Structure and mechanism of the human NHE1-CHP1 complex

Abstract

Sodium/proton exchanger 1 (NHE1) is an electroneutral secondary active transporter present on the plasma membrane of most mammalian cells and plays critical roles in regulating intracellular pH and volume homeostasis. Calcineurin B-homologous protein 1 (CHP1) is an obligate binding partner that promotes NHE1 biosynthetic maturation, cell surface expression and pH-sensitivity. Dysfunctions of either protein are associated with neurological disorders. Here, we elucidate structures of the human NHE1-CHP1 complex in both inward- and inhibitor (cariporide)-bound outward-facing conformations. We find that NHE1 assembles as a symmetrical homodimer, with each subunit undergoing an elevator-like conformational change during cation exchange. The cryo-EM map reveals the binding site for the NHE1 inhibitor cariporide, illustrating how inhibitors block transport activity. The CHP1 molecule differentially associates with these two conformational states of each NHE1 monomer, and this association difference probably underlies the regulation of NHE1 pH-sensitivity by CHP1.

Structure, mechanism and lipid-mediated remodeling of the mammalian Na+/H+ exchanger NHA2

“…Na + /H + exchangers form physiological homodimers 2 , 21 , with the monomers made up of a 6-transmembrane (TM) ion-translocation domain (or core domain) and a dimerization domain 22 – 27 . Recent structures of mammalian NHE1 25 and NHE9 23 were found to be highly similar to bacterial Na + /H + antiporter structures with 13 TMs 22 , 24 , 26 , 28 . So far, the core domain has proven to be structurally similar, with most of the structural divergence in the dimerization domain instead 23 .…”

“…So far, the core domain has proven to be structurally similar, with most of the structural divergence in the dimerization domain instead 23 . Na + /H + exchangers operate by an ‘elevator’ alternating-access mechanism 23 – 25 , 29 , 30 . In an elevator mechanism, the ion is transported by the core domain against the dimerization domain, which remains fixed due to oligomerization 30 .…”

Intracellular pH Control by Membrane Transport in Mammalian Cells. Insights Into the Selective Advantages of Functional Redundancy

“…It also represents the inner acid base chemistry that consumes or generates the transported acid-base equivalents. of NHE1 and nine structures in (Winklemann et al, 2020;Dong et al, 2021). Other important structures have been obtained by X-ray diffraction, for AE1 in (Arakawa et al, 2015), and for monocarboxylate transporters (Bosshart et al, 2019;Zhang et al, 2020).…”

Synthesis and multifaceted pharmacological activity of novel quinazoline NHE-1 inhibitors

“…zoniporide, rimeporide, cariporide and benzoylguanidine 16 , 17 or (furan-2-ylcarbonyl)guanidines 18 derivatives, respectively. Structure of cariporide/NHE-1 complex was recently solved using cryo-EM 19 . It was demonstrated that acylguanidine moiety plays a crucial role in the binding.…”