Sun L, Adebanjo O A, Moonga B S, Corisdeo S, Anandatheerthavarada H K, Biswas G, Arakawa T, Hakeda Y, Koval A, Sodam B, Bevis P J, Moser A J, Lai F A, Epstein S, Troen B R, Kumegawa M, Zaidi M
Center for Osteoporosis and Skeletal Aging, Department of Medicine, Medical College of Pennsylvania and Veterans Affairs Medical Center, Philadelphia, Pennsylvania 19104, USA.
J Cell Biol. 1999 Sep 6;146(5):1161-72. doi: 10.1083/jcb.146.5.1161.
The multifunctional ADP-ribosyl cyclase, CD38, catalyzes the cyclization of NAD(+) to cyclic ADP-ribose (cADPr). The latter gates Ca(2+) release through microsomal membrane-resident ryanodine receptors (RyRs). We first cloned and sequenced full-length CD38 cDNA from a rabbit osteoclast cDNA library. The predicted amino acid sequence displayed 59, 59, and 50% similarity, respectively, to the mouse, rat, and human CD38. In situ RT-PCR revealed intense cytoplasmic staining of osteoclasts, confirming CD38 mRNA expression. Both confocal microscopy and Western blotting confirmed the plasma membrane localization of the CD38 protein. The ADP-ribosyl cyclase activity of osteoclastic CD38 was next demonstrated by its ability to cyclize the NAD(+) surrogate, NGD(+), to its fluorescent derivative cGDP-ribose. We then examined the effects of CD38 on osteoclast function. CD38 activation by an agonist antibody (A10) in the presence of substrate (NAD(+)) triggered a cytosolic Ca(2+) signal. Both ryanodine receptor modulators, ryanodine, and caffeine, markedly attenuated this cytosolic Ca(2+) change. Furthermore, the anti-CD38 agonist antibody expectedly inhibited bone resorption in the pit assay and elevated interleukin-6 (IL-6) secretion. IL-6, in turn, enhanced CD38 mRNA expression. Taken together, the results provide compelling evidence for a new role for CD38/ADP-ribosyl cyclase in the control of bone resorption, most likely exerted via cADPr.
多功能ADP - 核糖基环化酶CD38催化NAD(+)环化生成环ADP - 核糖（cADPr）。后者通过微粒体膜驻留的兰尼碱受体（RyRs）控制Ca(2+)释放。我们首先从兔破骨细胞cDNA文库中克隆并测序了全长CD38 cDNA。预测的氨基酸序列与小鼠、大鼠和人类CD38分别具有59%、59%和50%的相似性。原位RT - PCR显示破骨细胞有强烈的细胞质染色，证实了CD38 mRNA的表达。共聚焦显微镜和蛋白质印迹均证实了CD38蛋白定位于质膜。破骨细胞CD38的ADP - 核糖基环化酶活性随后通过其将NAD(+)替代物NGD(+)环化为其荧光衍生物cGDP - 核糖的能力得以证明。然后我们研究了CD38对破骨细胞功能的影响。在底物（NAD(+)）存在的情况下，激动剂抗体（A10）激活CD38引发了胞质Ca(2+)信号。兰尼碱受体调节剂兰尼碱和咖啡因均显著减弱了这种胞质Ca(2+)变化。此外，抗CD38激动剂抗体在凹坑试验中预期会抑制骨吸收并提高白细胞介素 - 6（IL - 6）的分泌。IL - 6反过来又增强了CD38 mRNA的表达。综上所述，这些结果为CD38/ADP - 核糖基环化酶在骨吸收控制中的新作用提供了有力证据，最有可能是通过cADPr发挥作用。
