Dynamic Na+/H+ exchanger 1 (NHE1) – calmodulin complexes of varying stoichiometry and structure regulate Ca2+-dependent NHE1 activation

• DOI: 10.7554/elife.60889
• Publication Date: 2021-03-03T13:00:33Z
• Authors: Lise M Sjøgaard-F...; Andreas Prestel; Emilie S Pedersen; Marc Severin; Kristian Kølby Kr...; Johan G Olsen; Birthe B Kragelund; Stine Falsig Pede...
• Keywords: Isothermal Titration Calorimetry; Stoichiometry; Affinities

Calmodulin (CaM) engages in Ca 2+ -dependent interactions with numerous proteins, including a still incompletely understood physical and functional interaction the human Na + /H -exchanger NHE1. Using nuclear magnetic resonance (NMR) spectroscopy, isothermal titration calorimetry, fibroblasts stably expressing wildtype mutant NHE1, we discovered multiple accessible states of this functionally important complex existing different NHE1:CaM stoichiometries structures. We determined NMR solution structure ternary which CaM links two NHE1 cytosolic tails. In vitro , affinities could be tuned by variations ratio calcium ([Ca ]) phosphorylation S648 first CaM-binding α-helix. cells, -CaM-induced activity was reduced mimicking mutation α-helix, whereas it unaffected inhibition Akt, one several kinases phosphorylating S648. Our results demonstrate diversity modes suggest that may contribute to dimerization thereby augment regulation. propose similar structural is relevance many other complexes.