State-dependent cross-inhibition between transmitter-gated cation channels

Khakh, Baljit S.; Zhou, Xiaoping; Sydes, Jason; Galligan, James J.; Lester, Henry A.

doi:10.1038/35019066

Cited by 173 publications

(136 citation statements)

References 27 publications

Supporting

Mentioning

118

Contrasting

Unclassified

Order By: Relevance

“…Application of ATP did not gate or modulate GABA C receptors, and GABA did not activate or modulate P2X 2 receptors, showing that nonspecific cross-activation or cross-desensitization between one type of transmitter and the other type of receptor could not explain the cross-inhibition observed during co-application. A similar reciprocity of cross-inhibition was observed between P2X 2 and nicotinic or 5-HT 3 receptors (24,26). Interestingly, an inhibitory cross-talk between P2X and GABA A channels reported in dorsal root ganglion neurons indicates a more pronounced inhibitory effect of GABA receptors on P2X channels than the reverse (25).…”

Section: Discussionsupporting

confidence: 49%

“…Functional cross-inhibition between receptors activated by ATP and either acetylcholine or GABA has been reported lately in neurons or transfected cells (21)(22)(23)(24)(25), and we recently demonstrated that a physical interaction between P2X and 5-HT 3 receptors leads to an activity-dependent cross inhibition between the two cationic channels (26). We decided to explore the possibility that ligandgated chloride channels may also interact with P2X ATP-gated channels through similar mechanisms.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Cross-talk and Co-trafficking between ρ1/GABA Receptors and ATP-gated Channels

Boué‐Grabot

Émerit

Toulmé

et al. 2004

Journal of Biological Chemistry

View full text Add to dashboard Cite

␥-Aminobutyric-acid (GABA) and ATP ionotropic receptors represent two structurally and functionally different classes of neurotransmitter-gated channels involved in fast synaptic transmission. We demonstrate here that, when the inhibitory 1/GABA and the excitatory P2X 2 receptor channels are co-expressed in Xenopus oocytes, activation of one channel reduces the currents mediated by the other one. This reciprocal inhibitory cross-talk is a receptor-mediated phenomenon independent of agonist cross-modulation, membrane potential, direction of ionic flux, or channel densities. Functional interaction is disrupted when the cytoplasmic C-terminal domain of P2X 2 is deleted or in competition experiments with minigenes coding for the Cterminal domain of P2X 2 or the main intracellular loop of 1 subunits. We also show a physical interaction between P2X 2 and 1 receptors expressed in oocytes and the co-clustering of these receptors in transfected hippocampal neurons. Co-expression with P2X 2 induces retargeting and recruitment of mainly intracellular 1/ GABA receptors to surface clusters. Therefore, molecular and functional cross-talk between inhibitory and excitatory ligand-gated channels may regulate synaptic strength both by activity-dependent current occlusion and synaptic receptors co-trafficking.Neuronal activity is regulated by a number of transmitters acting on different receptor types (1). Fast neurotransmission is achieved through different classes of transmitter-gated channels, including the P2X and nicotinic receptor superfamilies (1, 2). The family of P2X ATP-gated cation channels is composed of seven genes coding for subunits with two transmembrane domains, intracellular N and C termini, and a large extracellular loop (2). The nicotinic superfamily includes the GABA-gated 1 channels along with the acetylcholine, 5-HT 3 , and glycine receptors that share several structural features, including a large extracellular N-terminal domain, four hydrophobic transmembrane domains (M1-M4), and a long cytoplasmic loop connecting M3 and M4 (1). GABA receptor channels have been classified into two subtypes based on their pharmacological properties. GABA A receptors are inhibited by bicuculline, whereas GABA C receptors are insensitive to this antagonist (1). Diversity of GABA A receptors is achieved by pentameric assembly of multiple subunits, including ␣1-6, ␤1-3, ␥1-3, ␦, , and ⑀. GABA C receptors are composed of 1-3 subunits that can assemble into homo-oligomers (3, 4). Recent data suggest that a 1 subunit could co-assemble with a GABA A subunit (5, 6). Neuronal ATP and GABA C ionotropic receptors are involved in fast excitatory and inhibitory synaptic transmission, respectively, and display overlapping distribution in many regions of the nervous system, including DRG, dorsal horn of the spinal cord (7, 8), retina (9 -13), hippocampus (14 -15), cerebellum (14, 16), and anterior pituitary (17, 18).Recently, Jo and co-workers described ATP and GABA corelease from the same axon terminals into the dorsal horn of the spinal ...

show abstract

Section: Discussionsupporting

confidence: 49%

mentioning

confidence: 99%

Cross-talk and Co-trafficking between ρ1/GABA Receptors and ATP-gated Channels

Boué‐Grabot

Émerit

Toulmé

et al. 2004

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…4C). T18A mutant receptors are useful because they allow P2X 2 receptor responses to be assigned to a particular channel state, and we interpret the rapid desensitization kinetics in T18A mutants as indicative of the presence of only the I 1 state (23). Overall these data imply that P2X 2 -GFP receptor redistribution and varicosity formation require prolonged P2X 2 receptor function, for instance, as produced by the I 2 state.…”

Section: Materials and Methods)mentioning

confidence: 81%

Activation-dependent changes in receptor distribution and dendritic morphology in hippocampal neurons expressing P2X ₂ -green fluorescent protein receptors

