A Voltage Dependent Non-Inactivating Na+ Channel Activated during Apoptosis in Xenopus Oocytes: e88381

• Published in: PloS one 2014-02, Vol.9 (2)
• Main Authors: Englund, Ulrika H, Gertow, Jens, Kagedal, Katarina, Elinder, Fredrik
• Format: Article
• Language: English
• Subjects: Anura; Xenopus laevis
• ISSN: 1932-6203
• DOI: 10.1371/journal.pone.0088381

Ion channels in the plasma membrane are important for the apoptotic process. Different types of voltage-gated ion channels are up-regulated early in the apoptotic process and block of these channels prevents or delays apoptosis. In the present investigation we examined whether ion channels are up-regulated in oocytes from the frog Xenopus laevis during apoptosis. The two-electrode voltage-clamp technique was used to record endogenous ion currents in the oocytes. During staurosporine-induced apoptosis a voltage-dependent Na+ current increased three-fold. This current was activated at voltages more positive than 0 mV (midpoint of the open-probability curve was +55 mV) and showed almost no sign of inactivation during a 1-s pulse. The current was resistant to the Na+-channel blockers tetrodotoxin (1 mu M) and amiloride (10 mu M), while the Ca2+-channel blocker verapamil (50 mu M) in the bath solution completely blocked the current. The intracellular Na+ concentration increased in staurosporine-treated oocytes, but could be prevented by replacing extracellular Na+ whith either K+ or Choline+. Prevention of this influx of Na+ also prevented the STS-induced up-regulation of the caspase-3 activity, suggesting that the intracellular Na+ increase is required to induce apoptosis. Taken together, we have found that a voltage dependent Na+ channel is up-regulated during apoptosis and that influx of Na+ is a crucial step in the apoptotic process in Xenopus oocytes.