Identification of a fibronectin interaction site in the extracellular matrix protein ameloblastin

Beyeler, Michael; Schild, Christof; Lutz, Roman; Chiquet, Matthias; Trueb, Beat (2010). Identification of a fibronectin interaction site in the extracellular matrix protein ameloblastin. Experimental cell research, 316(7), pp. 1202-12. San Diego, Calif.: Elsevier 10.1016/j.yexcr.2009.12.019

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Mammalian teeth are composed of hydroxyapatite crystals that are embedded in a rich extracellular matrix. This matrix is produced by only two cell types, the mesenchymal odontoblasts and the ectodermal ameloblasts. Ameloblasts secrete the enamel proteins amelogenin, ameloblastin, enamelin and amelotin. Odontoblasts secrete collagen type I and several calcium-binding phosphoproteins including dentin sialophosphoprotein, dentin matrix protein, bone sialoprotein and osteopontin. The latter four proteins have recently been grouped in the family of the SIBLINGs (small integrin-binding ligand, N-linked glycoproteins) because they display similar gene structures and because they contain an RGD tripeptide sequence that binds to integrin receptors and thus mediates cell adhesion. We have prepared all the other tooth-specific proteins in recombinant form and examined whether they might also promote cell adhesion similar to the SIBLINGs. We found that only ameloblastin consistently mediated adhesion of osteoblastic and fibroblastic cells to plastic or titanium surfaces. The activity was dependent on the intact three-dimensional structure of ameloblastin and required de novo protein synthesis of the adhering cells. By deletion analysis and in vitro mutagenesis, the active site could be narrowed down to a sequence of 13 amino acid residues (VPIMDFADPQFPT) derived from exon 7 of the rat ameloblastin gene or exons 7-9 of the human gene. Kinetic studies and RNA interference experiments further demonstrated that this sequence does not directly bind to a cell surface receptor but that it interacts with cellular fibronectin, which in turn binds to integrin receptors. The identification of a fibronectin-binding domain in ameloblastin might permit interesting applications for dental implantology. Implants could be coated with peptides containing the active sequence, which in turn would recruit fibronectin from the patient's blood. The recruited fibronectin should then promote cell adhesion on the implant surface, thereby accelerating osseointegration of the implant.

Item Type:	Journal Article (Original Article)
Division/Institute:	04 Faculty of Medicine > Department of Dermatology, Urology, Rheumatology, Nephrology, Osteoporosis (DURN) > Clinic of Rheumatology and Immunology 04 Faculty of Medicine > Department of Haematology, Oncology, Infectious Diseases, Laboratory Medicine and Hospital Pharmacy (DOLS) > Institute of Clinical Chemistry 04 Faculty of Medicine > School of Dental Medicine > Department of Orthodontics
UniBE Contributor:	Beyeler, Michael, Schild, Christof, Chiquet, Matthias, Trueb, Beat
ISSN:	0014-4827
Publisher:	Elsevier
Language:	English
Submitter:	Eveline Carmen Schuler
Date Deposited:	04 Oct 2013 14:09
Last Modified:	05 Dec 2022 14:00
Publisher DOI:	10.1016/j.yexcr.2009.12.019
PubMed ID:	20043904
Web of Science ID:	000276479000012
URI:	https://boris.unibe.ch/id/eprint/1203 (FactScience: 202228)