scholarly journals Gγ and Gα Identity Dictate a G-Protein Heterotrimer Plasma Membrane Targeting

Cells ◽  
2019 ◽  
Vol 8 (10) ◽  
pp. 1246 ◽  
Author(s):  
Paweł Mystek ◽  
Beata Rysiewicz ◽  
Jan Gregrowicz ◽  
Marta Dziedzicka-Wasylewska ◽  
Agnieszka Polit
Keyword(s):  
Plasma Membrane ◽  
G Protein ◽  
G Proteins ◽  
Protein Localization ◽  
Present Report ◽  
Lateral Diffusion ◽  
Resonance Energy ◽  
Fluorescence Lifetime Imaging ◽  
Heterotrimeric G Proteins ◽  
Protein Subunit

Heterotrimeric G-proteins along with G-protein-coupled receptors (GPCRs) regulate many biochemical functions by relaying the information from the plasma membrane to the inside of the cell. The lipid modifications of Gα and Gγ subunits, together with the charged regions on the membrane interaction surface, provide a peculiar pattern for various heterotrimeric complexes. In a previous study, we found that Gαs and Gαi3 prefer different types of membrane-anchor and subclass-specific lipid domains. In the present report, we examine the role of distinct Gγ subunits in the membrane localization and spatiotemporal dynamics of Gαs and Gαi3 heterotrimers. We characterized lateral diffusion and G-protein subunit interactions in living cells using fluorescence recovery after photobleaching (FRAP) microscopy and fluorescence resonance energy transfer (FRET) detected by fluorescence lifetime imaging microscopy (FLIM), respectively. The interaction of Gγ subunits with specific lipids was confirmed, and thus the modulation of heterotrimeric G-protein localization. However, the Gα subunit also modulates trimer localization, and so the membrane distribution of heterotrimeric G-proteins is not dependent on Gγ only.

scholarly journals Ligand-Induced Partitioning of Human CXCR1 Chemokine Receptors with Lipid Raft Microenvironments Facilitates G-Protein-Dependent Signaling

2005 ◽  
Vol 25 (13) ◽  
pp. 5752-5762 ◽  
Author(s):  
Xuanmao Jiao ◽  
Ning Zhang ◽  
Xuehua Xu ◽  
Joost J. Oppenheim ◽  
Tian Jin
Keyword(s):  
Ligand Binding ◽  
G Protein ◽  
G Proteins ◽  
Lipid Raft ◽  
Chemokine Receptors ◽  
Fluorescent Protein ◽  
Lateral Diffusion ◽  
Resonance Energy ◽  
Fluorescence Probes ◽  
Heterotrimeric G Proteins

ABSTRACT Ligand binding to a chemokine receptor triggers signaling events through heterotrimeric G-proteins. The mechanisms underlying receptor-mediated G-protein activation in the heterogeneous microenvironments of the plasma membrane are unclear. Here, using live-cell fluorescence resonance energy transfer imaging to detect the proximity between CXCR1-cyan fluorescent protein (CFP) and fluorescence probes that label lipid raft or non-lipid raft microdomains and using fluorescence recovery after photobleaching analysis to measure the lateral diffusion of CXCR1-CFP, we found that interleukin-8 induces association between the receptors and lipid raft microenvironments. Disruption of lipid rafts impaired G-protein-dependent signaling, such as Ca2+ responses and phosphatidylinositol 3-kinase activation, but had no effect on ligand-binding function and did not completely abolish ligand-induced receptor phosphorylation. Our results suggest a novel mechanism by which ligand binding to CXCR1 promotes lipid raft partitioning of receptors and facilitates activation of heterotrimeric G-proteins.

scholarly journals Variable G protein determinants of GPCR coupling selectivity

2019 ◽  
pp. 201905993 ◽  
Author(s):  
Najeah Okashah ◽  
Qingwen Wan ◽  
Soumadwip Ghosh ◽  
Manbir Sandhu ◽  
Asuka Inoue ◽  
...  
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Heterotrimeric G Proteins ◽  
C Terminus ◽  
General Rules ◽  
Primary Determinant ◽  
Bret Assay ◽  
G Protein Coupled

G protein-coupled receptors (GPCRs) activate four families of heterotrimeric G proteins, and individual receptors must select a subset of G proteins to produce appropriate cellular responses. Although the precise mechanisms of coupling selectivity are uncertain, the Gα subunit C terminus is widely believed to be the primary determinant recognized by cognate receptors. Here, we directly assess coupling between 14 representative GPCRs and 16 Gα subunits, including one wild-type Gα subunit from each of the four families and 12 chimeras with exchanged C termini. We use a sensitive bioluminescence resonance energy transfer (BRET) assay that provides control over both ligand and nucleotide binding, and allows direct comparison across G protein families. We find that the Gs- and Gq-coupled receptors we studied are relatively promiscuous and always couple to some extent to Gi1 heterotrimers. In contrast, Gi-coupled receptors are more selective. Our results with Gα subunit chimeras show that the Gα C terminus is important for coupling selectivity, but no more so than the Gα subunit core. The relative importance of the Gα subunit core and C terminus is highly variable and, for some receptors, the Gα core is more important for selective coupling than the C terminus. Our results suggest general rules for GPCR-G protein coupling and demonstrate that the critical G protein determinants of selectivity vary widely, even for different receptors that couple to the same G protein.

