Expression and potential functions of G-protein alpha subunits in embryos of Xenopus laevis

Development ◽  
1992 ◽  
Vol 116 (1) ◽  
pp. 141-146 ◽  
Author(s):  
A.P. Otte ◽  
L.L. McGrew ◽  
J. Olate ◽  
N.M. Nathanson ◽  
R.T. Moon
Keyword(s):  
Signal Transduction ◽  
G Protein ◽  
G Proteins ◽  
Expression Patterns ◽  
Neural Induction ◽  
Neural Tissue ◽  
Signal Transduction Pathways ◽  
Alpha Subunits ◽  
Whole Mount

During early embryonic development, many inductive interactions between tissues depend on signal transduction processes. We began to test the possibility that G-proteins participate in the signal transduction pathways that mediate neural induction. The expression during Xenopus development of three G alpha subunits, G alpha 0, G alpha i-1 and G alpha s-1, was characterized. The three maternally expressed genes showed different expression patterns during early development. Whole-mount in situ hybridization revealed that all three genes were expressed almost exclusively in the gastrula ectoderm and predominantly in the neuroectoderm in the neurula embryo. In order to investigate the involvement of these proteins in neural induction, we overexpressed the G-protein alpha subunits by injecting the G alpha mRNAs into fertilized eggs. Overexpression of G alpha s-1 increased the ability of gastrula ectoderm to become induced to neural tissue approximately four-fold. Overexpression of G alpha 0 and G alpha i-1 had less pronounced effects on neural competence, and inhibition of the G alpha 0 and G alpha i-1 proteins by pertussis toxin did not change the neural competence of the exposed gastrula ectoderm. Overexpression of the G alpha 0 and G alpha i-1 genes did, however, inhibit the normal disappearance of the blastocoel during gastrulation, suggesting a role for these G-proteins in regulating this process. The data also suggest a specific role for the G alpha s subunit in mediating the initial phases of neural induction.

Biogenesis of G-protein Mediated Calcium Signaling in Human Megakaryocytes

2001 ◽  
Vol 86 (10) ◽  
pp. 1106-1113 ◽  
Author(s):  
Gertie Gorter ◽  
Hans van der Vuurst ◽  
Johan Heemskerk ◽  
Jan-Willem Akkerman ◽  
Els den Dekker
Keyword(s):  
Signal Transduction ◽  
Stem Cells ◽  
G Protein ◽  
G Proteins ◽  
Signal Transduction Pathways ◽  
Human Stem Cells ◽  
Early Expression ◽  
Prostacyclin Analog ◽  
Late Expression ◽  
Constant Expression

SummaryTo understand how platelet signal transduction pathways develop during megakaryocytopoiesis, we isolated human stem cells from umbilical cord blood and cultured the cells in the presence of thrombopoietin (TPO). Based on the early expression of CD61 and late expression of CD42b, immature (CD61+/CD42blow) and mature (CD61+/ CD42bhigh) megakaryocytes were immunomagnetically purified and, together with stem cells (CD34+), characterized for G -protein expression and agonist-induced [Ca2+]i increases. Megakaryocytopoiesis was accompanied by down-regulation of the 43 kDa and 46 kDa variants of G16α, constant expression of Gsα, and up-regulation of Gqα and Giα1/2. The increase in Gq and Gi 1/2 expression was accompanied by an increase in Ca2+ signaling triggered by thrombin and other agonists known to signal to Ca2+ via these G-proteins in platelets. The prostacyclin analog iloprost and TPO also induced [Ca2+]i increases, and the iloprost-induced Ca2+ response disappeared during maturation. These data reveal sharp changes in Ca2+ regulation during megakaryocytopoiesis.

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 The involvement of three signal transduction pathways in botryllid ascidian astogeny, as revealed by expression patterns of representative genes

2014 ◽  
Vol 58 (9) ◽  
pp. 677-692 ◽  
Author(s):  
Amalia Rosner ◽  
Gilad Alfassi ◽  
Elizabeth Moiseeva ◽  
Guy Paz ◽  
Claudette Rabinowitz ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Expression Patterns ◽  
Signal Transduction Pathways

scholarly journals Genomic signatures of G-protein-coupled receptor expansions reveal functional transitions in the evolution of cephalopod signal transduction

2019 ◽  
Vol 286 (1897) ◽  
pp. 20182929 ◽  
Author(s):  
Elena A. Ritschard ◽  
Robert R. Fitak ◽  
Oleg Simakov ◽  
Sönke Johnsen
Keyword(s):  
Signal Transduction ◽  
Positive Selection ◽  
G Protein ◽  
Evolutionary History ◽  
Expression Profiles ◽  
Phylogenetic Analyses ◽  
Expression Patterns ◽  
Genomic Signatures ◽  
History Of ◽  
G Protein Coupled

