Extracellular calcium regulates distribution and transport of heparan sulfate proteoglycans in a rat parathyroid cell line.
The regulation of the cellular distribution of proteoglycans in a clonal rat parathyroid cell line by extracellular Ca2+ concentrations ([Ca2+]e) was studied. Proteoglycans synthesized by the cells metabolically labeled with [35S]sulfate have been shown to be almost exclusively heparan sulfate (HS) proteoglycans (Yanagishita, M., Brandi, M.L., and Sakaguchi, K. (1989) J. Biol. Chem. 264, 15714-15720), which are generally associated with the plasma membrane. The proportion of HS proteoglycans on the cell surface was approximately 20% in 2.1 mM (high) [Ca2+]e, whereas it increased to 50-60% in 0.05 mM (low) [Ca2+]e. Cell-associated HS proteoglycans redistribute in response to changing [Ca2+]e with a t 1/2 less than 4 min; HS proteoglycans appear on the cell surface as [Ca2+]e decreases and disappear from the cell surface as [Ca2+]e increases. Further, HS proteoglycans on the cell surface recycle to and from an intracellular compartment approximately 10 times before their degradation in low [Ca2+]e but do not recycle in high [Ca2+]e. The distribution of newly synthesized HS proteoglycans is regulated by [Ca2+]e but is independent of [Ca2+]e during biosynthesis. In low [Ca2+]e, at least 50% of the HS proteoglycans pulse-labeled for 10 min are transported from the Golgi complex to the cell surface or to the recycling compartment with a t 1/2 of approximately 20 min. Another approximately 10% appear on the cell surface in either low or high [Ca2+]e in a compartment with a long half-life. Addition of Mg2+ or Ba2+ to the low [Ca2+]e cultures had little effect on the distribution of HS proteoglycans. These observations suggest that [Ca2+]e specifically regulates the distribution and recycling of cell-associated HS proteoglycans in the parathyroid cells.
Takeuchi
Y
Y
Bone Research Branch, National Institute of Dental Research, National Institutes of Health, Bethesda, Maryland 20892.
Sakaguchi
K
K
Yanagishita
M
M
Aurbach
G D
GD
Hascall
V C
VC
D000818:Animals; D001464:Barium / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000494:pharmacology*; D002460:Cell Line; D011508:Chondroitin Sulfate Proteoglycans / Q000378:metabolism*; D002852:Chromatography, Ion Exchange; D002999:Clone Cells; D006023:Glycoproteins / Q000096:biosynthesis / Q000302:isolation & purification; D006025:Glycosaminoglycans / Q000378:metabolism*; D019812:Heparan Sulfate Proteoglycans; D006497:Heparan Sulfate / Q000378:metabolism*; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D010280:Parathyroid Glands / Q000187:drug effects / Q000378:metabolism*; D011509:Proteoglycans / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D014357:Trypsin / Q000378:metabolism
D001464:Barium; D002118:Calcium; D011508:Chondroitin Sulfate Proteoglycans; D006023:Glycoproteins; D006025:Glycosaminoglycans; D019812:Heparan Sulfate Proteoglycans; D006497:Heparan Sulfate; D008274:Magnesium; D011509:Proteoglycans; D014357:Trypsin