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Báo cáo khóa học: Large aggregating and small leucine-rich proteoglycans are degraded by different pathways and at different rates in tendon

This work investigated the kinetics of catabolism and the catabolic fate of the newly synthesized 35 S-labelled proteo-glycans present in explant cultures of tendon. Tissue from the proximal region of bovine deep flexor tendon was incu-bated with [ 35 S]sulfate for 6 h and then placed in explant cultures for periods of up to 15 days. The amount of radi-olabel associatedwithproteoglycans and free [ 35 S]sulfate lost to themediumand retained in thematrixwas determined for each day in culture. | Eur. J. Biochem. 271 3612-3620 2004 FEBS 2004 doi 10.1046 j.1432-1033.2003.04307.x Large aggregating and small leucine-rich proteoglycans are degraded by different pathways and at different rates in tendon Tom Samiric Mirna Z. Ilic and Christopher J. Handley School of Human Biosciences La Trobe University Melbourne Victoria Australia This work investigated the kinetics of catabolism and the catabolic fate of the newly synthesized 35S-labelled proteoglycans present in explant cultures of tendon. Tissue from the proximal region of bovine deep flexor tendon was incubated with 35S sulfate for 6 h and then placed in explant cultures for periods of up to 15 days. The amount of radiolabel associated with proteoglycans and free 35S sulfate lost to the medium and retained in the matrix was determined for each day in culture. It was shown that the rate of catabolism of radiolabelled small proteoglycans decorin and biglycan was significantly slower T Ị4 20 days compared with the radiolabelled large proteoglycans aggrecan and versican that were rapidly lost from the tissue Ti 2 w 2 days . Both the small and large newly synthesized proteoglycans were lost from the matrix with either intact or proteolytically modified core proteins. When explant cultures of tendon were maintained either at 4 C or in the presence of the lysosomotrophic agent ammonium chloride inhibition of the cellular catabolic pathway for small proteoglycans was demonstrated indicating the involvement of cellular activity and lysosomes in the catabolism of small proteoglycans. It was estimated from these studies that approximately 60 of the radiolabelled small proteoglycans that were lost from the tissue were degraded by the intracellular pathway present in tendon cells. This work shows that the pathways of catabolism for large aggregating and small leucine-rich proteoglycans are different in tendon and this may reflect the roles that these two populations of proteoglycans play in the maintenance of the .