scholarly journals Calcium influx in mammalian eggs

Reproduction ◽  
2013 ◽  
Vol 145 (4) ◽  
pp. R97-R105 ◽  
Author(s):  
Chunmin Wang ◽  
Zoltan Machaty
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Assisted Reproductive Technologies ◽  
Calcium Influx ◽  
Critical Role ◽  
Reproductive Technologies ◽  
Signaling Cascades ◽  
Mammalian Eggs ◽  
Stimulation Of

Calcium (Ca2+) signals are involved in the regulation of oocyte maturation and play a critical role during fertilization. In the egg, Ca2+is stored in the lumen of the endoplasmic reticulum and a signal is generated when the stored Ca2+is released through specialized channels in the membrane of the endoplasmic reticulum to elevate the free Ca2+concentration in the cytoplasm. Extracellular Ca2+is also important, indicated by the fact that the mobilization of luminal Ca2+is typically followed by Ca2+entry across the plasma membrane. The transmembrane Ca2+flux replenishes the endoplasmic reticulum, and thus, it is essential to sustain prolonged Ca2+signals. It also seems to be responsible for the stimulation of important signaling cascades required for complete egg activation. Characterization of the pathway that mediates Ca2+entry implies that its major components include STIM1, a protein that senses the filling status of the stores, and ORAI1, a channel protein located in the plasma membrane. Defining the mechanism and functions of Ca2+entry will not only lead to a better understanding of egg physiology but may also help improving the efficiency of a number of assisted reproductive technologies.

scholarly journals The endosomal transcriptional regulator RNF11 integrates degradation and transport of EGFR

2016 ◽  
Vol 215 (4) ◽  
pp. 543-558 ◽  
Author(s):  
Sandra Scharaw ◽  
Murat Iskar ◽  
Alessandro Ori ◽  
Gaelle Boncompain ◽  
Vibor Laketa ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Egf Receptor ◽  
Regulatory Mechanism ◽  
Transcriptional Regulator ◽  
Transport Efficiency ◽  
Early Endosomes ◽  
Epidermal Growth ◽  
Partial Degradation ◽  
Stimulation Of

Stimulation of cells with epidermal growth factor (EGF) induces internalization and partial degradation of the EGF receptor (EGFR) by the endo-lysosomal pathway. For continuous cell functioning, EGFR plasma membrane levels are maintained by transporting newly synthesized EGFRs to the cell surface. The regulation of this process is largely unknown. In this study, we find that EGF stimulation specifically increases the transport efficiency of newly synthesized EGFRs from the endoplasmic reticulum to the plasma membrane. This coincides with an up-regulation of the inner coat protein complex II (COPII) components SEC23B, SEC24B, and SEC24D, which we show to be specifically required for EGFR transport. Up-regulation of these COPII components requires the transcriptional regulator RNF11, which localizes to early endosomes and appears additionally in the cell nucleus upon continuous EGF stimulation. Collectively, our work identifies a new regulatory mechanism that integrates the degradation and transport of EGFR in order to maintain its physiological levels at the plasma membrane.

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.

scholarly journals Reversible Ca Gradients between the Subplasmalemma and Cytosol Differentially Activate Ca-dependent Cl Currents

1999 ◽  
Vol 113 (2) ◽  
pp. 249-266 ◽  
Author(s):  
Khaled Machaca ◽  
H. Criss Hartzell
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Confocal Microscopy ◽  
Driving Force ◽  
Xenopus Oocytes ◽  
Biophysical Properties ◽  
Temporal Features ◽  
Cl Channels ◽  
Spatio Temporal ◽  
Stimulation Of

Xenopus oocytes express several different Ca-activated Cl currents that have different waveforms and biophysical properties. We compared the stimulation of Ca-activated Cl currents measured by two-microelectrode voltage clamp with the Ca transients measured in the same cell by confocal microscopy and Ca-sensitive fluorophores. The purpose was to determine how the amplitude and/or spatio-temporal features of the Ca signal might explain how these different Cl currents were activated by Ca. Because Ca release from stores was voltage independent, whereas Ca influx depended upon the electrochemical driving force, we were able to separately assess the contribution of Ca from these two sources. We were surprised to find that Ca signals measured with a cytosolic Ca-sensitive dye, dextran-conjugated Ca-green-1, correlated poorly with Cl currents. This suggested that Cl channels located at the plasma membrane and the Ca-sensitive dye located in the bulk cytosol were sensing different [Ca]. This was true despite Ca measurement in a confocal slice very close to the plasma membrane. In contrast, a membrane-targeted Ca-sensitive dye (Ca-green-C18) reported a Ca signal that correlated much more closely with the Cl currents. We hypothesize that very local, transient, reversible Ca gradients develop between the subplasmalemmal space and the bulk cytosol. [Ca] is higher near the plasma membrane when Ca is provided by Ca influx, whereas the gradient is reversed when Ca is released from stores, because Ca efflux across the plasma membrane is faster than diffusion of Ca from the bulk cytosol to the subplasmalemmal space. Because dissipation of the gradients is accelerated by inhibition of Ca sequestration into the endoplasmic reticulum with thapsigargin, we conclude that [Ca] in the bulk cytosol declines slowly partly due to futile recycling of Ca through the endoplasmic reticulum.

