Kumar Sivakumar Prasanth, Nadendla Eswar Kumar, Malireddi R K Subbarao, Haque Syed Asfarul, Mall Raghvendra, Neuwald Andrew F, Kanneganti Thirumala-Devi
Department of Immunology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA.
Cryo-Electron Microscopy Center, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA.
Mol Biol Evol. 2025 Apr 30;42(5). doi: 10.1093/molbev/msaf096.
Caspases are evolutionarily conserved proteins essential for driving cell death in development and host defense. Caspase-8, a key member of the caspase family, is implicated in nonlytic apoptosis, as well as lytic forms of cell death. Recently, caspase-8 has been identified as an integral component of PANoptosomes, multiprotein complexes formed in response to innate immune sensor activation. Several innate immune sensors can nucleate caspase-8-containing PANoptosome complexes to drive inflammatory lytic cell death, PANoptosis. However, how the evolutionarily conserved and diverse functions of caspase-8 drive PANoptosis remains unclear. To address this, we performed evolutionary, sequence, structural, and functional analyses to decode caspase-8's complex-forming abilities and its interaction with the PANoptosome adaptor ASC. Our study distinguished distinct subgroups within the death domain superfamily based on their evolutionary and functional relationships, identified homotypic traits among subfamily members, and captured key events in caspase evolution. We also identified critical residues defining the heterotypic interaction between caspase-8's death effector domain and ASC's pyrin domain, validated through cross-species analyses, dynamic simulations, and in vitro experiments. Overall, our study elucidated recent evolutionary adaptations of caspase-8 that allowed it to interact with ASC, improving our understanding of critical molecular associations in PANoptosome complex formation and the underlying PANoptotic responses in host defense and inflammation. These findings have implications for understanding mammalian immune responses and developing new therapeutic strategies for inflammatory diseases.
半胱天冬酶是在进化上保守的蛋白质，对于驱动发育和宿主防御中的细胞死亡至关重要。半胱天冬酶 -8是半胱天冬酶家族的关键成员，与非裂解性凋亡以及细胞死亡的裂解形式有关。最近，半胱天冬酶 -8已被确定为PANoptosomes的一个组成部分，PANoptosomes是响应先天免疫传感器激活而形成的多蛋白复合物。几种先天免疫传感器可以使含半胱天冬酶 -8的PANoptosome复合物成核，以驱动炎性裂解性细胞死亡，即PANoptosis。然而，半胱天冬酶 -8在进化上保守且多样的功能如何驱动PANoptosis仍不清楚。为了解决这个问题，我们进行了进化、序列、结构和功能分析，以解码半胱天冬酶 -8的复合物形成能力及其与PANoptosome衔接蛋白ASC的相互作用。我们的研究根据其进化和功能关系，在死亡结构域超家族中区分了不同的亚组，确定了亚家族成员之间的同型特征，并捕捉了半胱天冬酶进化中的关键事件。我们还确定了定义半胱天冬酶 -8的死亡效应结构域与ASC的pyrin结构域之间异型相互作用的关键残基，并通过跨物种分析、动态模拟和体外实验进行了验证。总体而言，我们的研究阐明了半胱天冬酶 -8最近的进化适应性，使其能够与ASC相互作用，增进了我们对PANoptosome复合物形成中关键分子关联以及宿主防御和炎症中潜在PANoptotic反应的理解。这些发现对于理解哺乳动物免疫反应和开发炎症性疾病的新治疗策略具有重要意义。
