Emergence by Design in Self-Assembling Protein Shells

Voltage controlled shutter regulates channel size and motion direction of protein aperture as durable nano-electric rectifier-----An opinion in biomimetic nanoaperture

In optical devices such as camera or microscope, an aperture is used to regulate light intensity for imaging. Here we report the discovery and construction of a durable bio-aperture at nanometerscale that can regulate current at the pico-ampere scale. The nano-aperture is made of 12 identical protein subunits that form a 3.6-nm channel with a shutter and "one-way traffic" property. This shutter responds to electrical potential differences across the aperture and can be turned off for double stranded DNA translocation. This voltage enables directional control, and three-step regulation for opening and closing. The nano-aperture was constructed in vitro and purified into homogeneity. The aperture was stable at pH2-12, and a temperature of -85C-60C. When an electrical potential was held, three reproducible discrete steps of current flowing through the channel were recorded. Each step reduced 32% of the channel dimension evident by the reduction of the measured current flowing through the aperture. The current change is due to the change of the resistance of aperture size. The transition between these three distinct steps and the direction of the current was controlled via the polarity of the voltage applied across the aperture. When the C-terminal of the aperture was fused to an antigen, the antibody and antigen interaction resulted in a 32% reduction of the channel size. This phenomenon was used for disease diagnosis since the incubation of the antigen-nano-aperture with a specific cancer antibody resulted in a change of 32% of current. The purified truncated cone-shape aperture automatically self-assembled efficiently into a sheet of the tetragonal array via head-to-tail self-interaction. The nano-aperture discovery with a controllable shutter, discrete-step current regulation, formation of tetragonal sheet, and one-way current traffic provides a nanoscale electrical circuit rectifier for nanodevices and disease diagnosis.

Organelle-inspired supramolecular nanomedicine to precisely abolish liver tumor growth and metastasis

Organelles are responsible for the efficient storage and transport of substances in living systems. A myriad of extracellular vesicles (EVs) acts as a bridge to exchange signaling molecules in cell–cell communication, and the highly dynamic tubulins and actins contribute to efficient intracellular substance transport. The inexhaustible cues of natural cargo delivery by organelles inspire researchers to explore the construction of biomimetic architectures for “smart” delivery carriers. Herein, we report a 10-hydroxycamptothecin (HCPT)-peptide conjugate HpYss that simulates the artificial EV-to-filament transformation process for precise liver cancer therapy. Under the sequential stimulus of extracellular alkaline phosphatase (ALP) and intracellular glutathione (GSH), HpYss proceeds via tandem self-assembly with a morphological transformation from nanoparticles to nanofibers. The experimental phase diagram elucidates the influence of ALP and GSH contents on the self-assembled nanostructures. In addition, the dynamic transformation of organelle-mimetic architectures that are formed by HpYss in HepG2 cells enables the efficient delivery of the anticancer drug HCPT to the nucleus, and the size–shape change from extracellular nanoparticles (50–100 nm) to intracellular nanofibers (4–9 nm) is verified to be of key importance for nuclear delivery. Nuclear targeting of HpYss amplifies apoptosis, thus significantly enhancing the inhibitory effect of HCPT (>10-fold) to HepG2 cells. Benefitting from the spatiotemporally controlled nanostructures, HpYss exhibited deep penetration, enhanced accumulation, and long-term retention in multicellular spheroid and xenograft models, potently abolishing liver tumor growth and preventing lung metastasis. We envision that our organelle-mimicking delivery strategy provides a novel paradigm for designing nanomedicine to cancer therapy.

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An organelle-inspired nanomedicine for precise liver cancer therapy is proposed.

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The delivery process mimics the transport of extracellular vesicles and filaments.

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The extra- and intracellular tandem self-assembly influence the nanostructures.

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The dynamic size–shape change of nanomedicine actuates the nuclear delivery.

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Spatiotemporally controlled nanomedicine abolishes liver tumor growth and lung metastasis.

Designer protein pseudo-capsids targeting intracellular bacteria

The emergence of multidrug-resistant bacteria stimulates the search for antimicrobial materials capable of addressing challenges conventional antibiotics fail to address. The ability to target intracellular bacteria remains one of the most fundamental tasks for contemporary antimicrobial treatments. Here we report engineered protein pseudo-capsids targeting bacteria internalised in macrophages. Using a combination of live-cell imaging and single-cell electron microscopy analysis we show that these materials effectively disrupt the bacteria without affecting the host cells. The study offers a disruptive antimicrobial strategy demonstrating potential for developing principally more challenging mechanisms for bacteria to overcome.

Conjugated Protein Domains as Engineered Scaffold Proteins

Assembly of proteins into higher-order complexes generates specificity and selectivity in cellular signaling. Signaling complex formation is facilitated by scaffold proteins that use modular scaffolding domains, which recruit specific pathway enzymes. Multimerization and recombination of these conjugated native domains allows the generation of libraries of engineered multidomain scaffold proteins. Analysis of these engineered proteins has provided molecular insight into the regulatory mechanism of the native scaffold proteins and the applicability of these synthetic variants. This topical review highlights the use of engineered, conjugated multidomain scaffold proteins on different length scales in the context of synthetic signaling pathways, metabolic engineering, liquid-liquid phase separation, and hydrogel formation.