G-Protein β-Subunit Specificity in the Fast Membrane-Delimited Inhibition of Ca<sup>2+</sup>Channels

García, David; Li, Bin; García-Ferreiro, Rafael E.; Hernández‐Ochoa, Erick O.; Yan, Kang; Gautam, N.; Catterall, William A.; Mackie, Ken; Hille, Bertil

doi:10.1523/jneurosci.18-22-09163.1998

Cited by 110 publications

(96 citation statements)

References 33 publications

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“…After overnight culture the SCG neurons were microinjected intranuclearly with an Eppendorf 5242 pressure microinjector and 5171 micromanipulator system (Eppendorf, Madison, W I), as previously described (Garcia et al, 1998). The injection solution contained DNA plasmids for KC NQ2 (0.12 mg /ml) and for green fluorescent protein (GFP) as an expression reporter (0.04 mg /ml) and 0.05% 10,000 kDa dextran-fluorescein (Molecular Probes) as an injection marker.…”

Section: Methodsmentioning

confidence: 99%

Reconstitution of Muscarinic Modulation of the KCNQ2/KCNQ3 K⁺Channels That Underlie the Neuronal M Current

Shapiro¹,

Roche²,

Kaftan³

et al. 2000

J. Neurosci.

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Channels from KCNQ2 and KCNQ3 genes have been suggested to underlie the neuronal M-type K ϩ current. The M current is modulated by muscarinic agonists via G-proteins and an unidentified diffusible cytoplasmic messenger. Using wholecell clamp, we studied tsA-201 cells in which cloned KCNQ2/ KCNQ3 channels were coexpressed with M 1 muscarinic receptors. Heteromeric KCNQ2/KCNQ3 currents were modulated by the muscarinic agonist oxotremorine-M (oxo-M) in a manner having all of the characteristics of modulation of native M current in sympathetic neurons. Oxo-M also produced obvious intracellular Ca 2ϩ transients, observed by using indo-1 fluorescence. However, modulation of the current remained strong even when Ca 2ϩ signals were abolished by the combined use of strong intracellular Ca 2ϩ buffers, an inhibitor of IP 3 receptors, and thapsigargin to deplete Ca 2ϩ stores. Muscarinic modulation was not blocked by staurosporine, a broad-spectrum protein kinase inhibitor, arguing against involvement of protein kinases. The modulation was not associated with a shift in the voltage dependence of channel activation. Homomeric KCNQ2 and KCNQ3 channels also expressed well and were modulated individually by oxo-M, suggesting that the motifs for modulation are present on both channel subtypes. Homomeric KCNQ2 and KCNQ3 currents were blocked, respectively, at very low and at high concentrations of tetraethylammonium ion. Finally, when KCNQ2 subunits were overexpressed by intranuclear DNA injection in sympathetic neurons, total M current was fully modulated by the endogenous neuronal muscarinic signaling mechanism. Our data further rule out Ca 2ϩ as the diffusible messenger. The reconstitution of muscarinic modulation of the M current that uses cloned components should facilitate the elucidation of the muscarinic signaling mechanism. Key words: K ϩ channel; muscarinic receptor; G-protein; calcium; patch clamp; M current A diverse family of neurotransmitters and hormones regulates Ca 2ϩ and K ϩ channels via G-protein-mediated signaling pathways (Wickman and Clapham, 1995;Brown et al., 1997;Dolphin, 1998). Nearly 20 years ago, several investigators gave the name M current to a noninactivating K ϩ current with slow kinetics in sympathetic neurons that is strongly suppressed by muscarinic acetylcholine receptor (mAChR) agonists (Brown and Adams, 1980;Constanti and Brown, 1981). The M current is thought to play an important role in neuronal excitability, and its suppression increases responses to excitatory synaptic inputs (Jones et al., 1995;Wang and McKinnon, 1995). Modulation of the M current by muscarinic receptor agonists and by angiotensin (Constanti and Brown, 1981; Marrion, 1997;Shapiro et al., 1994a) is mediated by a G-protein of the G q /11 class (Delmas et al., 1998; Haley et al., 1998) via a diffusible cytoplasmic second messenger (Selyanko et al., 1992) that is yet to be identified.Although the buffering of intracellular free Ca 2ϩ ([Ca 2ϩ ] i ) to very low levels prevents muscarinic suppression of the M current in rat sym...

