期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 280, 期 38, 页码 32655-32661出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M504778200
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资金
- NHLBI NIH HHS [R01 HL049081-09, R01 HL049081-08, R01 HL049081-11, R01 HL049081-07, R01 HL049081, R01 HL049081-13, R01 HL049081-10, R01 HL049081-12] Funding Source: Medline
- NIA NIH HHS [R56 AG022021, R01 AG022021] Funding Source: Medline
Cartilage oligomeric matrix protein/ thrombospondin 5 ( COMP/ TSP5) is a major component of the extracellular matrix of the musculoskeletal system. Although COMP/ TSP5 abnormalities are associated with several pathological conditions, its normal function remains unclear. This study was undertaken to delineate the function( s) of COMP/ TSP5 in cartilage, especially regarding its interaction with chondrocytes. We show that COMP/ TSP5 can support chondrocyte attachment and that the RGD sequence in COMP/ TSP5 and the integrin receptors alpha 5 beta 1 and alpha V beta 3 on the chondrocytes are involved in mediating this attachment. The interactions of COMP/ TSP5 with the integrins are dependent on COMP/ TSP5 conformation. Chondrocyte attachment to COMP/ TSP5 in the calcium- replete conformation was inhibited by function- blocking integrin alpha 5 and beta 1 antibodies, suggesting the involvement of the alpha 5 beta 1 integrin. Under this condition, a function- blocking antibody against alpha V beta 3 did not have any effect on cell attachment. On the other hand, chondrocyte attachment to reduced COMP/ TSP5 was instead sensitive to alpha V beta 3 function- blocking antibodies, suggesting that COMP/ TSP5 mediates attachment through chondrocyte alpha V beta 3 integrin under this condition. Cell attachment to reduced COMP/ TSP5 was not inhibited by beta 1 antibodies. These data indicate that COMP/ TSP5 in different conformations can utilize different integrin receptors. These results are the first to demonstrate that COMP/ TSP5 can mediate chondrocyte attachment through interactions with integrins. Through these interactions, COMP/ TSP5 may be able to regulate cellular activities and respond to environment in the surrounding cartilage matrix.
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