Endoplasmic reticulum-associated protein degradation contributes to Toll innate immune defense in Drosophila melanogaster

Cul2 Is Essential for the Drosophila IMD Signaling-Mediated Antimicrobial Immune Defense

Cullin 2 (Cul2), a core component of the Cullin-RING E3 ubiquitin ligase complex, is integral to regulating distinct biological processes. However, its role in innate immune defenses remains poorly understood. In this study, we investigated the functional significance of Cul2 in the immune deficiency (IMD) signaling-mediated antimicrobial immune reactions in Drosophila melanogaster (fruit fly). We demonstrated that loss-of-function of Cul2 led to a marked reduction in antimicrobial peptide induction following bacterial infection, which was associated with increased fly mortality and bacterial load. The proteomic analysis further revealed that loss-of-function of Cul2 reduced the expression of Effete (Eff), a key E2 ubiquitin-conjugating enzyme during IMD signaling. Intriguingly, ectopic expression of eff effectively rescued the immune defects caused by loss of Cul2. Taken together, the results of our study underscore the critical role of Cul2 in ensuring robust IMD signaling activation, highlighting its importance in the innate immune defense against microbial infection in Drosophila.

Drosophila eIF3f1 mediates host immune defense by targeting dTak1

Eukaryotic translation initiation factors have long been recognized for their critical roles in governing the translation of coding RNAs into peptides/proteins. However, whether they harbor functional activities at the post-translational level remains poorly understood. Here, we demonstrate that eIF3f1 (eukaryotic translation initiation factor 3 subunit f1), which encodes an archetypal deubiquitinase, is essential for the antimicrobial innate immune defense of Drosophila melanogaster. Our in vitro and in vivo evidence indicate that the immunological function of eIF3f1 is dependent on the N-terminal JAMM (JAB1/MPN/Mov34 metalloenzymes) domain. Mechanistically, eIF3f1 physically associates with dTak1 (Drosophila TGF-beta activating kinase 1), a key regulator of the IMD (immune deficiency) signaling pathway, and mediates the turnover of dTak1 by specifically restricting its K48-linked ubiquitination. Collectively, these results provide compelling insight into a noncanonical molecular function of a translation initiation factor that controls the post-translational modification of a target protein.

Recent Advances in Effector Research of Magnaporthe oryzae

Recalcitrant rice blast disease is caused by Magnaporthe oryzae, which has a significant negative economic reverberation on crop productivity. In order to induce the disease onto the host, M. oryzae positively generates many types of small secreted proteins, here named as effectors, to manipulate the host cell for the purpose of stimulating pathogenic infection. In M. oryzae, by engaging with specific receptors on the cell surface, effectors activate signaling channels which control an array of cellular activities, such as proliferation, differentiation and apoptosis. The most recent research on effector identification, classification, function, secretion, and control mechanism has been compiled in this review. In addition, the article also discusses directions and challenges for future research into an effector in M. oryzae.