Mitchell P G, Pledger W J, Cheung H S
Department of Medicine, Medical College of Wisconsin, Milwaukee 53226.
J Biol Chem. 1989 Aug 25;264(24):14071-7.
Synovial tissue hyperplasia in basic calcium phosphate deposition disease has been suggested to develop through the stimulation of cell growth by basic calcium phosphate (BCP) crystals deposited in joints. These crystals have been used in vitro to stimulate DNA synthesis in quiescent fibroblasts to experimentally study this proliferative disease. The stimulation of DNA synthesis, in density-arrested Balb/c 3T3 cells, by BCP crystals was inhibited after down-regulating protein kinase C activity with 12-O-tetradecanoyl-phorbol 13-acetate (TPA). No effect on platelet-derived growth factor (PDGF)-stimulated DNA synthesis was observed under the same conditions. The expression of c-myc and c-fos increased in response to BCP stimulation in a manner similar to the increase produced by stimulation with PDGF. The BCP stimulation of c-fos and c-myc messages was inhibited 60 and 90%, respectively, in TPA-pretreated, protein kinase C-down-regulated cells. The induction of these transcripts by PDGF was unaffected in cells pretreated with TPA. TPA was unable to stimulate c-fos and c-myc expression or DNA synthesis following protein kinase C down-regulation. Both PDGF and TPA stimulated phosphorylation of an 80-kDa protein, whereas BCP crystals had no effect on phosphorylation of this protein. The exposure of density-arrested Balb/c 3T3 cells to BCP crystals had no effect on high affinity epidermal growth factor receptor binding under conditions in which PDGF and TPA reduced epidermal growth factor binding. The data suggest that PDGF can act to stimulate c-fos and c-myc expression as well as DNA synthesis through a protein kinase C-independent pathway, whereas BCP crystals require at least endogenous levels of protein kinase C to stimulate these events.
碱性磷酸钙沉积病中的滑膜组织增生被认为是由沉积在关节中的碱性磷酸钙（BCP）晶体刺激细胞生长而发生的。这些晶体已被用于体外实验，以刺激静止成纤维细胞中的DNA合成，从而对这种增殖性疾病进行实验研究。在用12 - O - 十四烷酰佛波醇13 - 乙酸酯（TPA）下调蛋白激酶C活性后，BCP晶体对密度抑制的Balb/c 3T3细胞中DNA合成的刺激作用受到抑制。在相同条件下，未观察到对血小板衍生生长因子（PDGF）刺激的DNA合成有影响。c - myc和c - fos的表达响应BCP刺激而增加，其方式类似于PDGF刺激所产生的增加。在TPA预处理、蛋白激酶C下调的细胞中，BCP对c - fos和c - myc信使的刺激分别被抑制了60%和90%。TPA预处理的细胞中，PDGF对这些转录本的诱导不受影响。在蛋白激酶C下调后，TPA无法刺激c - fos和c - myc表达或DNA合成。PDGF和TPA均刺激一种80 kDa蛋白的磷酸化，而BCP晶体对该蛋白的磷酸化没有影响。在PDGF和TPA降低表皮生长因子结合的条件下，密度抑制的Balb/c 3T3细胞暴露于BCP晶体对高亲和力表皮生长因子受体结合没有影响。数据表明，PDGF可以通过一条不依赖蛋白激酶C的途径刺激c - fos和c - myc表达以及DNA合成，而BCP晶体至少需要内源性水平的蛋白激酶C来刺激这些事件。
