Enamel matrix protein interactions.
The recognized structural proteins of the enamel matrix are amelogenin, ameloblastin, and enamelin. While a large volume of data exists showing that amelogenin self-assembles into multimeric units referred to as nanospheres, other reports of enamel matrix protein-protein interactions are scant. We believe that each of these enamel matrix proteins must interact with other organic components of ameloblasts and the enamel matrix. Likely protein partners would include integral membrane proteins and additional secreted proteins.


BACKGROUND
The purpose of this study was to identify and catalog additional proteins that play a significant role in enamel formation.


METHODS
We used the yeast two-hybrid assay to identify protein partners for amelogenin, ameloblastin, and enamelin. Once identified, RT-PCR was used to assess gene transcription of these newly identified and potential "enamel" proteins in ameloblast-like LS8 cells.


RESULTS
In the context of this yeast assay, we identified a number of secreted proteins and integral membrane proteins that interact with amelogenin, ameloblastin, and enamelin. Additionally, proteins whose functions range from the inhibition of soft tissue mineralization, calcium ion transport, and phosphorylation events have been identified as protein partners to these enamel matrix proteins. For each protein identified using this screening strategy, future studies are planned to confirm this physiological relationship to biomineralization in vivo.


CONCLUSIONS
Identifying integral membrane proteins of the secretory surface of ameloblast cells (Tomes' processes) and additional enamel matrix proteins, based on their abilities to interact with the most abundant enamel matrix proteins, will better define the molecular mechanisms of enamel formation at its most rudimentary level.
Wang
HongJun
H
Center for Craniofacial Molecular Biology, University of Southern California, School of Dentistry, Los Angeles, California 90033, USA.
Tannukit
Sissada
S
Zhu
DanHong
D
Snead
Malcolm L
ML
Paine
Michael L
ML
D000565:Ameloblasts / Q000378:metabolism; D053523:Amelogenin; D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis; D058578:Biglycan; D001798:Blood Proteins / Q000378:metabolism; D037281:Calnexin / Q000096:biosynthesis / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D003743:Dental Enamel / Q000378:metabolism*; D003746:Dental Enamel Proteins / Q000737:chemistry / Q000378:metabolism; D003804:Dentin / Q000378:metabolism; D016326:Extracellular Matrix Proteins; D051379:Mice; D008954:Models, Biological; D016366:Open Reading Frames; D010766:Phosphorylation; D010980:Platelet Membrane Glycoproteins / Q000096:biosynthesis; D011485:Protein Binding; D011509:Proteoglycans / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D060149:Tetraspanin 30; D013997:Time Factors; D014158:Transcription, Genetic; D020798:Two-Hybrid System Techniques; D060749:alpha-2-HS-Glycoprotein; D000509:alpha-Fetoproteins / Q000378:metabolism
C556357:Ahsg protein, mouse; C490890:Ambn protein, mouse; D053523:Amelogenin; C507200:Amelx protein, mouse; D015703:Antigens, CD; C546885:Bgn protein, mouse; D058578:Biglycan; D001798:Blood Proteins; C554587:Cd63 protein, mouse; D018076:DNA, Complementary; D003746:Dental Enamel Proteins; D016326:Extracellular Matrix Proteins; D010980:Platelet Membrane Glycoproteins; D011509:Proteoglycans; D012333:RNA, Messenger; D060149:Tetraspanin 30; D060749:alpha-2-HS-Glycoprotein; D000509:alpha-Fetoproteins; C038456:tuftelin; D037281:Calnexin