Coxon Fraser P, Ebetino Frank H, Mules Emilie H, Seabra Miguel C, McKenna Charles E, Rogers Michael J
Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK.
Bone. 2005 Sep;37(3):349-58. doi: 10.1016/j.bone.2005.04.021.
Nitrogen-containing bisphosphonate drugs such as risedronate act by inhibiting farnesyl diphosphate synthase, thereby disrupting protein prenylation in osteoclasts. We recently found that an anti-resorptive phosphonocarboxylate analogue of risedronate, 3-PEHPC (previously referred to as NE10790), selectively prevents prenylation of Rab GTPases in vitro by specifically inhibiting Rab geranylgeranyl transferase. In this study, we demonstrate that unprenylated Rab6 could be detected in J774 cells after treatment with 3-PEHPC or risedronate for as little as 4 h, and reached 50% after 24 h. Furthermore, treatment of J774 cells or osteoclasts with either 3-PEHPC or risedronate disrupted membrane association of several Rab family proteins. Like risedronate, the effects of 3-PEHPC are likely to be restricted to osteoclasts in vivo, since both risedronate and 3-PEHPC inhibited Rab prenylation in osteoclasts, but not in general bone marrow cells, when administered to rabbits in vivo. Analysis of two new phosphonocarboxylate analogues of 3-PEHPC (3-PEPC and 2-PEPC) revealed that, first, the geminal hydroxyl group is not essential for inhibition of Rab prenylation by phosphonocarboxylates, but does contribute to their anti-resorptive potency, most likely by enhancing their affinity for bone mineral. Second, the position of the nitrogen in the side chain of phosphonocarboxylates is crucial for their ability to inhibit Rab prenylation and hence to inhibit bone resorption. In addition, there is a good correlation between the ability of the phosphonocarboxylates to inhibit Rab prenylation and to inhibit bone resorption in vitro, indicating that these compounds are a new class of pharmacological agents that inhibit bone resorption by specifically preventing prenylation of Rab proteins. Furthermore, although phosphonocarboxylates are analogues of bisphosphonates, the structure-activity relationships of phosphonocarboxylates for inhibiting Rab geranylgeranyltransferase appear to differ from the structure-activity relationships of bisphosphonates for inhibiting farnesyl diphosphate synthase.
含氮双膦酸盐药物（如利塞膦酸盐）通过抑制法尼基二磷酸合酶发挥作用，从而破坏破骨细胞中的蛋白质异戊二烯化。我们最近发现，利塞膦酸盐的一种抗吸收膦羧酸盐类似物3-PEHPC（以前称为NE10790），通过特异性抑制Rab香叶基香叶基转移酶，在体外选择性地阻止Rab GTP酶的异戊二烯化。在本研究中，我们证明，用3-PEHPC或利塞膦酸盐处理J774细胞仅4小时后，即可检测到未异戊二烯化的Rab6，24小时后达到50%。此外，用3-PEHPC或利塞膦酸盐处理J774细胞或破骨细胞会破坏几种Rab家族蛋白的膜结合。与利塞膦酸盐一样，3-PEHPC的作用在体内可能仅限于破骨细胞，因为将利塞膦酸盐和3-PEHPC给兔子体内给药时，两者均抑制破骨细胞中的Rab异戊二烯化，但不抑制一般骨髓细胞中的Rab异戊二烯化。对3-PEHPC的两种新的膦羧酸盐类似物（3-PEPC和2-PEPC）的分析表明，首先，偕二羟基对于膦羧酸盐抑制Rab异戊二烯化并非必不可少，但确实有助于它们的抗吸收效力，很可能是通过增强它们对骨矿物质的亲和力。其次，膦羧酸盐侧链中氮的位置对于它们抑制Rab异戊二烯化从而抑制骨吸收的能力至关重要。此外，膦羧酸盐抑制Rab异戊二烯化的能力与体外抑制骨吸收的能力之间存在良好的相关性，表明这些化合物是一类新的通过特异性阻止Rab蛋白异戊二烯化来抑制骨吸收的药物。此外，尽管膦羧酸盐是双膦酸盐的类似物，但膦羧酸盐抑制Rab香叶基香叶基转移酶的构效关系似乎与双膦酸盐抑制法尼基二磷酸合酶的构效关系不同。
