The βγ Subunits of G Proteins Gate a K+ Channel by Pivoted Bending of a Transmembrane Segment

Jin, Taihao; Peng, Luying; Mirshahi, Tooraj; Rohács, Tibor; Chan, Kim W.; Sánchez, Roberto; Logothetis, Diomedes E.

doi:10.1016/s1097-2765(02)00659-7

Cited by 121 publications

(126 citation statements)

References 54 publications

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“…In Ca V 1.2, G422A slowed inactivation kinetics with a small positive shift in the activation gating, whereas G338A did not significantly alter either parameter. In contrast to our results on HVA Ca V channels, mutations of the universal glycine residue to alanine in voltage-gated K ϩ channels produced channels that were either nonfunctional (but present at the plasma membrane) (78, 79) or showed a reduced level of activity (80). Even when channels were functional, mutation of the glycine residue significantly shifted the channel activation potential toward more positive voltages, as in the case for the human calcium-activated K ϩ channel BK (78).…”

Section: Discussioncontrasting

confidence: 99%

“…The introduction of the fast inactivating E462R mutation in the I-II linker into the G436R background did not cancel out the slow VDI kinetics brought by G436R, indicating that the glycine residue at position 436 plays a pivotal role in bringing the channel into the inactivated state. One could envision that intracellular elements impinge directly on inactivation gating in a manner partially akin to the MthK, KirBac, and GirK channels, gated by ligand binding of intracellular domains (11,13,80,84). This model could also apply to the HVA Ca V 2.3 channel, since the distal Gly 352 was also shown to be specifically critical for VDI in Ca V 2.3.…”

Section: Camentioning

confidence: 99%

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The Role of the GX9GX3G Motif in the Gating of High Voltage-activated Ca2+ Channels

Raybaud

Dodier

Bissonnette

et al. 2006

Journal of Biological Chemistry

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The putative hinge point revealed by the crystal structure of the MthK potassium channel is a glycine residue that is conserved in many ion channels. In high voltage-activated (HVA) Ca V channels, the mid-S6 glycine residue is only present in IS6 and IIS6, corresponding to G422 and G770 in Ca V 1.2. Two additional glycine residues are found in the distal portion of IS6 (Gly 432 and Gly 436 in Ca V 1.2) to form a triglycine motif unique to HVA Ca V channels. Lethal arrhythmias are associated with mutations of glycine residues in the human L-type Ca 2؉ channel. Hence, we undertook a mutational analysis to investigate the role of S6 glycine residues in channel gating. In Ca V 1.2, ␣-helix-breaking proline mutants (G422P and G432P) as well as the double G422A/G432A channel did not produce functional channels. The macroscopic inactivation kinetics were significantly decreased with Ca V 1.2 wild type > G770A > G422A Х G436A Ͼ Ͼ G432A (from the fastest to the slowest). Mutations at position Gly 432 produced mostly nonfunctional mutants. Macroscopic inactivation kinetics were markedly reduced by mutations of Gly 436 to Ala, Pro, Tyr, Glu, Arg, His, Lys, or Asp residues with stronger effects obtained with charged and polar residues. Mutations within the distal GX 3 G residues blunted Ca 2؉ -dependent inactivation kinetics and prevented the increased voltage-dependent inactivation kinetics brought by positively charged residues in the I-II linker. In Ca V 2.3, mutation of the distal glycine Gly 352 impacted significantly on the inactivation gating. Altogether, these data highlight the role of the GX 3 G motif in the voltage-dependent activation and inactivation gating of HVA Ca V channels with the distal glycine residue being mostly involved in the inactivation gating.Voltage-dependent calcium channels are membrane-bound proteins that form large aqueous pores for the selective diffusion of Ca 2ϩ ions across the plasma membrane (1, 2). Native Ca 2ϩ channels are composed of the pore-forming Ca V ␣1, the disulfur-linked dimer Ca V ␣2␦, the intracellular Ca V ␤ subunits (␤1-␤4), and in some cases the Ca V ␥ subunit (3). To date, molecular cloning has identified the primary structures for 10 distinct calcium channel Ca V ␣ 1 subunits (1, 4 -9) that are classified into three main subfamilies according to their gating properties (Ca V 1, Ca V 2, and Ca V 3). Whereas all voltage-gated Ca 2ϩ channel ␣1 subunits activate and inactivate in response to membrane depolarization, the high voltage-activated (HVA) 2 Ca V 1 and Ca V 2 ␣1 subunits operate at markedly more positive membrane potentials than low voltage-activated Ca V 3 channel ␣1 subunits.In the absence of a crystal structure for these proteins, details regarding the structural determinants of the channel inner pore as well as the molecular mechanism underlying the activation of Ca V ␣1 subunits remain sketchy. Structural studies have revealed that the architecture of the ion-selective pore is conserved in the homologous ␣ subunit of different K ϩ channels (10 -15) with the ...

