Heterotrimeric G Proteins in Plants: Canonical and Atypical Gα Subunits

Heterotrimeric GTP-binding proteins (G proteins), consisting of Gα, Gβ and Gγ subunits, transduce signals from a diverse range of extracellular stimuli, resulting in the regulation of numerous cellular and physiological functions in Eukaryotes. According to the classic G protein paradigm established in animal models, the bound guanine nucleotide on a Gα subunit, either guanosine diphosphate (GDP) or guanosine triphosphate (GTP) determines the inactive or active mode, respectively. In plants, there are two types of Gα subunits: canonical Gα subunits structurally similar to their animal counterparts and unconventional extra-large Gα subunits (XLGs) containing a C-terminal domain homologous to the canonical Gα along with an extended N-terminal domain. Both Gα and XLG subunits interact with Gβγ dimers and regulator of G protein signalling (RGS) protein. Plant G proteins are implicated directly or indirectly in developmental processes, stress responses, and innate immunity. It is established that despite the substantial overall similarity between plant and animal Gα subunits, they convey signalling differently including the mechanism by which they are activated. This review emphasizes the unique characteristics of plant Gα subunits and speculates on their unique signalling mechanisms.

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Plant hormone perception and action: a role for G–protein signal transduction?

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.1998.0297 ◽

1998 ◽

Vol 353 (1374) ◽

pp. 1425-1430 ◽

Cited By ~ 13

Author(s):

Richard Hooley

Keyword(s):

Signal Transduction ◽

G Protein ◽

G Proteins ◽

Plant Hormone ◽

Higher Plants ◽

Signalling Pathways ◽

Heterotrimeric G Proteins ◽

Extracellular Signals ◽

G Protein Signalling ◽

Auxin Signalling

Plants perceive and respond to a profusion of environmental and endogenous signals that influence their growth and development. The G–protein signalling pathway is a mechanism for transducing extracellular signals that is highly conserved in a range of eukaryotes and prokaryotes. Evidence for the existence of G–protein signalling pathways in higher plants is reviewed, and their potential involvement in plant hormone signal transduction evaluated. A range of biochemical and molecular studies have identified potential components of G–protein signalling in plants, most notably a homologue of the G–protein coupled receptor superfamily ( GCR1 ) and the G α and G β subunits of heterotrimeric G–proteins. G–protein agonists and antagonists are known to influence a variety of signalling events in plants and have been used to implicate heterotrimeric G–proteins in gibberellin and possibly auxin signalling. Antisense suppression of GCR1 in Arabidopsis leads to a phenotype which supports a role for this receptor in cytokinin signalling. These observations suggest that higher plants have at least some of the components of G–protein signalling pathways and that these might be involved in the action of certain plant hormones.

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3.6.5.2 Small monomeric GTPases (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

IUPHAR/BPS Guide to Pharmacology CITE ◽

10.2218/gtopdb/f896/2019.4 ◽

2019 ◽

Vol 2019 (4) ◽

Author(s):

Elena Faccenda

Keyword(s):

G Protein ◽

G Proteins ◽

Small Gtpase ◽

Alpha Subunit ◽

Heterotrimeric G Proteins ◽

Guanosine Triphosphate ◽

Guanosine Diphosphate ◽

Ras Gtpases ◽

Small G Proteins

Small G-proteins, are a family of hydrolase enzymes that can bind and hydrolyze guanosine triphosphate (GTP). They are a type of G-protein found in the cytosol that are homologous to the alpha subunit of heterotrimeric G-proteins, but unlike the alpha subunit of G proteins, a small GTPase can function independently as a hydrolase enzyme to bind to and hydrolyze a guanosine triphosphate (GTP) to form guanosine diphosphate (GDP). The best-known members are the Ras GTPases and hence they are sometimes called Ras subfamily GTPases.

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Optogenetic activation of heterotrimeric G-proteins by LOV2GIVe, a rationally engineered modular protein

eLife ◽

10.7554/elife.60155 ◽

2020 ◽

Vol 9 ◽

Cited By ~ 2

Author(s):

Mikel Garcia-Marcos ◽

Kshitij Parag-Sharma ◽

Arthur Marivin ◽

Marcin Maziarz ◽

Alex Luebbers ◽

...