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Section: Methodsmentioning

confidence: 99%

Reconstitution of Muscarinic Modulation of the KCNQ2/KCNQ3 K⁺Channels That Underlie the Neuronal M Current

Shapiro¹,

Roche²,

Kaftan³

et al. 2000

J. Neurosci.

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200

243

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“…While most studies of cannabinoid receptor action on I Ca have focused on modulation of N and P/Q type calcium channels-presumably via direct G␤␥ subunit interactions with these channels (Garcia et al 1998;Herlitze et al 1996;Ikeda 1996)-several reports indicate that CB1 activation can also modulate L-type calcium channels in some systems (Gebremedhin et al 1999;Straiker et al 1999a). There is reason to think that GPCR modulation of L-type calcium currents in photoreceptors is mediated by cAMP via PKA.…”

Section: Mechanism Of Actionmentioning

confidence: 99%

Cannabinoid Receptor Activation Differentially Modulates Ion Channels in Photoreceptors of the Tiger Salamander

Straiker

Sullivan

2003

Journal of Neurophysiology

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Staiker, Alex and Jane M. Sullivan. Cannabinoid receptor activation differentially modulates ion channels in photoreceptors of the tiger salamander. J Neurophysiol 89: 2647-2654, 2003; 10.1152/jn.00268.2002. Cannabinoid CB1 receptors have been detected in retinas of numerous species, with prominent labeling in photoreceptor terminals of the chick and monkey. CB1 labeling is well-conserved across species, suggesting that CB1 receptors might also be present in photoreceptors of the tiger salamander. Synaptic transmission in vertebrate photoreceptors is mediated by L-type calcium currents-currents that are modulated by CB1 receptors in bipolar cells of the tiger salamander. Presence of CB1 receptors in photoreceptor terminals would therefore be consistent with presynaptic modulation of synaptic transmission, a role seen for cannabinoids in other parts of the brain. Here we report immunohistochemical and electrophysiological evidence for the presence of functional CB1 receptors in rod and cone photoreceptors of the tiger salamander. The cannabinoid receptor agonist WIN 55212-2 enhances calcium currents of rod photoreceptors by 39% but decreases calcium currents of large single cones by 50%. In addition, WIN 55212-2 suppresses potassium currents of rods and large single cones by 44 and 48%, respectively. Thus functional CB1 receptors, present in the terminals of rod and cone photoreceptors, differentially modulate calcium and potassium currents in rods and large single cones. CB1 receptors are therefore well positioned to modulate neurotransmitter release at the first synapse of the visual system. I N T R O D U C T I O NCannabinoid CB1 receptors have been detected in the retinas of numerous species, including salamander, goldfish, chick, rat, mouse, monkey, and human (Straiker et al. 1999a,b;Yazulla et al. 1999) with a well-conserved pattern of staining that is particularly intense in both synaptic layers. In species for which double labeling has been performed-chick and monkey-outer plexiform layer staining is found to localize to photoreceptor terminals. CB1 is a member of the Gi/o-type G-protein-coupled receptor family and mediates a wide range of effects on ion channels, including voltage-dependent calcium and potassium channels (Deadwyler et al. 1995;Mackie and Hille 1992;Mackie et al. 1995;Mu et al. 1999). Retinal cannabinoid receptor activation has been shown to inhibit dopamine release in the guinea pig (Schlicker et al. 1996), to inhibit a delayed rectifier K ϩ current in ON cone bipolar cells of the goldfish (Yazulla et al. 2000), and to inhibit L-type calcium currents in bipolar cells of the tiger salamander (Straiker et al. 1999a). Three recent reports have described G-protein-coupled receptor-dependent modulation of ion channel function in photoreceptors of the tiger salamander by dopamine, adenosine, and somatostatin (Akopian et al. 2000;Stella and Thoreson 2000;Stella et al. 2002). These studies find that the calcium currents (I Ca ) of rods and large single cones respond differentially to activation ...

