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Inactivation of Ca(2+) action potential channels by the MEK inhibitor PD98059
1Instituto de Biología Celular y Molecular, Ensenada, B.C, 22800, México. mgould@faro.ens.uabc.mx
Abstract:
In a previous study involving the inhibition of mitogen-activated protein kinase (MAPK) activation during fertilization of the marine worm Urechis caupo, we found that PD98059, but not U0126, caused multiple sperm penetrations in oocytes (Gould and Stephano, 1999, Dev. Biol. 216, 348-358). Since these oocytes are protected against polyspermy by a positive shift in membrane potential at fertilization (Gould-Somero et al., 1979, J. Cell Biol. 82, 426-440), we investigated the effects of PD98059 on the electrical properties of the oocyte membrane. PD98059, but not U0126, selectively blocked the voltage-dependent Ca(2+) channels that participate in the electrical polyspermy block. We also noted previously that PD98059 had more serious effects than U0126 on chromosome behavior during meiosis. This, too, could be explained by the effect on Ca(2+) channels, since when U0126-treated eggs were fertilized in low Ca(2+) seawater to reduce Ca(2+) uptake, similar effects were produced. These results show that PD98059 has side effects unrelated to the inhibition of MAPK activation and underscores the need for caution in interpreting the results of experiments with this widely used MEK inhibitor.
Insights
The MEK inhibitor PD98059, unlike U0126, causes polyspermy in marine worm oocytes by blocking calcium channels involved in fertilization. This highlights PD98059
Area of Science:
- Developmental Biology
- Cellular Physiology
- Marine Biology
Background:
- Oocytes are protected from polyspermy by a positive membrane potential shift during fertilization.
- Mitogen-activated protein kinase (MAPK) activation is involved in fertilization processes.
- Previous studies noted differential effects of PD98059 and U0126 on fertilization and meiosis.
Purpose of the Study:
- To investigate the effects of PD98059 on the electrical properties of Urechis caupo oocyte membranes.
- To determine if PD98059's effects on fertilization are related to MAPK inhibition or other mechanisms.
- To clarify the side effects of PD98059 as a mitogen-activated protein kinase kinase (MEK) inhibitor.
Main Methods:
- Electrophysiological recordings of oocyte membrane potential.
- Fertilization assays with PD98059 and U0126 in Urechis caupo.
- Experimental manipulation of calcium ion (Ca2+) concentration during fertilization.
Main Results:
- PD98059, but not U0126, selectively blocked voltage-dependent Ca2+ channels essential for the electrical polyspermy block.
- PD98059 exhibited more severe effects on chromosome behavior during meiosis compared to U0126.
- Similar meiotic effects were observed in U0126-treated eggs fertilized in low Ca2+ seawater, suggesting a Ca2+-dependent mechanism.
Conclusions:
- PD98059 possesses significant side effects unrelated to its primary function of inhibiting MAPK activation.
- The observed effects of PD98059 on fertilization and meiosis are likely mediated by its impact on Ca2+ channels.
- Caution is necessary when interpreting results from experiments using PD98059 due to its off-target effects.