μ-Opioid receptor regulates CFTR coexpressed in Xenopus oocytes in a cAMP independent manner

Wotta, Diane R.; Wilcox, George L.; Elde, Robert; Law, Ping Yee

doi:10.1016/s0169-328x(96)00189-1

Cited by 5 publications

(6 citation statements)

References 42 publications

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“…The unexpected positive coupling of G i/o -coupled receptors, including MOR, can occur through G βγ -activation of type-II adenylyl cyclase, provided Gα s is present [22,23,24]. Because oocytes express type-II adenylyl cyclase endogenously [25], we hypothesized that the unexpected activation of HCN2 by MOR occurred in those oocytes that expressed a low level of the Gα s subunit. To investigate whether Gα s subunits provide the missing factor for activating type-II adenylyl cyclase via MOR in all oocytes, we coexpressed a constitutively active Gα s mutant (Gα s Q227L) in all following experiments, similar to previous experiments performed in mammalian cells [24].…”

Section: Resultsmentioning

confidence: 99%

“…In summary, G i/o -coupled receptors are able to modulate I h in opposing manner, depending on the isotype of adenylyl cyclase co-existing within the same neuron or heterologous expression system. If βγ-stimulated adenylyl cyclases co-exist (as endogenously expressed in Xenopus oocytes [25]), the receptor will cause an increase of the intracellular cAMP concentration, in turn enhancing I h .…”

Section: Discussionmentioning

confidence: 99%

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G i - and G s -coupled receptors up-regulate the cAMP cascade to modulate HCN2, but not HCN1 pacemaker channels

Ulens

Tytgat

2001

Pfl�gers Archiv European Journal of Physiology

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A hallmark of native pacemaker channels is their regulation by neurotransmitters and hormones acting through the second messenger cAMP. In this study, we investigated the modulation of two cloned pacemaker channels, HCN1 and HCN2, by activation of coexpressed inhibitory G protein (Gi)-coupled (p-opioid) or stimulatory G protein (Gs)-coupled [serotonin 5-HT4(a)] receptors in Xenopus oocytes. Both receptors enhanced HCN2, but not HCN1 currents. Receptor activation increased HCN2 current amplitude, increased the activation rate sixfold and decreased the deactivation rate two-fold. In addition, the fully-activated current for HCN2 increased due to a receptor-induced increase of the maximal conductance. These effects were inhibited by 9-(tetrahydro-2'-furyl)adenine (SQ22536), were independent of protein kinases A and C and could be explained by a cAMP-induced shift of the voltage dependence of activation by 15 mV to more positive potentials. The pathway through which these effects occurred involved Gbetagamma-activation of adenylyl cyclase and, in the case of the p-opioid receptor, required co-expression of Galphas. The effect of the 5-HT4(a)-receptor, in part caused by its constitutive activity, occurred directly through Galphas-activation. This suggests that 5-HT4(a) receptors may contribute to functional heterogeneity of pacemaker currents (Ih) in those neurons in which 5-HT4(a)R and HCN2 coexist.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

G i - and G s -coupled receptors up-regulate the cAMP cascade to modulate HCN2, but not HCN1 pacemaker channels

Ulens

Tytgat

2001

Pfl�gers Archiv European Journal of Physiology

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“…Oligonucleotides designed against the C1 domain of the Xenopus AC2 fragment described by Wotta et al (1997), were used to amplify by PCR a DNA fragment from a cDNA Xenopus oocyte library (Clontech, Palo Alto, CA, USA). The forward primer was 5 0 -CTCATC-GATGGGGACTCTTATTATTGTGT-3 0 which corresponds to the 5 0 -conserved LIDGDCYYCV sequence.…”