scholarly journals Presynaptic Endoplasmic Reticulum Contributes Crucially to Short-term Plasticity in Small Hippocampal Synapses

2018 ◽  
Author(s):  
Nishant Singh ◽  
Thomas Bartol ◽  
Herbert Levine ◽  
Terrence Sejnowski ◽  
Suhita Nadkarni
Keyword(s):  
Endoplasmic Reticulum ◽  
Calcium Influx ◽  
Critical Role ◽  
Presynaptic Terminal ◽  
Calcium Stores ◽  
Pathological State ◽  
Calcium Dynamics ◽  
Short Term ◽  
Short Term Plasticity ◽  
Release Probability

Short-term plasticity (STP) of the presynaptic terminal maintains a brief history of activity experienced by the synapse that may otherwise remain unseen by the postsynaptic neuron. These synaptic changes are primarily regulated by calcium dynamics in the presynaptic terminal. A rapid increase in intracellular calcium is initiated by the opening of voltage-dependent calcium channels in response to depolarization, the main source of calcium required for vesicle fusion. Separately, electron-microscopic studies of hippocampal CA3-CA1 synapses reveal the strong presence of endoplasmic reticulum (ER) in all presynaptic terminals. However, the precise role of the ER in modifying STP at the presynaptic terminal remains unexplored. To investigate the contribution of ER in modulating calcium dynamics in small hippocampal boutons, we performed in silico experiments in a physiologically-realistic canonical synaptic geometry based on reconstructions of CA3-CA1 Schaffer collaterals in the rat hippocampus. The model predicts that presynaptic calcium stores are critical in generating the observed paired-pulse ratio (PPR) of normal CA3-CA1 synapses. In control synapses with intact ER, SERCA pumps act as additional calcium buffers, lowering the intrinsic release probability of vesicle release and increasing PPR. In addition, the presence of ER allows ongoing activity to trigger calcium influx from the presynaptic ER via ryanodine receptors (RyRs) and inositol trisphosphate receptors (IP3Rs). Intracellular stores and their associated machinery also allows a synapse with a low release probability to operate more reliably due to attenuation of calcium fluctuations. Finally, blocking ER activity in the presynaptic terminal mimics the pathological state of a low facilitating synapse characterized in animal models of Alzheimer’s disease, and underscores the critical role played by presynaptic stores in normal function.

scholarly journals Perfringolysin O-Induced Plasma Membrane Pores Trigger Actomyosin Remodeling and Endoplasmic Reticulum Redistribution

Toxins ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 419
Author(s):  
Cláudia Brito ◽  
Francisco S. Mesquita ◽  
Christopher K. E. Bleck ◽  
James R. Sellers ◽  
Didier Cabanes ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Calcium Influx ◽  
Cell Cortex ◽  
Perfringolysin O ◽  
Membrane Pores ◽  
Cellular Events ◽  
Severe Infections ◽  
Cytoskeletal Responses ◽  
Actomyosin Cytoskeleton

Clostridium perfringens produces an arsenal of toxins that act together to cause severe infections in humans and livestock animals. Perfringolysin O (PFO) is a cholesterol-dependent pore-forming toxin encoded in the chromosome of virtually all C. perfringens strains and acts in synergy with other toxins to determine the outcome of the infection. However, its individual contribution to the disease is poorly understood. Here, we intoxicated human epithelial and endothelial cells with purified PFO to evaluate the host cytoskeletal responses to PFO-induced damage. We found that, at sub-lytic concentrations, PFO induces a profound reorganization of the actomyosin cytoskeleton culminating into the assembly of well-defined cortical actomyosin structures at sites of plasma membrane (PM) remodeling. The assembly of such structures occurs concomitantly with the loss of the PM integrity and requires pore-formation, calcium influx, and myosin II activity. The recovery from the PM damage occurs simultaneously with the disassembly of cortical structures. PFO also targets the endoplasmic reticulum (ER) by inducing its disruption and vacuolation. ER-enriched vacuoles were detected at the cell cortex within the PFO-induced actomyosin structures. These cellular events suggest the targeting of the endothelium integrity at early stages of C. perfringens infection, in which secreted PFO is at sub-lytic concentrations.

