Pedersen, E. S. | bioRxiv Science

bioRxiv2020

Dynamic NHE1-Calmodulin complexes of varying stoichiometry and structure regulate Ca2+-dependent NHE1 activation

Calmodulin (CaM) engages in Ca2+-dependent interactions with numerous proteins, including human Na+/H+-exchanger NHE1. Using nuclear magnetic resonance (NMR) spectroscopy, isothermal titration calorimetry, and fibroblasts expressing wildtype and mutant NHE1, we discovered multiple accessible states of this important complex existing in different NHE1:CaM stoichiometries and structures. We solved the NMR solution structure of a ternary complex in which CaM links two NHE1 cytosolic tails. In vitro, stoichiometries and affinities were tunable by variations in NHE1:CaM ratio and calcium ([Ca2+]) and by phosphorylation of S648 in the first CaM-binding -helix. In cells, Ca2+-CaM-induced NHE1 activity was reduced by mimicking S648 phosphorylation or mutating the first CaM-binding helix, whereas Ca2+-induced NHE1 activity was unaffected by inhibition of Akt, one of several kinases phosphorylating S648. Our results reveal the diversity of NHE1:CaM interactions and suggest that CaM may contribute to NHE1 dimerization. We propose that similar structural diversity is relevant to other CaM complexes.

cell biology↗

bioRxiv2019

Do clinical investigations predict long-term outcome? A follow-up of paediatric respiratory outpatients

IntroductionThe contribution of clinical investigations to prediction of long-term outcomes of children investigated for asthma is unclear. AimWe performed a broad range of clinical tests and investigated whether they helped to predict long-term wheeze among children referred for evaluation of possible asthma. MethodsWe studied children aged 6-16 years referred to two Swiss pulmonary outpatient clinics with a history of wheeze, dyspnoea, or cough in 2007. The initial assessment included spirometry, body plethysmography, fractional exhaled nitric oxide, skin prick tests, and bronchial provocation tests (BPT) by exercise, methacholine, and mannitol. Respiratory symptoms were assessed with questionnaires at baseline and at follow-up seven years later. Associations between baseline factors and wheeze at follow-up were investigated by logistic regression. ResultsAt baseline, 111 children were examined in 2007. Seven years after baseline, 85 (77%) completed the follow-up questionnaire, among whom 61 (72%) had wheeze at baseline, while at follow-up 39 (46%) reported wheeze. Adjusting for age and sex, the following characteristics predicted wheeze at adolescence: wheeze triggered by pets (odds ratio 4.2, 95% CI 1.2-14.8), pollen (2.8, 1.1-7.0), and exercise (3.1, 1.2-8.0). Of the clinical tests, only a positive exercise test (3.2, 1.1-9.7) predicted wheeze at adolescence. ConclusionReported exercise-induced wheeze and wheeze triggered by pets or pollen were important predictors of wheeze persistence into adolescence. None of the clinical tests predicted wheeze more strongly than reported symptoms. Clinical tests might be important for asthma diagnosis but medical history is more helpful in predicting prognosis in children referred for asthma.

epidemiology↗