Coleoid cephalopods show unique morphological and neural novelties, such as arms with tactile and chemosensory suckers and a large complex nervous system. The evolution of such cephalopod novelties has been attributed at a genomic level to independent gene family expansions, yet the exact association and the evolutionary timing remain unclear. In the octopus genome, one such expansion occurred in the G-protein-coupled receptors (GPCRs) repertoire, a superfamily of proteins that mediate signal transduction. Here, we assessed the evolutionary history of this expansion and its relationship with cephalopod novelties. Using phylogenetic analyses, at least two cephalopod- and two octopus-specific GPCR expansions were identified. Signatures of positive selection were analysed within the four groups, and the locations of these sequences in the Octopus bimaculoides genome were inspected. Additionally, the expression profiles of cephalopod GPCRs across various tissues were extracted from available transcriptomic data. Our results reveal the evolutionary history of cephalopod GPCRs. Unexpanded cephalopod GPCRs shared with other bilaterians were found to be mainly nervous tissue specific. By contrast, duplications that are shared between octopus and the bobtail squid or specific to the octopus' lineage generated copies with divergent expression patterns devoted to tissues outside of the brain. The acquisition of novel expression domains was accompanied by gene order rearrangement through either translocation or duplication and gene loss. Lastly, expansions showed signs of positive selection and some were found to form tandem clusters with shared conserved expression profiles in cephalopod innovations such as the axial nerve cord. Altogether, our results contribute to the understanding of the molecular and evolutionary history of signal transduction and provide insights into the role of this expansion during the emergence of cephalopod novelties and/or adaptations.

Fluoride mobilizes intracellular calcium and promotes Ca2+ influx in rat proximal tubules

1991 ◽  
Vol 261 (2) ◽  
pp. F318-F327 ◽  
Author(s):  
J. H. Dominguez ◽  
J. G. Garcia ◽  
J. K. Rothrock ◽  
D. English ◽  
C. Mann
Keyword(s):  
Signal Transduction ◽  
Parathyroid Hormone ◽  
Proximal Tubule ◽  
G Protein ◽  
Pertussis Toxin ◽  
Time Course ◽  
Proximal Tubules ◽  
Signal Transduction Pathways ◽  
Pi Hydrolysis

In the renal proximal tubule, external Ca2+ ([Ca2+]o) is required for parathyroid hormone to elevate cytosolic Ca2+ ([Ca2+]i). However, other hormones increase [Ca2+]i in the absence of [Ca2+]o. These differences may arise from a diversity of signal transduction pathways acting on external and internal Ca2+ pools. However, Ca2+ influx may be necessary to expedite and maintain the rise of [Ca2+]i for a period after the initial surge. In this study, F- was used to probe the roles of intracellular Ca2+ mobilization, Ca2+ influx, and phosphoinositide (PI) hydrolysis on the surge of [Ca2+]i in rat proximal tubules. In the presence of external Ca2+; 1-20 mM F- evoked incremental rises of [Ca2+]i in tubules loaded with aequorin. Whereas 10 mM F- increased [Ca2+]i in the absence of [Ca2+]o, the time constant for the [Ca2+]i surge was increased. These findings are consistent with a role of Ca2+ influx on the effect of F- on [Ca2+]i. Indeed, 10 mM F- also enhanced the uptake of 45Ca2+, and promoted Ca2+ influx in aequorin- and fura-2-loaded, Ca(2+)-deprived tubules. In tubules, F- also activated PI hydrolysis with a time course that paralleled Ca2+ mobilization. The effect of F- on [Ca2+]i was not altered when the 39-kDa pertussis toxin substrate was inactivated with the toxin. This G protein was most likely Gi, because prostaglandin E2, an activator of Gi in tubules, dissociated the pertussis toxin-sensitive protein. The results support the notion that activation of a signal-transduction complex, the F- substrate, causes Ca2+ influx, mobilizes internal Ca2+, and activates PI hydrolysis in rat proximal tubules.(ABSTRACT TRUNCATED AT 250 WORDS)

New thoughts on the role of the βγ subunit in G protein signal transduction

2000 ◽  
Vol 78 (5) ◽  
pp. 537-550 ◽  
Author(s):  
Barbara Vanderbeld ◽  
Gregory M Kelly
Keyword(s):  
Signal Transduction ◽  
G Protein ◽  
G Proteins ◽  
G Protein Coupled Receptors ◽  
Limited Information ◽  
Α Subunit ◽  
Downstream Effectors ◽  
Receptor Signal ◽  
G Protein Coupled

Heterotrimeric G proteins are involved in numerous biological processes, where they mediate signal transduction from agonist-bound G-protein-coupled receptors to a variety of intracellular effector molecules and ion channels. G proteins consist of two signaling moieties: a GTP-bound α subunit and a βγ heterodimer. The βγ dimer, recently credited as a significant modulator of G-protein-mediated cellular responses, is postulated to be a major determinant of signaling fidelity between G-protein-coupled receptors and downstream effectors. In this review we have focused on the role of βγ signaling and have included examples to demonstrate the heterogeneity in the heterodimer composition and its implications in signaling fidelity. We also present an overview of some of the effectors regulated by βγ and draw attention to the fact that, although G proteins and their associated receptors play an instrumental role in development, there is rather limited information on βγ signaling in embryogenesis.Key words: G protein, βγ subunit, G-protein-coupled receptor, signal transduction, adenylyl cyclase.

mRNA expression patterns of the IGF system during mouse limb bud development, determined by whole mount in situ hybridization

1998 ◽  
Vol 138 (1-2) ◽  
pp. 151-161 ◽  
Author(s):  
Marjolein van Kleffens ◽  
Cora Groffen ◽  
Roberto R. Rosato ◽  
Stefan M. van den Eijnde ◽  
Johan W. van Neck ◽  
...  
Keyword(s):  
In Situ Hybridization ◽  
Mrna Expression ◽  
Expression Patterns ◽  
Limb Bud ◽  
Bud Development ◽  
Igf System ◽  
Whole Mount ◽  
Mouse Limb

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

1998 ◽  
Vol 353 (1374) ◽  
pp. 1425-1430 ◽  
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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