Stimulation of ovulation in program of auxiliary reproductive technologies in women over 40 years (review of literature)

GYNECOLOGY ◽  
2017 ◽  
Vol 19 (6) ◽  
pp. 46-50
Author(s):  
D A Kuleshova ◽  
N Yu Melekhova ◽  
T A Gustovarova ◽  
A L Chernyakova ◽  
O A Gruzdova
Keyword(s):  
Assisted Reproductive Technologies ◽  
Reproductive Technologies ◽  
Economic Effectiveness ◽  
Modern Literature ◽  
Review Of Literature ◽  
Advantages And Disadvantages ◽  
Ovarian Induction ◽  
Over 40 Years ◽  
Stimulation Of

The article presents modern literature data on the stimulation of ovulation in programs of assisted reproductive technologies in women over 40, the advantages and disadvantages of conventional ovarian induction schemes, the clinical and economic effectiveness of the use of coryphollitropine-a for folliculogenesis.

scholarly journals Characterization of In Vivo Function(s) of Members of the Plant Mitochondrial Carrier Family

Biomolecules ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1226
Author(s):  
Adriano Nunes-Nesi ◽  
João Henrique F. Cavalcanti ◽  
Alisdair R. Fernie
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Genetic Variants ◽  
Mitochondrial Carrier ◽  
Wide Range ◽  
Mitochondrial Carrier Family ◽  
Insight Into ◽  
Green Lineage

Although structurally related, mitochondrial carrier family (MCF) proteins catalyze the specific transport of a range of diverse substrates including nucleotides, amino acids, dicarboxylates, tricarboxylates, cofactors, vitamins, phosphate and H+. Despite their name, they do not, however, always localize to the mitochondria, with plasma membrane, peroxisomal, chloroplast and thylakoid and endoplasmic reticulum localizations also being reported. The existence of plastid-specific MCF proteins is suggestive that the evolution of these proteins occurred after the separation of the green lineage. That said, plant-specific MCF proteins are not all plastid-localized, with members also situated at the endoplasmic reticulum and plasma membrane. While by no means yet comprehensive, the in vivo function of a wide range of these transporters is carried out here, and we discuss the employment of genetic variants of the MCF as a means to provide insight into their in vivo function complementary to that obtained from studies following their reconstitution into liposomes.

scholarly journals The sarcoplasmic–endoplasmic reticulum Ca2+ ATPase 2b regulates the Ca2+ transients elicited by P2Y2 activation in PC Cl3 thyroid cells

2006 ◽  
Vol 190 (3) ◽  
pp. 641-649 ◽  
Author(s):  
Luca Ulianich ◽  
Maria Giovanna Elia ◽  
Antonella Sonia Treglia ◽  
Antonella Muscella ◽  
Bruno Di Jeso ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Thyroid Cell ◽  
Myristate Acetate ◽  
Thyroid Cells ◽  
Pkc Inhibitor ◽  
Kinase C ◽  
Thyroid Cell Line ◽  
Rat Thyroid ◽  
Stimulation Of

In PC Cl3 cells, a continuous, fully differentiated rat thyroid cell line, P2Y2 purinoceptor activation provoked a transient increase of [Ca2+]i, followed by a decreasing sustained phase. The α and β1 protein kinase C (PKC) inhibitor Gö6976 decreased the rate of decrement to the basal [Ca2+]i level and increased the peak of Ca2+ entry of the P2Y2-provoked Ca2+transients. These effects of Gö 6976 were not caused by an increased permeability of the plasma membrane, since the Mn2+ and Ba2+ uptake were not changed by Gö 6976. Similarly, the Na+/Ca2+ exchanger was not implicated, since the rate of decrement to the basal [Ca2+]i level was equally decreased in physiological and Na+-free buffers, in the presence of Gö 6976. On the contrary, the activity of the sarcoplasmic–endoplasmic reticulum Ca2+ATPase (SERCA) 2b was profoundly affected by Gö 6976 since the drug was able to completely inhibit the stimulation of the SERCA 2b activity elicited by P2-purinergic agonists. Finally, the PKC activator phorbol myristate acetate had effects opposite to Gö 6976, in that it markedly increased the rate of decrement to the basal [Ca2+]i level after P2Y2 stimulation and also increased the activity of SERCA 2b. These results suggest that SERCA 2b plays a role in regulating the sustained phase of Ca2+ transients caused by P2Y2 stimulation.

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