The Amino Terminus of LeuT Changes Conformation in an Environment Sensitive Manner.

Neurotransmitter:sodium symporters are highly expressed in the human brain and catalyze the uptake of substrate through the plasma membrane by using the electrochemical gradient of sodium as the energy source. The bacterial homolog LeuT, a small amino acid transporter isolated from the bacteria Aquifex aeolicus, is the founding member of the family and has been crystallized in three conformations. The N-terminus is structurally well defined and strongly interacts with the transporter core in the outward-facing conformations. However, it could not be resolved in the inward-facing conformation, which indicates enhanced mobility. Here we investigate conformations and dynamics of the N-terminus, by combining molecular dynamics simulations with experimental verification using distance measurements and accessibility studies. We found strongly increased dynamics of the N-terminus, but also that helix TM1A is subject to enhanced mobility. TM1A moves towards the transporter core in the membrane environment, reaching a conformation that is closer to the structure of LeuT with wild type sequence, indicating that the mutation introduced to create the inward-facing structure might have altered the position of helix TM1A. The mobile N-terminus avoids entering the open vestibule of the inward-facing state, as accessibility studies do not show any reduction of quenching by iodide of a fluorophore attached to the N-terminus.

Pulmonary matrix-derived hydrogels from patients with idiopathic pulmonary fibrosis induce a proinflammatory state in lung fibroblasts in vitro.

Idiopathic pulmonary fibrosis (IPF), one of the most common forms of interstitial lung disease, is a poorly understood, chronic, and often fatal fibroproliferative condition with only two FDA-approved medications. Understanding the pathobiology of the fibroblast in IPF is critical to evaluating and discovering novel therapeutics. Using a decellularized lung matrix derived from patients with IPF, we generate three-dimensional hydrogels as in vitro models of lung physiology and characterize the phenotype of fibroblasts seeded into the hydrogels. When cultured in IPF extracellular matrix hydrogels, IPF fibroblasts display differential contractility compared with their normal counterparts, lose the classical myofibroblast marker α-smooth muscle actin, and increase expression of proinflammatory cytokines compared with fibroblasts seeded two-dimensionally on tissue culture dishes. We validate this proinflammatory state in fibroblast-conditioned media studies with monocytes and monocyte-derived macrophages. These findings add to a growing understanding of the lung microenvironment effect on fibroblast phenotypes, shed light on the potential role of fibroblasts as immune signaling hubs during lung fibrosis, and suggest intervention in fibroblast-immune cell cross-talk as a possible novel therapeutic avenue.

Frequency of Interstitial Lung Disease in Rheumatoid Arthritis Patients: A Hospital-Based Study.

INTRODUCTION: Among various extra-articular manifestations of rheumatoid arthritis (RA), interstitial lung disease (ILD) is the most frequent and concerning manifestation. The reported frequency of RA-associated ILD (RA-ILD) varies in the literature. The objective of the present study was to determine the frequency of ILD in RA patients at a teaching hospital in Rawalpindi. METHODS: 175 male and female patients between 18-70 years were enrolled in the study from January 21, 2022, till July 24, 2022. Patients diagnosed with RA were screened for the concomitant presence of ILD (increased pulmonary markings on chest X-rays and total lung capacity ≤ 80%, predicted on pulmonary function tests). In addition, the frequency of RA-ILD was noted and compared across various subgroups of patients based on age, gender, and disease duration. RESULTS: The mean age of the patients was 45.3 ± 11.5 years. The male-to-female ratio was 1:3.1. The mean disease duration was 6.2 ± 3.5 years at the time of presentation. A total of 118 (67.4%) patients were diagnosed with RA-ILD. The frequency of RA-ILD was significantly higher among patients with a prolonged duration of disease, < 5 years vs. ≥ 5 years (59.1% vs. 75.9%; p-value=0.018). Among 118 patients with RA-ILD, usual interstitial pneumonia (UIP) was the most frequent pattern and was noted in 74 (62.7%) patients, followed by nonspecific interstitial pneumonitis (NSIP), which was noted in 44 (37.3%) patients. When compared, there was no statistically significant difference in the frequency of high-resolution CT (HRCT) pattern of RA-ILD across various subgroups of patients based on age (p-value=0.969), gender (p-value=0.934), and duration of disease (p-value=0.881). CONCLUSION: In the present study, a substantial proportion of RA patients suffered RA-ILD, which warrants routine screening of these patients for undiagnosed pulmonary involvement so that timely identification and anticipated management may improve the outcome of such cases in future clinical practice.