The synthesis of proteoglycans by human T lymphocytes.
We have examined the proteoglycans produced by highly-purified cultures of human T-lymphocytes. The proteoglycans were metabolically labelled with [35S]sulphate and analysed in cellular and medium fractions using DEAE-cellulose chromatography, gel filtration and specific enzymatic and chemical degradations. The results showed that the T cells synthesized a relatively homogeneous, proteinase-resistant chondroitin 4-sulphate proteoglycan that accumulated in the culture medium during a 48 h incubation period. The cellular fraction contained a significant amount of free chondroitin sulphate chains that were not secreted into the medium. These polysaccharides were formed by intracellular degradation of proteoglycan in a chloroquine-sensitive process, indicating a requirement for an acidic environment. In contrast to chondroitin sulphate derived from proteoglycan, chondroitin sulphates synthesized on the exogenous primer, beta-D-xyloside, were mainly secreted by the cells. beta-D-Xylosides caused an 8-fold stimulation in the synthesis of chondroitin sulphate, but decreased the synthesis of proteoglycan by about 50%. These proteoglycans contained shorter chondroitin sulphate chains than their normal counterparts. The results indicate that although proteoglycans are mainly secretory components in human T-cell cultures, a specific metabolic step leads to the intracellular accumulation of free glycosaminoglycans. Separate functions are likely to be associated with the intracellular and secretory pools of chondroitin sulphate.
Steward
W P
WP
CRC Dept. Medical Oncology, Christie Hospital, Manchester, U.K.
Christmas
S E
SE
Lyon
M
M
Gallagher
J T
JT
D002478:Cells, Cultured; D002738:Chloroquine / Q000494:pharmacology; D006025:Glycosaminoglycans / Q000378:metabolism; D006027:Glycosides / Q000494:pharmacology; D006801:Humans; D011509:Proteoglycans / Q000096:biosynthesis*; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism*
D006025:Glycosaminoglycans; D006027:Glycosides; D011509:Proteoglycans; C010807:xylosides; D002738:Chloroquine