Ophiobolin A Covalently Targets Mitochondrial Complex IV Leading to Metabolic Collapse in Cancer Cells

Ophiobolin
A (OPA) is a sesterterpenoid fungal natural product
with broad anticancer activity. While OPA possesses multiple electrophilic
moieties that can covalently react with nucleophilic amino acids on
proteins, the proteome-wide targets and mechanism of OPA remain poorly
understood in many contexts. In this study, we used covalent chemoproteomic
platforms to map the proteome-wide reactivity of the OPA in a highly
sensitive lung cancer cell line. Among several proteins that OPA engaged,
we focused on two targets: lysine-72 of cytochrome c oxidase subunit
5A (COX5A) and cysteine-53 of mitochondrial hypoxia induced gene 1
domain family member 2A (HIGD2A). These two subunit proteins are part
of complex IV (cytochrome C oxidase) within the electron transport
chain and contributed significantly to the antiproliferative activity
of OPA. OPA activated mitochondrial respiration in a COX5A- and HIGD2A-dependent
manner, leading to an initial spike in mitochondrial ATP and heightened
mitochondrial oxidative stress. OPA compromised mitochondrial membrane
potential, ultimately leading to ATP depletion. We have used chemoproteomic
strategies to discover a unique anticancer mechanism of OPA through
activation of complex IV leading to compromised mitochondrial energetics
and rapid cell death.

Ophiobolin A（OPA）是一种广谱抗癌活性的四萜类真菌天然产物。尽管OPA含有多个亲电基团，能够与蛋白质上亲核的氨基酸共价反应，但在许多情况下，OPA的蛋白质组广谱靶标及其作用机制仍不甚明了。在本研究中，我们利用共价化学蛋白质组学平台，在高度敏感的肺癌细胞系中，对OPA的蛋白质组广谱反应性进行了映射。在OPA所作用的多种蛋白质中，我们聚焦于两种靶标：细胞色素c氧化酶亚基5A（COX5A）的赖氨酸72位和线粒体低氧诱导基因1家族成员2A（HIGD2A）的半胱氨酸53位。这两种亚基蛋白是电子传递链中复合物IV（细胞色素C氧化酶）的组成部分，对OPA的抗增殖活性作出了显著贡献。OPA通过依赖COX5A和HIGD2A的方式激活线粒体呼吸，导致线粒体ATP初始激增和线粒体氧化应激增强。OPA损害了线粒体膜电位，最终导致ATP耗竭。我们利用化学蛋白质组学策略，通过激活复合物IV，导致线粒体能量代谢受损和细胞快速死亡，从而发现了OPA的独特抗癌机制。