Changes of matrilin forms during endochondral ossification. Molecular basis of oligomeric assembly.
To understand the molecular properties of matrilin-3, a newly discovered member of the novel extracellular matrix protein family, we cloned a MAT-3 cDNA from developing chicken sterna. Real time quantitative reverse-transcription polymerase chain reaction indicates that MAT-3 mRNA is mainly expressed in the proliferation zone of a growth plate. It is also expressed in the maturation zone, overlapping with that of the mature chondrocyte-abundant matrilin-1 mRNA. This suggests that matrilin-3 may self-assemble in the proliferation zone, in addition to its co-assembly with matrilin-1 during endochondral ossification. Transfection of a MAT-3 cDNA into COS-7 cells shows that MAT-3 predominantly forms a homotetramer but also a trimer and a dimer. Co-transfection of both MAT-3 and MAT-1 cDNAs results in three major matrilins as follows: (MAT-1)(3), (MAT-3)(4), and (MAT-1)(2)(MAT-3)(2). Thus matrilin-3 may assemble into both homotypic and heterotypic oligomers. Our analysis shows that the assembly of MAT-3 does not depend on the number of epidermal growth factor repeats within the molecule, but the presence of Cys(412) and Cys(414) within the coiled-coil domain, which form covalent disulfide linkage responsible for both homo-oligomerization of MAT-3 and hetero-oligomerization of MAT-3 and MAT-1. Our data suggest that the varying synthetic levels of matrilins in different zones of a growth plate may result in a change of matrilin oligomeric forms during endochondral ossification.
Zhang
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Musculoskeletal Research Laboratory, Departments of Orthopaedics and Rehabilitation and Cell and Molecular Physiology, the Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA.
Chen
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D000818:Animals; D019556:COS Cells; D002356:Cartilage / Q000196:embryology; D002642:Chick Embryo; D002645:Chickens; D003001:Cloning, Molecular; D003094:Collagen / Q000235:genetics; D016326:Extracellular Matrix Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D006023:Glycoproteins / Q000235:genetics; D006132:Growth Plate / Q000196:embryology* / Q000378:metabolism; D064235:Matrilin Proteins; D010012:Osteogenesis; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic; D014162:Transfection
D016326:Extracellular Matrix Proteins; D006023:Glycoproteins; D064235:Matrilin Proteins; D011994:Recombinant Proteins; D003094:Collagen