Studies on physiological functions of vacuolar type H^+-ATPase using low molecular weight probes

观察了空泡型H~+-ATPase(V-ATPase)特异性抑制剂刀豆素B和抑制V-ATPase质子泵活性但不影响其活性的灵芝菌素25-C对破骨细胞内酸性颗粒酸化和破骨细胞性骨吸收的影响。这两种抑制剂抑制了颗粒的酸化和骨吸收。已知能抑制V-ATPase质子泵活性的去甲氧西林A、B和B不能抑制破骨细胞内酸性颗粒的酸化。然而，它们通过诱导破骨细胞的形态变化来抑制破骨细胞性骨吸收，这在刀豆素B或灵芝菌素25-C处理的破骨细胞中没有观察到。清楚地证明，去腐生素引起的形态变化是由于破骨细胞中肌动蛋白环的破坏，而破骨细胞是骨吸收所必需的细胞骨架结构。分子中含有环氧化物部分的破碎素E的破坏能力是破碎素A和B的30倍，表明环氧化物在生物活性的表达中起着重要作用。

Effects of concanamycin B, a specific inhibitor of vacuolar type H^+-ATPase (V-ATPase), and prodigiosin 25-C, which inhibits proton pump activity of V-ATPase without affecting its ATPase activity, on acidification of acidic intracellular granules in osteoclasts and on osteoclastic bone resorption were determined. These two inhibitors suppressed the acidification of the granules as well as bone resorption. Destruxins A, B and B, which are known to inhibit proton pump activity of V-ATPase, did not inhibit acidification of acidic intracellular granules in osteoclasts. However, they inhibited osteoclastic bone resorption by inducing morphological changes of osteoclasts that are not observed in the osteoclasts treated with concanamycin B or prodigiosin 25-C.It is clearly demonstrated that the morphological changes caused by destruxins are attributable to disruption of actin rings in osteoclasts which are essential cytoskeletal structures for bone resorption. The disruptive potency of destruxin E, which contains epoxide moiety in the molecule, was 30 times more evident than that of destruxin A and B, suggesting that the epoxide plays an important role in the expression of biological activities.