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The Journal of Neuroscience, February 23, 2005, 25(8):1914-1923; doi:10.1523/JNEUROSCI.4790-04.2005
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Cellular/Molecular
A Protein Phosphatase 2c -Ca2+ Channel Complex for Dephosphorylation of Neuronal Ca2+ Channels Phosphorylated by Protein Kinase C
Dongjun Li,
Fushun Wang,
Meizan Lai,
Yuan Chen, and
Ji-fang Zhang
Department of Physiology, Jefferson Medical College, Philadelphia, Pennsylvania 19107
Phosphorylation and dephosphorylation are primary means for rapid regulation of a variety of neuronal functions, such as membrane excitability, neurotransmitter release, and gene expression. Voltage-gated Ca2+ channels are targets for phosphorylation by a variety of second messengers through activation of different types of protein kinases (PKs). Protein phosphatases (PPs), like PKs, are equally important in regulating Ca2+ channels in neurons. However, much less is understood about whether and how a particular type of PP contributes to regulating neuronal Ca2+ channel activities. This is primarily because of the lack of specific inhibitors/activators for different types of PPs, particularly the PP2c family. The functional roles of PP2c and its substrates in the brain remain virtually unknown. During our yeast two-hybrid screening, PP2c was pulled out by both N- and P/Q-type Ca2+ channel C termini. This raised the possibility that PP2c might be associated with voltage-gated Ca2+ channels for regulation of the Ca2+ channel activity. Biochemical studies show that PP2c binds directly to neuronal Ca2+ channels forming a functional protein complex in vivo. PP2c , unlike PP1, PP2a and PP2b, is more effective in dephosphorylation of neuronal Ca2+ channels after their phosphorylation by PKC. In hippocampal neurons, disruption of the PP2c -Ca2+ channel interaction significantly enhances the response of Ca2+ channels to modulation by PKC. Thus, the PP2c -Ca2+ channel complex is responsible for rapid dephosphorylation of Ca2+ channels and may contribute to regulation of synaptic transmission in neurons.
Key words: voltage-gated calcium channels; modulation; protein kinases; protein phosphatases; signal transduction; synaptic transmission
Received Nov 23, 2004;
revised January 2, 2005;
accepted January 5, 2005.
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