HSC71 acetylation confers protection against Spiroplasma eriocheiris infection by inhibiting apoptosis and promoting ROS production in arthropods

Abstract

Heat shock proteins (HSP) are increasingly recognized as pivotal regulators of host innate immunity. However, the role of HSP70 post-translational modifications in modulating the immunologic functions during pathogenic infection remains poorly understood. Here, we demonstrated that heat shock cognate 71 kDa protein (HSC71), a member of the HSP70 family, was deacetylated following infection with intracellular pathogen Spiroplasma eriocheiris. HSC71 deficiency exacerbated hemocyte apoptosis and increased host susceptibility to S. eriocheiris infection. Conversely, ectopic expression of hyperacetylation-mimetic HSC71(K579Q) in Drosophila S2 cells conferred robust protection against S. eriocheiris by suppressing apoptosis and augmenting reactive oxygen species (ROS) production. Mechanistically, carnitine O-acetyltransferase (Crat) was identified as the specific acetyltransferase for HSC71. Crat acetylated HSC71 at lysine 579 (K579), which in turn impeded its interaction with the E3 ubiquitin ligase CHIP, thereby stabilizing HSC71 by attenuating ubiquitin-mediated degradation. Crat deficiency induced apoptosis and reduced ROS levels in hemocytes, thereby exacerbating S. eriocheiris intracellular proliferation. Furthermore, acetylation of HSC71 at K579 weakened its binding to superoxide dismutase (SOD), resulting in impaired SOD activity and consequent accumulation of microbicidal ROS. Pharmacological inhibition of the deacetylase SIRT1 with EX-527 enhanced HSC71 acetylation and ROS production, conferring resistance to S. eriocheiris infection in crabs. Notably, EX-527 similarly enhanced the acetylation of Drosophila HSC71 homolog, HSPA8, which in turn impaired its interaction with SOD. This led to elevated ROS levels and restricted intracellular proliferation of S. eriocheiris in S2 cells, demonstrating evolutionary conservation of this mechanism among arthropods. Therefore, this study established the modulation of HSC71 acetylation as a promising strategy to enhance arthropod immunity. Author summaryMembers of the HSP70 family are indispensable components of host innate immunity, and their functions are finely tuned by post-translational modifications. This study investigated the mechanisms that underlie acetylation modification of HSC71 mediated resistance to S. eriocheiris infection in crab. Our results revealed that the acetyltransferase Crat and the antioxidant enzyme SOD directly interacted with HSC71. Mechanistically, Crat acetylated HSC71 at K579, which prevented its ubiquitination by promoting the disassociation of E3 ubiquitin ligase CHIP, thereby improving HSC71 stability. In HSC71-deficient or Crat-deficient crabs, hemocyte apoptosis was markedly enhanced, leading to higher host mortality upon S. eriocheiris challenge. Meanwhile, K579 acetylation on HSC71 weakened the interaction between HSC71 and SOD, resulting in the accumulation of intracellular ROS and thereby restricting S. eriocheiris propagation. Administration of the SIRT1 inhibitor EX-527 enhanced HSC71 acetylation, elevated ROS production and reduced host susceptibility to S. eriocheiris infection. These findings revealed a novel role for Crat-mediated acetylation of HSC71 in orchestrating host defense through two synergistic mechanisms: suppressing apoptosis and promoting ROS accumulation. Thus, targeting HSC71 acetylation may represent a promising avenue to combat S. eriocheiris infection.