Amelogenin Nanoparticles in Suspension: Deviations from Spherical Shape and pH-Dependent Aggregation

Aichmayer, Barbara; Bidlack, Felicitas B.; Gilow, Christoph; Simmer, James P.; Yamakoshi, Yasuo; Emmerling, Franziska; Margolis, Henry C.; Fratzl, Peter

doi:10.1021/bm900983b

Cited by 33 publications

(59 citation statements)

References 44 publications

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“…This difference in effects on mineralization may again be related to prior findings showing that truncated P148 and its recombinant analogues from pig (rP147) and mouse (rM166) form random protein assemblies (Fang et al 2011;Kwak et al 2011;Wiedemann-Bidlack et al 2011). In contrast, full-length P173, rP172, and rM179 (from mouse) undergo a stepwise hierarchical self-assembly process from monomers to nanospheres (Fang et al 2011;Fang et al 2013) to more highly ordered chain-like structures (Aichmayer et al 2005;Aichmayer et al 2010;Wiedemann-Bidlack et al 2011).…”

Section: Discussionmentioning

confidence: 56%

MMP20 Proteolysis of Native Amelogenin Regulates Mineralization In Vitro

et al. 2016

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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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Section: Discussionmentioning

confidence: 56%

MMP20 Proteolysis of Native Amelogenin Regulates Mineralization In Vitro

et al. 2016

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“…1 B and H, and Fig. S3 A-D), which were identified as amelogenin nanospheres (12)(13)(14). A few short chains of the nanospheres were also observed at this stage ( Fig.…”

Section: Resultsmentioning

confidence: 79%

Hierarchical self-assembly of amelogenin and the regulation of biomineralization at the nanoscale

Fang

Conway

Margolis³

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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Enamel is a highly organized hierarchical nanocomposite, which consists of parallel arrays of elongated apatitic crystallites forming an intricate three-dimensional microstructure. Amelogenin, the major extracellular matrix protein of dental enamel, regulates the formation of these crystalline arrays via cooperative interactions with forming mineral phase. Using cryoelectron microscopy, we demonstrate that amelogenin undergoes stepwise hierarchical self-assembly. Furthermore, our results indicate that interactions between amelogenin hydrophilic C-terminal telopeptides are essential for oligomer formation and for subsequent steps of hierarchical self-assembly. We further show that amelogenin assemblies stabilize mineral prenucleation clusters and guide their arrangement into linear chains that organize as parallel arrays. The prenucleation clusters subsequently fuse together to form needle-shaped mineral particles, leading to the formation of bundles of crystallites, the hallmark structural organization of the forming enamel at the nanoscale. These findings provide unique insight into the regulation of biological mineralization by specialized macromolecules and an inspiration for bottom-up strategies for the materials design.

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“…Amelogenin assembles into spherical or oblate-shaped aggregates, called nanospheres, 15 to 20 nm in diameter (Fincham et al, 1994;Aichmayer et al, 2010;Wiedemann-Bidlack et al, 2007) via a multistep hierarchical process (Fang et al, 2011a,b). Amelogenin exists in monomeric form at low pH and self-assembles at neutral and moderately basic pH values (Wiedemann-Bidlack et al, 2007).…”

Section: Introduction Tmentioning

confidence: 99%