Small-molecule screen identifies inhibitors of the neuronal K-Cl cotransporter KCC2

Proc Natl Acad Sci U S A. 2009 Mar 31;106(13):5383-8. doi: 10.1073/pnas.0812756106. Epub 2009 Mar 11.

Abstract

KCC2, a neuronal-specific K-Cl cotransporter, plays a major role in maintaining intracellular Cl(-) concentration in neurons below its electrochemical equilibrium potential, thus favoring robust GABA hyperpolarizing or inhibitory responses. The pharmacology of the K-Cl cotransporter is dominated by loop diuretics such as furosemide and bumetanide, molecules used in clinical medicine because they inhibit the loop of Henle Na-K-2Cl cotransporter with much higher affinity. To identify molecules that affect KCC2 activity, we developed a fluorescence-based assay suitable for high-throughput screening (HTS) and used the assay to screen a library of 234,000 small molecules. We identified a large number of molecules that either decrease or increase the activity of the cotransporter. Here, we report the characterization of a small number of inhibitors, some of which inhibit KCC2 activity in the submicomolar range without substantially affecting NKCC1 activity. Using medicinal chemistry, we synthesized a number of variants, tested their effect on KCC2 function, and provide an analysis of structure/activity relationships. We also used one of the compounds to demonstrate competitive inhibition in regard to external [K(+)] versus noncompetitive inhibition in respect to external [Cl(-)].

Publication types

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

MeSH terms

  • Binding, Competitive
  • Cell Line
  • Drug Discovery / methods*
  • Humans
  • K Cl- Cotransporters
  • Neurons
  • Small Molecule Libraries*
  • Structure-Activity Relationship
  • Symporters / antagonists & inhibitors*

Substances

  • Small Molecule Libraries
  • Symporters