G-Protein Modulators Alter the Swimming Behavior and Calcium Influx of Paramecium tetraurelia

2003 ◽  
Vol 50 (5) ◽  
pp. 349-355 ◽  
Author(s):  
JOSE ONDARZA ◽  
STEVEN B. SYMINGTON ◽  
JUDITH L. HOUTEN ◽  
J. MARSHALL CLARK
Keyword(s):  
G Protein ◽  
Calcium Influx ◽  
Swimming Behavior ◽  
Paramecium Tetraurelia

scholarly journals OR1D2 receptor mediates bourgeonal-induced human CatSper activation in a G-protein dependent manner

2019 ◽  
Author(s):  
Yi-min Cheng ◽  
Tao Luo ◽  
Zhen Peng ◽  
Hou-yang Chen ◽  
Jin Zhang ◽  
...  
Keyword(s):  
G Protein ◽  
Olfactory Receptor ◽  
Intracellular Signaling ◽  
Calcium Influx ◽  
Human Sperm ◽  
Camp Level ◽  
Dependent Manner ◽  
Intracellular Signaling Pathway ◽  
Camp Pathway ◽  
Sperm Chemotaxis

AbstractDuring fertilization, sperm are guided towards eggs by physiological chemokines, a process named sperm chemotaxis. Human sperm chemotaxis is speculated to be mediated by olfactory receptor OR1D2 in a pathway requiring calcium influx. Bourgeonal, an artificial ligand of OR1D2, can activate CatSper, the primary calcium channel in human sperm. However, whether bourgeonal-induced CatSper activation requires OR1D2 and how CatSper is activated remain unclear. Herein, we show that OR1D2 antibody can inhibit bourgeonal-induced CatSper activation and sperm chemotaxis, proving that OR1D2 mediates bourgeonal-induced CatSper activation. Furthermore, bourgeonal-evoked CatSper currents can be greatly suppressed by either GDP-β-S or antibody of Gαs. Interestingly, bourgeonal can transiently increase sperm cAMP level, and this effect can be abolished by OR1D2 antibody. Consistently, bourgeonal-induced CatSper activation can be inhibited by membrane adenylate cyclases inhibitor. Overall, our results indicate that bourgeonal activates CatSper via OR1D2-G protein-cAMP pathway. Although CatSper can be activated by various physiological and environmental factors, this study represents the most recent progress proving that CatSper can be indirectly activated by extracellular regulators through a G-protein-dependent intracellular signaling pathway.

Stimulation of calcium influx by platelet activating factor in Dictyostelium

1995 ◽  
Vol 108 (4) ◽  
pp. 1597-1603
Author(s):  
R. Schaloske ◽  
C. Sordano ◽  
S. Bozzaro ◽  
D. Malchow
Keyword(s):  
Plasma Membrane ◽  
G Protein ◽  
Dictyostelium Discoideum ◽  
Calcium Influx ◽  
Platelet Activating Factor ◽  
Inactive Compound ◽  
Time Period ◽  
Dependent Pathway ◽  
Stimulation Of

Platelet activating factor (PAF) induces Ca2+ influx in Dictyostelium discoideum. In this investigation we used this activity to analyze the mechanism of PAF action. We found that PAF activity was confined to the period of spike-shaped oscillations and suggest that the role of PAF is to augment cAMP relay. PAF seems to act only a few times during this time period of two hours, since Ca2+ entry adapted to a subsequent stimulus for about 30 minutes. PAF showed a reduced response in the G protein beta- strain LW14 and was unable to induce Ca2+ influx in the G alpha 2- strains HC85 and JM1. The latter expresses the cAMP receptors cAR1 constitutively, and exhibits cAMP-induced Ca2+ influx, albeit at a reduced level. In order to decide whether the inability of PAF to elicit a Ca2+ response in JM1 cells was due to the lack of differentiation and/or the lack of G alpha 2, we inhibited the IP3-dependent pathway with compound U73122 and found that Ca2+ entry was blocked, whereas a closely related inactive compound, U73343, did not alter the response. In agreement with this, NBD-Cl, an inhibitor of Ca2+ uptake into the IP3-sensitive store in Dictyostelium, also abolished PAF activity. The latter was not inhibited by the plasma membrane antagonists BN-52021 or WEB 2170. Therefore PAF seems to operate intracellularly via the IP3-signalling pathway at or upstream of the IP3-sensitive store.

