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Synaptic excitation mediated by glutamate-gated ion channels
an excellent example of an experimental approach to examine channel regulation using purified protein phosphatases. WHITE
RE,
SCHONBRLINN
A,
ARMSTRONG
matostatin Stimulates Cazf-activated Through Protein Dephosphorylation. 351:570-573.
DL:
So-
Kf Channels Na&‘ure 1991,
This study shows that the opening of Ca2+ -activated K+ channels is mediated1 by an okadaic acid-sensitive protein phosphatase. The results suggest a new route of signal transduction via changes in cellular protein phosphatase activity.
Ca*+ channels: diversity of form and function by Terry P. Snutch and Peter B. Reiner WILLIAMS ME, FELDIMAN DH, MCCUE AF, BFENNER R, VELICELEBI G, ELLIS SB, HARPOLDMM: Structure and
Functional Fxpres:sion of al, a2 and B subunits of a Novel Human N~euronal Calcium Channel Subtype. Neuron 1992, 8:71-84.
This thorough study reports the primary sequences of human brain class D aI-, a$- and. ~-subunits. Microinjection of synthetic RNA into Xenopus oocytes shows that in the presence of a brain j&subunit the class D a,subunit encodes an L-type Ca2 + channel. Also described is the intriguing re:sult that amicroinjection of j%subunit alone into oocytes induces the expression of DHP-insensitive Ca2+ channels that resemble the endogenous oocyte Ca2+ channel. REGAN LJ, SAH DWY, BEAN BP:
Ca2+ Channels in Rat Central and Peripheral Neurons: High-Threshold Current Resistant to Dihydropyridine Blockers and w-Conotoxin. Neuron 1991, 6:269-280.
An excellent study demonstrating that different types of dissociated rat neurons possess varying amounts of a high-threshold C&l+ current that is insensitive to both DHPs and w-CgTx. Second Messenger Mediates One of the Pathways Coupling Receptors to Calcium Channels in Rat Sympathetic Neurons. Neuron 1991, 6:859-867.
Synaptic excitation mediated by glutamate-gated ion channels by Craig E. Jahr and Robin A.J. Lester BENVENISTE M, MAYER ML: Kinetic
Analysis of Antagonist Action at N-Methyl-D-Aspartic Acid Receptors: Two Binding Sites Each for Glutamate and Glycine. Siophys J 1991, 59560-573.
Using rapid drug perfusion techniques combined with whole-cell recordings, the authors were able to study the kinetics of onset and recovery of antagonism at the glycine and glutamate binding sites of the NMDA receptor. Their data was best fitted assuming the existence of two independent, but identical binding sites for both glutamate and glycine. This model is supported by the additional findings that the rate constants for the onset and recovery from antagonism agree well with antagonist equilibrium afhnity estimates. SILVER RA, TRAYNELIS SF, CULL-CANDY SG: RapidTime-Course Miniature and Evoked Excitatory Currents at Cerebellar Synapses In Situ. Nature 1992, 355:163-166.
The authors demonstrate that the decay of AMPA-receptor mediated excitatory postsynaptic currents is rapid at the well-clamped mossy fiber-granule cell synpase in the cerebellar slice preparation. The authors speculate that slower decays of AMPA excitatory postsynaptic currents observed at some other CNS synapses may arise either from dendritic filtering or, more interestingly, from the expression of AMPA subunits with different kinetic properties. Recordings of the NMDA receptor component of spontaneous excitatory postsynaptic currents clearly show openings of single channels, suggesting that very few receptors are active at individual synapses. e
Synaptic plasticity: long-term potentiation the hippocampus by Zafar I. Bashir and Graham L. Collingridge
in
BERNHEIM L, BEEC:H DJ, HILCE B: A Diffusible
This paper shows that there are two pathways leading to Ca2+ channel inhibition in sympathetic neurons, and at least one of them is due to activation of a soluble second messenger. Surprisingly, this intracellular message is not carried by either Ca2+, cGMP, CAMP or protein kinase C.
292
WANG L-Y, SAETER MW, MACDONALD JF: Regulation
of Kainate Receptors by CAMP-Dependent Protein Kinase and Phosphatases. Science 1991, 253:1132-1135.
Tha amplitudes of kainate-induced currents in cultured hippocampal neurons are increased by agents which specifically stimulate CAMP, or by the phosphatase inhibitor, okadaic acid, and are reduced by an inhibitor of PKA. These data suggest that AMPA receptors are regulated by endogenous PKA.
