共查询到20条相似文献,搜索用时 15 毫秒
1.
Victor Nicolai Friedhoff Gabriela Antunes Martin Falcke Fabio M. Simões de Souza 《Biophysical journal》2021,120(11):2112-2123
Calcium (Ca2+) is a second messenger assumed to control changes in synaptic strength in the form of both long-term depression and long-term potentiation at Purkinje cell dendritic spine synapses via inositol trisphosphate (IP3)-induced Ca2+ release. These Ca2+ transients happen in response to stimuli from parallel fibers (PFs) from granule cells and climbing fibers (CFs) from the inferior olivary nucleus. These events occur at low numbers of free Ca2+, requiring stochastic single-particle methods when modeling them. We use the stochastic particle simulation program MCell to simulate Ca2+ transients within a three-dimensional Purkinje cell dendritic spine. The model spine includes the endoplasmic reticulum, several Ca2+ transporters, and endogenous buffer molecules. Our simulations successfully reproduce properties of Ca2+ transients in different dynamical situations. We test two different models of the IP3 receptor (IP3R). The model with nonlinear concentration response of binding of activating Ca2+ reproduces experimental results better than the model with linear response because of the filtering of noise. Our results also suggest that Ca2+-dependent inhibition of the IP3R needs to be slow to reproduce experimental results. Simulations suggest the experimentally observed optimal timing window of CF stimuli arises from the relative timing of CF influx of Ca2+ and IP3 production sensitizing IP3R for Ca2+-induced Ca2+ release. We also model ataxia, a loss of fine motor control assumed to be the result of malfunctioning information transmission at the granule to Purkinje cell synapse, resulting in a decrease or loss of Ca2+ transients. Finally, we propose possible ways of recovering Ca2+ transients under ataxia. 相似文献
2.
In this study, we numerically analyzed the nonlinear Ca2+-dependent gating dynamics of a single, nonconducting inositol 1,4,5-trisphosphate receptor (IP3R) channel, using an exact and fully stochastic simulation algorithm that includes channel gating, Ca2+ buffering, and Ca2+ diffusion. The IP3R is a ubiquitous intracellular Ca2+ release channel that plays an important role in the formation of complex spatiotemporal Ca2+ signals such as waves and oscillations. Dynamic subfemtoliter Ca2+ microdomains reveal low copy numbers of Ca2+ ions, buffer molecules, and IP3Rs, and stochastic fluctuations arising from molecular interactions and diffusion do not average out. In contrast to models treating calcium dynamics deterministically, the stochastic approach accounts for this molecular noise. We varied Ca2+ diffusion coefficients and buffer reaction rates to tune the autocorrelation properties of Ca2+ noise and found a distinct relation between the autocorrelation time τac, the mean channel open and close times, and the resulting IP3R open probability PO. We observed an increased PO for shorter noise autocorrelation times, caused by increasing channel open times and decreasing close times. In a pure diffusion model the effects become apparent at elevated calcium concentrations, e.g., at [Ca2+] = 25 μM, τac = 0.082 ms, the IP3R open probability increased by ≈20% and mean open times increased by ≈4 ms, compared to a zero noise model. We identified the inactivating Ca2+ binding site of IP3R subunits as the primarily noise-susceptible element of the De Young and Keizer model. Short Ca2+ noise autocorrelation times decrease the probability of Ca2+ association and consequently increase IP3R activity. These results suggest a functional role of local calcium noise properties on calcium-regulated target molecules such as the ubiquitous IP3R. This finding may stimulate novel experimental approaches analyzing the role of calcium noise properties on microdomain behavior. 相似文献
3.
Don-On Daniel Mak King-Ho Cheung Patrick Toglia J. Kevin Foskett Ghanim Ullah 《PLoS computational biology》2015,11(10)
Familial Alzheimer’s disease (FAD)-causing mutant presenilins (PS) interact with inositol 1,4,5-trisphosphate (IP3) receptor (IP3R) Ca2+ release channels resulting in enhanced IP3R channel gating in an amyloid beta (Aβ) production-independent manner. This gain-of-function enhancement of IP3R activity is considered to be the main reason behind the upregulation of intracellular Ca2+ signaling in the presence of optimal and suboptimal stimuli and spontaneous Ca2+ signals observed in cells expressing mutant PS. In this paper, we employed computational modeling of single IP3R channel activity records obtained under optimal Ca2+ and multiple IP3 concentrations to gain deeper insights into the enhancement of IP3R function. We found that in addition to the high occupancy of the high-activity (H) mode and the low occupancy of the low-activity (L) mode, IP3R in FAD-causing mutant PS-expressing cells exhibits significantly longer mean life-time for the H mode and shorter life-time for the L mode, leading to shorter mean close-time and hence high open probability of the channel in comparison to IP3R in cells expressing wild-type PS. The model is then used to extrapolate the behavior of the channel to a wide range of IP3 and Ca2+ concentrations and quantify the sensitivity of IP3R to its two ligands. We show that the gain-of-function enhancement is sensitive to both IP3 and Ca2+ and that very small amount of IP3 is required to stimulate IP3R channels in the presence of FAD-causing mutant PS to the same level of activity as channels in control cells stimulated by significantly higher IP3 concentrations. We further demonstrate with simulations that the relatively longer time spent by IP3R in the H mode leads to the observed higher frequency of local Ca2+ signals, which can account for the more frequent global Ca2+ signals observed, while the enhanced activity of the channel at extremely low ligand concentrations will lead to spontaneous Ca2+ signals in cells expressing FAD-causing mutant PS. 相似文献
4.