scholarly journals Heterotrimeric G proteins promote FLS2 protein accumulation through inhibition of FLS2 autophagic degradation

2018 ◽  
Author(s):  
Jimi C. Miller ◽  
Stacey A. Lawrence ◽  
Nicole K. Clay
Keyword(s):  
Plasma Membrane ◽  
G Protein ◽  
G Proteins ◽  
Protein Complex ◽  
Heterotrimeric G Proteins ◽  
Immune Signaling ◽  
Heterotrimeric G Protein ◽  
Protein Levels ◽  
Autophagic Degradation ◽  
Protein Components

ABSTRACTFLAGELLIN-SENSITIVE 2 (FLS2) is a plant immune receptor that binds bacterial flagellin to activate immune signaling. This immune signal is transduced by a heterotrimeric G protein complex at the plasma membrane and activates downstream signaling. However, it is unknown whether the heterotrimeric G proteins have functions at other subcellular locations away from the plasma membrane. Here, we show that components of the heterotrimeric G protein complex stabilize FLS2 protein levels by inhibiting the autophagic degradation of FLS2. Using genetic analysis, we determined that mutations of G protein components resulted in reduced immune signaling in part due to decreased FLS2 protein levels. Furthermore, reduction of FLS2 protein levels was caused by elevated proteasomal and autophagic degradation of FLS2. Genetic inhibition of autophagy in G protein mutants rescued FLS2 levels and immunity. Our findings suggest that the heterotrimeric G protein components, in addition to being part of the heterotrimeric G protein complex that transduces signals at the plasma membrane, also function away from the plasma membrane to control FLS2 protein levels. These results expand the functional capacity of the heterotrimeric G protein complexes in plant immunity.

scholarly journals Every Detail Matters. That Is, How the Interaction between Gα Proteins and Membrane Affects Their Function

Membranes ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 222
Author(s):  
Agnieszka Polit ◽  
Paweł Mystek ◽  
Ewa Błasiak
Keyword(s):  
Signal Transduction ◽  
G Protein ◽  
G Proteins ◽  
Lipid Membranes ◽  
Signaling Proteins ◽  
Heterotrimeric G Proteins ◽  
Membrane Attachment ◽  
The Individual ◽  
Multicellular Organisms ◽  
G Protein Coupled

In highly organized multicellular organisms such as humans, the functions of an individual cell are dependent on signal transduction through G protein-coupled receptors (GPCRs) and subsequently heterotrimeric G proteins. As most of the elements belonging to the signal transduction system are bound to lipid membranes, researchers are showing increasing interest in studying the accompanying protein–lipid interactions, which have been demonstrated to not only provide the environment but also regulate proper and efficient signal transduction. The mode of interaction between the cell membrane and G proteins is well known. Despite this, the recognition mechanisms at the molecular level and how the individual G protein-membrane attachment signals are interrelated in the process of the complex control of membrane targeting of G proteins remain unelucidated. This review focuses on the mechanisms by which mammalian Gα subunits of G proteins interact with lipids and the factors responsible for the specificity of membrane association. We summarize recent data on how these signaling proteins are precisely targeted to a specific site in the membrane region by introducing well-defined modifications as well as through the presence of polybasic regions within these proteins and interactions with other components of the heterocomplex.

scholarly journals Signaling from G Protein-coupled Receptors to ERK5/Big MAPK 1 Involves Gαqand Gα12/13Families of Heterotrimeric G Proteins

2000 ◽  
Vol 275 (28) ◽  
pp. 21730-21736 ◽  
Author(s):  
Shigetomo Fukuhara ◽  
Maria Julia Marinissen ◽  
Mario Chiariello ◽  
J. Silvio Gutkind
Keyword(s):  
G Protein ◽  
G Proteins ◽  
G Protein Coupled Receptors ◽  
Heterotrimeric G Proteins ◽  
G Protein Coupled

scholarly journals Physiological Regulation of G Protein-Linked Signaling

1999 ◽  
Vol 79 (4) ◽  
pp. 1373-1430 ◽  
Author(s):  
Andrew J. Morris ◽  
Craig C. Malbon
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Chemokine Receptors ◽  
Transcriptional Control ◽  
Heterotrimeric G Proteins ◽  
Protein Prenylation ◽  
Physiological Control ◽  
Physiological Regulation ◽  
Surface Receptors ◽  
Genes Encoding

