Gating of a G protein-sensitive Mammalian Kir3.1 Prokaryotic Kir Channel Chimera in Planar Lipid Bilayers

Leal-Pinto, Edgar; Gomez‐Llorente, Yacob; Sundaram, Shobana; Tang, Qiong-Yao; Ivanova-Nikolova, Tatyana T.; Mahajan, Rohit; Baki, Lia; Zhang, Zhe; Chavez, Jose; Ubarretxena-Belandia, Iban; Logothetis, Diomedes E.

doi:10.1074/jbc.m110.151373

Cited by 38 publications

(38 citation statements)

References 58 publications

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“…Rather, an inhibitory regulation of GIRK1/4 by G␣ i1 GTP␥S (but not G␣ i3 GTP␥S ) has been observed at very low expression levels of the channel, suggesting a mechanism involving interference with endogenous G␣ i/o (12,14). However, a synergistic, mutually obligatory activation by G␣ i GTP and G␤␥ in artificial membranes has been recently found in a chimeric channel composed of a transmembrane domain of a bacterial K ϩ channel and a truncated cytosolic domain of mammalian GIRK1 (15). Furthermore, coexpression of a constitutively active (GTP-bound) mutant of G␣ i3 significantly modified G␤␥-induced conformational changes in the cytosolic domains of GIRK1 and GIRK2 subunits within the GIRK1/2 heterotetrameric channel, also suggesting more than additive effects of G␣ i3 GTP and G␤␥ (16).…”

Section: Discussionmentioning

confidence: 99%

Two Distinct Aspects of Coupling between Gαi Protein and G Protein-activated K+ Channel (GIRK) Revealed by Fluorescently Labeled Gαi3 Protein Subunits

Berlin

Tsemakhovich

Castel

et al. 2011

Journal of Biological Chemistry

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Section: Discussionmentioning

confidence: 99%

Two Distinct Aspects of Coupling between Gαi Protein and G Protein-activated K+ Channel (GIRK) Revealed by Fluorescently Labeled Gαi3 Protein Subunits

Berlin

Tsemakhovich

Castel

et al. 2011

Journal of Biological Chemistry

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“…We have recently implemented this strategy to determine the three-dimensional reconstruction of a detergent-solubilized ϳ160-kDa membrane protein (45). An initial data set of 150,000 particles was automatically selected from 550 CCD images using EMAN (46).…”

Section: Methodsmentioning

confidence: 99%

Structure of γ-Secretase and Its Trimeric Pre-activation Intermediate by Single-particle Electron Microscopy

Renzi

Zhang

Rice

et al. 2011

Journal of Biological Chemistry

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The ␥-secretase membrane protein complex is responsible for proteolytic maturation of signaling precursors and catalyzes the final step in the production of the amyloid ␤-peptides implicated in the pathogenesis of Alzheimer disease. The incorporation of PEN-2 (presenilin enhancer 2) into a pre-activation intermediate, composed of the catalytic subunit presenilin and the accessory proteins APH-1 (anterior pharynx-defective 1) and nicastrin, triggers the endoproteolysis of presenilin and results in an active tetrameric ␥-secretase. We have determined the three-dimensional reconstruction of a mature and catalytically active ␥-secretase using single-particle cryo-electron microscopy. ␥-Secretase has a cup-like shape with a lateral belt of ϳ40 -50 Å in height that encloses a water-accessible internal chamber. Active site labeling with a gold-coupled transition state analog inhibitor suggested that the ␥-secretase active site faces this chamber. Comparison with the structure of a trimeric pre-activation intermediate suggested that the incorporation of PEN-2 might contribute to the maturation of the active site architecture.Alzheimer disease is a prevalent cause of dementia in adults (1). The neuropathological hallmarks of Alzheimer disease include the presence of senile plaques and neurofibrillary tangles throughout the cerebral cortex and hippocampus and the loss of neurons in these specific brain areas (2). Senile plaques are composed of dystrophic neurites surrounding extracellular aggregates of amyloid ␤-peptides (A␤) 4 that are derived from the sequential proteolytic degradation of amyloid precursor proteins (APPs) to produce A␤ peptides that range from 34 to 42 amino acids in length (3, 4). APP is first cleaved in its ectodomain segment by BACE1, and the resulting C-terminal membrane-associated derivatives are subsequently hydrolyzed within their transmembrane domain (TMD) by ␥-secretase. This intramembrane proteolytic activity of ␥-secretase is critical in other cellular processes, such as the activation of Notchand ErbB4-dependent signaling (4, 5), and in the processing of a growing list of additional type I integral membrane proteins, including APP-like proteins, E-cadherin, CD44, and lipoprotein receptor-related protein (reviewed in Ref. 6).Reconstitution experiments in Saccharomyces cerevisiae have demonstrated that the integral membrane proteins presenilin (PS; 52.7 kDa), nicastrin (NCT; 78.4 kDa if non-glycosylated), APH-1 (anterior pharynx-defective 1; 29 kDa), and PEN-2 (presenilin enhancer 2; 12 kDa) are essential and sufficient for ␥-secretase activity (7). It is now widely accepted that PS, a polypeptide with nine predicted TMDs (8) and two absolutely conserved catalytic aspartates in the hydrophobic region of adjacent TMD6 and TMD7 (9), is the catalytic subunit of ␥-secretase. In fact, PS is now considered to be the founding member of diaspartyl intramembrane proteases, which are also found in other eukaryotes (10, 11) and in archaea (12). In vivo, PS undergoes endoproteolysis in the intracellular...

