scholarly journals Modulation of Ins(2,4,5)P3-stimulated Ca2+ mobilization by Ins(1,3,4,5)P4: enhancement by activated G-proteins, and evidence for the involvement of a GAP1 protein, a putative Ins(1,3,4,5)P4 receptor

1998 ◽  
Vol 331 (3) ◽  
pp. 947-952 ◽  
Author(s):  
Jefferson W. LOOMIS-HUSSELBEE ◽  
Christopher D. WALKER ◽  
Joanna R. BOTTOMLEY ◽  
Peter J. CULLEN ◽  
Robin F. IRVINE ◽  
...  
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Protein A ◽  
Related Protein ◽  
L1210 Cells ◽  
Putative Receptor ◽  
Specific Enhancement ◽  
Insp3 Receptor

We have previously shown that addition of Ins(1,3,4,5)P4 to permeabilized L1210 cells increases the amount of Ca2+ mobilized by a submaximal concentration of Ins(2,4,5)P3, and we suggested that, in doing this, Ins(1,3,4,5)P4 is not working via an InsP3 receptor but indirectly via an InsP4 receptor [Loomis-Husselbee, Cullen, Dreikhausen, Irvine and Dawson (1996) Biochem. J. 314, 811–816]. Here we have investigated whether this effect might be mediated by GAP1IP4BP, recently identified as a putative receptor for Ins(1,3,4,5)P4. GAP1IP4BP is a protein that interacts with one or more monomeric G-proteins, so we sought evidence for involvement of monomeric G-proteins in the effects of Ins(1,3,4,5)P4 in permeabilized L1210 cells. Guanosine 5´-[γ-thio]triphosphate (GTP[S]) enhanced the effect of Ins(1,3,4,5)P4 on Ins(2,4,5)P3-stimulated Ca2+ mobilization, but had no effect on the action of Ins(2,4,5)P3 alone. A specific enhancement of only the action of Ins(1,3,4,5)P4 was also seen with GTP[S]-loaded R-Ras or Rap1a (two G-proteins known to interact with GAP1IP4BP), whereas H-Ras was inactive at similar concentrations. Guanosine 5´-[β-thio]diphosphate (GDP[S]) did not alter the action of either Ins(2,4,5)P3 or Ins(1,3,4,5)P4. Finally, the addition of exogenous GAP1IP4BP, purified from platelets, markedly enhanced the effect of Ins(1,3,4,5)P4, and again, the amount of Ca2+ mobilized by Ins(2,4,5)P3 alone was unaltered. We conclude that the increase in Ins(2,4,5)P3-stimulated Ca2+ mobilization by Ins(1,3,4,5)P4 may be mediated by GAP1IP4BP or a closely related protein (such as GAP1m), and if so, the action of the GAP1 is not solely to regulate GTP loading of a G-protein, but rather it acts with a G-protein to cause its effect.

scholarly journals An Autocrine Proliferation Repressor Regulates Dictyostelium discoideum Proliferation and Chemorepulsion Using the G Protein-Coupled Receptor GrlH

mBio ◽  
2018 ◽  
Vol 9 (1) ◽  
Author(s):  
Yu Tang ◽  
Yuantai Wu ◽  
Sarah E. Herlihy ◽  
Francisco J. Brito-Aleman ◽  
Jose H. Ting ◽  
...  
Keyword(s):  
G Protein ◽  
Dictyostelium Discoideum ◽  
Protein A ◽  
G Protein Coupled Receptors ◽  
Eukaryotic Cells ◽  
Putative Receptor ◽  
Large Numbers ◽  
Eukaryotic Microbes ◽  
G Protein Coupled ◽  
Eukaryotic Microbe

ABSTRACT In eukaryotic microbes, little is known about signals that inhibit the proliferation of the cells that secrete the signal, and little is known about signals (chemorepellents) that cause cells to move away from the source of the signal. Autocrine proliferation repressor protein A (AprA) is a protein secreted by the eukaryotic microbe Dictyostelium discoideum. AprA is a chemorepellent for and inhibits the proliferation of D. discoideum. We previously found that cells sense AprA using G proteins, suggesting the existence of a G protein-coupled AprA receptor. To identify the AprA receptor, we screened mutants lacking putative G protein-coupled receptors. We found that, compared to the wild-type strain, cells lacking putative receptor GrlH (grlH¯ cells) show rapid proliferation, do not have large numbers of cells moving away from the edges of colonies, are insensitive to AprA-induced proliferation inhibition and chemorepulsion, and have decreased AprA binding. Expression of GrlH in grlH¯ cells (grlH¯/grlH OE ) rescues the phenotypes described above. These data indicate that AprA signaling may be mediated by GrlH in D. discoideum. IMPORTANCE Little is known about how eukaryotic cells can count themselves and thus regulate the size of a tissue or density of cells. In addition, little is known about how eukaryotic cells can sense a repellant signal and move away from the source of the repellant, for instance, to organize the movement of cells in a developing embryo or to move immune cells out of a tissue. In this study, we found that a eukaryotic microbe uses G protein-coupled receptors to mediate both cell density sensing and chemorepulsion.

