Correlation of the size of type II transforming growth factor beta (TGF-beta) receptor with TGF-beta responses of isolated bovine articular chondrocytes.
OBJECTIVE
Transforming growth factor beta (TGF-beta) is a multipotent regulator of cell proliferation and extracellular matrix production. The effect of TGF-beta on chondrocyte matrix production was studied in relation to the expression of TGF-beta binding proteins. The effect of TGF-beta on proteoglycan synthesis of isolated articular chondrocytes depended on the culture period. Proteoglycan synthesis of chondrocytes which were cultured for one day was inhibited by TGF-beta whereas proteoglycan synthesis of chondrocytes cultured in monolayer for seven days or longer was stimulated by TGF-beta. To investigate if this differential response is related to a distinct expression of TGF-beta receptors, this parameter was studied by affinity labelling.


METHODS
Chondrocytes were incubated with 100 pM TGF-beta labelled with iodine-125. Crosslinking was performed using 0.25 mM disuccinimidyl suberate. Membrane proteins were extracted and analysed by denaturating sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE) and autoradiography.


RESULTS
Freshly isolated and cultured chondrocytes expressed types I, II, and III TGF-beta receptors. The type II TGF-beta receptor of cultured chondrocytes appeared to be about 15 kilodaltons smaller than the type II TGF-beta receptor expressed on freshly isolated chondrocytes, however.


CONCLUSIONS
As the type II TGF-beta receptors appears to be involved in signal transduction, this change in size of the type II TGF-beta receptor might be related to the differential effect of TGF-beta on proteoglycan synthesis of freshly isolated and cultured bovine articular chondrocytes.
Glansbeek
H L
HL
Department of Rheumatology, University Hospital Nijmegen, The Netherlands.
van der Kraan
P M
PM
Vitters
E L
EL
van den Berg
W B
WB
D000345:Affinity Labels; D000818:Animals; D002358:Cartilage, Articular / Q000187:drug effects / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D017364:Collagenases / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D008970:Molecular Weight; D011509:Proteoglycans / Q000096:biosynthesis*; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D000345:Affinity Labels; D011509:Proteoglycans; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta; D017364:Collagenases