Deneddylation by SENP8 restricts hepatitis B virus propagation

Structural diversity of the CE-clan proteases in bacteria to disarm host ubiquitin defenses

Ubiquitin (Ub) and ubiquitin-like (UbL) modifications are critical regulators of multiple cellular processes in eukaryotes. These modifications are dynamically controlled by proteases that balance conjugation and deconjugation. In eukaryotes, these proteases include deubiquitinases (DUBs), mostly belonging to the CA-clan of cysteine proteases, and ubiquitin-like proteases (ULPs), belonging to the CE-clan proteases. Intriguingly, infectious bacteria exploit the CE-clan protease fold to generate deubiquitinating activities to disarm the immune system and degradation defenses of the host during infection. In this review, we explore the substrate preferences encoded within the CE-clan proteases and the structural determinants in the protease fold behind its selectivity, in particular those from infectious bacteria and viruses. Understanding this protease family provides crucial insights into the molecular mechanisms underlying infection and transmission of pathogenic organisms.

NFIC attenuates rheumatoid arthritis-induced inflammatory response in mice by regulating PTEN/SENP8 transcription

OBJECTIVE

To explore whether nuclear factor I C (NFIC) alleviated inflammatory response of synovial fibroblasts (SFs) caused by rheumatoid arthritis (RA) by regulating transcription levels of phosphatase and tension homolog deleted on chromosome 10 (PTEN) and sentrin-specific protease 8 (SENP8).

METHODS

NFIC, PTEN, and SENP8 levels in RASFs and normal SFs (NSFs) were measured by qRT-PCR and western blotting. The levels of Bax, Bcl-2, MMP-3, and MMP-13, as well as the content of superoxide dismutase (SOD) and malondialdehyde (MDA) were determined in RASFs and NSFs using western blotting and ELISA. The binding of NFIC to promoter sequences of PTEN and SENP8 was predicted and verified. A mouse model of collagen-induced arthritis (CIA) was established and evaluated according to the degree of joint swelling and arthritis index.

RESULTS

NFIC, PTEN, and SENP8 were downregulated in RASFs. RASFs had increased viability and MDA levels as well as decreased cell apoptosis and SOD content. NFIC was demonstrated to modulate the transcription of PTEN and SENP8 as their transcription factor. NFIC ameliorated the inflammatory response induced by RA in vivo by promoting the transcription of PTEN and SENP8.

CONCLUSION

NFIC acted as a transcription factor to facilitate the transcription of PTEN and SENP8, thereby inducing apoptosis of RASFs and effectively attenuating inflammatory response in CIA mice.

SUMOylation targeting mitophagy in cardiovascular diseases

Small ubiquitin-like modifier (SUMO) plays a key regulatory role in cardiovascular diseases, such as cardiac hypertrophy, hypertension, atherosclerosis, and cardiac ischemia-reperfusion injury. As a multifunctional posttranslational modification molecule in eukaryotic cells, SUMOylation is essentially associated with the regulation of mitochondrial dynamics, especially mitophagy, which is involved in the progression and development of cardiovascular diseases. SUMOylation targeting mitochondrial-associated proteins is admittedly considered to regulate mitophagy activation and mitochondrial functions and dynamics, including mitochondrial fusion and fission. SUMOylation triggers mitochondrial fusion to promote mitochondrial dysfunction by modifying Fis1, OPA1, MFN1/2, and DRP1. The interaction between SUMO and DRP1 induces SUMOylation and inhibits lysosomal degradation of DRP1, which is further involved in the regulation of mitochondrial fission. Both SUMOylation and deSUMOylation contribute to the initiation and activation of mitophagy by regulating the conjugation of MFN1/2 SERCA2a, HIF1α, and PINK1. SUMOylation mediated by the SUMO molecule has attracted much attention due to its dual roles in the development of cardiovascular diseases. In this review, we systemically summarize the current understanding underlying the expression, regulation, and structure of SUMO molecules; explore the biochemical functions of SUMOylation in the initiation and activation of mitophagy; discuss the biological roles and mechanisms of SUMOylation in cardiovascular diseases; and further provide a wider explanation of SUMOylation and deSUMOylation research to provide a possible therapeutic strategy for cardiovascular diseases. Considering the precise functions and exact mechanisms of SUMOylation in mitochondrial dysfunction and mitophagy will provide evidence for future experimental research and may serve as an effective approach in the development of novel therapeutic strategies for cardiovascular diseases. Regulation and effect of SUMOylation in cardiovascular diseases via mitophagy. SUMOylation is involved in multiple cardiovascular diseases, including cardiac hypertrophy, hypertension, atherosclerosis, and cardiac ischemia-reperfusion injury. Since it is expressed in multiple cells associated with cardiovascular disease, SUMOylation can be regulated by numerous ligases, including the SENP family proteins PIAS1, PIASy/4, UBC9, and MAPL. SUMOylation regulates the activation and degradation of PINK1, SERCA2a, PPARγ, ERK5, and DRP1 to mediate mitochondrial dynamics, especially mitophagy activation. Mitophagy activation regulated by SUMOylation further promotes or inhibits ventricular diastolic dysfunction, perfusion injury, ventricular remodelling and ventricular noncompaction, which contribute to the development of cardiovascular diseases.