scholarly journals Differential reactivity of serum immunoglobulins from Brazilian wild mammals to staphylococcal A and streptococcal G proteins

2012 ◽  
Vol 24 (1) ◽  
pp. 148-152 ◽  
Author(s):  
Afonso Pelli ◽  
Lucio R. Castellano ◽  
Marcos R. S. Cardoso ◽  
Luís A. S. Vasconcelos ◽  
Marcos A. Domingues ◽  
...  
Keyword(s):  
Protein Binding ◽  
G Protein ◽  
G Proteins ◽  
Protein A ◽  
Human Beings ◽  
Human Pathogens ◽  
Wild Mammals ◽  
Detection Systems ◽  
Differential Reactivity ◽  
Human Illness

Human pathogens have evolved to infect vertebrate hosts other than human beings without causing symptoms of the disease, thus permitting them to complete their life cycle and to develop into infectious forms. The identification and management of infected animals are alternatives to control dissemination of the disease and to prevent human illness. In the current study, the potential use of staphylococcal A or streptococcal G proteins was evaluated with enzyme-linked immunosorbent assays (ELISAs) for seroepidemiological studies. Sera were collected from animals that were representative of 23 different Brazilian wild mammals. A high protein A binding rate was observed in all animals, except for the orders Didelphimorphia, Artiodactyla, and Rodentia, in which affinity was medium or low. Affinity for streptococcal G protein was higher in animals of the order Artiodactyla, whereas no streptococcal G protein binding was observed in samples obtained from felines (order Carnivora). Bacterial protein binding to mammalian immunoglobulins was confirmed by immunoblotting. The results suggest that secondary detection systems should be better investigated in ELISA protocols before their implementation in seroepidemiological studies involving wild mammals.

scholarly journals Reaction of cell membrane bilayers “as a variable capacitor” with G-protein: a reason for neurotransmitter signaling

2019 ◽  
Vol 9 (2) ◽  
pp. 3874-3883
Keyword(s):  
Cell Membrane ◽  
G Protein ◽  
G Proteins ◽  
Quantum Effect ◽  
Dynamical Behavior ◽  
Protein A ◽  
Phospholipid Bilayers ◽  
Membrane Thickness ◽  
Conformational Structure ◽  
Helical Coils

Cell membranes have unique features to store bio-energy in the physiology subjects. This work demonstrates a model of biological capacitors in the phospholipids bilayers membrane including DPPC, DOPG, DOPE, DOPS and DMPC structures. The electron densities profiles, electron localization function (ELF) and local information entropies have been used for studyng the interaction of G-proteins with phospholipid bilayers. The quantum and columbic blockade effects in different sizes and thicknesses of the membrane have also been specifically studied. It has been shown the quantum effect might appear in the small regions of the free spaces through membrane thickness due to the number and variant of phospholipids layer. In addition, based on Heisenberg rule, it has been exhibited the quantum tunneling effects are allowed the micro position while they are not allowed in other shapes of membrane capacitors. Due to the dynamical behavior of the bilayers in the membrane, their capacitances are not fixed which mean they are variable capacitors. Although the G protein successor does not interact to the phospholipid bilayers but stabilizes a true activated situation of the receptor, for stabilizing an activated conformational structure is tightly influenced through the lipidic situation in G proteins in viewpoint of capacitors model. Through an external field the G- protein trance membrane, charges exert forces that can influence the state of the cell membrane. Consequently the charge capacitive susceptibility could resonate with self-induction of helical coils in the (GTP) or (GDP) likes digital switches. These resonances are the main reason for any biological pulses in cell signaling cooperation.

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 Production, processing and partial purification of functional G protein βγ subunits in baculovirus-infected insect cells

1992 ◽  
Vol 286 (3) ◽  
pp. 677-680 ◽  
Author(s):  
J D Robishaw ◽  
V K Kalman ◽  
K L Proulx
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Insect Cells ◽  
Expression System ◽  
Baculovirus Expression System ◽  
Partial Purification ◽  
Baculovirus Expression ◽  
Gamma Subunits ◽  
Infected Insect ◽  
Beta 2

As a result of the inability to resolve the heterogeneous mixture of G protein beta gamma subunits present in tissues, it has not been possible to compare different beta gamma subunits of the G proteins in terms of their proposed roles in receptor-effector coupling. This study was undertaken to establish the utility of the baculovirus expression system in producing homogeneous beta gamma subunits of defined composition for the comparative analysis of these subunits in reconstitution systems. In this study we report the expression, and appropriate post-translational processing, of recombinant beta 2, gamma 2 and gamma 3 subunits. In addition, we show that the recombinant beta gamma subunits can be readily purified, and can functionally interact with the alpha subunits of the G proteins.

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