Heterotrimeric G proteins in vertebrates constitute a family molecular switches that transduce the activation of a populous group of cell-surface receptors to a group of diverse effector units. The receptors include the photopigments such as rhodopsin and prominent families such as the adrenergic, muscarinic acetylcholine, and chemokine receptors involved in regulating a broad spectrum of responses in humans. Signals from receptors are sensed by heterotrimeric G proteins and transduced to effectors such as adenylyl cyclases, phospholipases, and various ion channels. Physiological regulation of G protein-linked receptors allows for integration of signals that directly or indirectly effect the signaling from receptor→G protein→effector(s). Steroid hormones can regulate signaling via transcriptional control of the activities of the genes encoding members of G protein-linked pathways. Posttranscriptional mechanisms are under physiological control, altering the stability of preexisting mRNA and affording an additional level for regulation. Protein phosphorylation, protein prenylation, and proteolysis constitute major posttranslational mechanisms employed in the physiological regulation of G protein-linked signaling. Drawing upon mechanisms at all three levels, physiological regulation permits integration of demands placed on G protein-linked signaling.

scholarly journals Class Frizzled GPCRs (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

2019 ◽  
Vol 2019 (4) ◽  
Author(s):  
Elisa Arthofer ◽  
Jacomijn Dijksterhuis ◽  
Belma Hot ◽  
Paweł Kozielewicz ◽  
Matthias Lauth ◽  
...  
Keyword(s):  
G Proteins ◽  
Conformational Changes ◽  
Hedgehog Signaling ◽  
Cell Signalling ◽  
Resonance Energy Transfer ◽  
Rho Kinase ◽  
Density Lipoprotein ◽  
Resonance Energy ◽  
Scaffolding Protein ◽  
Heterotrimeric G Proteins

Receptors of the Class Frizzled (FZD, nomenclature as agreed by the NC-IUPHAR subcommittee on the Class Frizzled GPCRs [156]), are GPCRs originally identified in Drosophila [17], which are highly conserved across species. While SMO shows structural resemblance to the 10 FZDs, it is functionally separated as it mediates effects in the Hedgehog signaling pathway [156]. FZDs are activated by WNTs, which are cysteine-rich lipoglycoproteins with fundamental functions in ontogeny and tissue homeostasis. FZD signalling was initially divided into two pathways, being either dependent on the accumulation of the transcription regulator β-catenin or being β-catenin-independent (often referred to as canonical vs. non-canonical WNT/FZD signalling, respectively). WNT stimulation of FZDs can, in cooperation with the low density lipoprotein receptors LRP5 (O75197) and LRP6 (O75581), lead to the inhibition of a constitutively active destruction complex, which results in the accumulation of β-catenin and subsequently its translocation to the nucleus. β-Catenin, in turn, modifies gene transcription by interacting with TCF/LEF transcription factors. β-Catenin-independent FZD signalling is far more complex with regard to the diversity of the activated pathways. WNT/FZD signalling can lead to the activation of heterotrimeric G proteins [28, 159, 135], the elevation of intracellular calcium [164], activation of cGMP-specific PDE6 [2] and elevation of cAMP as well as RAC-1, JNK, Rho and Rho kinase signalling [48]. Novel resonance energy transfer-based tools have allowed the study of the GPCR-like nature of FZDs in greater detail. Upon ligand stimulation, FZDs undergo conformational changes and signal via heterotrimeric G proteins [213, 214]. Furthermore, the phosphoprotein Dishevelled constitutes a key player in WNT/FZD signalling. Importantly, FZDs exist in at least two distinct conformational states that regulate the pathway selection [214]. As with other GPCRs, members of the Frizzled family are functionally dependent on the arrestin scaffolding protein for internalization [19], as well as for β-catenin-dependent [12] and -independent [80, 13] signalling. The pattern of cell signalling is complicated by the presence of additional ligands, which can enhance or inhibit FZD signalling (secreted Frizzled-related proteins (sFRP), Wnt-inhibitory factor (WIF), sclerostin or Dickkopf (DKK)), as well as modulatory (co)-receptors with Ryk, ROR1, ROR2 and Kremen, which may also function as independent signalling proteins.

scholarly journals Heterotrimeric G-Proteins Are Indispensable for FLT3-ITD autophosphorylation and Oncogenic Function

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 2712-2712
Author(s):  
Maike Rehage ◽  
Susanne Wingert ◽  
Nadine Haetscher ◽  
Sabrina Bothur ◽  
Hubert Serve ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
G Protein ◽  
G Proteins ◽  
B Cell Lymphoma ◽  
Physical Interaction ◽  
Heterotrimeric G Proteins ◽  
Leukemic Transformation ◽  
Hematopoietic Stem ◽  
Oncogenic Function

