Structural basis for inhibition of the Cation-chloride cotransporter NKCC1 by the diuretic drug bumetanide

Nat Commun. 2022 May 18;13(1):2747. doi: 10.1038/s41467-022-30407-3.


Cation-chloride cotransporters (CCCs) NKCC1 and NKCC2 catalyze electroneutral symport of 1 Na+, 1 K+, and 2 Cl- across cell membranes. NKCC1 mediates trans-epithelial Cl- secretion and regulates excitability of some neurons and NKCC2 is critical to renal salt reabsorption. Both transporters are inhibited by the so-called loop diuretics including bumetanide, and these drugs are a mainstay for treating edema and hypertension. Here, our single-particle electron cryo-microscopy structures supported by functional studies reveal an outward-facing conformation of NKCC1, showing bumetanide wedged into a pocket in the extracellular ion translocation pathway. Based on these and the previously published inward-facing structures, we define the translocation pathway and the conformational changes necessary for ion translocation. We also identify an NKCC1 dimer with separated transmembrane domains and extensive transmembrane and C-terminal domain interactions. We further define an N-terminal phosphoregulatory domain that interacts with the C-terminal domain, suggesting a mechanism whereby (de)phosphorylation regulates NKCC1 by tuning the strength of this domain association.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bumetanide* / pharmacology
  • Cations / metabolism
  • Chlorides / metabolism
  • Diuretics / pharmacology
  • Solute Carrier Family 12, Member 2
  • Symporters*


  • Cations
  • Chlorides
  • Diuretics
  • Solute Carrier Family 12, Member 2
  • Symporters
  • Bumetanide