Khakh

Smith²,

Chiu³

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

View full text Add to dashboard Cite

ATP-gated P2X2 receptors are widely expressed in neurons, but the cellular effects of receptor activation are unclear. We engineered functional green fluorescent protein (GFP)-tagged P2X 2 receptors and expressed them in embryonic hippocampal neurons, and report an approach to determining functional and total receptor pool sizes in living cells. ATP application to dendrites caused receptor redistribution and the formation of varicose hot spots of higher P2X2-GFP receptor density. Redistribution in dendrites was accompanied by an activation-dependent enhancement of the ATP-evoked current. Substate-specific mutant T18A P2X2-GFP receptors showed no redistribution or activation-dependent enhancement of the ATP-evoked current. Thus fluorescent P2X 2-GFP receptors function normally, can be quantified, and reveal the dynamics of P2X 2 receptor distribution on the seconds time scale.ion channel ͉ ATP ͉ filopodia C ationic P2X receptors mediate the ''fast'' milliseconds time scale actions of ATP in the nervous system (1, 2). The identity of most natively expressed P2X receptors is unclear, but many neurons express P2X 2 mRNA, P2X 2 proteins, and functional P2X 2 -like receptors (2). For example, ATP mediates synaptic transmission in a portion of CA1 neurons (3), and postnatal hippocampal neurons express P2X receptors, which include P2X 2 subunits (3-7). Moreover, cytosolic ATP concentration is 1-5 mM, and ATP released during tissue damage activates neuronal P2X receptors in the periphery (1). ATP released as a synaptic transmitter and during ischemia of brain neurons may contribute to pathophysiology, but there are no available data on the cellular consequences of P2X 2 receptor activation or on the dynamic aspects of P2X 2 receptor distribution in brain neurons.This study used P2X 2 receptors tagged with green fluorescent protein (GFP) in a quantitative method to study receptors expressed with recombinant Sindbis virus in embryonic hippocampal neurons. We report (i) the properties of functional GFP-tagged P2X 2 receptors, (ii) an optical and electrophysiological approach to measuring receptor numbers in living cells, and (iii) the cellular effects of P2X receptor activation. Materials and MethodsMolecular Biology. By PCR the P2X 2 stop codon was removed and the FLAG (f) epitope was inserted in frame with the P2X 2 cDNA cDNA (9). In the same PCR we inserted an XhoI site in the DNA. We generated GFP37 (10) with a XhoI site before the start codon and subcloned it into P2X 2 -f between the XhoI site 3Ј of the FLAG epitope and HindIII in the pcDNA3 polylinker to yield P2X 2 -GFP. The P2X 2 -f-GFP fragment was inserted into pSinRep5 between the StuI and ApaI sites, and infective Sindbis particles were generated with the use of the Sindbis Expression System (http:͞͞www.invitrogen.com͞). Site-directed mutagenesis was performed on the cDNAs with the use of synthetic oligonucleotides to generate K69A and T18A mutants (Quick Change; Stratagene).Electrophysiology and Imaging. All cell preparations, twoelectrode voltage-clamp record...

show abstract

“…10). There is evidence for direct protein-protein interactions (cross-talk) between the intracellular domains of different channels in close proximity (15,16). It is possible that GABARAP, by aggregating receptors, promotes interaction(s) between the intracellular domains of the closely packed receptors so that several pentameric channels open cooperatively.…”

Section: Discussionmentioning

confidence: 99%

Conductance of Recombinant GABA Channels Is Increased in Cells Co-expressing GABAA A Receptor-associated Protein

Everitt

Luu

Cromer

et al. 2004

Journal of Biological Chemistry

View full text Add to dashboard Cite

High conductance ␥-aminobutyric acid type A (GABA A ) channels (>40 picosiemens (pS)) have been reported in some studies on GABA A channels in situ but not in others, whereas recombinant GABA A channels do not appear to display conductances above 40 pS. Furthermore, the conductance of some native GABA A channels can be increased by diazepam or pentobarbital, which are effects not reported for expressed GABA A channels. GABARAP, a protein associated with native GABA A channels, has been reported to cause clustering of GABA A receptors and changes in channel kinetics. We have recorded single channel currents activated by GABA in L929 cells expressing ␣ 1 , ␤ 1 , and ␥ 2S subunits of human GABA A receptors. Channel conductance was never higher than 40 pS and was not significantly increased by diazepam or pentobarbital, although open probability was increased. In contrast, in cells expressing the same three subunits together with GABARAP, channel conductance could be significantly higher than 40 pS, and channel conductance was increased by diazepam and pentobarbital. GABARAP caused clustering of receptors in L929 cells, and we suggest that there may be interactions between subunits of clustered GABA A receptors that make them open co-operatively to give high conductance "channels." Recombinant channels may require the influence of GABARAP and perhaps other intracellular proteins to adopt a fuller repertoire of properties of native channels.

show abstract

State-dependent cross-inhibition between transmitter-gated cation channels

Cited by 173 publications

References 27 publications

Cross-talk and Co-trafficking between ρ1/GABA Receptors and ATP-gated Channels

Cross-talk and Co-trafficking between ρ1/GABA Receptors and ATP-gated Channels

Activation-dependent changes in receptor distribution and dendritic morphology in hippocampal neurons expressing P2X ₂ -green fluorescent protein receptors

Conductance of Recombinant GABA Channels Is Increased in Cells Co-expressing GABAA A Receptor-associated Protein

Contact Info

Product

Resources

About

State-dependent cross-inhibition between transmitter-gated cation channels

Cited by 173 publications

References 27 publications

Cross-talk and Co-trafficking between ρ1/GABA Receptors and ATP-gated Channels

Cross-talk and Co-trafficking between ρ1/GABA Receptors and ATP-gated Channels

Activation-dependent changes in receptor distribution and dendritic morphology in hippocampal neurons expressing P2X 2 -green fluorescent protein receptors

Conductance of Recombinant GABA Channels Is Increased in Cells Co-expressing GABAA A Receptor-associated Protein

Contact Info

Product

Resources

About

Activation-dependent changes in receptor distribution and dendritic morphology in hippocampal neurons expressing P2X ₂ -green fluorescent protein receptors