Extracellular Ca(2+)-sensing receptors modulate matrix production and mineralization in chondrogenic RCJ3.1C5.18 cells.
Previous studies in chondrogenic RCJ3.1C5.18 (C5.18) cells showed that growth of these cells at high extracellular Ca(2+) concentrations ([Ca(2+)](o)) reduced the expression of markers of early chondrocyte differentiation. These studies addressed whether raising [Ca(2+)](o) accelerates C5.18 cell differentiation and whether Ca(2+) receptors (CaRs) are involved in coupling changes in [Ca(2+)](o) to cellular responses. We found that high [Ca(2+)](o) increased expression of osteopontin (OP), osteonectin, and osteocalcin, all markers of terminal differentiation, in C5.18 cells and increased the production of matrix mineral. Overexpression of wild-type CaR cDNA in C5.18 cells suppressed proteoglycan synthesis and aggrecan RNA, two early differentiation markers, and increased OP expression. The sensitivity of these parameters to changes in [Ca(2+)](o) was significantly increased, as indicated by left-shifted dose-responses. In contrast, stable expression of a signaling-defective CaR mutant (Phe707Trp CaR) in C5.18 cells, presumably through dominant-negative inhibition of endogenous CaRs, blocked the suppression of aggrecan RNA levels and proteoglycan accumulation and the enhancement of OP expression by high [Ca(2+)](o). These data support a role for CaRs in mediating high [Ca(2+)](o)-induced differentiation of C5.18 cells.
Chang
Wenhan
W
Endocrine Research Unit, Department of Veterans Affairs Medical Center, University of California, San Francisco, California 94121, USA.
Tu
Chialing
C
Pratt
Stacy
S
Chen
Tsui-Hua
TH
Shoback
Dolores
D
D000256:Adenoviridae / Q000235:genetics; D053674:Aggrecans; D000818:Animals; D015152:Blotting, Northern; D002113:Calcification, Physiologic / Q000502:physiology*; D002118:Calcium / Q000494:pharmacology; D002356:Cartilage / Q000187:drug effects / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology; D002460:Cell Line; D019902:Chondrocytes / Q000378:metabolism*; D002807:Chondroitin / Q000096:biosynthesis*; D004396:Coloring Agents; D005109:Extracellular Matrix / Q000502:physiology*; D016326:Extracellular Matrix Proteins; D015151:Immunoblotting; D037181:Lectins, C-Type; D053495:Osteopontin; D011509:Proteoglycans / Q000096:biosynthesis / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D044169:Receptors, Calcium-Sensing; D011956:Receptors, Cell Surface / Q000502:physiology*; D012795:Sialoglycoproteins / Q000096:biosynthesis; D014162:Transfection
C508321:Acan protein, rat; D053674:Aggrecans; D004396:Coloring Agents; D016326:Extracellular Matrix Proteins; D037181:Lectins, C-Type; D011509:Proteoglycans; D012333:RNA, Messenger; D044169:Receptors, Calcium-Sensing; D011956:Receptors, Cell Surface; D012795:Sialoglycoproteins; C506897:Spp1 protein, rat; C473605:extracellular calcium cation-sensing receptor, rat; D053495:Osteopontin; D002807:Chondroitin; D002118:Calcium