Keyword(s):

G Protein ◽

G Proteins ◽

Protein Domain ◽

Heterotrimeric G Proteins ◽

Protein Activity ◽

Signal Transducers ◽

Non Invasive ◽

Experimental Systems ◽

Extracellular Stimuli ◽

G Protein Coupled

Heterotrimeric G-proteins are signal transducers involved in mediating the action of many natural extracellular stimuli and many therapeutic agents. Non-invasive approaches to manipulate the activity of G-proteins with high precision are crucial to understand their regulation in space and time. Here, we developed LOV2GIVe, an engineered modular protein that allows the activation of heterotrimeric G-proteins with blue light. This optogenetic construct relies on a versatile design that differs from tools previously developed for similar purposes, that is metazoan opsins, which are light-activated G-protein-coupled receptors (GPCRs). Instead, LOV2GIVe consists of the fusion of a G-protein activating peptide derived from a non-GPCR regulator of G-proteins to a small plant protein domain, such that light uncages the G-protein activating module. Targeting LOV2GIVe to cell membranes allowed for light-dependent activation of Gi proteins in different experimental systems. In summary, LOV2GIVe expands the armamentarium and versatility of tools available to manipulate heterotrimeric G-protein activity.

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PRECOG: PREdicting COupling probabilities of G-protein coupled receptors

Nucleic Acids Research ◽

10.1093/nar/gkz392 ◽

2019 ◽

Vol 47 (W1) ◽

pp. W395-W401 ◽

Cited By ~ 2

Author(s):

Gurdeep Singh ◽

Asuka Inoue ◽

J Silvio Gutkind ◽

Robert B Russell ◽

Francesco Raimondi

Keyword(s):

G Protein ◽

G Proteins ◽

Protein Sequence ◽

Web Server ◽

Structural Features ◽

G Protein Coupled Receptors ◽

Heterotrimeric G Proteins ◽

Eukaryotic Organism ◽

Extracellular Stimuli ◽

G Protein Coupled

Abstract G-protein coupled receptors (GPCRs) control multiple physiological states by transducing a multitude of extracellular stimuli into the cell via coupling to intra-cellular heterotrimeric G-proteins. Deciphering which G-proteins couple to each of the hundreds of GPCRs present in a typical eukaryotic organism is therefore critical to understand signalling. Here, we present PRECOG (precog.russelllab.org): a web-server for predicting GPCR coupling, which allows users to: (i) predict coupling probabilities for GPCRs to individual G-proteins instead of subfamilies; (ii) visually inspect the protein sequence and structural features that are responsible for a particular coupling; (iii) suggest mutations to rationally design artificial GPCRs with new coupling properties based on predetermined coupling features.

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RGS3 interacts with 14-3-3 via the N-terminal region distinct from the RGS (regulator of G-protein signalling) domain

Biochemical Journal ◽

10.1042/bj20020390 ◽

2002 ◽

Vol 365 (3) ◽

pp. 677-684 ◽

Cited By ~ 38

Author(s):

Jiaxin NIU ◽

Astrid SCHESCHONKA ◽

Kirk M. DRUEY ◽

Amanda DAVIS ◽

Eleanor REED ◽

...

Keyword(s):

