Phosphorylation Modulates Ameloblastin Self-assembly and Ca2+ Binding
Ameloblastin (AMBN), an important component of the self-assembled enamel extra cellular matrix, contains several in silico predicted phosphorylation sites. However, to what extent these sites actually are phosphorylated and the possible effects of such post-translational modifications are still larg...
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| Format: | Article |
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Frontiers Media S.A.
2017-07-01
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| Series: | Frontiers in Physiology |
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| Online Access: | http://journal.frontiersin.org/article/10.3389/fphys.2017.00531/full |
| _version_ | 1819263961712820224 |
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| author | Øystein Stakkestad Ståle P. Lyngstadaas Bernd Thiede Jiri Vondrasek Bjørn S. Skålhegg Janne E. Reseland |
| author_facet | Øystein Stakkestad Ståle P. Lyngstadaas Bernd Thiede Jiri Vondrasek Bjørn S. Skålhegg Janne E. Reseland |
| author_sort | Øystein Stakkestad |
| collection | DOAJ |
| description | Ameloblastin (AMBN), an important component of the self-assembled enamel extra cellular matrix, contains several in silico predicted phosphorylation sites. However, to what extent these sites actually are phosphorylated and the possible effects of such post-translational modifications are still largely unknown. Here we report on in vitro experiments aimed at investigating what sites in AMBN are phosphorylated by casein kinase 2 (CK2) and protein kinase A (PKA) and the impact such phosphorylation has on self-assembly and calcium binding. All predicted sites in AMBN can be phosphorylated by CK2 and/or PKA. The experiments show that phosphorylation, especially in the exon 5 derived part of the molecule, is inversely correlated with AMBN self-assembly. These results support earlier findings suggesting that AMBN self-assembly is mostly dependent on the exon 5 encoded region of the AMBN gene. Phosphorylation was significantly more efficient when the AMBN molecules were in solution and not present as supramolecular assemblies, suggesting that post-translational modification of AMBN must take place before the enamel matrix molecules self-assemble inside the ameloblast cell. Moreover, phosphorylation of exon 5, and the consequent reduction in self-assembly, seem to reduce the calcium binding capacity of AMBN suggesting that post-translational modification of AMBN also can be involved in control of free Ca2+ during enamel extra cellular matrix biomineralization. Finally, it is speculated that phosphorylation can provide a functional crossroad for AMBN either to be phosphorylated and act as monomeric signal molecule during early odontogenesis and bone formation, or escape phosphorylation to be subsequently secreted as supramolecular assemblies that partake in enamel matrix structure and mineralization. |
| first_indexed | 2024-12-23T20:21:55Z |
| format | Article |
| id | doaj.art-ba0abe0ddb6d4fcaad735832c737888f |
| institution | Directory Open Access Journal |
| issn | 1664-042X |
| language | English |
| last_indexed | 2024-12-23T20:21:55Z |
| publishDate | 2017-07-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Physiology |
| spelling | doaj.art-ba0abe0ddb6d4fcaad735832c737888f2022-12-21T17:32:30ZengFrontiers Media S.A.Frontiers in Physiology1664-042X2017-07-01810.3389/fphys.2017.00531276789Phosphorylation Modulates Ameloblastin Self-assembly and Ca2+ BindingØystein Stakkestad0Ståle P. Lyngstadaas1Bernd Thiede2Jiri Vondrasek3Bjørn S. Skålhegg4Janne E. Reseland5Department of Biomaterials, Institute of Clinical Dentistry, University of OsloOslo, NorwayDepartment of Biomaterials, Institute of Clinical Dentistry, University of OsloOslo, NorwaySection for Biochemistry and Molecular Biology, Department of Biosciences, University of OsloOslo, NorwayDepartment of Bioinformatics, Institute of Organic Chemistry and Biochemistry, Czech Academy of SciencesPrague, CzechiaDivision of Molecular Nutrition, Department of Nutrition, University of OsloOslo, NorwayDepartment of Biomaterials, Institute of Clinical Dentistry, University of OsloOslo, NorwayAmeloblastin (AMBN), an important component of the self-assembled enamel extra cellular matrix, contains several in silico predicted phosphorylation sites. However, to what extent these sites actually are phosphorylated and the possible effects of such post-translational modifications are still largely unknown. Here we report on in vitro experiments aimed at investigating what sites in AMBN are phosphorylated by casein kinase 2 (CK2) and protein kinase A (PKA) and the impact such phosphorylation has on self-assembly and calcium binding. All predicted sites in AMBN can be phosphorylated by CK2 and/or PKA. The experiments show that phosphorylation, especially in the exon 5 derived part of the molecule, is inversely correlated with AMBN self-assembly. These results support earlier findings suggesting that AMBN self-assembly is mostly dependent on the exon 5 encoded region of the AMBN gene. Phosphorylation was significantly more efficient when the AMBN molecules were in solution and not present as supramolecular assemblies, suggesting that post-translational modification of AMBN must take place before the enamel matrix molecules self-assemble inside the ameloblast cell. Moreover, phosphorylation of exon 5, and the consequent reduction in self-assembly, seem to reduce the calcium binding capacity of AMBN suggesting that post-translational modification of AMBN also can be involved in control of free Ca2+ during enamel extra cellular matrix biomineralization. Finally, it is speculated that phosphorylation can provide a functional crossroad for AMBN either to be phosphorylated and act as monomeric signal molecule during early odontogenesis and bone formation, or escape phosphorylation to be subsequently secreted as supramolecular assemblies that partake in enamel matrix structure and mineralization.http://journal.frontiersin.org/article/10.3389/fphys.2017.00531/fullameloblastinphosphorylationself-assemblyCa2+- bindingenamelintrinsically disordered proteins |
| spellingShingle | Øystein Stakkestad Ståle P. Lyngstadaas Bernd Thiede Jiri Vondrasek Bjørn S. Skålhegg Janne E. Reseland Phosphorylation Modulates Ameloblastin Self-assembly and Ca2+ Binding Frontiers in Physiology ameloblastin phosphorylation self-assembly Ca2+- binding enamel intrinsically disordered proteins |
| title | Phosphorylation Modulates Ameloblastin Self-assembly and Ca2+ Binding |
| title_full | Phosphorylation Modulates Ameloblastin Self-assembly and Ca2+ Binding |
| title_fullStr | Phosphorylation Modulates Ameloblastin Self-assembly and Ca2+ Binding |
| title_full_unstemmed | Phosphorylation Modulates Ameloblastin Self-assembly and Ca2+ Binding |
| title_short | Phosphorylation Modulates Ameloblastin Self-assembly and Ca2+ Binding |
| title_sort | phosphorylation modulates ameloblastin self assembly and ca2 binding |
| topic | ameloblastin phosphorylation self-assembly Ca2+- binding enamel intrinsically disordered proteins |
| url | http://journal.frontiersin.org/article/10.3389/fphys.2017.00531/full |
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