@ 1992 Current Biology
RE,
SCHONBRLINN
A,
ARMSTRONG
matostatin Stimulates Cazf-activated Through Protein Dephosphorylation. 351:570-573.
DL:
So-
Kf Channels Na&‘ure 1991,
This study shows that the opening of Ca2+ -activated K+ channels is mediated1 by an okadaic acid-sensitive protein phosphatase. The results suggest a new route of signal transduction via changes in cellular protein phosphatase activity.
Ca*+ channels: diversity of form and function by Terry P. Snutch and Peter B. Reiner WILLIAMS ME, FELDIMAN DH, MCCUE AF, BFENNER R, VELICELEBI G, ELLIS SB, HARPOLDMM: Structure and
Functional Fxpres:sion of al, a2 and B subunits of a Novel Human N~euronal Calcium Channel Subtype. Neuron 1992, 8:71-84.
This thorough study reports the primary sequences of human brain class D aI-, a$- and. ~-subunits. Microinjection of synthetic RNA into Xenopus oocytes shows that in the presence of a brain j&subunit the class D a,subunit encodes an L-type Ca2 + channel. Also described is the intriguing re:sult that amicroinjection of j%subunit alone into oocytes induces the expression of DHP-insensitive Ca2+ channels that resemble the endogenous oocyte Ca2+ channel. REGAN LJ, SAH DWY, BEAN BP:
Ca2+ Channels in Rat Central and Peripheral Neurons: High-Threshold Current Resistant to Dihydropyridine Blockers and w-Conotoxin. Neuron 1991, 6:269-280.
An excellent study demonstrating that different types of dissociated rat neurons possess varying amounts of a high-threshold C&l+ current that is insensitive to both DHPs and w-CgTx. Second Messenger Mediates One of the Pathways Coupling Receptors to Calcium Channels in Rat Sympathetic Neurons. Neuron 1991, 6:859-867.
Synaptic excitation mediated by glutamate-gated ion channels by Craig E. Jahr and Robin A.J. Lester BENVENISTE M, MAYER ML: Kinetic
Analysis of Antagonist Action at N-Methyl-D-Aspartic Acid Receptors: Two Binding Sites Each for Glutamate and Glycine. Siophys J 1991, 59560-573.
Using rapid drug perfusion techniques combined with whole-cell recordings, the authors were able to study the kinetics of onset and recovery of antagonism at the glycine and glutamate binding sites of the NMDA receptor. Their data was best fitted assuming the existence of two independent, but identical binding sites for both glutamate and glycine. This model is supported by the additional findings that the rate constants for the onset and recovery from antagonism agree well with antagonist equilibrium afhnity estimates. SILVER RA, TRAYNELIS SF, CULL-CANDY SG: RapidTime-Course Miniature and Evoked Excitatory Currents at Cerebellar Synapses In Situ. Nature 1992, 355:163-166.
The authors demonstrate that the decay of AMPA-receptor mediated excitatory postsynaptic currents is rapid at the well-clamped mossy fiber-granule cell synpase in the cerebellar slice preparation. The authors speculate that slower decays of AMPA excitatory postsynaptic currents observed at some other CNS synapses may arise either from dendritic filtering or, more interestingly, from the expression of AMPA subunits with different kinetic properties. Recordings of the NMDA receptor component of spontaneous excitatory postsynaptic currents clearly show openings of single channels, suggesting that very few receptors are active at individual synapses. e
Synaptic plasticity: long-term potentiation the hippocampus by Zafar I. Bashir and Graham L. Collingridge
in
BERNHEIM L, BEEC:H DJ, HILCE B: A Diffusible
This paper shows that there are two pathways leading to Ca2+ channel inhibition in sympathetic neurons, and at least one of them is due to activation of a soluble second messenger. Surprisingly, this intracellular message is not carried by either Ca2+, cGMP, CAMP or protein kinase C.
292
WANG L-Y, SAETER MW, MACDONALD JF: Regulation
of Kainate Receptors by CAMP-Dependent Protein Kinase and Phosphatases. Science 1991, 253:1132-1135.
Tha amplitudes of kainate-induced currents in cultured hippocampal neurons are increased by agents which specifically stimulate CAMP, or by the phosphatase inhibitor, okadaic acid, and are reduced by an inhibitor of PKA. These data suggest that AMPA receptors are regulated by endogenous PKA.
@ 1992 Current Biology