State-dependent blocking mechanism of Kv 1.3 channels by the antimycobacterial drug clofazimine

Br J Pharmacol. 2015 Nov;172(21):5161-73. doi: 10.1111/bph.13283. Epub 2015 Oct 9.


Background and purpose: Kv 1.3 potassium channels are promising pharmaceutical targets for treating immune diseases as they modulate Ca(2+) signalling in T cells by regulating the membrane potential and with it the driving force for Ca(2+) influx. The antimycobacterial drug clofazimine has been demonstrated to attenuate antigen-induced Ca(2+) oscillations, suppress cytokine release and prevent skin graft rejection by inhibiting Kv 1.3 channels with high potency and selectivity.

Experimental approach: We used patch-clamp methodology to investigate clofazimine's mechanism of action in Kv 1.3 channels expressed in HEK293 cells.

Key results: Clofazimine blocked Kv 1.3 channels by involving two discrete mechanisms, both of which contribute to effective suppression of channels: (i) a use-dependent open-channel block during long depolarizations, resulting in accelerated K(+) current inactivation and (ii) a block of closed deactivated channels after channels were opened by brief depolarizations. Both modes of block were use-dependent and state-dependent in that they clearly required prior channel opening. The clofazimine-sensitive closed-deactivated state of the channel was distinct from the resting closed state because channels at hyperpolarized voltages were not inhibited by clofazimine. Neither were channels in the C-type inactivated state significantly affected. Kv 1.3 channels carrying the H399T mutation and lacking C-type inactivation were insensitive to clofazimine block of the closed-deactivated state, but retained their susceptibility to open-channel block.

Conclusions and implications: Given the prominent role of Kv 1.3 in shaping Ca(2+) oscillations, the use-dependent and state-dependent block of Kv 1.3 channels by clofazimine offers therapeutic potential for selective immunosuppression in the context of autoimmune diseases in which Kv 1.3-expressing T cells play a significant role.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcium Channel Blockers / pharmacology*
  • Clofazimine / pharmacology*
  • HEK293 Cells
  • Humans
  • Ion Channel Gating / drug effects
  • Kinetics
  • Kv1.3 Potassium Channel / antagonists & inhibitors*
  • Kv1.3 Potassium Channel / genetics
  • Leprostatic Agents / pharmacology*
  • Mutation
  • Patch-Clamp Techniques


  • Calcium Channel Blockers
  • Kv1.3 Potassium Channel
  • Leprostatic Agents
  • Clofazimine