Bezprozvanny I 《Neurochemical research》2011,36(7):1186-1197
Huntington’s disease (HD) and spinocerebellar ataxias (SCAs) are autosomal-dominant neurodegenerative disorders. HD is caused
by polyglutamine (polyQ) expansion in the amino-terminal region of a protein huntingtin (Htt) and primarily affects medium
spiny striatal neurons (MSN). Many SCAs are caused by polyQ-expansion in ataxin proteins and primarily affect cerebellar Purkinje
cells. The reasons for neuronal dysfunction and death in HD and SCAs remain poorly understood and no cure is available for
the patients. Our laboratory discovered that mutant huntingtin, ataxin-2 and ataxin-3 proteins specifically bind to the carboxy-terminal
region of the type 1 inositol 1,4,5-trisphosphate receptor (IP3R1), an intracellular Ca2+ release channel. Moreover, we found that association of mutant huntingtin or ataxins with IP3R1 causes sensitization of IP3R1 to activation by IP3 in planar lipid bilayers and in neuronal cells. These results suggested that deranged neuronal Ca2+ signaling might play an important role in pathogenesis of HD, SCA2 and SCA3. In support of this idea, we demonstrated a connection
between abnormal Ca2+ signaling and neuronal cell death in experiments with HD, SCA2 and SCA3 transgenic mouse models. Additional data in the literature
indicate that abnormal neuronal Ca2+ signaling may also play an important role in pathogenesis of SCAl, SCA5, SCA6, SCA14 and SCA15/16. Based on these results
I propose that IP3R and other Ca2+ signaling proteins should be considered as potential therapeutic targets for treatment of HD and SCAs. 相似文献
5.
Liberation of Ca2+ from the endoplasmic reticulum (ER) through inositol trisphosphate receptors (IP3R) is modulated by the ER Ca2+ content, and overexpression of SERCA2b to accelerate Ca2+ sequestration into the ER has been shown to potentiate the frequency and amplitude of IP3-evoked Ca2+ waves in Xenopus oocytes. Here, we examined the effects of SERCA overexpression on the elementary IP3-evoked puffs to elucidate whether ER [Ca2+] may modulate IP3R function via luminal regulatory sites in addition to simply determining the size of the available store and electrochemical driving force for Ca2+ release. SERCA2b and Ca2+ permeable nicotinic plasmalemmal channels were expressed in oocytes, and hyperpolarizing pulses were delivered to induce Ca2+ influx and thereby load ER stores. Puffs evoked by photoreleased IP3 were significantly potentiated in terms of numbers of responding sites, frequency and amplitude following transient Ca2+ influx in SERCA-overexpressing cells, whereas little change was evident with SERCA overexpression alone or following Ca2+ influx in control cells not overexpressing SERCA. Intriguingly, we observed the appearance of a new population of puffs that arose after long latencies and had prolonged durations supporting the notion of luminal regulation of IP3R gating kinetics. 相似文献
6.
Calcium puffs are localized Ca2+ signals mediated by Ca2+ release from the endoplasmic reticulum (ER) through clusters of inositol trisphosphate receptor (IP3R) channels. The recruitment of IP3R channels during puffs depends on Ca2+-induced Ca2+ release, a regenerative process that must be terminated to maintain control of cell signaling and prevent Ca2+ cytotoxicity. Here, we studied puff termination using total internal reflection microscopy to resolve the gating of individual IP3R channels during puffs in intact SH-SY5Y neuroblastoma cells. We find that the kinetics of IP3R channel closing differ from that expected for independent, stochastic gating, in that multiple channels tend to remain open together longer than predicted from their individual open lifetimes and then close in near-synchrony. This behavior cannot readily be explained by previously proposed termination mechanisms, including Ca2+-inhibition of IP3Rs and local depletion of Ca2+ in the ER lumen. Instead, we postulate that the gating of closely adjacent IP3Rs is coupled, possibly via allosteric interactions, suggesting an important mechanism to ensure robust puff termination in addition to Ca2+-inactivation. 相似文献
7.