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“…This would reduce free Gβγ levels but enrich the substrate for Li + action (Gαβγ), thereby enhancing the relative effect Li + in promoting Gαβγ dissociation (27,29). A modulatory role of Gα i itself (28,32) is also plausible, although the mechanisms of Gα regulations of GIRK remain unclear.…”

Section: Molecular Mechanism Of LImentioning

confidence: 99%

Dual regulation of G proteins and the G-protein–activated K ⁺ channels by lithium

Tselnicker

Tsemakhovich

Rishal

et al. 2014

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

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Lithium (Li +) is widely used to treat bipolar disorder (BPD). Cellular targets of Li + , such as glycogen synthase kinase 3β (GSK3β) and G proteins, have long been implicated in BPD etiology; however, recent genetic studies link BPD to other proteins, particularly ion channels. Li + affects neuronal excitability, but the underlying mechanisms and the relevance to putative BPD targets are unknown. We discovered a dual regulation of G protein-gated K + (GIRK) channels by Li + , and identified the underlying molecular mechanisms. In hippocampal neurons, therapeutic doses of Li + (1-2 mM) increased GIRK basal current (I basal ) but attenuated neurotransmitter-evoked GIRK currents (I evoked ) mediated by G i/o -coupled G-protein-coupled receptors (GPCRs). Molecular mechanisms of these regulations were studied with heterologously expressed GIRK1/2. In excised membrane patches, Li + increased I basal but reduced GPCR-induced GIRK currents. Both regulations were membrane-delimited and G protein-dependent, requiring both Gα and Gβγ subunits. Li + did not impair direct activation of GIRK channels by Gβγ, suggesting that inhibition of I evoked results from an action of Li + on Gα, probably through inhibition of GTP-GDP exchange. In direct binding studies, Li + promoted GPCR-independent dissociation of Gα i GDP from Gβγ by a Mg 2+ -independent mechanism. This previously unknown Li + action on G proteins explains the second effect of Li + , the enhancement of GIRK's I basal . The dual effect of Li + on GIRK may profoundly regulate the inhibitory effects of neurotransmitters acting via GIRK channels. Our findings link between Li + , neuronal excitability, and both cellular and genetic targets of BPD: GPCRs, G proteins, and ion channels.is a common disease of poorly understood molecular mechanisms comprising both neurodevelopmental and genetic factors (1, 2). Lithium (Li + ) stabilizes the condition in many BPD patients. Historically, the etiology of BPD has been linked to cellular targets of Li + , including G proteins, enzymes of phosphoinositide (PI) turnover, and Akt/GSK3β cascade (3-5). However, recent genetic studies have identified a multitude of BPD-associated genes, with a preponderance of proteins related to G-protein-coupled receptors (GPCRs) and ion channels (6), particularly Ca 2+ channels (2, 7, 8). Linkages with ion channel genes extend to other major psychiatric diseases as well, especially schizophrenia (9, 10). To date, no substantial links between BPD and genes of PI turnover enzymes and GSK3β have been identified.To understand BPD, it is important to bridge the gap between protein targets of BPD suggested by genetic vs. cellular studies, and to understand how ion channels are involved. Li + may provide a clue. Li + has neuroprotective and neurotrophic effects (11) and affects neuronal excitability (12, 13) by largely unknown mechanisms. Li + acts intracellularly (14), entering neurons through several nonspecific cation channels and voltage-dependent Na + channels (15). Therapeutic doses of Li + are 0.6-1.2...

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Gating of a G protein-sensitive Mammalian Kir3.1 Prokaryotic Kir Channel Chimera in Planar Lipid Bilayers

Cited by 38 publications

References 58 publications

Two Distinct Aspects of Coupling between Gαi Protein and G Protein-activated K+ Channel (GIRK) Revealed by Fluorescently Labeled Gαi3 Protein Subunits

Two Distinct Aspects of Coupling between Gαi Protein and G Protein-activated K+ Channel (GIRK) Revealed by Fluorescently Labeled Gαi3 Protein Subunits

Structure of γ-Secretase and Its Trimeric Pre-activation Intermediate by Single-particle Electron Microscopy

Dual regulation of G proteins and the G-protein–activated K ⁺ channels by lithium

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Gating of a G protein-sensitive Mammalian Kir3.1 Prokaryotic Kir Channel Chimera in Planar Lipid Bilayers

Cited by 38 publications

References 58 publications

Two Distinct Aspects of Coupling between Gαi Protein and G Protein-activated K+ Channel (GIRK) Revealed by Fluorescently Labeled Gαi3 Protein Subunits

Two Distinct Aspects of Coupling between Gαi Protein and G Protein-activated K+ Channel (GIRK) Revealed by Fluorescently Labeled Gαi3 Protein Subunits

Structure of γ-Secretase and Its Trimeric Pre-activation Intermediate by Single-particle Electron Microscopy

Dual regulation of G proteins and the G-protein–activated K + channels by lithium

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Dual regulation of G proteins and the G-protein–activated K ⁺ channels by lithium