Knockdown of Mg2+/Mn2+ dependent protein phosphatase 1A promotes apoptosis in BV2 cells infected with Brucella suis strain 2 vaccine

The effector protein BspE affects Brucella survival by regulating the inflammatory response and apoptosis

Brucella T4SS secretes numerous effector proteins to disrupt host immune responses and apoptosis, enabling long-term survival. One such effector protein is BspE, whose role remains largely unknown. In this study, we demonstrated that BspE promotes the growth of Brucella, enhances its survival in macrophages, and affects the release of macrophage inflammatory factors. Furthermore, BspE facilitates Brucella colonization and pathological damage in mice. Our findings reveal that BspE can be translated in the host cell nucleus, where it interacts with the host RNA-binding protein PCBP1 to promote Brucella replication in macrophages. Knockdown of PCBP1 affects BspE-mediated proliferation of Brucella in macrophages. Furthermore, the BspE-PCBP1 interaction hinders P53 signaling and inhibits macrophage apoptosis. Although this interaction affects inflammatory cytokines, it does not significantly involve the NF-κB pathway. These findings contribute to a better understanding of how the Brucella effector protein BspE regulates host immune responses and apoptosis to influence its own survival.

A selective PPM1A inhibitor activates autophagy to restrict the survival of Mycobacterium tuberculosis

Metal-dependent protein phosphatases (PPMs) have essential roles in a variety of cellular processes, including inflammation, proliferation, differentiation, and stress responses, which are intensively investigated in cancer and metabolic diseases. Targeting PPMs to modulate host immunity in response to pathogens is an ambitious proposition. The feasibility of such a strategy is unproven because development of inhibitors against PPMs is challenging and suffers from poor selectivity. Combining a biomimetic modularization strategy with function-oriented synthesis, we design, synthesize and screen more than 500 pseudo-natural products, resulting in the discovery of a potent, selective, and non-cytotoxic small molecule inhibitor for PPM1A, SMIP-30. Inhibition of PPM1A with SMIP-30 or its genetic ablation (ΔPPM1A) activated autophagy through a mechanism dependent on phosphorylation of p62-SQSTM1, which restricted the intracellular survival of Mycobacterium tuberculosis in macrophages and in the lungs of infected mice. SMIP-30 provides proof of concept that PPMs are druggable and promising targets for the development of host-directed therapies against tuberculosis.