Faculty of Medicine, MV Lomonosov Moscow State University, Moscow, Russia, 119991.
Belozersky Institute of Physicochemical Biology, MV Lomonosov Moscow State University, Moscow, Russia, 119991.
Cell Death Dis. 2020 Oct 3;11(10):825. doi: 10.1038/s41419-020-03023-6.
Caspase-2 is a unique and conservative cysteine protease which plays an important role in several cellular processes including apoptotic cell death. Although the molecular mechanisms of its activation remain largely unclear, a major role belongs to the architecture of the caspase-2 active center. We demonstrate that the substitution of the putative phosphorylation site of caspase-2, Serine-384 to Alanine, blocks caspase-2 processing and decreases its enzymatic activity. Strikingly, in silico analysis using molecular dynamics simulations has shown that Serine-384 is crucially involved in interactions within the caspase-2 active center. It stabilizes Arginine-378, which forms a crucial hydrogen bond with the aspartate residue of a substrate. Hence, Serine-384 is essential for supporting a proper architecture of the active center of caspase-2. Moreover, molecular modeling strongly proved steric inaccessibility of Ser-384 to be phosphorylated. Importantly, a multiple alignment has demonstrated that both Serine-384 and Arg-378 residues are highly conservative across all members of caspase family, which allows us to suggest that this diade is indispensable for caspase processing and activity. Spontaneous mutations in this diade might influence oncosuppressive function of caspases, in particular of caspase-2. Likewise, the mutation of Ser-384 is associated with the development of lung squamous cell carcinoma and adenocarcinoma. Taken together, we have uncovered a central feature of the caspase-2 activation mechanism which is crucial for the regulation of its signaling network.
半胱天冬酶-2 是一种独特且保守的半胱氨酸蛋白酶，在包括细胞凋亡在内的几种细胞过程中发挥重要作用。尽管其激活的分子机制在很大程度上仍不清楚，但主要作用属于半胱天冬酶-2 活性中心的结构。我们证明，半胱天冬酶-2 的假定磷酸化位点丝氨酸-384 突变为丙氨酸，可阻断半胱天冬酶-2 的加工并降低其酶活性。引人注目的是，使用分子动力学模拟的计算机分析表明，丝氨酸-384 对半胱天冬酶-2 活性中心内的相互作用至关重要。它稳定了精氨酸-378，后者与底物的天冬氨酸残基形成关键氢键。因此，丝氨酸-384 对半胱天冬酶-2 活性中心的适当结构是必不可少的。此外，分子建模强烈证明丝氨酸-384 不能被磷酸化是由于空间位阻。重要的是，多重比对表明，丝氨酸-384 和精氨酸-378 残基在半胱天冬酶家族的所有成员中高度保守，这使我们能够提出，这个二联体对半胱天冬酶的加工和活性是不可或缺的。该二联体的自发突变可能会影响半胱天冬酶的抑瘤功能，特别是对半胱天冬酶-2 的影响。同样，丝氨酸-384 的突变与肺鳞状细胞癌和腺癌的发生有关。总之，我们揭示了半胱天冬酶-2 激活机制的核心特征，这对半胱天冬酶信号网络的调节至关重要。
