembly of porcine amelogenin and its regulation of mineralization in vitro. J Struct Biol 2013; 183:250-7. [PMID: 23707542 DOI: 10.1016/j.jsb.2013.05.011] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2013] [Revised: 04/22/2013] [Accepted: 05/15/2013] [Indexed: 11/21/2022]
Abstract
Amelogenin, the major extracellular enamel matrix protein, plays a critical role in regulating the growth and organization of enamel. Assembly and mineralization of full-length native (P173) and recombinant (rP172) porcine amelogenins were studied by cryogenic Transmission Electron Microscopy (cryoTEM). The cryoTEM revealed that both native and recombinant porcine amelogenins undergo step-wise self-assembly. Although the overall structural organization of P173 and rP172 oligomers was similar and resembled oligomers of murine recombinant amelogenin rM179, there were subtle differences suggesting that a single phosphorylated serine present in P173 might affect amelogenin self-assembly. Our mineralization studies demonstrated that both P173 and rP172 oligomers stabilize initial mineral clusters. Importantly, however, rP172 regulated the organization of initial mineral clusters into linear chains and guided the formation of parallel arrays of elongated mineral particles, which are the hallmark of enamel structural organization. These results are similar to those obtained previously using full-length recombinant murine amelogenin (Fang et al., 2011a). In contrast to that seen with rP172, phosphorylated P173 strongly inhibits mineralization for extended periods of time. We propose that these differences might be due to the differences in the structural organization and charge distribution between P173 and rP172. Overall our studies indicate that self-assembly of amelogenin and the mechanisms of its control over mineralization might be universal across different mammalian species. Our data also provide new insight into the effect of phosphorylation on amelogenin self-assembly and its regulation of mineralization.
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13
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Beniash E, Simmer JP, Margolis HC. Structural changes in amelogenin upon self-assembly and mineral interactions. J Dent Res 2012; 91:967-72. [PMID: 22933608 DOI: 10.1177/0022034512457371] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Amelogenin, the major protein of forming dental enamel, plays a crucial role in the biomineralization of this tissue. Amelogenin is soluble at low pH and self-assembles to form higher order structures at physiological pH. To understand the mechanisms of its assembly and interactions with calcium phosphate mineral, we conducted FTIR spectroscopy (FTIRS) studies of pH-triggered assembly of recombinant porcine amelogenin rP172 and its interactions with mature hydroxyapatite and apatitic mineral formed in situ. Analysis of our data indicated that rP172 at pH 3.0 exists in an unfolded disordered state, while increases in pH led to structural ordering, manifested by increases in intra- and intermolecular β-sheet structures and a decrease in random coil and β-turns. Amelogenin assembled at pH 7.2 was also found to contain large portions of extended intramolecular β-sheet and PPII. These FTIRS findings are consistent with those previously obtained with other techniques, thus verifying the validity of our experimental approach. Interestingly, interactions with mineral led to a reduction in protein structural organization. The findings obtained show that amelogenin has intrinsic structural flexibility to accommodate interactions with both forming and mature calcium phosphate mineral phases, providing new insights into the potential importance of amelogenin-mineral interactions in enamel biomineralization.
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Affiliation(s)
- E Beniash
- Department of Oral Biology, University of Pittsburgh, School of Dental Medicine, Center for Craniofacial Regeneration, McGowan Institute for Regenerative Medicine, Bioengineering, Swanson School of Engineering, 589 Salk Hall, 3501 Terrace Street, Pittsburgh, PA 15261, USA.
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Abstract
Enamel is a hard nanocomposite bioceramic with significant resilience that protects the mammalian tooth from external physical and chemical damages. The remarkable mechanical properties of enamel are associated with its hierarchical structural organization and its thorough connection with underlying dentin. This dynamic mineralizing system offers scientists a wealth of information that allows the study of basic principels of organic matrix-mediated biomineralization and can potentially be utilized in the fields of material science and engineering for development and design of biomimetic materials. This chapter will provide a brief overview of enamel hierarchical structure and properties and the process and stages of amelogenesis. Particular emphasis is given to current knowledge of extracellular matrix protein and proteinases, and the structural chemistry of the matrix components and their putative functions. The chapter will conclude by discussing the potential of enamel for regrowth.
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Affiliation(s)
- Janet Moradian-Oldak
- Center for Craniofacial Molecular Biology, Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90033, USA.
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Chen CL, Bromley KM, Moradian-Oldak J, DeYoreo JJ. In situ AFM study of amelogenin assembly and disassembly dynamics on charged surfaces provides insights on matrix protein self-assembly. J Am Chem Soc 2011; 133:17406-13. [PMID: 21916473 PMCID: PMC3427831 DOI: 10.1021/ja206849c] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Because self-assembly of matrix proteins is a key step in hard tissue mineralization, developing an understanding of the assembly pathways and underlying mechanisms is likely to be important for successful hard tissue engineering. While many studies of matrix protein assembly have been performed on bulk solutions, in vivo these proteins are likely to be in contact with charged biological surfaces composed of lipids, proteins, or minerals. Here we report the results of an in situ atomic force microscopy (AFM) study of self-assembly by amelogenin--the principal protein of the extracellular matrix in developing enamel--in contact with two different charged substrates: hydrophilic negatively charged bare mica and positively charged 3-aminopropyl triethoxysilane (APS) silanized mica. First we demonstrate an AFM-based protocol for determining the size of both amelogenin monomers and oligomers. Using this protocol, we find that, although amelogenin exists primarily as ~26 nm in diameter nanospheres in bulk solution at a pH of 8.0 studied by dynamic light scattering, it behaves dramatically differently upon interacting with charged substrates at the same pH and exhibits complex substrate-dependent assembly pathways and dynamics. On positively charged APS-treated mica surfaces, amelogenin forms a relatively uniform population of decameric oligomers, which then transform into two main populations: higher-order assemblies of oligomers and amelogenin monomers, while on negatively charged bare mica surfaces, it forms a film of monomers that exhibits tip-induced desorption and patterning. The present study represents a successful attempt to identify the size of amelogenin oligomers and to directly monitor assembly and disassembly dynamics on surfaces. The findings have implications for amelogenin-controlled calcium phosphate mineralization in vitro and may offer new insights into in vivo self-assembly of matrix proteins as well as their control over hard tissue formation.
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Affiliation(s)
- Chun-Long Chen
- The Molecular Foundry, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, United States
| | - Keith M. Bromley
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90033, United States
| | - Janet Moradian-Oldak
- Center for Craniofacial Molecular Biology, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, CA 90033, United States
| | - James J. DeYoreo
- The Molecular Foundry, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, United States
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