Interaction between capacitative Ca2+ influx and Ca2+-dependent Cl- currents in Xenopus oocytes

Area of Science:

• Cellular Physiology
• Neuroscience
• Molecular Biology

Background:

• Capacitative calcium entry is crucial for cellular signaling.
• Calcium-dependent chloride channels play roles in various physiological processes.
• Understanding the interplay between calcium influx and channel activity is essential.

Purpose of the Study:

• To investigate the relationship between capacitative calcium influx and the activation of calcium-dependent chloride channels.
• To elucidate the mechanisms underlying the secondary inward current following 5-hydroxytryptamine (5-HT) receptor stimulation.
• To characterize the properties of hump currents generated by depletion-activated calcium entry.

Main Methods:

• Utilized the double-electrode voltage-clamp technique in intact Xenopus oocytes.
• Stimulated 5-hydroxytryptamine (5-HT) receptors to evoke currents.
• Employed heparin injection to prevent inositol 1,4,5-triphosphate [Ins(1,4,5)P3]-evoked calcium release and thapsigargin to inhibit Ca2+ ATPase.

Main Results:

• 5-HT evoked transient and secondary inward currents, with the latter reflecting depletion-activated calcium entry.
• Hyperpolarizing pulses during secondary current generated inactivating hump currents dependent on external calcium.
• Cytoskeletal disruption reduced hump current amplitude, suggesting a role in channel modulation.

Conclusions:

• Calcium influx, particularly through depletion-activated pathways, influences the inactivation and behavior of calcium-dependent chloride channels.
• The observed inactivation of hump currents is linked to calcium entry, potentially involving calcium inhibition of entry and chloride channel clustering.
• These findings provide insights into the complex regulation of calcium signaling and ion channel function.