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“…These include structural determinants in the mGluRs (13), the G proteins (14), or the Ca 2ϩ channels (15-16) as well as the differential coupling of the Ca 2ϩ channels to the release process (17)(18). An additional factor that should also be considered when contemplating the selective inhibition of the N-type Ca 2ϩ channel by mGluR7 is that of the co-localization of the receptor and target Ca 2ϩ channel at nerve terminals.…”

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confidence: 99%

Co-expression of Metabotropic Glutamate Receptor 7 and N-type Ca2+ Channels in Single Cerebrocortical Nerve Terminals of Adult Rats

Millán

Castro

Torres

et al. 2003

Journal of Biological Chemistry

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The modulation of calcium channels by metabotropic glutamate receptors (mGluRs) is a key event in the finetuning of neurotransmitter release. Here we report that, in cerebrocortical nerve terminals of adult rats, the inhibition of glutamate release is mediated by mGluR7. In this preparation, the major component of glutamate release is supported by P/Q-type Ca 2؉ channels (72.7%). However, mGluR7 selectively reduced the release component that is associated with N-type Ca 2؉ channels (29.9%). Inhibition of P/Q channels by mGluR7 is not masked by the higher efficiency of these channels in driving glutamate release when compared with N-type channels. Thus, activation of mGluR7 failed to reduce the release associated with P/Q channels when the extracellular calcium concentration, ([Ca 2؉ ] o ), was reduced from 1.3 to 0.5 mM. Through Ca 2؉ imaging, we show that Ca 2؉ channels are distributed in a heterogeneous manner in individual nerve terminals. Indeed, in this preparation, nerve terminals were observed that contain N-type (31.1%; conotoxin GVIA-sensitive) or P/Qtype (64.3%; agatoxin IVA-sensitive) channels or that were insensitive to these two toxins (4.6%). Interestingly, the great majority of the responses to L-AP4 (95.4%) were observed in nerve terminals containing Ntype channels. This specific co-localization of mGluR7 and N-type Ca 2؉ -channels could explain the failure of the receptor to inhibit the P/Q channel-associated release component and also reveal the existence of specific targeting mechanisms to localize the two proteins in the same nerve terminal subset.

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G-Protein β-Subunit Specificity in the Fast Membrane-Delimited Inhibition of Ca²⁺Channels

Cited by 110 publications

References 33 publications

Reconstitution of Muscarinic Modulation of the KCNQ2/KCNQ3 K⁺Channels That Underlie the Neuronal M Current

Reconstitution of Muscarinic Modulation of the KCNQ2/KCNQ3 K⁺Channels That Underlie the Neuronal M Current

Cannabinoid Receptor Activation Differentially Modulates Ion Channels in Photoreceptors of the Tiger Salamander

Co-expression of Metabotropic Glutamate Receptor 7 and N-type Ca2+ Channels in Single Cerebrocortical Nerve Terminals of Adult Rats

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G-Protein β-Subunit Specificity in the Fast Membrane-Delimited Inhibition of Ca2+Channels

Cited by 110 publications

References 33 publications

Reconstitution of Muscarinic Modulation of the KCNQ2/KCNQ3 K+Channels That Underlie the Neuronal M Current

Reconstitution of Muscarinic Modulation of the KCNQ2/KCNQ3 K+Channels That Underlie the Neuronal M Current

Cannabinoid Receptor Activation Differentially Modulates Ion Channels in Photoreceptors of the Tiger Salamander

Co-expression of Metabotropic Glutamate Receptor 7 and N-type Ca2+ Channels in Single Cerebrocortical Nerve Terminals of Adult Rats

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Product

Resources

About

G-Protein β-Subunit Specificity in the Fast Membrane-Delimited Inhibition of Ca²⁺Channels

Reconstitution of Muscarinic Modulation of the KCNQ2/KCNQ3 K⁺Channels That Underlie the Neuronal M Current

Reconstitution of Muscarinic Modulation of the KCNQ2/KCNQ3 K⁺Channels That Underlie the Neuronal M Current