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Section: Discussioncontrasting

confidence: 99%

Section: Camentioning

confidence: 99%

The Role of the GX9GX3G Motif in the Gating of High Voltage-activated Ca2+ Channels

Raybaud

Dodier

Bissonnette

et al. 2006

Journal of Biological Chemistry

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“…Specifically, it has been previously shown that the glycine in the middle of the inner helix, which, as described above, was suggested to play a role of a central hinge in K ϩ channel gating, is 80% conserved among potassium and cyclic nucleotide-gated channel sequences (60). Therefore, we propose that if cholesterol binds to the region immediately adjacent to this residue, it might interfere with the hinging motion of the inner helix during channel gating in multiple channels.…”

mentioning

confidence: 58%

“…Specifically, comparative analysis of the crystal structures of two related bacterial channels, KcsA and MthK, reveals that a highly conserved central glycine of the inner TM helix plays the role of a gating hinge (59). Furthermore, the corresponding central glycine of the homomeric Kir3.4* channel was shown to play a central role in Kir gating, and it was suggested that the flexibility of the glycine at this position is required for ensuring the frequent gating of the helix bundle crossing of the channel (60). Our further analysis of the neighboring residues of this key glycine residue in these channels suggested that hinging occurs not at the glycine itself but at the residue immediately preceding the central glycine of the inner helix (61).…”

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confidence: 99%

Identification of Novel Cholesterol-binding Regions in Kir2 Channels

Rosenhouse‐Dantsker

Noskov

Durdağı

et al. 2013

Journal of Biological Chemistry

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Background: Cholesterol modulates inwardly rectifying potassium (Kir) channels. Results: Using a combined computational-experimental approach, we identified two putative cholesterol-binding regions in Kir2.1 that suggest the existence of a novel cholesterol binding motif. Conclusion: Cholesterol binds to nonannular surfaces in the transmembrane domain of Kir2.1. Significance: These findings provide new insights into the mechanisms underlying lipid regulation of ion channels.

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“…Nevertheless, proline-or glycine-mediated kinks or swivels in ␣-helices of ion channels can play roles in ion channel function (10,26,27). For example, proline or glycine swivels in the pore-lining helix TM2 of the inward rectifier potassium channels of the GIRK family have profound effects on its open probability (28,29). Likewise, a swivel motion of a glycine in the M2 helix of KcsA, which is equivalent to TM2 of GIRK, is involved in conformational fluctuations (30,31), and glycine and proline-based hinges in the S6 transmembrane segment of Shaker-type K ϩ channels play important functional roles in determining the pore features (27,32).…”

Section: Discussionmentioning

confidence: 99%

A helix-breaking mutation in TRPML3 leads to constitutive activity underlying deafness in the varitint-waddler mouse

Cuajungco

Aken

Schnee

et al. 2007

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

146

197

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Homozygote varitint-waddler (Va) mice, expressing a mutant isoform (A419P) of TRPML3 (mucolipin 3), are profoundly deaf and display vestibular and pigmentation deficiencies, sterility, and perinatal lethality. Here we show that the varitint-waddler isoform of TRPML3 carrying an A419P mutation represents a constitutively active cation channel that can also be identified in native varitintwaddler hair cells as a distinct inwardly rectifying current. We hypothesize that the constitutive activation of TRPML3 occurs as a result of a helix-breaking proline substitution in transmembranespanning domain 5 (TM5). A proline substitution scan demonstrated that the inner third of TRPML3's TM5 is highly susceptible to proline-based kinks. Proline substitutions in TM5 of other TRP channels revealed that TRPML1, TRPML2, TRPV5, and TRPV6 display a similar susceptibility at comparable positions, whereas other TRP channels were not affected. We conclude that the molecular basis for deafness in the varitint-waddler mouse is the result of hair cell death caused by constitutive TRPML3 activity. To our knowledge, our study provides the first direct mechanistic link of a mutation in a TRP ion channel with mammalian hearing loss.cation channel ͉ cochlea ͉ hair cell ͉ inner ear ͉ TRP channel T ransient receptor potential (TRP) cation channels are important components of many cellular and sensory systems, such as osmosensation, photosensation, taste sensation, and thermosensation (1, 2). In Drosophila, Caenorhabditis elegans, and lower vertebrates, mutations in TRP channels have also been associated with loss of sensitivity to touch and other forms of mechanical stimulation (3-5). Besides the general notion that they conduct cations, TRP channels have quite diverse structural and functional properties (1, 2).The identification of mutations in the human mucolipin (TRPML1) gene as the cause of mucolipidosis type IV, a neurodegenerative, recessive, lysosomal storage disorder characterized by psychomotor retardation and visual impairment, led to the initial description of the TRPML subfamily (6, 7). The mammalian TRPML subfamily consists of three members: TRPML1, TRPML2, and TRPML3. Like other TRP channels TRPML proteins contain six putative transmembrane domains with cytosolic amino and carboxyl termini. A mutant isoform of murine Trpml3 has recently been identified as the underlying cause of the varitint-waddler (Va) phenotype that is manifested in profound deafness, vestibular defects, pigmentation deficiencies, sterility, and perinatal lethality (8, 9). The Trpml3 (Va) allele displays an alanine to proline substitution at amino acid position 419 (A419P) in the fifth transmembrane domain of TRPML3 (8) [supporting information (SI) Fig. 5]. A second amino acid substitution (I362T) positioned at the second extracellular loop arose in cis to A419P, resulting in the Va J allele that attenuates and partially rescues the severe Va phenotype by an unknown mechanism.The present work was conducted to determine the specific role of the varitint-waddl...

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The βγ Subunits of G Proteins Gate a K+ Channel by Pivoted Bending of a Transmembrane Segment

Cited by 121 publications

References 54 publications

The Role of the GX9GX3G Motif in the Gating of High Voltage-activated Ca2+ Channels

The Role of the GX9GX3G Motif in the Gating of High Voltage-activated Ca2+ Channels

Identification of Novel Cholesterol-binding Regions in Kir2 Channels

A helix-breaking mutation in TRPML3 leads to constitutive activity underlying deafness in the varitint-waddler mouse

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