GTP-binding protein beta gamma subunits mediate presynaptic calcium current inhibition by GABA(B) receptor.

Kajikawa Y; Saitoh N; Takahashi T

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GTP-binding protein beta gamma subunits mediate presynaptic calcium current inhibition by GABA(B) receptor.

机译：GTP-binding protein beta gamma subunits mediate presynaptic calcium current inhibition by GABA(B) receptor.

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摘要

A variety of GTP-binding protein (G protein)-coupled receptors are expressed at the nerve terminals of central synapses and play modulatory roles in transmitter release. At the calyx of Held, a rat auditory brainstem synapse, activation of presynaptic gamma-aminobutyric acid type B receptors (GABA(B) receptors) or metabotropic glutamate receptors inhibits presynaptic P/Q-type Ca(2+) channel currents via activation of G proteins, thereby attenuating transmitter release. To identify the heterotrimeric G protein subunits involved in this presynaptic inhibition, we loaded G protein beta gamma subunits (G beta gamma) directly into the calyceal nerve terminal through whole-cell patch pipettes. G beta gamma slowed the activation of presynaptic Ca(2+) currents (I(pCa)) and attenuated its amplitude in a manner similar to the externally applied baclofen, a GABA(B) receptor agonist. The effects of both G beta gamma and baclofen were relieved after strong depolarization of the nerve terminal. In addition, G beta gamma partially occluded the inhibitory effect of baclofen on I(pCa). In contrast, guanosine 5'-O-(3-thiotriphosphate)-bound G(o)alpha loaded into the calyx had no effect. Immunocytochemical examination revealed that the subtype of G proteins G(o), but not the G(i), subtype, is expressed in the calyceal nerve terminal. These results suggest that presynaptic inhibition mediated by G protein-coupled receptors occurs primarily by means of the direct interaction of G(o) beta gamma subunits with presynaptic Ca(2+) channels.

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《Proceedings of the National Academy of Sciences of the United States of America》 |2001年第14期|8054-8058|共5页
作者
Kajikawa Y; Saitoh N; Takahashi T;
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作者单位

Department of Neurophysiology, University of Tokyo Faculty of Medicine, Tokyo 113-0033, Japan.;

hylo.life.uiuc.edu;

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收录信息美国《科学引文索引》(SCI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
原文格式 PDF
正文语种英语
中图分类自然科学总论;
关键词
Calcium; Heterotrimeric GTP Binding Proteins physiology; Receptors; GABA; 钙; 受体; 突触;

GTP-binding protein beta gamma subunits mediate presynaptic calcium current inhibition by GABA(B) receptor.

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