Apoptosis-Amplified Assembly of Porphyrin Nanofiber Enhances Photodynamic Therapy of Oral Tumor.

Oral squamous cell carcinoma (OSCC) is the most common oral cancer, having high recurrence and metastasis features. In addition to surgery, photodynamic therapy (PDT) is considered as another effective approach for OSCC treatment. The water solubility of currently available PDT photosensitizers (PSs) is poor, lowering their singlet oxygen (1O2) yield and consequent PDT efficiency. Strategies of PS assembly have been reported to increase 1O2 yield, but it is still possible to further enhance PDT efficiency. In this work, we utilized apoptosis to amplify the assembly of porphyrin nanofibers for enhanced PDT of OSCC. A water-soluble porphyrin derivative, Ac-Asp-Glu-Val-Asp-Asp-TPP (Ac-DEVDD-TPP), was designed for this purpose. Upon caspase-3 (Casp3, an activated enzyme during apoptosis) cleavage and laser irradiation, Ac-DEVDD-TPP was converted to D-TPP, which spontaneously self-assembled into porphyrin nanofibers, accompanied by 1.4-fold and 2.1-fold 1O2 generations in vitro and in cells, respectively. The as-formed porphyrin nanofiber induced efficient cell apoptosis and pyroptosis. In vivo experiments demonstrated that, compared with the scrambled control compound Ac-DEDVD-TPP, Ac-DEVDD-TPP led to 6.2-fold and 1.3-fold expressions of Casp3 in subcutaneous and orthotopic oral tumor models, respectively, and significantly suppressed the tumors. We envision that our strategy of apoptosis-amplified porphyrin assembly might be applied for OSCC treatment in the clinic in the near future.

Dual Aggregations of a Near-Infrared Aggregation-Induced Emission Luminogen for Enhanced Imaging of Alzheimer's Disease.

Aggregation-induced emission (AIE) enables "Turn-On" imaging generally through single aggregation of the AIE luminogen (AIEgen). Dual aggregrations of the AIEgen might further enhance the imaging intensity and the consequent sensitivity. Herein, we rationally designed a near-infrared (NIR) AIEgen Ac-Trp-Glu-His-Asp-Cys(StBu)-Pra(QMT)-CBT (QMT-CBT) which, upon caspase1 (Cas1) activation, underwent a CBT-Cys click reaction to form cyclic dimers QMT-Dimer (the first aggregation) and assembled into nanoparticles (the second aggregation), turning the AIE signal "on" for enhanced imaging of Alzheimer's disease (AD). Molecular dynamics simulations validated that the fluorogen QMT in QMT-NPs stacked much tighter with each other than in the single aggregates of the control compound Ac-Trp-Glu-His-Asp-Cys(tBu)-Pra(QMT)-CBT (QMT-CBT-Ctrl). Dual aggregations of QMT rendered 1.9-, 1.7-, and 1.4-fold enhanced fluorescence intensities of its single aggregation in vitro, in cells, and in a living AD mouse model, respectively. We anticipate this smart fluorogen to be used for sensitive diagnosis of AD in the clinic in the near future.

The truncated TNL receptor TN2-mediated immune responses require ADR1 function.

The loss of function of exocyst subunit EXO70B1 leads to autoimmunity, which is dependent on TIR-NBS2 (TN2), a truncated intracellular nucleotide-binding and leucine-rich repeat receptor (NLR). However, how TN2 triggers plant immunity and whether typical NLRs are required in TN2-activated resistance remain unclear. Through the CRISPR/Cas9 gene editing system and knockout analysis, we found that the spontaneous cell death and enhanced resistance in exo70B1-3 were independent of the full-length NLR SOC3 and its closest homolog SOC3-LIKE 1 (SOC3-L1). Additionally, knocking out SOC3-L1 or TN2 did not suppress the chilling sensitivity conferred by chilling sensitive 1-2 (chs1-2). The ACTIVATED DISEASE RESISTANCE 1 (ADR1) family and the N REQUIREMENT GENE 1 (NRG1) family have evolved as helper NLRs for many typical NLRs. Through CRISPR/Cas9 gene editing methods, we discovered that the autoimmunity of exo70B1-3 fully relied on ADR1s, but not NRG1s, and ADR1s contributed to the upregulation of TN2 transcript levels in exo70B1-3. Furthermore, overexpression of TN2 also led to ADR1-dependent autoimmune responses. Taken together, our genetic analysis highlights that the truncated TNL protein TN2-triggered immune responses require ADR1s as helper NLRs to activate downstream signaling, revealing the importance and complexity of ADR1s in plant immunity regulation.

Assembly drives regioselective azide-alkyne cycloaddition reaction.

