Importance of the G protein γ subunit in activating G protein‐coupled inward rectifier K<sup>+</sup> channels

Kawano, Takeharu; Chen, Lei; Watanabe, Shinju Y.; Yamauchi, Junji; Kaziro, Yoshito; Nakajima, Yoshiaki; Nakajima, Shigehiro; Itoh, Hiroshi

doi:10.1016/s0014-5793(99)01656-7

Cited by 19 publications

(15 citation statements)

References 35 publications

(39 reference statements)

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“…These small currents would have been derived from the transfected GIRK1/GIRK2 activated by the endogenous G␤␥. If neither GIRK1/GIRK2 nor G␤␥ was transfected, the current was very small (about one third of the current with GIRK1/GIRK2 only) (Kawano et al, 1999). …”

Section: Resultsmentioning

confidence: 99%

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Interaction of G Protein β Subunit with Inward Rectifier K⁺Channel Kir3

Zhao

Kawano²,

Nakata³

et al. 2003

Mol Pharmacol

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G protein ␤␥ subunits bind and activate G protein-coupled inward rectifier K ϩ (GIRK) channels. This protein-protein interaction is crucial for slow hyperpolarizations of cardiac myocytes and neurons. The crystal structure of G␤ shows a sevenbladed propeller with four ␤ strands in each blade. The G␤/G␣ interacting surface contains sites for activating GIRK channels. Furthermore, our recent investigation using chimeras between G␤ 1 and yeast ␤ (STE4) suggested that the outer strands of blades 1 and 2 of G␤1 could be an interaction area between G␤1 and GIRK. In this study, we made point mutations on suspected residues on these outer strands and investigated their ability to activate GIRK1/GIRK2 channels. Mutations at Thr-86, Thr-87, and Gly-131, all located on the loops between ␤-strands, substantially reduced GIRK channel activation, suggesting that these residues are G␤/GIRK interaction sites. These mutations did not affect the expression of G␤1 or its ability to stimulate PLC␤2. These residues are surface-accessible and located outside G␤/G␣ interaction sites. These results suggest that the residues on the outer surface of blades 1 and 2 are involved in the interaction of G␤␥ with GIRK channels. Our study suggests a mechanism by which different effectors use different blades to achieve divergence of signaling. We also observed that substitution of alanine for Trp-332 of G␤1 impaired the functional interaction of G␤1 with GIRK, in agreement with the data on native neuronal GIRK channels. Trp-332 plays a critical role in the interaction of G␤1 with G␣ as well as all effectors so far tested.

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Section: Resultsmentioning

confidence: 99%

“…This small current would have originated from unknown channels endogenous in HEK293 cells (Kawano et al, 1999).…”

Section: Resultsmentioning

confidence: 99%

Interaction of G Protein β Subunit with Inward Rectifier K⁺Channel Kir3

Zhao

Kawano²,

Nakata³

et al. 2003

Mol Pharmacol

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“…G␤ 1 subunits alone were shown to bind to GIRK channels, but they failed to enhance channel currents without forming a dimer with the G␥ 2 subunits (49), suggesting the importance of the G␥ 2 subunits on channel activation. Here, we added the 35 N-terminal end amino acids of the yeast G␤ onto the mammalian G␤ 1 protein and produced a chimeric G␤ protein.…”

Section: Discussionmentioning

confidence: 99%

Critical Determinants of the G Protein γ Subunits in the Gβγ Stimulation of G Protein-activated Inwardly Rectifying Potassium (GIRK) Channel Activity

