Discovery and characterization of a new cell-penetrating protein

Self-assembling, pH-responsive nanoflowers for inhibiting PAD4 and neutrophil extracellular trap formation and improving the tumor immune microenvironment

Self-assembling carrier-free nanodrugs are attractive agents because they accumulate at tumor by an enhanced permeability and retention (EPR) effect without introduction of inactive substances, and some nanodrugs can alter the immune environment. We synthesized a peptidyl arginine deiminase 4 (PAD4) molecular inhibitor, ZD-E-1M. It could self-assembled into nanodrug ZD-E-1. Using confocal laser scanning microscopy, we observed its cellular colocalization, PAD4 activity and neutrophil extracellular traps (NETs) formation. The populations of immune cells and expression of immune-related proteins were determined by single-cell mass cytometry. ZD-E-1 formed nanoflowers in an acidic environment, whereas it formed nanospheres at pH 7.4. Accumulation of ZD-E-1 at tumor was pH-responsive because of its pH-dependent differences in the size and shape. It could enter the nucleus and bind to PAD4 to prolong the intracellular retention time. In mice, ZD-E-1 inhibited tumor growth and metastasis by inhibiting PAD4 activity and NETs formation. Besides, ZD-E-1 could regulate the ratio of immune cells in LLC tumor-bearing mice. Immunosuppressive proteins like LAG3 were suppressed, while IFN-γ and TNF-α as stimulators of tumor immune response were upregulated. Overall, ZD-E-1 is a self-assembling carrier-free nanodrug that responds to pH, inhibits PAD4 activity, blocks neutrophil extracellular traps formation, and improves the tumor immune microenvironment.

B1 protein: a novel cell penetrating protein for in vitro and in vivo delivery of HIV-1 multi-epitope DNA constructs

Objectives

Enhancement of the potential ability of biomacromolecules to cross cell membranes is a critical step for development of effective therapeutic vaccine especially DNA vaccine against human immunodeficiency virus-1 (HIV-1) infection. The supercharged proteins were known as powerful weapons for delivery of different types of cargoes such as DNA and protein. Hence, we applied B1 protein with + 43 net charges obtained from a single frameshift in the gene encoding enhanced green fluorescent protein (eGFP) for delivery of two multi-epitope DNA constructs (nef-vpu-gp160-p24 and nef-vif-gp160-p24) in vitro and in vivo for the first time. For this purpose, B1 protein was generated in bacterial expression system under native conditions, and used to interact with both DNA constructs.

Results

Our data indicated that B1 protein (~ 27 kDa) was able to form a stable nanoparticle (~ 80–110 nm) with both DNA constructs at nitrogen: phosphate (N: P) ratio of 1:1. Moreover, the transfection efficiency of B1 protein for DNA delivery into HEK-293T cell line indicated that the cellular uptake of nef-vif-gp160-p24 DNA/ B1 and nef-vpu-gp160-p24 DNA/ B1 nanoparticles was about 32–35% with lower intensity as compared to TurboFect commercial reagent. On the other hand, immunization of BALB/c mice with different modalities demonstrated that B1 protein could enhance the levels of antibody, IFN-gamma and Granzyme B eliciting potent and strong Th1-directed cellular immunity.

Conclusion

Generally, our findings showed the potency of B1 protein as a promising gene delivery system to improve an effective therapeutic vaccine against HIV-1 infection.

A screen for genetic suppressor elements of hepatitis C virus identifies a supercharged protein inhibitor of viral replication

Genetic suppressor elements (GSEs) are biomolecules derived from a gene or genome of interest that act as transdominant inhibitors of biological functions presumably by disruption of critical biological interfaces. We exploited a cell death reporter cell line for hepatitis C virus (HCV) infection, n4mBid, to develop an iterative selection/enrichment strategy for the identification of anti-HCV GSEs. Using this approach, a library of fragments of an HCV genome was screened for sequences that suppress HCV infection. A 244 amino acid gene fragment, B1, was strongly enriched after 5 rounds of selection. B1 derives from a single-base frameshift of the enhanced green fluorescent protein (eGFP) which was used as a filler during fragment cloning. B1 has a very high net positive charge of 43 at neutral pH and a high charge-to-mass (kDa) ratio of 1.5. We show that B1 expression specifically inhibits HCV replication. In addition, five highly positively charged B1 fragments produced from progressive truncation at the C-terminus all retain the ability to inhibit HCV, suggesting that a high positive charge, rather than a particular motif in B1, likely accounts for B1's anti-HCV activity. Another supercharged protein, +36GFP, was also found to strongly inhibit HCV replication when added to cells at the time of infection. This study reports a new methodology for HCV inhibitor screening and points to the anti-HCV potential of positively charged proteins/peptides.