Cold-induced decrease of K+ conductance and its inhibition by a calmodulin antagonist, W-7, in Paramecium tetraurelia

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T Kuriu1, Y Nakaoka, Y Oosawa

  • 1International Institute for Advanced Research, Matsushita Electric Industrial Co., Ltd., Kyoto, Japan.

Cell Structure and Function
|May 20, 1998
PubMed

Insights

Cooling Paramecium cells triggers an inward current due to decreased potassium (K+) conductance. This cold-induced current is calcium (Ca2+)-dependent and can be blocked by the calmodulin antagonist W-7.

Area of Science:

  • Cellular electrophysiology
  • Ion channel function
  • Calcium signaling

Background:

  • Paramecium tetraurelia is a model organism for studying cellular responses.
  • Temperature changes can affect ion channel activity and cell membrane potential.
  • Calmodulin plays a crucial role in calcium-dependent cellular processes.

Purpose of the Study:

  • To investigate the nature of cold-induced inward currents in Paramecium tetraurelia.
  • To determine the ion selectivity and regulatory mechanisms of this cold-induced current.
  • To examine the role of calcium and calmodulin in the response to cooling.

Main Methods:

  • Voltage clamp electrophysiology was used to measure membrane currents.
  • Experiments involved manipulating ion concentrations (CsCl, tetraethylammonium) and applying W-7.
  • EGTA microinjection was performed to assess intracellular calcium levels.

Main Results:

  • Cooling induced a significant inward current in Paramecium cells.
  • The current was primarily mediated by a decrease in potassium (K+) conductance.
  • The cold-induced current was reversibly inhibited by W-7 and reduced by EGTA, indicating Ca2+-dependence.

Conclusions:

  • The cold-induced inward current in Paramecium is linked to a calcium-dependent decrease in K+ conductance.
  • Calmodulin appears to be involved in regulating this response to cooling.
  • W-7 acts as an inhibitor of the cold-induced current, highlighting its potential role in modulating ion channel activity.

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