Guidance for Cardiopulmonary Resuscitation of Children With Suspected or Confirmed COVID-19.

This article aims to provide guidance to health care workers for the provision of basic and advanced life support to children and neonates with suspected or confirmed coronavirus disease 2019 (COVID-19). It aligns with the 2020 American Heart Association Guidelines for Cardiopulmonary Resuscitation (CPR) and Emergency Cardiovascular care while providing strategies for reducing risk of transmission of severe acute respiratory syndrome coronavirus 2 to health care providers. Patients with suspected or confirmed COVID-19 and cardiac arrest should receive chest compressions and defibrillation, when indicated, as soon as possible. Because of the importance of ventilation during pediatric and neonatal resuscitation, oxygenation and ventilation should be prioritized. All CPR events should therefore be considered aerosol-generating procedures. Thus, personal protective equipment (PPE) appropriate for aerosol-generating procedures (including N95 respirators or an equivalent) should be donned before resuscitation, and high-efficiency particulate air filters should be used. Any personnel without appropriate PPE should be immediately excused by providers wearing appropriate PPE. Neonatal resuscitation guidance is unchanged from standard algorithms, except for specific attention to infection prevention and control. In summary, health care personnel should continue to reduce the risk of severe acute respiratory syndrome coronavirus 2 transmission through vaccination and use of appropriate PPE during pediatric resuscitations. Health care organizations should ensure the availability and appropriate use of PPE. Because delays or withheld CPR increases the risk to patients for poor clinical outcomes, children and neonates with suspected or confirmed COVID-19 should receive prompt, high-quality CPR in accordance with evidence-based guidelines.

Molecular basis for peptidoglycan recognition by a bactericidal lectin.

RegIII proteins are secreted C-type lectins that kill Gram-positive bacteria and play a vital role in antimicrobial protection of the mammalian gut. RegIII proteins bind their bacterial targets via interactions with cell wall peptidoglycan but lack the canonical sequences that support calcium-dependent carbohydrate binding in other C-type lectins. Here, we use NMR spectroscopy to determine the molecular basis for peptidoglycan recognition by HIP/PAP, a human RegIII lectin. We show that HIP/PAP recognizes the peptidoglycan carbohydrate backbone in a calcium-independent manner via a conserved "EPN" motif that is critical for bacterial killing. While EPN sequences govern calcium-dependent carbohydrate recognition in other C-type lectins, the unusual location and calcium-independent functionality of the HIP/PAP EPN motif suggest that this sequence is a versatile functional module that can support both calcium-dependent and calcium-independent carbohydrate binding. Further, we show HIP/PAP binding affinity for carbohydrate ligands depends on carbohydrate chain length, supporting a binding model in which HIP/PAP molecules "bind and jump" along the extended polysaccharide chains of peptidoglycan, reducing dissociation rates and increasing binding affinity. We propose that dynamic recognition of highly clustered carbohydrate epitopes in native peptidoglycan is an essential mechanism governing high-affinity interactions between HIP/PAP and the bacterial cell wall.

Regulation of C-type lectin antimicrobial activity by a flexible N-terminal prosegment.

Members of the RegIII family of intestinal C-type lectins are directly antibacterial proteins that play a vital role in maintaining host-bacterial homeostasis in the mammalian gut, yet little is known about the mechanisms that regulate their biological activity. Here we show that the antibacterial activities of mouse RegIIIgamma and its human ortholog, HIP/PAP, are tightly controlled by an inhibitory N-terminal prosegment that is removed by trypsin in vivo. NMR spectroscopy revealed a high degree of conformational flexibility in the HIP/PAP inhibitory prosegment, and mutation of either acidic prosegment residues or basic core protein residues disrupted prosegment inhibitory activity. NMR analyses of pro-HIP/PAP variants revealed distinctive colinear backbone amide chemical shift changes that correlated with antibacterial activity, suggesting that prosegment-HIP/PAP interactions are linked to a two-state conformational switch between biologically active and inactive protein states. These findings reveal a novel regulatory mechanism governing C-type lectin biological function and yield new insight into the control of intestinal innate immunity.

An unstructured initiation site is required for efficient proteasome-mediated degradation.

The proteasome is the main ATP-dependent protease in eukaryotic cells and controls the concentration of many regulatory proteins in the cytosol and nucleus. Proteins are targeted to the proteasome by the covalent attachment of polyubiquitin chains. The ubiquitin modification serves as the proteasome recognition element but by itself is not sufficient for efficient degradation of folded proteins. We report that proteolysis of tightly folded proteins is accelerated greatly when an unstructured region is attached to the substrate. The unstructured region serves as the initiation site for degradation and is hydrolyzed first, after which the rest of the protein is digested sequentially. These results identify the initiation site as a novel component of the targeting signal, which is required to engage the proteasome unfolding machinery efficiently. The proteasome degrades a substrate by first binding to its ubiquitin modification and then initiating unfolding at an unstructured region.