SARS-CoV-2 Nsp5 Activates NF-κB Pathway by Upregulating SUMOylation of MAVS

The COVID-19 is an infectious disease caused by SARS-CoV-2 infection. A large number of clinical studies found high-level expression of pro-inflammatory cytokines in patients infected with SARS-CoV-2, which fuels the rapid development of the disease. However, the specific molecular mechanism is still unclear. In this study, we found that SARS-CoV-2 Nsp5 can induce the expression of cytokines IL-1β, IL-6, TNF-α, and IL-2 in Calu-3 and THP1 cells. Further research found that Nsp5 enhances cytokine expression through activating the NF-κB signaling pathway. Subsequently, we investigated the upstream effectors of the NF-κB signal pathway on Nsp5 overexpression and discovered that Nsp5 increases the protein level of MAVS. Moreover, Nsp5 can promote the SUMOylation of MAVS to increase its stability and lead to increasing levels of MAVS protein, finally triggering activation of NF-κB signaling. The knockdown of MAVS and the inhibitor of SUMOylation treatment can attenuate Nsp5-mediated NF-κB activation and cytokine induction. We identified a novel role of SARS-CoV-2 Nsp5 to enhance cytokine production by activating the NF-κB signaling pathway.

High-Level Expression of Palmitoylated MPP1 Recombinant Protein in Mammalian Cells

Our recent studies have pointed to an important role of the MAGUK family member, MPP1, as a crucial molecule interacting with flotillins and involved in the lateral organization of the erythroid plasma membrane. The palmitoylation of MPP1 seems to be an important element in this process; however, studies on the direct effect of palmitoylation on protein–protein or protein–membrane interactions in vitro are still challenging due to the difficulties in obtaining functional post-translationally modified recombinant proteins and the lack of comprehensive protocols for the purification of palmitoylated proteins. In this work, we present an optimized approach for the high-yield overexpression and purification of palmitoylated recombinant MPP1 protein in mammalian HEK-293F cells. The presented approach facilitates further studies on the molecular mechanism of lateral membrane organization and the functional impact of the palmitoylation of MPP1, which could also be carried out for other palmitoylated proteins.

Neuropilin-2 Is Associated With Increased Hepatoblastoma Cell Viability and Motility

The neuropilins NRP1 and NRP2 are multifunctional glycoproteins that have been implicated in several cancer-related processes including cell survival, migration, and invasion in various tumor types. Here, we examine the role of neuropilins in hepatoblastoma (HB), the most common pediatric liver malignancy. Using a combination of immunohistochemistry, RNA analysis and western blotting, we observed high level expression of NRP1 and NRP2 in 19 of 20 HB specimens and in a majority of human HB cell lines (HUH6 and five cell lines established from patient-derived xenografts) studied but not in normal hepatocytes. Silencing of NRP2 expression in HUH6 and HB-282 HB cells resulted in decreased cell viability, impaired cytoskeleton remodeling, and reduced cell motility, suggesting that NRP2 contributes to the malignant phenotype. We propose that neuropilins warrant further investigation as biomarkers of HB and potential therapeutic targets.