The Dynamic Plasticity of P. aeruginosa CueR Copper Transcription Factor upon Cofactor and DNA Binding.

Bacteria use specialized proteins, like transcription factors, to rapidly control metal ion balance. CueR is a Gram-negative bacterial copper regulator. The structure of E. coli CueR complexed with Cu(I) and DNA was published, since then many studies have shed light on its function. However, P. aeruginosa CueR, which shows high sequence similarity to E. coli CueR, has been less studied. Here, we applied room-temperature electron paramagnetic resonance (EPR) measurements to explore changes in dynamics of P. aeruginosa CueR in dependency of copper concentrations and interaction with two different DNA promoter regions. We showed that P. aeruginosa CueR is less dynamic than the E. coli CueR protein and exhibits much higher sensitivity to DNA binding as compared to its E. coli CueR homolog. Moreover, a difference in dynamical behavior was observed when P. aeruginosa CueR binds to the copZ2 DNA promoter sequence compared to the mexPQ-opmE promoter sequence. Such dynamical differences may affect the expression levels of CopZ2 and MexPQ-OpmE proteins in P. aeruginosa. Overall, such comparative measurements of protein-DNA complexes derived from different bacterial systems reveal insights about how structural and dynamical differences between two highly homologous proteins lead to quite different DNA sequence-recognition and mechanistic properties.

Revealing the DNA Binding Modes of CsoR by EPR Spectroscopy.

In pathogens, a unique class of metalloregulator proteins, called gene regulatory proteins, sense specific metal ions that initiate gene transcription of proteins that export metal ions from the cell, thereby preventing toxicity and cell death. CsoR is a metalloregulator protein found in various bacterial systems that "sense" Cu(I) ions with high affinity. Upon copper binding, CsoR dissociates from the DNA promoter region, resulting in initiation of gene transcription. Crystal structures of CsoR in the presence and absence of Cu(I) from various bacterial systems have been reported, suggesting either a dimeric or tetrameric structure of these helical proteins. However, structural information about the CsoR-DNA complex is missing. Here, we applied electron paramagnetic resonance (EPR) spectroscopy to follow the conformational and dynamical changes that Mycobacterium tuberculosis CsoR undergoes upon DNA binding in solution. We showed that the quaternary structure is predominantly dimeric in solution, and only minor conformational and dynamical changes occur in the DNA bound state. Also, labeling of the unresolved C- terminus revealed no significant change in dynamics upon DNA binding. These observations are unique, since for other bacterial copper metalloregulators, such as the MerR and CopY families, major conformational changes were observed upon DNA binding, indicating a different mode of action for this protein family.

Langerhans cells shape postnatal oral homeostasis in a mechanical-force-dependent but microbiota and IL17-independent manner.

The postnatal interaction between microbiota and the immune system establishes lifelong homeostasis at mucosal epithelial barriers, however, the barrier-specific physiological activities that drive the equilibrium are hardly known. During weaning, the oral epithelium, which is monitored by Langerhans cells (LC), is challenged by the development of a microbial plaque and the initiation of masticatory forces capable of damaging the epithelium. Here we show that microbial colonization following birth facilitates the differentiation of oral LCs, setting the stage for the weaning period, in which adaptive immunity develops. Despite the presence of the challenging microbial plaque, LCs mainly respond to masticatory mechanical forces, inducing adaptive immunity, to maintain epithelial integrity that is also associated with naturally occurring alveolar bone loss. Mechanistically, masticatory forces induce the migration of LCs to the lymph nodes, and in return, LCs support the development of immunity to maintain epithelial integrity in a microbiota-independent manner. Unlike in adult life, this bone loss is IL-17-independent, suggesting that the establishment of oral mucosal homeostasis after birth and its maintenance in adult life involve distinct mechanisms.

Scurvy-induced pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is a progressive disease of the pulmonary vasculature that results in precapillary pulmonary hypertension. PAH is caused by a group of clinical conditions involving multiple organ systems. Several cases have been reported in the literature demonstrating an association between vitamin C deficiency and PAH. Low endothelial nitric oxide levels in the pulmonary vasculature, combined with the inappropriate activation of hypoxia-inducible transcription factors, seen in patients with ascorbic acid deficiency, are believed to be the main contributors to the pathogenesis of pulmonary vasculopathy and the exaggerated pulmonary vasoconstrictive response seen in patients with scurvy-induced PAH. Vitamin C supplementation is considered the definitive treatment.

Rituximab-Induced Immune Dysregulation Leading to Organizing Pneumonia, Bronchiectasis, and Pulmonary Fibrosis.

We present a case of rituximab-induced organizing pneumonia (OP) along with bronchiectasis and pulmonary fibrosis, in a patient with a history of granulomatosis with polyangiitis (GPA), on long-term maintenance therapy with rituximab. T-cell dysregulation and B-cell depletion associated with the chronic use of rituximab often lead to a profound immunosuppressed state with hypogammaglobulinemia and unbalanced T-cell response. This acquired immunodeficient state with severe immune dysregulation predisposed this patient to recurrent pulmonary infection and ultimately led to bronchiectasis and pulmonary fibrosis.

Microbiota-dependent and -independent postnatal development of salivary immunity.

While saliva regulates the interplay between the microbiota and the oral immune system, the mechanisms establishing postnatal salivary immunity are ill-defined. Here, we show that high levels of neutrophils and neonatal Fc receptor (FcRn)-transferred maternal IgG are temporarily present in the neonatal murine salivary glands in a microbiota-independent manner. During weaning, neutrophils, FcRn, and IgG decrease in the salivary glands, while the polymeric immunoglobulin receptor (pIgR) is upregulated in a growth arrest-specific 6 (GAS6)-dependent manner independent of the microbiota. Production of salivary IgA begins following weaning and relies on CD4-help, IL-17, and the microbiota. The weaning phase is characterized by a transient accumulation of dendritic cells capable of migrating from the oral mucosa to the salivary glands upon exposure to microbial challenges and activating T cells. This study reveals the postnatal mechanisms developed in the salivary glands to induce immunity and proposes the salivary glands as an immune inductive site.

Parkinsonism-Hyperpyrexia Syndrome: A Case Series and Literature Review.

Parkinsonism-hyperpyrexia syndrome (PHS) is a rare, potentially fatal neurological emergency, that is seen in Parkinson's Disease (PD) patients and mimics neuroleptic malignant syndrome. The most common trigger for PHS is sudden withdrawal of anti-parkinsonian medications, specifically levodopa. However, it can also be due to Deep Brain Stimulation (DBS) device malfunction. In this work, we describe three cases of PHS; the first of which is related to DBS battery depletion, and the remaining two to dopaminergic withdrawal. Additionally, we will include the results of a literature review on PHS, its etiologies, presentation, and management.