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Apoptotic surge of potassium currents is mediated by p38 phosphorylation of Kv2.1
Patrick T Redman1, Kai He, Karen A Hartnett
1Department of Neurobiology and Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
Abstract:
Kv2.1, the primary delayed rectifying potassium channel in neurons, is extensively regulated by phosphorylation. Previous reports have described Kv2.1 phosphorylation events affecting channel gating and the impact of this process on cellular excitability. Kv2.1, however, also provides the critical exit route for potassium ions during neuronal apoptosis via p38 MAPK-dependent membrane insertion, resulting in a pronounced enhancement of K(+) currents. Here, electrophysiological and viability studies using Kv2.1 channel mutants identify a p38 phosphorylation site at Ser-800 (S800) that is required for Kv2.1 membrane insertion, K(+) current surge, and cell death. In addition, a phospho-specific antibody for S800 detects a p38-dependent increase in Kv2.1 phosphorylation in apoptotic neurons and reveals phosphorylation of S800 in immunopurified channels incubated with active p38. Consequently, phosphorylation of Kv2.1 residue S800 by p38 leads to trafficking and membrane insertion during apoptosis, and remarkably, the absence of S800 phosphorylation is sufficient to prevent completion of the cell death program.
Insights
Phosphorylation of the Kv2.1 potassium channel at Ser-800 by p38 MAPK is crucial for neuronal apoptosis. This modification drives channel membrane insertion and potassium current surges, essential for cell death.
Area of Science:
- Neuroscience
- Molecular Biology
- Cell Biology
Background:
- Kv2.1 (a delayed rectifier potassium channel) is vital for neuronal function and excitability.
- Kv2.1 phosphorylation regulates channel gating and cellular excitability.
- Kv2.1 facilitates potassium ion efflux during neuronal apoptosis.
Purpose of the Study:
- To identify the specific phosphorylation site on Kv2.1 involved in apoptosis.
- To elucidate the role of p38 MAPK in Kv2.1-mediated neuronal cell death.
- To investigate the mechanism of Kv2.1 membrane insertion during apoptosis.
Main Methods:
- Electrophysiological recordings to measure potassium currents.
- Cell viability assays to assess neuronal survival.
- Site-directed mutagenesis to create Kv2.1 channel mutants.
- Development and use of a phospho-specific antibody for Ser-800.
Main Results:
- A specific p38 MAPK phosphorylation site at Ser-800 (S800) was identified on Kv2.1.
- S800 phosphorylation is essential for Kv2.1 membrane insertion, increased K+ currents, and neuronal apoptosis.
- A phospho-specific antibody confirmed increased S800 phosphorylation in apoptotic neurons and in vitro.
Conclusions:
- p38 MAPK-dependent phosphorylation of Kv2.1 at S800 is a critical regulator of neuronal apoptosis.
- This phosphorylation event promotes Kv2.1 trafficking and membrane insertion, enhancing potassium efflux.
- Inhibition of S800 phosphorylation effectively prevents the completion of the neuronal cell death program.
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