beta ig-h3 interacts directly with biglycan and decorin, promotes collagen VI aggregation, and participates in ternary complexing with these macromolecules

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dc.contributor.authorReinboth, B.
dc.contributor.authorThomas, J.
dc.contributor.authorHanssen, E.
dc.contributor.authorGibson, M.
dc.date.issued2006
dc.description© 2006 by The American Society for Biochemistry and Molecular Biology, Inc.
dc.description.abstractRecombinant human βig-h3 was found to bind 125I-labeled small leucine-rich proteoglycans (SLRPs), biglycan, and decorin, in co-immunoprecipitation experiments. In each instance the binding could be blocked by an excess of the unlabeled proteoglycan, confirming the specificity of the interaction. Scatchard analysis showed that biglycan bound βig-h3 more avidly than decorin with Kd values estimated as 5.88 x 10–8 and 1.02 x 10–7 M, respectively. In reciprocal blocking experiments both proteoglycans inhibited the others binding to βig-h3 indicating that they may share the same binding site or that the two binding sites are in close proximity on the βig-h3 molecule. Since βig-h3 and the SLRPs are known to be associated with the amino-terminal region of collagen VI in tissue microfibrils, the effects of including collagen VI in the incubations were investigated. Co-immunoprecipitation of 125I-labeled biglycan incubated with equimolar mixtures of βig-h3 and pepsin-collagen VI was increased 6-fold over βig-h3 alone and 3-fold over collagen VI alone. Similar increases were also observed for decorin. The findings indicate that βig-h3 participates in a ternary complex with collagen VI and SLRPs. Static light scattering techniques were used to show that βig-h3 rapidly forms very high molecular weight complexes with both native and pepsin-collagen VI, either alone or with the SLRPs. Indeed βig-h3 was shown to form a complex with collagen VI and biglycan, which appeared to be much more extensive than that formed by βig-h3 with collagen VI and decorin or those formed between the collagen and βig-h3, biglycan, or decorin alone. Biglycan core protein was shown to inhibit the extent of complexing of βig-h3 with native and pepsin-collagen VI suggesting that the glycosaminoglycan side chains of the proteoglycan were important for the formation of the large ternary complexes. Further studies showed that the direct interaction between βig-h3 and biglycan and between biglycan and collagen VI were also important for the formation of these complexes. The globular domains of collagen VI also appeared to have an influence on the interaction of the three components. Overall the results indicate that βig-h3 can differentially modulate the aggregation of collagen VI with biglycan and decorin. Thus this interplay is likely to be important in tissues such as cornea where such complexes are considered to occur.
dc.description.statementofresponsibilityBetty Reinboth, John Thomas, Eric Hanssen and Mark A. Gibson
dc.identifier.citationJournal of Biological Chemistry, 2006; 281(12):7816-7824
dc.identifier.doi10.1074/jbc.M511316200
dc.identifier.issn0021-9258
dc.identifier.issn1083-351X
dc.identifier.urihttp://hdl.handle.net/2440/23084
dc.language.isoen
dc.publisherAmer Soc Biochemistry Molecular Biology Inc
dc.source.urihttp://www.jbc.org/cgi/content/abstract/281/12/7816
dc.subjectHumans
dc.subjectElectrolytes
dc.subjectMacromolecular Substances
dc.subjectCollagen
dc.subjectPepsin A
dc.subjectPolysaccharides
dc.subjectGlycosaminoglycans
dc.subjectProteoglycans
dc.subjectTransforming Growth Factor beta
dc.subjectExtracellular Matrix Proteins
dc.subjectCollagen Type VI
dc.subjectElectrophoresis, Polyacrylamide Gel
dc.subjectImmunoprecipitation
dc.subjectTemperature
dc.subjectBinding Sites
dc.subjectProtein Structure, Tertiary
dc.subjectProtein Binding
dc.subjectDose-Response Relationship, Drug
dc.subjectKinetics
dc.subjectMutation
dc.subjectLight
dc.subjectScattering, Radiation
dc.subjectTime Factors
dc.subjectDecorin
dc.subjectBiglycan
dc.titlebeta ig-h3 interacts directly with biglycan and decorin, promotes collagen VI aggregation, and participates in ternary complexing with these macromolecules
dc.typeJournal article
pubs.publication-statusPublished

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