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Background: Many individuals with cystic fibrosis (CF) have chronic rhinosinusitis resulting in nasal obstruction, sinus infections, and repeated surgeries. Elexacaftor-tezacaftor-ivacaftor is a highly effective modulator therapy approved for individuals aged 6 years or older with CF who have at least one F508del allele or other responsive mutation. The current study tests the hypothesis that ELX/TEZ/IVA improves sinonasal disease in CF., Methods: The study was a pre/post, observational cohort study conducted at two sites. Participants underwent a study visit prior to starting ELX/TEZ/IVA and a second visit at a median of 9 months on therapy. Each visit included sinus CT scan, rigid nasal endoscopy, and sweat chloride measurement. Symptoms were measured with the 22 item Sinonasal Outcome Test at scheduled intervals during the study. Regression models were used to test for improvement in symptoms, endoscopy, and CT scales., Results: The study enrolled 34 individuals, with a median age of 27 years (range 12-60). Symptoms improved within 7 days of therapy and plateaued by day 28. Endoscopic crusting resolved and nasal polyposis improved, with a decrease in size or resolution of polyps. Sinus opacification and mucosal thickening improved on CT radiographs with treatment., Conclusions: Sinonasal symptoms improved rapidly and durably for at least 180 days on ELX/TEZ/IVA therapy. Objective measures of disease including endoscopic and CT findings improved with ELX/TEZ/IVA., Competing Interests: Declaration of Competing Interest No authors have competing interests with this work., (Copyright © 2022 The Author(s). Published by Elsevier B.V. All rights reserved.)

Diverse extracellular signals regulate seven transmembrane-spanning receptors to modulate cellular physiology. These receptors signal primarily through activation of heterotrimeric guanine nucleotide binding proteins (G proteins). A major determinant of heterotrimeric G protein signaling in vivo and in vitro is the intrinsic GTPase activity of the Galpha subunit. RGS (regulator of G protein signaling) domain-containing proteins are GTPase accelerating proteins specific for Galpha subunits. In this article, we describe the use of the ribose-conjugated fluorescent guanine nucleotide analog BODIPYFL-GTP as a spectroscopic probe to measure intrinsic and RGS protein-catalyzed nucleotide hydrolysis by Galphao. BODIPYFL-GTP bound to Galphao exhibits a 200% increase in fluorescence quantum yield. Hydrolysis of BODIPYFL-GTP to BODIPYFL-GDP reduces the quantum yield to 27% above its unbound value. We demonstrate that BODIPYFL-GTP can be used as a rapid real-time probe for measuring RGS domain-catalyzed GTP hydrolysis by Galphao. We demonstrate the effectiveness of this assay in the analysis of loss-of-function point mutants of both Galphao and RGS12. This assay should be useful in screening for and analyzing RGS protein inhibitory compounds.

Proteins encoding phosphotyrosine binding (PTB) domains function as adaptors or scaffolds to organize the signaling complexes involved in wide-ranging physiological processes including neural development, immunity, tissue homeostasis and cell growth. There are more than 200 proteins in eukaryotes and nearly 60 human proteins having PTB domains. Six PTB domain encoded proteins have been found to have mutations that contribute to inherited human diseases including familial stroke, hypercholesteremia, coronary artery disease, Alzheimer's disease and diabetes, demonstrating the importance of PTB scaffold proteins in organizing critical signaling complexes. PTB domains bind both peptides and headgroups of phosphatidylinositides, utilizing two distinct binding motifs to mediate spatial organization and localization within cells. The structure of PTB domains confers specificity for binding peptides having a NPXY motif with differing requirements for phosphorylation of the tyrosine within this recognition sequence. In this review, we use structural, evolutionary and functional analysis to divide PTB domains into three groups represented by phosphotyrosine-dependent Shc-like, phosphotyrosine-dependent IRS-like and phosphotyrosine-independent Dab-like PTBs, with the Dab-like PTB domains representing nearly 75% of proteins encoding PTB domains. In addition, we further define the binding characteristics of the cognate ligands for each group of PTB domains. The signaling complexes organized by PTB domain encoded proteins are largely unknown and represents an important challenge in systems biology for the future.