Peng

Mirshahi

Zhang

et al. 2003

Journal of Biological Chemistry

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The ␤␥ subunits of G proteins modulate inwardly rectifying potassium (GIRK) channels through direct interactions. Although GIRK currents are stimulated by mammalian G␤␥ subunits, we show that they were inhibited by the yeast G␤␥ (Ste4/Ste18) subunits. A chimera between the yeast and the mammalian G␤ 1 subunits (ym␤) stimulated or inhibited GIRK currents, depending on whether it was co-expressed with mammalian or yeast G␥ subunits, respectively. This result underscores the critical functional influence of the G␥ subunits on the effectiveness of the G␤␥ complex. A series of chimeras between G␥ 2 and the yeast G␥ revealed that the C-terminal half of the G␥ 2 subunit is required for channel activation by the G␤␥ complex. Point mutations of G␥ 2 to the corresponding yeast G␥ residues identified several amino acids that reduced significantly the ability of G␤␥ to stimulate channel activity, an effect that was not due to improper association with G␤. Most of the identified critical G␥ residues clustered together, forming an intricate network of interactions with the G␤ subunit, defining an interaction surface of the G␤␥ complex with GIRK channels. These results show for the first time a functional role for G␥ in the effector role of G␤␥.

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“…that the current caused by the basal activity of GIRK2(wt)͞ GIRK1(wt) (without expression of exogenous G␤1␥2) is only about 1͞5 of the current amplitude in the presence of the exogenous G␤1␥2 (11).…”

Section: Mutation Of Girk2 E315 To Alanine and The Corresponding Mutamentioning

confidence: 94%

“…cDNAs for GIRK1, GIRK2, and IRK2 were isolated from a rat brain cDNA library by PCR or by colony hybridization (11). Point mutations were introduced into the cDNAs by using the QuickChange Site-directed Mutagenesis kit (Stratagene).…”

Section: Methodsmentioning

confidence: 99%

A glutamate residue at the C terminus regulates activity of inward rectifier K ⁺ channels: Implication for Andersen's syndrome

Chen

Kawano

Bajic

et al. 2002

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

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G protein-coupled inward rectifiers (GIRKs) are activated directly by G protein ␤␥ subunits, whereas classical inward rectifiers (IRKs) are constitutively active. We found that a glutamate residue of GIRK2 (E315), located on a hydrophobic domain of the C terminus, is crucial for the channel activation. This glutamate (or aspartate) residue is conserved in all members of the Kir family. Substitution of alanine for the glutamate on GIRK1, GIRK2, and IRK2, expressed in HEK293 cells, greatly reduced the whole-cell currents. The whole-cell current of GIRK channels with a constitutively active gate, GIRK2 (

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Importance of the G protein γ subunit in activating G protein‐coupled inward rectifier K⁺ channels

Cited by 19 publications

References 35 publications

Interaction of G Protein β Subunit with Inward Rectifier K⁺Channel Kir3

Interaction of G Protein β Subunit with Inward Rectifier K⁺Channel Kir3

Critical Determinants of the G Protein γ Subunits in the Gβγ Stimulation of G Protein-activated Inwardly Rectifying Potassium (GIRK) Channel Activity

A glutamate residue at the C terminus regulates activity of inward rectifier K ⁺ channels: Implication for Andersen's syndrome

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Importance of the G protein γ subunit in activating G protein‐coupled inward rectifier K+ channels

Cited by 19 publications

References 35 publications

Interaction of G Protein β Subunit with Inward Rectifier K+Channel Kir3

Interaction of G Protein β Subunit with Inward Rectifier K+Channel Kir3

Critical Determinants of the G Protein γ Subunits in the Gβγ Stimulation of G Protein-activated Inwardly Rectifying Potassium (GIRK) Channel Activity

A glutamate residue at the C terminus regulates activity of inward rectifier K + channels: Implication for Andersen's syndrome

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Importance of the G protein γ subunit in activating G protein‐coupled inward rectifier K⁺ channels

Interaction of G Protein β Subunit with Inward Rectifier K⁺Channel Kir3

Interaction of G Protein β Subunit with Inward Rectifier K⁺Channel Kir3

A glutamate residue at the C terminus regulates activity of inward rectifier K ⁺ channels: Implication for Andersen's syndrome