Azide-alkyne cycloaddition reaction is a very common organic reaction to synthesize nitrogen-containing heterocycles. Once catalyzed by Cu(I) or Ru(II), it turns out to be a click reaction and thus is widely applied in chemical biology for labeling. However, besides their poor regioselectivity towards this reaction, these metal ions are not biologically friendly. Hence, it is an urgent need to develop a metal-free azide-alkyne cycloaddition reaction for biomedical applications. In this work, we found that, in the absence of metal ions, supramolecular self-assembly in an aqueous solution could realize this reaction with excellent regioselectivity. Nap-Phe-Phe-Lys(azido)-OH firstly self-assembled into nanofibers. Then, Nap-Phe-Phe-Gly(alkynyl)-OH at equivalent concentration approached to react with the assembly to yield the cycloaddition product Nap-Phe-Phe-Lys(triazole)-Gly-Phe-Phe-Nap to form nanoribbons. Due to space confinement effect, the product was obtained with excellent regioselectivity. Employing the excellent properties of supramolecular self-assembly, we are applying this strategy to realize more reactions without metal ion catalysis.

Force tuning explains changes in phasic dopamine signaling during stimulus-reward learning.

According to a popular hypothesis, phasic dopamine (DA) activity encodes a reward prediction error (RPE) necessary for reinforcement learning. However, recent work showed that DA neurons are necessary for performance rather than learning. One limitation of previous work on phasic DA signaling and RPE is the limited behavioral measures. Here, we measured subtle force exertion while recording and manipulating DA activity in the ventral tegmental area (VTA) during stimulus-reward learning. We found two major populations of DA neurons that increased firing before forward and backward force exertion. Force tuning is the same regardless of learning, reward predictability, or outcome valence. Changes in the pattern of force exertion can explain results traditionally used to support the RPE hypothesis, such as modulation by reward magnitude, probability, and unpredicted reward delivery or omission. Thus VTA DA neurons are not used to signal RPE but to regulate force exertion during motivated behavior.

Seed priming with calcium chloride enhances stress tolerance in rice seedlings.

Calcium is a crucial second messenger in plant cells and contributes to plant resistance against biotic and abiotic stress. Plant defense priming with natural or synthetic compounds leads to quicker and stronger resistance responses. However, whether pretreatment of plant seeds with calcium could improve their resistance to stress remains poorly understood. In this study, we showed that rice seedlings grown from calcium chloride (CaCl2)-pretreated seeds displayed enhanced resistance to the rice blast fungus Magnaporthe oryzae and the rice bacterial pathogen Xanthomonas oryzae pv. Oryzae (Xoo). Seed priming with CaCl2 also led to enhanced rice tolerance to salt and cold. Furthermore, the reactive oxygen species (ROS) burst increased significantly upon immunity activation in the leaves of rice seedlings grown from CaCl2-pretreated seeds. Additionally, we analyzed the rice calmodulin-binding protein 60 (OsCBP60) family and found that there were 19 OsCBP60s in rice cultivar Zhonghua 11 (ZH11). The transcripts of several OsCBP60s were chitin- and M. oryzae-inducible, suggesting that they may contribute to rice resistance. Taken together, these data indicate that seed priming with CaCl2 can effectively enhance rice tolerance to multiple stresses, perhaps by boosting the burst of ROS, and OsCBP60 family members may also play an essential role in this process.

An ultrapotent pan-ß-coronavirus lineage B (ß-CoV-B) neutralizing antibody locks the receptor-binding domain in closed conformation by targeting its conserved epitope.

New threats posed by the emerging circulating variants of SARS-CoV-2 highlight the need to find conserved neutralizing epitopes for therapeutic antibodies and efficient vaccine design. Here, we identified a receptor-binding domain (RBD)-binding antibody, XG014, which potently neutralizes ß-coronavirus lineage B (ß-CoV-B), including SARS-CoV-2, its circulating variants, SARS-CoV and bat SARSr-CoV WIV1. Interestingly, antibody family members competing with XG014 binding show reduced levels of cross-reactivity and induce antibody-dependent SARS-CoV-2 spike (S) protein-mediated cell-cell fusion, suggesting a unique mode of recognition by XG014. Structural analyses reveal that XG014 recognizes a conserved epitope outside the ACE2 binding site and completely locks RBD in the non-functional "down" conformation, while its family member XG005 directly competes with ACE2 binding and position the RBD "up". Single administration of XG014 is effective in protection against and therapy of SARS-CoV-2 infection in vivo. Our findings suggest the potential to develop XG014 as pan-ß-CoV-B therapeutics and the importance of the XG014 conserved antigenic epitope for designing broadly protective vaccines against ß-CoV-B and newly emerging SARS-CoV-2 variants of concern.

Self-assembly of peptide nanofibers for imaging applications.

Pathological stimuli-responsive self-assembly of peptide nanofibers enables selective accumulation of imaging agent cargos in the stimuli-rich regions of interest. It provides enhanced imaging signals, biocompatibility, and tumor/disease accessibility and retention, thereby promoting smart, precise, and sensitive tumor/disease imaging both in vitro and in vivo. Considering the remarkable significance and recent encouraging breakthroughs of self-assembled peptide nanofibers in tumor/disease diagnosis, this reivew is herein proposed. We emphasize the recent advances particularly in the past three years, and provide an outlook in this field.