Section: Xenopus Oocyte Ac Cloningmentioning

confidence: 99%

“…To identify this AC, at the molecular level, we synthesized specific oligonucleotides based in a short Xenopus AC2 cDNA sequence (Wotta et al, 1997) and a Xenopus EST (BJ068695). Through this approach, we amplified by PCR a gene encoding an AC, which showed higher identity to the subgroup of Gbg-stimulated mammalian ACs (44% to AC7, 38% to AC2, and 35% to AC4) than to the other isotypes (25% to AC1, 23% to AC6, 21% to AC5 and AC3, 19% to AC8, and 15% to AC9).…”

Section: Xenopus Oocyte Ac Activity Is Characteristic Of Ac2 Isoformmentioning

confidence: 99%

A Gβγ stimulated adenylyl cyclase is involved in xenopus laevis oocyte maturation

Guzmán

Romo

Grandy

et al. 2004

Journal Cellular Physiology

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Xenopus laevis oocyte maturation is induced by the steroid hormone progesterone through a nongenomic mechanism that implicates the inhibition of the effector system adenylyl cyclase (AC). Recently, it has been shown that the G protein betagamma heterodimer is involved in oocyte maturation arrest. Since AC is the proposed target for Gbetagamma action, we considered of importance to identify and characterize the Gbetagamma regulated AC isoform(s) that are expressed in the Xenopus oocyte. Through biochemical studies, we found that stage VI plasma membrane oocyte AC activity showed attributes of an AC2 isoform. Furthermore, exogenous Gbetagamma was capable to activate oocyte AC only in the presence of the activated form of Galphas (Galphas-GTPgammaS), which is in agreement with the Ggammabeta conditional activation reported for the mammalian AC2 and AC4 isotypes. In order to study the functional role of AC in oocyte maturation we cloned from a Xenopus oocyte cDNA library a gene encoding an AC with high identity to AC7 (xAC7). Based on this sequence, we constructed a minigene encoding the AC-Gbetagamma interacting region (xAC7pep) to block, within the oocyte, this interaction. We found that microinjection of the xAC7pep potentiated progesterone-induced maturation, as did the AC2 minigene. From these results we can conclude that a Gbetagamma-activated AC is playing an important role in Xenopus oocyte meiotic arrest in a Galphas-GTP dependent manner.

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“…In epithelial cells, cAMP also activated CFTR (Gadsby and Nairn, 1999), but no data are available concerning an elevation of cAMP by ␤ 2 -AR stimulation in those cells. However, in Xenopus laevis oocytes, the ␤ 2 -AR stimulation produced an activation of adenylyl cyclase that increased the concentration of intracellular cAMP, leading to an activation of CFTR channel gating (Wotta et al, 1997). Our group has demonstrated in a recombinant system, a human lung epithelialderived cell line (A549), that CFTR is regulated by ␤ 3 -AR stimulation produced either by isoproterenol (a nonselective ␤-AR agonist) in the presence of nadolol (a ␤ 1 , ␤ 2 -AR antagonist), SR 58611A (a preferential ␤ 3 -AR agonist), or CGP-12177 (a partial ␤ 3 -AR agonist) (Leblais et al, 1999).…”

mentioning

confidence: 99%

Transfected β3- but Not β2-Adrenergic Receptors Regulate Cystic Fibrosis Transmembrane Conductance Regulator Activity via a New Pathway Involving the Mitogen-Activated Protein Kinases Extracellular Signal-Regulated Kinases

et al. 2004

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μ-Opioid receptor regulates CFTR coexpressed in Xenopus oocytes in a cAMP independent manner

Cited by 5 publications

References 42 publications

G i - and G s -coupled receptors up-regulate the cAMP cascade to modulate HCN2, but not HCN1 pacemaker channels

G i - and G s -coupled receptors up-regulate the cAMP cascade to modulate HCN2, but not HCN1 pacemaker channels

A Gβγ stimulated adenylyl cyclase is involved in xenopus laevis oocyte maturation

Transfected β3- but Not β2-Adrenergic Receptors Regulate Cystic Fibrosis Transmembrane Conductance Regulator Activity via a New Pathway Involving the Mitogen-Activated Protein Kinases Extracellular Signal-Regulated Kinases

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