The C5 domain of Col6A3 is cleaved off from the Col6 fibrils immediately after secretion.
In articular cartilage, type VI collagen is concentrated in the pericellular matrix compartment. During protein synthesis and processing at least the alpha3(VI) chain undergoes significant posttranslational modification and cleavage. In this study, we investigated the processing of type VI collagen in articular cartilage. Immunostaining with a specific polyclonal antiserum against the C5 domain of alpha3(VI) showed strong cellular staining seen in nearly all chondrocytes of articular cartilage. Confocal laser-scanning microscopy and immunoelectron microscopy allowed localization of this staining mainly to the cytoplasm and the immediate pericellular matrix. Double-labeling experiments showed a narrow overlap of the C5 domain and the pericellular mature type VI collagen. Our results suggest that at least in human adult articular cartilage the C5 domain of alpha3(VI) collagen is synthesized and initially incorporated into the newly formed type VI collagen fibrils, but immediately after secretion is cut off and is not present in the mature pericellular type VI matrix of articular cartilage.
Aigner
T
T
Cartilage Research Group, Department of Pathology, University of Erlangen-Nürnberg, Erlangen, Federal Republic of Germany. thomas.aigner@patho.imed.uni-erlangen.de
Hambach
L
L
Söder
S
S
Schlötzer-Schrehardt
U
U
Pöschl
E
E
D000368:Aged; D000918:Antibody Specificity; D002358:Cartilage, Articular / Q000378:metabolism* / Q000648:ultrastructure; D024142:Collagen Type VI / Q000378:metabolism* / Q000648:ultrastructure; D003593:Cytoplasm / Q000378:metabolism / Q000648:ultrastructure; D000939:Epitopes / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D007150:Immunohistochemistry; D018613:Microscopy, Confocal; D016253:Microscopy, Immunoelectron; D008875:Middle Aged; D011499:Protein Processing, Post-Translational / Q000502:physiology*; D017434:Protein Structure, Tertiary / Q000502:physiology; D021122:Protein Subunits
D024142:Collagen Type VI; D000939:Epitopes; D021122:Protein Subunits