Phosphatase inhibitors remove the run-down of γ-aminobutyric acid type A receptors in the human epileptic brain

E. Palma, D. A. Ragozzino, S. Di Angelantonio, G. Spinelli, F. Trettel, A. Martinez-Torres, G. Torchia, A. Arcella, G. Di Gennaro, P. P. Quarato, V. Esposito, G. Cantore, R. Miledi, F. Eusebi

Research output: Contribution to journalArticle

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Abstract

The properties of γ-aminobutyric acid (GABA) type A receptors (GABAA receptors) microtransplanted from the human epileptic brain to the plasma membrane of Xenopus oocytes were compared with those recorded directly from neurons, or glial cells, in human brains slices. Cell membranes isolated from brain specimens, surgically obtained from six patients afflicted with drug-resistant temporal lobe epilepsy (TLE) were injected into frog oocytes. Within a few hours, these oocytes acquired GABAA receptors that generated GABA currents with an unusual run-down, which was inhibited by orthovanadate and okadaic acid. In contrast, receptors derived from membranes of a nonepileptic hippocampal uncus, membranes from mouse brain, or recombinant rat α1β2γ2-GABA receptors exhibited a much less pronounced GABA-current run-down. Moreover, the GABAA receptors of pyramidal neurons in temporal neocortex slices from the same six epileptic patients exhibited a stronger run-down than the receptors of rat pyramidal neurons. Interestingly, the GABAA receptors of neighboring glial cells remained substantially stable after repetitive activation. Therefore, the excessive GABA-current run-down observed in the membrane-injected oocytes recapitulates essentially what occurs in neurons, rather than in glial cells. Quantitative RT-PCR analyses from the same TLE neocortex specimens revealed that GABAA-receptor β1, β2, β3, and γ2 subunit mRNAs were significantly overexpressed (8- to 33-fold) compared with control autopsy tissues. Our results suggest that an abnormal GABA-receptor subunit transcription in the TLE brain leads to the expression of run-down-enhanced GABAA receptors. Blockage of phosphatases stabilizes the TLE GABAA receptors and strengthens GABAergic inhibition. It may be that this process can be targeted to develop new treatments for intractable epilepsy.

Original languageEnglish
Pages (from-to)10183-10188
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume101
Issue number27
DOIs
Publication statusPublished - Jul 6 2004

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Aminobutyrates
GABA-A Receptors
Phosphoric Monoester Hydrolases
Temporal Lobe Epilepsy
Brain
Oocytes
Neuroglia
gamma-Aminobutyric Acid
GABA Receptors
Pyramidal Cells
Neocortex
Membranes
Cell Membrane
Neurons
Okadaic Acid
Vanadates
Xenopus
Anura
Autopsy
Polymerase Chain Reaction

Keywords

  • γ-aminobutyric acid-current run-down
  • Human tissue slices
  • Microtransplantation into Xenopus oocyte
  • Okadaic acid
  • Temporal lobe epilepsy

ASJC Scopus subject areas

  • Genetics
  • General

Cite this

Phosphatase inhibitors remove the run-down of γ-aminobutyric acid type A receptors in the human epileptic brain. / Palma, E.; Ragozzino, D. A.; Di Angelantonio, S.; Spinelli, G.; Trettel, F.; Martinez-Torres, A.; Torchia, G.; Arcella, A.; Di Gennaro, G.; Quarato, P. P.; Esposito, V.; Cantore, G.; Miledi, R.; Eusebi, F.

In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 101, No. 27, 06.07.2004, p. 10183-10188.

Research output: Contribution to journalArticle

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abstract = "The properties of γ-aminobutyric acid (GABA) type A receptors (GABAA receptors) microtransplanted from the human epileptic brain to the plasma membrane of Xenopus oocytes were compared with those recorded directly from neurons, or glial cells, in human brains slices. Cell membranes isolated from brain specimens, surgically obtained from six patients afflicted with drug-resistant temporal lobe epilepsy (TLE) were injected into frog oocytes. Within a few hours, these oocytes acquired GABAA receptors that generated GABA currents with an unusual run-down, which was inhibited by orthovanadate and okadaic acid. In contrast, receptors derived from membranes of a nonepileptic hippocampal uncus, membranes from mouse brain, or recombinant rat α1β2γ2-GABA receptors exhibited a much less pronounced GABA-current run-down. Moreover, the GABAA receptors of pyramidal neurons in temporal neocortex slices from the same six epileptic patients exhibited a stronger run-down than the receptors of rat pyramidal neurons. Interestingly, the GABAA receptors of neighboring glial cells remained substantially stable after repetitive activation. Therefore, the excessive GABA-current run-down observed in the membrane-injected oocytes recapitulates essentially what occurs in neurons, rather than in glial cells. Quantitative RT-PCR analyses from the same TLE neocortex specimens revealed that GABAA-receptor β1, β2, β3, and γ2 subunit mRNAs were significantly overexpressed (8- to 33-fold) compared with control autopsy tissues. Our results suggest that an abnormal GABA-receptor subunit transcription in the TLE brain leads to the expression of run-down-enhanced GABAA receptors. Blockage of phosphatases stabilizes the TLE GABAA receptors and strengthens GABAergic inhibition. It may be that this process can be targeted to develop new treatments for intractable epilepsy.",
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AU - Ragozzino, D. A.

AU - Di Angelantonio, S.

AU - Spinelli, G.

AU - Trettel, F.

AU - Martinez-Torres, A.

AU - Torchia, G.

AU - Arcella, A.

AU - Di Gennaro, G.

AU - Quarato, P. P.

AU - Esposito, V.

AU - Cantore, G.

AU - Miledi, R.

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