Abstract：
Wnt signaling is essential for normal development and is a therapeutic target in cancer. The enzyme PORCN, or porcupine, is a membrane-bound O-acyltransferase (MBOAT) that is required for the post-translational modification of all Wnts, adding an essential mono-unsaturated palmitoleic acid to a serine on the tip of Wnt hairpin 2. Inherited mutations in PORCN cause focal dermal hypoplasia, and therapeutic inhibition of PORCN slows the growth of Wnt-dependent cancers. Based on homology to mammalian MBOAT proteins we developed and validated a structural model of PORCN. The model accommodates palmitoleoyl-CoA and Wnt hairpin 2 in two tunnels in the conserved catalytic core, shedding light on the catalytic mechanism. The model predicts how previously uncharacterized human variants of uncertain significance can alter PORCN function. Drugs including ETC-159, IWP-L6 and LGK-974 dock in the PORCN catalytic site, providing insights into PORCN pharmacologic inhibition. This structural model enhances our mechanistic understanding of PORCN substrate recognition and catalysis as well as the inhibition of its enzymatic activity and can facilitate the development of improved inhibitors and the understanding of disease relevant PORCN mutants.
摘要：
Wnt信号传导对于正常发育是必需的,并且是癌症中的治疗靶标。酶PORCN，或者豪猪,是所有Wnt的翻译后修饰所需的膜结合O-酰基转移酶（MBOAT），在Wnt发夹2的尖端上的丝氨酸中添加必需的单不饱和棕榈油酸。PORCN的遗传突变导致局灶性真皮发育不全，和治疗性抑制PORCN减缓Wnt依赖性癌症的生长。基于与哺乳动物MBOAT蛋白的同源性，我们开发并验证了PORCN的结构模型。该模型在保守的催化核心的两个隧道中容纳了棕榈油酰辅酶A和Wnt发夹2，在催化机理上发光。该模型预测了不确定意义的先前未表征的人类变体如何改变PORCN功能。包括ETC-159、IWP-L6和LGK-974在内的药物停靠在PORCN催化位点，提供对PORCN药物抑制的见解。该结构模型增强了我们对PORCN底物识别和催化以及对其酶活性的抑制的机理理解,并且可以促进改进的抑制剂的开发和对疾病相关PORCN突变体的理解。