Binding Site ◽

G Protein ◽

G Proteins ◽

Rgs Proteins ◽

Heterotrimeric G Proteins ◽

G Protein Signalling ◽

Vitro Binding ◽

Rgs Domain ◽

Hybrid Screening

RGS3 belongs to a family of the regulators of G-protein signalling (RGS), which bind and inhibit the Gα subunits of heterotrimeric G-proteins via a homologous RGS domain. Increasing evidence suggests that RGS proteins can also interact with targets other than G-proteins. Employing yeast two-hybrid screening of a cDNA library, we identified an interaction between RGS3 and the phosphoserine-binding protein 14-3-3. This interaction was confirmed by in vitro binding and co-immunoprecipitation experiments. RGS3-deletion analysis revealed the presence of a single 14-3-3-binding site located outside of the RGS domain. Ser264 was then identified as the 14-3-3-binding site of RGS3. The S264A mutation resulted in the loss of RGS3 binding to 14-3-3, without affecting its ability to bind Gαq. Signalling studies showed that the S264A mutant was more potent than the wild-type RGS3 in inhibition of G-protein-mediated signalling. Binding experiments revealed that RGS3 exists in two separate pools, either 14-3-3-bound or G-protein-bound, and that the 14-3-3-bound RGS3 is unable to interact with G-proteins. These data are consistent with the model wherein 14-3-3 serves as a scavenger of RGS3, regulating the amounts of RGS3 available for binding G-proteins. This study describes a new level in the regulation of G-protein signalling, in which the inhibitors of G-proteins, RGS proteins, can themselves be regulated by phosphorylation and binding 14-3-3.

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Regulators of G protein Signaling (RGS) proteins (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

IUPHAR/BPS Guide to Pharmacology CITE ◽

10.2218/gtopdb/f891/2019.4 ◽

2019 ◽

Vol 2019 (4) ◽

Author(s):

Mohammed Alqinyah ◽

Christopher Bodle ◽

Josephine Bou Dagher ◽

Bandana Chakravarti ◽

Shreoshi P. Choudhuri ◽

...

Keyword(s):

Sequence Analysis ◽

G Protein ◽

G Proteins ◽

G Protein Signaling ◽

Rgs Proteins ◽

Protein Signaling ◽

Heterotrimeric G Proteins ◽

Gtp Hydrolysis ◽

G Protein Signalling ◽

Rgs Domain

Regulators of G protein signalling (RGS) proteins display a common RGS domain that interacts with the GTP-bound Gα subunits of heterotrimeric G proteins, enhancing GTP hydrolysis by stabilising the transition state [29, 419, 418], leading to a termination of GPCR signalling. Interactions through protein:protein interactions of many RGS proteins have been identified for targets other than heteromeric G proteins. Sequence analysis of the 20 RGS proteins suggests four families of RGS: RZ, R4, R7 and R12 families. Many of these proteins have been identified to have effects other than through targetting G proteins. Included here is RGS4 for which a number of pharmacological inhibitors have been described.

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Heterotrimeric G protein signalling in the plant kingdom

Open Biology ◽

10.1098/rsob.120186 ◽

2013 ◽

Vol 3 (3) ◽

pp. 120186 ◽

Cited By ~ 145

Author(s):

Daisuke Urano ◽

Jin-Gui Chen ◽

José Ramón Botella ◽

Alan M. Jones

Keyword(s):

G Proteins ◽

Current Knowledge ◽

Effector Proteins ◽

Model Organisms ◽

Heterotrimeric G Proteins ◽

Hormonal Responses ◽

Surface Receptors ◽

Control Growth ◽

G Protein Signalling ◽

Extracellular Stimuli

In animals, heterotrimeric G proteins, comprising α-, β-and γ-subunits, perceive extracellular stimuli through cell surface receptors, and transmit signals to ion channels, enzymes and other effector proteins to affect numerous cellular behaviours. In plants, G proteins have structural similarities to the corresponding molecules in animals but transmit signals by atypical mechanisms and effector proteins to control growth, cell proliferation, defence, stomate movements, channel regulation, sugar sensing and some hormonal responses. In this review, we summarize the current knowledge on the molecular regulation of plant G proteins, their effectors and the physiological functions studied mainly in two model organisms: Arabidopsis thaliana and rice ( Oryza sativa ). We also look at recent progress on structural analyses, systems biology and evolutionary studies.

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Regulators of G-protein signalling: a novel protein family involved in timely deactivation and desensitization of signalling via heterotrimeric G proteins

Naunyn-Schmiedeberg s Archives of Pharmacology ◽

10.1007/s002109900031 ◽

1999 ◽

Vol 360 (1) ◽

pp. 14-26 ◽

Cited By ~ 51

Author(s):

T. Wieland ◽

C.-K. Chen

Keyword(s):

G Protein ◽

G Proteins ◽

Protein Family ◽

Heterotrimeric G Proteins ◽

G Protein Signalling ◽

Novel Protein

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

Membranes ◽

10.3390/membranes11030222 ◽

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.

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