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- Kalamajski, Sebastian, et al.
(författare)
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Asporin competes with decorin for collagen binding, binds calcium and promotes osteoblast collagen mineralization
- 2009
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Ingår i: Biochemical Journal. - 0264-6021. ; 423, s. 53-59
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Tidskriftsartikel (refereegranskat)abstract
- The interactions of the ECM (extracellular matrix) protein asporin with ECM components have previously not been investigated. Here, we show that asporin binds collagen type I. This binding is inhibited by recombinant asporin fragment LRR (leucine-rich repeat) 10-12 and by full-length decorin, but not by biglycan. We demonstrate that the polyaspartate domain binds calcium and regulates hydroxyapatite formation in vitro. In the presence of asporin, the number of collagen nodules, and mRNA of osteoblastic markers Osterix and Runx2 were increased. Moreover, decorin or the collagen-binding asporin fragment LRR 10-12 inhibited the pro-osteoblastic activity of full-length asporin. Our results suggest that asporin and decorin compete for binding to collagen and that the polyaspartate in asporin directly regulates collagen mineralization. Therefore asporin has a role in osteoblast-driven collagen biomineralization activity. We also show that asporin can be expressed in Escherichia coli (Rosettagami (TM)) with correctly positioned cysteine bridges, and a similar system can possibly be used for the expression of other SLRPs (small LRR proteoglycans/proteins).
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- Mörgelin, Matthias, et al.
(författare)
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Evidence of a defined spatial arrangement of hyaluronate in the central filament of cartilage proteoglycan aggregates
- 1995
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Ingår i: Biochemical Journal. - 0264-6021. ; 307:Pt 2, s. 595-601
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Tidskriftsartikel (refereegranskat)abstract
- Aggregates of proteoglycans from the Swarm rat chondrosarcoma reassembled in vitro have been studied by rotary-shadowing electron microscopy, and shown to be similar to native structures that have never been dissociated [Morgelin, Engel, Heinegard and Paulsson (1992) J. Biol. Chem. 267, 14275-14284]. A hyaluronate with defined chain length (HAshort) has now been prepared by autoclaving high-Mr hyaluronate and fractionation to a narrow size distribution by gel filtration. Proteoglycan monomers, core protein, hyaluronate-binding region and link protein were combined with HAshort. Free chains of HAshort and reconstituted complexes with proteoglycan, link protein and aggrecan fragments were examined by electron microscopy after rotary shadowing. Length measurements showed that the hyaluronate was condensed to about half of its original length on binding intact aggrecan monomers, any aggrecan fragment or link protein alone. This strongly implies that hyaluronate adopts a defined spatial arrangement within the central filament of the aggregate, probably different from its secondary structure in solution. No differences in length were observed between link-free and link-stabilized aggregates.
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