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.
Musculoskeletal Research Laboratory, Departments of Orthopaedics and Rehabilitation and Cell and Molecular Physiology, the Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA.
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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