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 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 Mutations in the ‘DRY’ motif of the CB1 cannabinoid receptor result in biased receptor variants

2014 ◽  
Vol 54 (1) ◽  
pp. 75-89 ◽  
Author(s):  
Pál Gyombolai ◽  
András D Tóth ◽  
Dániel Tímár ◽  
Gábor Turu ◽  
László Hunyady
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Double Mutant ◽  
Cannabinoid Receptor ◽  
Camp Accumulation ◽  
Protein Activation ◽  
Cb1 Cannabinoid Receptor ◽  
G Protein Activation ◽  
Dry Motif

The role of the highly conserved ‘DRY’ motif in the signaling of the CB1cannabinoid receptor (CB1R) was investigated by inducing single-, double-, and triple-alanine mutations into this site of the receptor. We found that the CB1R-R3.50A mutant displays a partial decrease in its ability to activate heterotrimeric Goproteins (∼80% of WT CB1R (CB1R-WT)). Moreover, this mutant showed an enhanced basal β-arrestin2 (β-arr2) recruitment. More strikingly, the double-mutant CB1R-D3.49A/R3.50A was biased toward β-arrs, as it gained a robustly increased β-arr1 and β-arr2 recruitment ability compared with the WT receptor, while its G-protein activation was decreased. In contrast, the double-mutant CB1R-R3.50A/Y3.51A proved to be G-protein-biased, as it was practically unable to recruit β-arrs in response to agonist stimulus, while still activating G-proteins, although at a reduced level (∼70% of CB1R-WT). Agonist-induced ERK1/2 activation of the CB1R mutants showed a good correlation with their β-arr recruitment ability but not with their G-protein activation or inhibition of cAMP accumulation. Our results suggest that G-protein activation and β-arr binding of the CB1R are mediated by distinct receptor conformations, and the conserved ‘DRY’ motif plays different roles in the stabilization of these conformations, thus mediating both G-protein- and β-arr-mediated functions of CB1R.

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.

G proteins activate ionic conductances at multiple sites in T84 cells

1997 ◽  
Vol 272 (4) ◽  
pp. C1222-C1231
Author(s):  
L. Izu ◽  
M. Li ◽  
R. DeMuro ◽  
M. E. Duffey
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Cell Voltage ◽  
Equilibrium Potential ◽  
T84 Cells ◽  
Ionic Conductances ◽  
Inward Currents ◽  
Cl Channels ◽  
K Current

We examined the role of G proteins in activation of ionic conductances in isolated T84 cells during cholinergic stimulation. When cells were whole cell voltage clamped to the K+ equilibrium potential (E(K)) or Cl- equilibrium potential (E(Cl)) under standard conditions, the cholinergic agonist, carbachol, induced a large oscillating K+ current but only a small inward current. Addition of the GDP analogue, guanosine 5'-O-(2-thiodiphosphate), to pipettes blocked the ability of carbachol to activate the K+ current. Addition of the nonhydrolyzable GTP analogue, guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS), to pipettes stimulated large oscillating K+ and inward currents. This occurred even when Ca2+ was absent from the bath but not when the Ca2+ chelator, ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid, was added to pipettes. When all pipette and bath K+ was replaced with Na+ and cells were voltage clamped between E(Na) and E(Cl), GTPgammaS activated oscillating Na+ and Cl- currents. Finally, addition of inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] to pipettes activated large oscillating K+ currents but only small inward currents. These results suggest that a carbachol-induced release of Ca2+ from intracellular stores is activated by a G protein through the phospholipase C-Ins(1,4,5)P3 signaling pathway. In addition, this or another G protein activates Cl- current by directly gating Cl- channels to increase their sensitivity to Ca2+.

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.

Endothelin-B receptors activate Gα13

1999 ◽  
Vol 276 (4) ◽  
pp. C930-C937 ◽  
Author(s):  
Kenichiro Kitamura ◽  
Naoki Shiraishi ◽  
William D. Singer ◽  
Mary E. Handlogten ◽  
Kimio Tomita ◽  
...  
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Guanine Nucleotides ◽  
Heterotrimeric G Proteins ◽  
Human Embryonic Kidney ◽  
Cellular Effects ◽  
293 Cells ◽  
Specific Antagonist ◽  
Α Chain ◽  
Endothelin B

Endothelin (ET) receptors activate heterotrimeric G proteins that are members of the Gi, Gq, and Gs families but may also activate members of other families such as Gα12/13. Gα13 has multiple complex cellular effects that are similar to those of ET. We studied the ability of ET receptors to activate Gα13 using an assay for G protein α-chain activation that is based on the fact that an activated (GTP-bound) α-chain is resistant to trypsinization compared with an inactive (GDP-bound) α-chain. Nonhydrolyzable guanine nucleotides and AlMgF protected Gα13 from degradation by trypsin. In membranes from human embryonic kidney 293 cells that coexpress ETB receptors and α13, ET-3 and 5′-guanylylimidodiphosphate [Gpp(NH)p] increased the protection of α13 compared with Gpp(NH)p alone. The specificity of ETBreceptor-α13 coupling was documented by showing that β2receptors and isoproterenol or ETAreceptors and ET-1 did not activate α13 and that a specific antagonist for ETB receptors blocked ET-3-dependent activation of α13.

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.

Sign in / Sign up

Export Citation Format

Share Document