Uncovering the Interaction between TRAF1 and MAVS in the RIG-I Pathway to Enhance the Upregulation of IRF1/ISG15 during Classical Swine Fever Virus Infection.

Classical swine fever (CSF) is caused by the classical swine fever virus (CSFV), which poses a threat to swine production. The activation of host innate immunity through linker proteins such as tumor necrosis factor receptor (TNF-R)-associated factor (TRAF) is crucial for the induction of the NF-κB pathway. Recent research has revealed the involvement of mitochondrial antiviral-signaling protein (MAVS) in the interaction with TRAF2, 3, 5, and 6 to activate both the NF-κB and IRF3 pathways. This study revealed that CSFV infection led to the upregulation of TRAF1 mRNA and protein levels; moreover, TRAF1 overexpression inhibited CSFV replication, while TRAF1 knockdown promoted replication, highlighting its importance in the host response to CSFV infection. Additionally, the expression of RIG-I, MAVS, TRAF1, IRF1, and ISG15 were detected in PK-15 cells infected with CSFV, revealing that TRAF1 plays a role in regulating IRF1 and ISG15 within the RIG-I pathway. Furthermore, Co-IP, GST pull-down, and IFA analyses demonstrated that TRAF1 interacted with MAVS and co-localized in the cytoplasm during CSFV infection. Ultimately, TRAF1 acted as a novel member of the TRAF family, bound to MAVS as a linker molecule, and functioned as a mediator downstream of MAVS in the RIG-I/MAVS pathway against CSFV replication.

Apolipoprotein D facilitates rabies virus propagation by interacting with G protein and upregulating cholesterol.

Rabies virus (RABV) causes a fatal neurological disease, consisting of unsegmented negative-strand RNA, which encodes five structural proteins (3'-N-P-M-G-L-5'). Apolipoprotein D (ApoD), a lipocalin, is upregulated in the nervous system after injury or pathological changes. Few studies have focused on the role of ApoD during virus infection so far. This study demonstrated that ApoD is upregulated in the mouse brain (in vivo) and C8-D1A cells (in vitro) after RABV infection. By upregulating ApoD expression in C8-D1A cells, we found that ApoD facilitated RABV replication. Additionally, Co-immunoprecipitation demonstrated that ApoD interacted with RABV glycoprotein (G protein). The interaction could promote RABV replication by upregulating the cholesterol level. These findings revealed a novel role of ApoD in promoting RABV replication and provided a potential therapeutic target for rabies.

Enhanced bone regeneration via spatiotemporal and controlled delivery of a genetically engineered BMP-2 in a composite Hydrogel.

Scaffolds functionalized with bone morphogenetic protein-2 (BMP-2) have shown great potential for bone regeneration. However, structural instability and the necessity for supra-physiological dose have thus far limited practical applications for BMP-2. Protein modification and site-specific covalent immobilization of BMP-2 to carrier materials might be optimal strategies to overcome these problems. Here, we report a broadly applicable strategy where the polyhistidine tag-T4 Lysozyme (His6-T4L) was genetically fused at the N-terminus of BMP-2 and used as a protein spacer, which on one hand enhanced protein solubility and stability, and on the other hand mediated site-specific covalent anchoring of BMP-2 upon binding to nickel-chelated nitrilotriacetic acid (Ni-NTA) microparticles (denoted as MPs-His6-T4L-BMP2) to further maximize its rescued activity. We also constructed a novel gelatin-based hydrogel that was crosslinked by transglutaminase (TG) and tannic acid (TA). This hydrogel, when incorporated with MPs-His6-T4L-BMP2, displayed excellent in-situ injectability, thermosensitivity, adhesiveness and improved mechanical properties. The effective loading mode led to a controlled and long-term sustained release of His6-T4L-BMP2, thereby resulting in enhancement of bone regeneration in a critical-sized bone defect. We believe that the protein modification strategy proposed here opens up new route not only for BMP-2 applications, but can be used to inform novel uses for other macromolecules.

Rationally designed protein cross-linked hydrogel for bone regeneration via synergistic release of magnesium and zinc ions.

The development of recombinant protein cross-linked injectable hydrogels with good mechanical strength and effective drug loading capacity for bone regeneration is extremely attractive and rarely reported. Here, we report the fabrication of a smart hydrogel delivery system by incorporating a rationally designed T4 lysozyme mutant (T4M) to mediate the localized delivery and synergistic release of Mg2+ and Zn2+ for bone repair. Apart from its intrinsic antibacterial properties, T4M bears abundant free amine groups on its surface to function as effective covalent crosslinkers to strengthen the hydrogel network as well as exhibits specific binding affinity to multivalent cations such as Zn2+. Moreover, the integrin receptor-binding Arg-Gly-Asp (RGD) sequence was introduced onto the C-terminus of T4 lysozyme to improve its cellular affinity and further facilitate rapid tissue regeneration. The final composite hydrogel displays excellent injectability, improved mechanical properties, antibacterial activity, and unique bioactivities. The effective loading of Mg2+/Zn2+ in the hydrogels could mediate the sequential and sustained release of Mg2+ and Zn2+, thereby resulting in synergistic enhancement on bone regeneration through modulation of the MAPK signaling pathway. We believe that the strategy proposed in this paper opens up a new route for developing protein cross-linked smart delivery systems for tissue regeneration.