Lysosomal Protease Expression in Mature Enamel

Tye, Coralee E.; Lorenz, Rachel L.; Bartlett, John D.

doi:10.1159/000151431

Cited by 13 publications

(9 citation statements)

References 23 publications

(15 reference statements)

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“…The most prominent enzyme in our proteomics analysis of mouse molar enamel organs was the lysosomal cysteine protease cathepsin B, which peaked on day 4 postnatal. Cathepsin B is an important lysosomal enzyme of the enamel matrix (Al Kawas et al, 1996 ; Tye et al, 2009 ) that has been shown to enhance the activity of other proteases such as metalloproteinases and cathepsin D (Hammarström et al, 1971 ; Blair et al, 1989 ). As such, cathepsin B may promote the proteolytic degradation of the enamel matrix by enhancing the activity of MMP20 and cathepsin D.…”

Section: Discussionmentioning

confidence: 99%

Integrative Temporo-Spatial, Mineralogic, Spectroscopic, and Proteomic Analysis of Postnatal Enamel Development in Teeth with Limited Growth

et al. 2017

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Tooth amelogenesis is a complex process beginning with enamel organ cell differentiation and enamel matrix secretion, transitioning through changes in ameloblast polarity, cytoskeletal, and matrix organization, that affects crucial biomineralization events such as mineral nucleation, enamel crystal growth, and enamel prism organization. Here we have harvested the enamel organ including the pliable enamel matrix of postnatal first mandibular mouse molars during the first 8 days of tooth enamel development to conduct a step-wise cross-sectional analysis of the changes in the mineral and protein phase. Mineral phase diffraction pattern analysis using single-crystal, powder sample X-ray diffraction analysis indicated conversion of calcium phosphate precursors to partially fluoride substituted hydroxyapatite from postnatal day 4 (4 dpn) onwards. Attenuated total reflectance spectra (ATR) revealed a substantial elevation in phosphate and carbonate incorporation as well as structural reconfiguration between postnatal days 6 and 8. Nanoscale liquid chromatography coupled with tandem mass spectrometry (nanoLC-MS/MS) demonstrated highest protein counts for ECM/cell surface proteins, stress/heat shock proteins, and alkaline phosphatase on postnatal day 2, high counts for ameloblast cytoskeletal proteins such as tubulin β5, tropomyosin, β-actin, and vimentin on postnatal day 4, and elevated levels of cofilin-1, calmodulin, and peptidyl-prolyl cis-trans isomerase on day 6. Western blot analysis of hydrophobic enamel proteins illustrated continuously increasing amelogenin levels from 1 dpn until 8 dpn, while enamelin peaked on days 1 and 2 dpn, and ameloblastin on days 1–5 dpn. In summary, these data document the substantial changes in the enamel matrix protein and mineral phase that take place during postnatal mouse molar amelogenesis from a systems biological perspective, including (i) relatively high levels of matrix protein expression during the early secretory stage on postnatal day 2, (ii) conversion of calcium phosphates to apatite, peak protein folding and stress protein counts, and increased cytoskeletal protein levels such as actin and tubulin on day 4, as well as (iii) secondary structure changes, isomerase activity, highest amelogenin levels, and peak phosphate/carbonate incorporation between postnatal days 6 and 8. Together, this study provides a baseline for a comprehensive understanding of the mineralogic and proteomic events that contribute to the complexity of mammalian tooth enamel development.

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Section: Discussionmentioning

confidence: 99%

Integrative Temporo-Spatial, Mineralogic, Spectroscopic, and Proteomic Analysis of Postnatal Enamel Development in Teeth with Limited Growth

et al. 2017

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“…In addition to the upregulation of all AP‐2 subunit transcripts during enamel maturation, many lysosome/endosome–specific transcripts are also upregulated, most notably Lamp1, Cd63, Cd68, Atp6v1b2, and Ctsk. In an earlier study by Tye and colleagues124 qPCR was used to demonstrate that many of the lysosomal proteases, including Ctsk, Ctss, Dpp7, and Tpp1, were expressed in mouse mature enamel organ cells; however, the changing expression levels at various stages of amelogenesis were not investigated 124. We have also investigated the expression of Clcn7, and other CLC family members, in the enamel organ of secretory stage and maturation stage enamel organ cells.…”

Section: Discussionmentioning

confidence: 99%

Adaptor protein complex 2–mediated, clathrin-dependent endocytosis, and related gene activities, are a prominent feature during maturation stage amelogenesis

Lacruz

Brookes

Wen

et al. 2012

Journal of Bone and Mineral Research

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Molecular events defining enamel matrix removal during amelogenesis are poorly understood. Early reports have suggested that adaptor proteins (AP) participate in ameloblast-mediated endocytosis. Enamel formation involves the secretory and maturation stages, with an increase in resorptive function during the latter. Here, using real time PCR, we show that the expression of clathrin and adaptor protein subunits are up-regulated in maturation stage rodent enamel organ cells. AP-2 is the most up-regulated of the four distinct adaptor protein complexes. Immunolocalization confirms the presence of AP-2 and clathrin in ameloblasts with strongest reactivity at the apical pole. These data suggest that the resorptive functions of enamel cells involve AP-2 mediated, clathrin dependent endocytosis, thus implying the likelihood of a specific membrane-bound receptor(s) of enamel matrix protein debris. The mRNA expression of other endocytosis-related gene products is also up-regulated during maturation including: lysosomal-associated membrane protein 1 (Lamp1), cluster of differentiation 63 and 68 (Cd63 and Cd68), ATPase, H+ transporting, lysosomal V0 subunit D2 (Atp6v0d2), ATPase, H+ transporting, lysosomal V1 subunit B2 (Atp6v1b2), chloride channel, voltage-sensitive 7 (Clcn7) and cathepsin K (Ctsk). Immunohistological data confirms the expression of a number of these proteins in maturation stage ameloblasts. The enamel of Cd63-null mice was also examined. Despite increased mRNA and protein expression in the enamel organ during maturation, the enamel of Cd63-null mice appeared normal. This may suggest inherent functional redundancies between Cd63 and related gene products, such as Lamp1 and Cd68. Ameloblast-like LS8 cells treated with the enamel matrix protein complex Emdogain® showed up-regulation of AP-2 and clathrin subunits, further supporting the existence of a membrane-bound receptor regulated pathway for the endocytosis of enamel matrix proteins. These data together define an endocytotic pathway likely used by ameloblasts to remove the enamel matrix during enamel maturation.

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“…Enamel without Klk4 has normal thickness and typical prismatic structure but there is a delay in hardening and a defect in mineralization near the DEJ is more apparent. The less severe phenotype might well be the result of a compensatory action of a third enzyme (143, 148, 158). …”

Section: The Extracellular Protein Matrixmentioning

confidence: 99%

Protein-mediated Enamel Mineralization

2012

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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 principals 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 as well as 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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Lysosomal Protease Expression in Mature Enamel

Cited by 13 publications

References 23 publications

Integrative Temporo-Spatial, Mineralogic, Spectroscopic, and Proteomic Analysis of Postnatal Enamel Development in Teeth with Limited Growth

Integrative Temporo-Spatial, Mineralogic, Spectroscopic, and Proteomic Analysis of Postnatal Enamel Development in Teeth with Limited Growth

Adaptor protein complex 2–mediated, clathrin-dependent endocytosis, and related gene activities, are a prominent feature during maturation stage amelogenesis

Protein-mediated Enamel Mineralization

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