Catecholamine modulation of calcium currents in clonal pancreatic beta-cells

1989 ◽  
Vol 257 (6) ◽  
pp. C1171-C1176 ◽  
Author(s):  
H. H. Keahey ◽  
A. E. Boyd ◽  
D. L. Kunze
Keyword(s):  
Beta Cell ◽  
G Protein ◽  
Beta Cells ◽  
Pancreatic Beta Cells ◽  
Calcium Influx ◽  
Pancreatic Beta Cell ◽  
Cytosolic Calcium ◽  
Calcium Currents ◽  
Secretory Process ◽  
Beta Cell Line

The mechanisms by which norepinephrine and epinephrine activate alpha 2-adrenergic receptors and inhibit insulin release from the pancreatic beta-cell (19, 21, 23) are not yet clear but may involve modulation at several sites. Because intracellular calcium has been implicated in the secretory process, it has been suggested that catecholamines may inhibit secretion by blocking calcium influx, thus reducing the free cytosolic calcium concentration (23). The present study examines the effects of epinephrine, norepinephrine, and clonidine on calcium current in an SV40-transformed hamster beta-cell line (HIT cells). Under voltage-clamp conditions, calcium currents were reversibly inhibited by norepinephrine, epinephrine, and clonidine in the low nanomolar range. The effects were blocked by 1) the alpha 2-antagonist yohimbine, 2) preincubation of the cells with pertussis toxin (PTX), and 3) guanosine 5'-O-(2-thiodiphosphate) (GDP beta S), the nonhydrolyzable GDP analogue that competitively inhibits the interaction of GTP with G proteins. In contrast, guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) caused irreversible blockade by catecholamines. These effects could not be overcome by adenosine 3',5'-cyclic monophosphate (cAMP), suggesting that the adenylate cyclase pathway is not involved in the G protein coupling with the channels. These studies show that catecholamines inhibit calcium currents in beta-cells through an alpha 2-adrenoreceptor PTX-sensitive G protein pathway and could inhibit insulin secretion by this mechanism.

Inhibition of Dendritic Calcium Influx by Activation of G-Protein–Coupled Receptors in the Hippocampus

1997 ◽  
Vol 78 (6) ◽  
pp. 3484-3488 ◽  
Author(s):  
Huanmian Chen ◽  
Nevin A. Lambert
Keyword(s):  
Calcium Channels ◽  
Action Potential ◽  
G Protein ◽  
Pyramidal Neuron ◽  
Action Potentials ◽  
Calcium Influx ◽  
G Protein Coupled Receptors ◽  
Voltage Gated ◽  
Voltage Gated Calcium Channels ◽  
G Protein Coupled

Chen, Huanmian and Nevin A. Lambert. Inhibition of dendritic calcium influx by activation of G-protein–coupled receptors in the hippocampus. J. Neurophysiol. 78: 3484–3488, 1997. Gi proteins inhibit voltage-gated calcium channels and activate inwardly rectifying K+ channels in hippocampal pyramidal neurons. The effect of activation of G-protein–coupled receptors on action potential-evoked calcium influx was examined in pyramidal neuron dendrites with optical and extracellular voltage recording. We tested the hypotheses that 1) activation of these receptors would inhibit calcium channels in dendrites; 2) hyperpolarization resulting from K+ channel activation would deinactivate low-threshold, T-type calcium channels on dendrites, increasing calcium influx mediated by these channels; and 3) activation of these receptors would inhibit propagation of action potentials into dendrites, and thus indirectly decrease calcium influx. Activation of adenosine receptors, which couple to Gi proteins, inhibited calcium influx in cell bodies and proximal dendrites without inhibiting action-potential propagation into the proximal dendrites. Inhibition of dendritic calcium influx was not changed in the presence of 50 μM nickel, which preferentially blocks T-type channels, suggesting influx through these channels is not increased by activation of G-proteins. Adenosine inhibited propagation of action potentials into the distal branches of pyramidal neuron dendrites, leading to a three- to fourfold greater inhibition of calcium influx in the distal dendrites than in the soma or proximal dendrites. These results suggest that voltage-gated calcium channels are inhibited in pyramidal neuron dendrites, as they are in cell bodies and terminals and thatG-protein–mediated inhibition of action-potential propagation can contribute substantially to inhibition of dendritic calcium influx.

scholarly journals Dopamine-D2S Receptor Inhibition of Calcium Influx, Adenylyl Cyclase, and Mitogen-Activated Protein Kinase in Pituitary Cells: Distinct Gα and Gβγ Requirements

2002 ◽  
Vol 16 (10) ◽  
pp. 2393-2404 ◽  
Author(s):  
Behzad Banihashemi ◽  
Paul R. Albert
Keyword(s):  
Adenylyl Cyclase ◽  
G Protein ◽  
Calcium Influx ◽  
Short Form ◽  
Mitogen Activated Protein Kinase ◽  
Pituitary Cells ◽  
Protein Receptor ◽  
Dependent Inhibition ◽  
Erk Kinase ◽  
In Cells