Abstract Heterotrimeric G-proteins transmit signals of G-protein coupled receptors and regulate many basic cellular functions. However, their role in normal and malignant hematopoietic stem cells remains obscure. Activating mutations in the heterotrimeric G-protein Gaq were found in various cancers and its expression is enhanced in diffuse large B-cell lymphoma and T-ALL. Our previous data suggested the involvement of heterotrimeric G-proteins in Flt3-ITD-mediated leukemic transformation. FMS-like tyrosine kinase 3 with internal tandem duplication (FLT3-ITD) is a frequent oncoprotein in acute myeloid leukemia causing constitutive active STAT5 signaling. Here, we investigated a novel role of Gaq in Flt3-ITD-induced leukemic transformation. We could show that Gaq is indispensable for aberrant FLT3-ITD activation and oncogenic function as Gaq activity is necessary to maintain the autophosphorylation of FLT3-ITD. Gaq abrogation resulted in diminished cell proliferation and colony formation as well as delayed leukemogenesis in vivo of Flt3-ITD leukemic cells. Importantly, the growth inhibition could be rescued by addition of IL3 and did not occur in the presence of FLT3 ligand-activated FLT3 wildtype receptor, demonstrating the specificity of Gaq requirement for FLT3-ITD oncogenic signaling. Interestingly, co-immunoprecipitations revealed a direct physical interaction between FLT3-ITD and Gaq which did not require phosphorylation of the receptor tyrosine kinase. Hence, FLT3-ITD hyperphosphorylation seems to be rather a consequence of the interaction than a prerequisite. Flt3-ITD-induced transformation of murine hematopoietic stem/progenitor cells (HSPCs) strictly depended on the presence of Gaq, and the ablation of Gaq/11 in transplanted Flt3-ITD-transduced HSPCs from conditional Gaq/11 double knock-out mice delayed leukemic burden. These findings of an unexpected, yet critical, role of Gaq place the molecule as an important target for antileukemic strategies. Disclosures No relevant conflicts of interest to declare.

scholarly journals Minireview: GPCR and G Proteins: Drug Efficacy and Activation in Live Cells

2009 ◽  
Vol 23 (5) ◽  
pp. 590-599 ◽  
Author(s):  
Jean-Pierre Vilardaga ◽  
Moritz Bünemann ◽  
Timothy N. Feinstein ◽  
Nevin Lambert ◽  
Viacheslav O. Nikolaev ◽  
...  
Keyword(s):  
Energy Transfer ◽  
G Protein ◽  
G Proteins ◽  
Intracellular Signaling ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Receptor Activation ◽  
Live Cells ◽  
Mechanical Stimuli ◽  
G Protein Coupled

Abstract Many biochemical pathways are driven by G protein-coupled receptors, cell surface proteins that convert the binding of extracellular chemical, sensory, and mechanical stimuli into cellular signals. Their interaction with various ligands triggers receptor activation that typically couples to and activates heterotrimeric G proteins, which in turn control the propagation of secondary messenger molecules (e.g. cAMP) involved in critically important physiological processes (e.g. heart beat). Successful transfer of information from ligand binding events to intracellular signaling cascades involves a dynamic interplay between ligands, receptors, and G proteins. The development of Förster resonance energy transfer and bioluminescence resonance energy transfer-based methods has now permitted the kinetic analysis of initial steps involved in G protein-coupled receptor-mediated signaling in live cells and in systems as diverse as neurotransmitter and hormone signaling. The direct measurement of ligand efficacy at the level of the receptor by Förster resonance energy transfer is also now possible and allows intrinsic efficacies of clinical drugs to be linked with the effect of receptor polymorphisms.

Multiple mechanisms of receptor-G protein signaling specificity

1995 ◽  
Vol 269 (2) ◽  
pp. F141-F158 ◽  
Author(s):  
J. R. Raymond
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Linear Models ◽  
G Protein Signaling ◽  
Protein Signaling ◽  
Heterotrimeric G Proteins ◽  
Cellular Functions ◽  
Signaling Specificity ◽  
Intracellular Signals ◽  
Specific Manner

The hormone-receptor-G protein complex transduces extracellular information into intracellular signals that ultimately regulate cellular functions in a highly specific manner. There are hundreds of receptor types that transduce signals through a relatively limited repertoire of heterotrimeric G proteins. Linear models of signaling specificity that require specific and highly selective coupling of hormone to receptor to G protein have proven inadequate to explain how highly particular signals are funneled through the G protein "bottleneck." Recent studies have uncovered a plethora of mechanisms that contribute to signaling specificity. This review focuses on the mechanisms that contribute to specificity in the interactions of receptors with G proteins.

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