Suppression of the carbachol-activated nonselective cationic current by antibody against alpha subunit of G o protein in guinea-pig gastric myocytes

Kim, Young Chul; Kim, Sung Joon; Sim, Jae Hoon; Cho, Chin Ho; Juhnn, Yong Sung; Suh, Suk Hyo; So, Insuk; Kim, Ki Whan

doi:10.1007/s004240050663

Cited by 42 publications

(38 citation statements)

References 7 publications

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“…However, a similar result was obtained in guinea-pig gastric myocytes where antibodies against Ga o were effective in blocking the muscarinic cation current (Kim et al, 1998).…”

Section: Discussionsupporting

confidence: 72%

Effects of G‐protein‐specific antibodies and Gβγ subunits on the muscarinic receptor‐operated cation current in guinea‐pig ileal smooth muscle cells

Yan

Okamoto

Unno

et al. 2003

British J Pharmacology

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1 The effects on the whole-cell carbachol-induced muscarinic cationic current (mIcat) of antibodies against the a-subunits of various G proteins, as well as the effect of a Gbg subunit, were studied in single guinea-pig ileal smooth muscle cells voltage-clamped at À50 mV. Ionized intracellular calcium concentration, [Ca 2+ ] i , was clamped at 100 nM using a 1,2-bis(2-aminophenoxyl-ethane-N,N,N 0 ,N 0 -tetraacetic acid)/Ca 2+ mixture. 2 Application of ascending concentrations of carbachol (1 -300 mM) activated mIcat (mean amplitude 0.83 nA at 300 mM carbachol; EC 50 8 mM; Hill slope 1.0). A 20 min or longer intracellular application via the pipette solution of G i3 /G o or G o antibodies resulted in about a 70% depression of the maximum response without change in the EC 50 value. In contrast, antibodies against a-subunits of G i1 , G i1 /G i2 , G i3 , G q /G 11 or G s protein over a similar or longer period did not significantly reduce mIcat. Antibodies to common Gb or infusion of the Gbg subunit itself had no effect on mIcat.3 If cells were exposed briefly to carbachol (50 or 100 mM) at early times (o3 min) after infusion of antibodies to Ga i3 /Ga o or to Ga o had begun, carbachol responses remained unchanged even after 20 -60 min; that is, the depression of mIcat by these antibodies was prevented. 4 These data show that Ga o protein couples the muscarinic receptor to the cationic channel in guinea-pig ileal longitudinal smooth muscle and that Gbg is not involved. They also show that prior activation of the muscarinic receptor presumably causes a long-lasting postactivation change of the G protein, which is not reflected in mIcat, but acts to hinder antibody binding.

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“…However, a similar result was obtained in guinea-pig gastric myocytes where antibodies against Ga o were effective in blocking the muscarinic cation current (Kim et al, 1998).…”

Section: Discussionsupporting

confidence: 72%

Effects of G‐protein‐specific antibodies and Gβγ subunits on the muscarinic receptor‐operated cation current in guinea‐pig ileal smooth muscle cells

Yan

Okamoto

Unno

et al. 2003

British J Pharmacology

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“…Thirdly, its activation depends on G-protein activity (8,9). We also showed that the Go type among GTP-binding proteins is responsible for activating the channel (10). Fourthly, the unitary conductance was about 25 -30 pS (1 -3).…”

mentioning

confidence: 88%

The Properties of Carbachol-Activated Nonselective Cation Channels at the Single Channel Level in Guinea Pig Gastric Myocytes

Kang

Kim

Sim

et al. 2001

Japanese Journal of Pharmacology

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ABSTRACT-We investigated the properties of carbachol (CCh)-activated nonselective cation channels (NSCCCh) at the single channel level in the gastric myocytes of guinea pigs using a magnified whole-cell mode or an outside-out mode. The channel activity (NPo) recorded in a magnified whole-cell mode increased with depolarization (from -120 to -20 mV) and had the half activation potential of -81 mV under the symmetrical 140 mM Cs + condition. with 33% Na + . These data suggested that the extracellular monovalent cations regulate the whole-cell current of NSCCCh by modulating both the open state probability and the unitary conductance, and there is one binding site for the extracellular cations within the pore.

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“…In these cell types, the I cat response is abolished by pertussis toxin (PTX) which selectively uncouples G i / G o proteins from the associated receptors (2, 7 -10). With the use of antibodies, the G protein involved in the signal transduction was identified as G o protein (11,12). Based on these results and the general thought that M2 receptors preferencially couple PTX-sensitive G proteins (8), the M2 subtype is supposed to mediate cationic channel opening through G o proteins.…”

Section: Introductionmentioning

confidence: 98%

Phospholipase C Involvement in Activation of the Muscarinic Receptor-Operated Cationic Current in Guinea Pig Ileal Smooth Muscle Cells

et al. 2004

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Abstract. In guinea pig single ileal smooth muscle cells held under voltage-clamp, the role of phospholipase C (PLC) in activation of the muscarinic receptor-operated cationic current (I cat ) was studied. U73122, a PLC inhibitor, prevented the generation of I cat by the muscarinic agonist carbachol. The effect did not involve muscarinic receptor block since it also blocked I cat which was evoked by GTPgS applied intracellularly to activate G proteins bypassing muscarinic receptors. Also, neither cationic channel block nor other possible nonspecific actions seemed to be involved since its analogue (U73343), structurally close but deficient of the PLC-inhibiting activity, did not significantly affect carbachol-or GTPgS-evoked I cat . Antibodies against the a subunits of G q / G 11 proteins (Ga q / Ga 11 -antibody) blocked only the small component of carbachol-evoked I cat , which was associated with an increase in [Ca 2+ ] i linked to an increase in G q/ 11 protein-regulated PLC activity. 1-Oleoyl-2-acetyl-sn-glycerol (OAG), an analogue of diacylglycerol (DAG) produced via PLC-catalyzed metabolism, produced no or only a small current by itself, with the carbachol-evoked I cat remaining unchanged. These results provide evidence for the importance of PLC in I cat generation, and they also strongly suggest that the activity of PLC involved in the primary activation of I cat is neither under regulation by G q/ 11 proteins nor dependent on the action of DAG.

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Suppression of the carbachol-activated nonselective cationic current by antibody against alpha subunit of G o protein in guinea-pig gastric myocytes

Cited by 42 publications

References 7 publications

Effects of G‐protein‐specific antibodies and Gβγ subunits on the muscarinic receptor‐operated cation current in guinea‐pig ileal smooth muscle cells

Effects of G‐protein‐specific antibodies and Gβγ subunits on the muscarinic receptor‐operated cation current in guinea‐pig ileal smooth muscle cells

The Properties of Carbachol-Activated Nonselective Cation Channels at the Single Channel Level in Guinea Pig Gastric Myocytes

Phospholipase C Involvement in Activation of the Muscarinic Receptor-Operated Cationic Current in Guinea Pig Ileal Smooth Muscle Cells

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