Abstract The G protein specificity of multiple signaling pathways of the dopamine-D2S (short form) receptor was investigated in GH4ZR7 lactotroph cells. Activation of the dopamine-D2S receptor inhibited forskolin-induced cAMP production, reduced BayK8644- activated calcium influx, and blocked TRH-mediated p42/p44 MAPK phosphorylation. These actions were blocked by pretreatment with pertussis toxin (PTX), indicating mediation by Gi/o proteins. D2S stimulation also decreased TRH-induced MAPK/ERK kinase phosphorylation. TRH induced c-Raf but not B-Raf activation, and the D2S receptor inhibited both TRH-induced c-Raf and basal B-Raf kinase activity. After PTX treatment, D2S receptor signaling was rescued in cells stably transfected with individual PTX-insensitive Gα mutants. Inhibition of adenylyl cyclase was partly rescued by Gαi2 or Gαi3, but Gαo alone completely reconstituted D2S-mediated inhibition of BayK8644-induced L-type calcium channel activation. Gαo and Gαi3 were the main components involved in D2S-mediated p42/44 MAPK inhibition. In cells transfected with the carboxyl-terminal domain of G protein receptor kinase to inhibit Gβγ signaling, only D2S-mediated inhibition of calcium influx was blocked, but not inhibition of adenylyl cyclase or MAPK. These results indicate that the dopamine-D2S receptor couples to distinct Gi/o proteins, depending on the pathway addressed, and suggest a novel Gαi3/Gαo-dependent inhibition of MAPK mediated by c-Raf and B-Raf-dependent inhibition of MAPK/ERK kinase.

scholarly journals Impaired Inhibitory G-Protein Function Contributes to Increased Calcium Currents in Rats With Diabetic Neuropathy

2001 ◽  
Vol 86 (2) ◽  
pp. 760-770 ◽  
Author(s):  
Karen E. Hall ◽  
Jackie Liu ◽  
Anders A. F. Sima ◽  
John W. Wiley
Keyword(s):  
G Protein ◽  
G Proteins ◽  
Dorsal Root ◽  
Calcium Influx ◽  
Opiate Receptors ◽  
Calcium Currents ◽  
High Threshold ◽  
Drg Neurons ◽  
Protein Activity ◽  
Inhibitory G Protein

There is a growing body of evidence that sensory neuropathy in diabetes is associated with abnormal calcium signaling in dorsal root ganglion (DRG) neurons. Enhanced influx of calcium via multiple high-threshold calcium currents is present in sensory neurons of several models of diabetes mellitus, including the spontaneously diabetic BioBred/Worchester (BB/W) rat and the chemical streptozotocin (STZ)-induced rat. We believe that abnormal calcium signaling in diabetes has pathologic significance as elevation of calcium influx and cytosolic calcium release has been implicated in other neurodegenerative conditions characterized by neuronal dysfunction and death. Using electrophysiologic and pharmacologic techniques, the present study provides evidence that significant impairment of G-protein-coupled modulation of calcium channel function may underlie the enhanced calcium entry in diabetes. N- and P-type voltage-activated, high-threshold calcium channels in DRGs are coupled to μ opiate receptors via inhibitory Go-type G proteins. The responsiveness of this receptor coupled model was tested in dorsal root ganglion (DRG) neurons from spontaneously-diabetic BB/W rats, and streptozotocin-induced (STZ) diabetic rats. Intracellular dialysis with GTPγS decreased calcium current amplitude in diabetic BB/W DRG neurons compared with those of age-matched, nondiabetic controls, suggesting that inhibitory G-protein activity was diminished in diabetes, resulting in larger calcium currents. Facilitation of calcium current density ( I DCa) by large-amplitude depolarizing prepulses (proposed to transiently inactivate G proteins), was significantly less effective in neurons from BB/W and STZ-induced diabetic DRGs. Facilitation was enhanced by intracellular dialysis with GTPγS, decreased by pertussis toxin, and abolished by GDPβS within 5 min. Direct measurement of GTPase activity using opiate-mediated GTPγ[35S] binding, confirmed that G-protein activity was significantly diminished in STZ-induced diabetic neurons compared with age-matched nondiabetic controls. Diabetes did not alter the level of expression of μ opiate receptors and G-protein α subunits. These studies indicate that impaired regulation of calcium channels by G proteins is an important mechanism contributing to enhanced calcium influx in diabetes.

scholarly journals Calcineurin Gene Subfunctionalization and Swimming Behavior in Paramecium tetraurelia

2018 ◽  
Vol 32 (S1) ◽  
Author(s):  
Madigan McKenna Strange ◽  
Alex Day ◽  
Dean Fraga ◽  
Jordan Welker ◽  
Ray Gaines ◽  
...  
Keyword(s):  
Swimming Behavior ◽  
Paramecium Tetraurelia
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