SARS-CoV-2 precipitates respiratory distress by infection of airway epithelial cells and is often accompanied by acute kidney injury. We report that Kidney Injury Molecule-1/T cell immunoglobulin mucin domain 1 (KIM-1/TIM-1) is expressed in lung and kidney epithelial cells in COVID-19 patients and is a receptor for SARS-CoV-2. Human and mouse lung and kidney epithelial cells express KIM-1 and endocytose nanoparticles displaying the SARS-CoV-2 spike protein (virosomes). Uptake was inhibited both by anti-KIM-1 antibodies and by TW-37, our newly discovered inhibitor of KIM-1-mediated endocytosis. Enhanced KIM-1 expression by human kidney tubuloids increased uptake of virosomes. KIM-1 positive cells express less angiotensin-converting enzyme 2 (ACE2), the well-known receptor for SARS-CoV-2. Using microscale thermophoresis, the EC50 for KIM-1-SARS-CoV-2 spike protein, and receptor binding domain (RBD) interactions, were 19 and 10 nM respectively. Thus KIM-1 is an alternative receptor to ACE2 for SARS-CoV-2. KIM-1 targeted therapeutics may prevent and/or treat COVID-19.
Rapid and precise detection of pathogens is a critical step in the prevention and identification of emergencies related to health and biosafety as well as the clinical management of community-acquired urinary tract infections or sexually transmitted diseases. However, a conventional culture-based pathogen diagnostic method is time-consuming, permitting physicians to use antibiotics without ample clinical data. Here, we present a nanophotonic Light-driven Integrated cell lysis and polymerase chain reaction (PCR) on a chip with Gravity-driven cell enrichment Health Technology (LIGHT) for rapid precision detection of pathogens (<20 min). We created the LIGHT, which has the three functions of (1) selective enrichment of pathogens, (2) photothermal cell lysis, and (3) photonic PCR on a chip. We designed the gravity-driven cell enrichment via a nanoporous membrane on a chip that allows an effective bacterial enrichment of 40 000-fold from a 1 mL sample in 2 min. We established a light-driven photothermal lysis of preconcentrated bacteria within 1 min by designing the network of nanoplasmonic optical antenna on a chip for ultrafast light-to-heat conversion, created the nanoplasmonic optical antenna network-based ultrafast photonic PCR on a chip, and identified Escherichia coli. Finally, we demonstrated the end-point detection of up to 103 CFU/mL of E. coli in 10 min. We believe that our nanophotonic LIGHT will provide rapid and precise identification of pathogens in both developing and developed countries.
Uracil phosphoribosyltransferase (UPRT) is a member of a large family of salvage and biosynthetic enzymes, the phosphoribosyltransferases, and catalyzes the transfer of ribose 5-phosphate from ␣-D-5-phosphoribosyl-1-pyrophosphate (PRPP) to the N1 nitrogen of uracil. The UPRT from the opportunistic pathogen Toxoplasma gondii represents a promising target for rational drug design, because it can create intracellular, lethal nucleotides from subversive substrates. However, the development of such compounds requires a detailed understanding of the catalytic mechanism. Toward this end we determined the crystal structure of the T. gondii UPRT bound to uracil and cPRPP, a nonhydrolyzable PRPP analogue, to 2.5-Å resolution. The structure suggests that the catalytic mechanism is substrate-assisted, and a tetramer would be the more active oligomeric form of the enzyme. Subsequent biochemical studies revealed that GTP binding, which has been suggested to play a role in catalysis by other UPRTs, causes a 6-fold activation of the T. gondii enzyme and strikingly stabilizes the tetramer form. The basis for stabilization was revealed in the 2.45-Å resolution structure of the UPRT-GTP complex, whereby residues from three subunits contributed to GTP binding. Thus, our studies reveal an allosteric mechanism involving nucleotide stabilization of a more active, higher order oligomer. Such regulation of UPRT could play a role in the balance of purine and pyrimidine nucleotide pools in the cell.
Recent outbreaks of deadly infectious diseases, such as Ebola and Middle East respiratory syndrome coronavirus, have motivated the research for accurate, rapid diagnostics that can be administered at the point of care. Nucleic acid biomarkers for these diseases can be amplified and quantified via polymerase chain reaction (PCR). In order to solve the problems of conventional PCR--speed, uniform heating and cooling, and massive metal heating blocks--an innovative optofluidic cavity PCR method using light-emitting diodes (LEDs) is accomplished. Using this device, 30 thermal cycles between 94 °C and 68 °C can be accomplished in 4 min for 1.3 μL (10 min for 10 μL). Simulation results show that temperature differences across the 750 μm thick cavity are less than 2 °C and 0.2 °C, respectively, at 94 °C and 68 °C. Nucleic acid concentrations as low as 10(-8) ng μL(-1) (2 DNA copies per μL) can be amplified with 40 PCR thermal cycles. This simple, ultrafast, precise, robust, and low-cost optofluidic cavity PCR is favorable for advanced molecular diagnostics and precision medicine. It is especially important for the development of lightweight, point-of-care devices for use in both developing and developed countries.
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