Panda D, DeLuca K, Williams D, Jordan M A, Wilson L
Department of Molecular Cellular and Developmental Biology, University of California at Santa Barbara, Santa Barbara, CA 93106, USA.
Proc Natl Acad Sci U S A. 1998 Aug 4;95(16):9313-8. doi: 10.1073/pnas.95.16.9313.
Cryptophycin-52 (LY355703) is a new synthetic member of the cryptophycin family of antimitotic antitumor agents that is currently undergoing clinical evaluation. At high concentrations (>/=10 times the IC50), cryptophycin-52 blocked HeLa cell proliferation at mitosis by depolymerizing spindle microtubules and disrupting chromosome organization. However, low concentrations of cryptophycin-52 inhibited cell proliferation at mitosis (IC50 = 11 pM) without significantly altering spindle microtubule mass or organization. Cryptophycin-52 appears to be the most potent suppressor of microtubule dynamics found thus far. It suppressed the dynamic instability behavior of individual microtubules in vitro (IC50 = 20 nM), reducing the rate and extent of shortening and growing without significantly reducing polymer mass or mean microtubule length. Using [3H]cryptophycin-52, we found that the compound bound to microtubule ends in vitro with high affinity (Kd, 47 nM, maximum of approximately 19.5 cryptophycin-52 molecules per microtubule). By analyzing the effects of cryptophycin-52 on dynamics in relation to its binding to microtubules, we determined that approximately 5-6 molecules of cryptophycin-52 bound to a microtubule were sufficient to decrease dynamicity by 50%. Cryptophycin-52 became concentrated in cells 730-fold, and the resulting intracellular cryptophycin-52 concentration was similar to that required to stabilize microtubule dynamics in vitro. The data suggest that cryptophycin-52 potently perturbs kinetic events at microtubule ends that are required for microtubule function during mitosis and that it acts by forming a reversible cryptophycin-52-tubulin stabilizing cap at microtubule ends.
隐藻素-52（LY355703）是抗有丝分裂抗肿瘤药物隐藻素家族的一种新型合成成员，目前正处于临床评估阶段。在高浓度（≥IC50的10倍）时，隐藻素-52通过使纺锤体微管解聚和破坏染色体组织，在有丝分裂时阻断HeLa细胞增殖。然而，低浓度的隐藻素-52在有丝分裂时抑制细胞增殖（IC50 = 11 pM），而不会显著改变纺锤体微管的质量或组织。隐藻素-52似乎是迄今为止发现的最有效的微管动力学抑制剂。它在体外抑制单个微管的动态不稳定性行为（IC50 = 20 nM），降低缩短和生长的速率及程度，而不会显著降低聚合物质量或平均微管长度。使用[3H]隐藻素-52，我们发现该化合物在体外以高亲和力结合到微管末端（Kd，47 nM，每个微管最多约19.5个隐藻素-52分子）。通过分析隐藻素-52对动力学的影响及其与微管的结合情况，我们确定大约5 - 6个结合到微管上的隐藻素-52分子足以使动态性降低50%。隐藻素-52在细胞内浓缩了730倍，由此产生的细胞内隐藻素-52浓度与体外稳定微管动力学所需的浓度相似。数据表明，隐藻素-52强烈干扰有丝分裂期间微管功能所需的微管末端的动力学事件，并且它通过在微管末端形成可逆的隐藻素-52 - 微管蛋白稳定帽发挥作用。