Nicolas Rosa Hristina Ivanova Larry E. Wagner nd Justin Kale Rita La Rovere Kirsten Welkenhuyzen Nikolaos Louros Spyridoula Karamanou Victoria Shabardina Irma Lemmens Elien Vandermarliere Kozo Hamada Hideaki Ando Frederic Rousseau Joost Schymkowitz Jan Tavernier Katsuhiko Mikoshiba Anastassios Economou David W. Andrews Jan B. Parys David I. Yule Geert Bultynck 《Cell death and differentiation》2022,29(4):788
Anti-apoptotic Bcl-2-family members not only act at mitochondria but also at the endoplasmic reticulum, where they impact Ca2+ dynamics by controlling IP3 receptor (IP3R) function. Current models propose distinct roles for Bcl-2 vs. Bcl-xL, with Bcl-2 inhibiting IP3Rs and preventing pro-apoptotic Ca2+ release and Bcl-xL sensitizing IP3Rs to low [IP3] and promoting pro-survival Ca2+ oscillations. We here demonstrate that Bcl-xL too inhibits IP3R-mediated Ca2+ release by interacting with the same IP3R regions as Bcl-2. Via in silico superposition, we previously found that the residue K87 of Bcl-xL spatially resembled K17 of Bcl-2, a residue critical for Bcl-2’s IP3R-inhibitory properties. Mutagenesis of K87 in Bcl-xL impaired its binding to IP3R and abrogated Bcl-xL’s inhibitory effect on IP3Rs. Single-channel recordings demonstrate that purified Bcl-xL, but not Bcl-xLK87D, suppressed IP3R single-channel openings stimulated by sub-maximal and threshold [IP3]. Moreover, we demonstrate that Bcl-xL-mediated inhibition of IP3Rs contributes to its anti-apoptotic properties against Ca2+-driven apoptosis. Staurosporine (STS) elicits long-lasting Ca2+ elevations in wild-type but not in IP3R-knockout HeLa cells, sensitizing the former to STS treatment. Overexpression of Bcl-xL in wild-type HeLa cells suppressed STS-induced Ca2+ signals and cell death, while Bcl-xLK87D was much less effective in doing so. In the absence of IP3Rs, Bcl-xL and Bcl-xLK87D were equally effective in suppressing STS-induced cell death. Finally, we demonstrate that endogenous Bcl-xL also suppress IP3R activity in MDA-MB-231 breast cancer cells, whereby Bcl-xL knockdown augmented IP3R-mediated Ca2+ release and increased the sensitivity towards STS, without altering the ER Ca2+ content. Hence, this study challenges the current paradigm of divergent functions for Bcl-2 and Bcl-xL in Ca2+-signaling modulation and reveals that, similarly to Bcl-2, Bcl-xL inhibits IP3R-mediated Ca2+ release and IP3R-driven cell death. Our work further underpins that IP3R inhibition is an integral part of Bcl-xL’s anti-apoptotic function.Subject terms: Cancer, Cell biology, Molecular biology 相似文献
8.
《生物化学与生物物理学报:生物膜》2023,1865(7):184195
Numerous cellular processes are regulated by Ca2+ signals, and the endoplasmic reticulum (ER) membrane's inositol triphosphate receptor (IP3R) is critical for modulating intracellular Ca2+ dynamics. The IP3Rs are seen to be clustered in a variety of cell types. The combination of IP3Rs clustering and IP3Rs-mediated Ca2+-induced Ca2+ release results in the hierarchical organization of the Ca2+ signals, which challenges the numerical simulation given the multiple spatial and temporal scales that must be covered. The previous methods rather ignore the spatial feature of IP3Rs or fail to coordinate the conflicts between the real biological relevance and the computational cost. In this work, a general and efficient reduced-lattice model is presented for the simulation of IP3Rs-mediated multiscale Ca2+ dynamics. The model highlights biological details that make up the majority of the calcium events, including IP3Rs clustering and calcium domains, and it reduces the complexity by approximating the minor details. The model's extensibility provides fresh insights into the function of IP3Rs in producing global Ca2+ events and supports the research under more physiological circumstances. Our work contributes to a novel toolkit for modeling multiscale Ca2+ dynamics and advances knowledge of Ca2+ signals. 相似文献
9.
Diptiman D. Bose 《Biochemical and biophysical research communications》2009,379(2):594-133
Regulation of bi-directional communication between intracellular Ca2+ pools and surface Ca2+ channels remains incompletely characterized. We report Ca2+ release mediated by inositol 1,4,5-trisphosphate receptor (IP3R) and ryanodine receptor (RyR) pathways is diminished under actin cytoskeleton disruption in NG115-401L (401L) neuronal cells, yet despite truncated Ca2+ release, Ca2+ influx was not significantly altered in these experiments. However, disruption of cortical actin networks completely abolished IP3R induced Ca2+ release, whereas RyR-mediated Ca2+ release was preserved, albeit attenuated. Moreover, cortical actin disruption completely abolished IP3R and RyR linked Ca2+ influx even though Ca2+ pool sensitivities were different. These findings suggest discrete Ca2+ store/Ca2+ channel coupling mechanisms in the IP3R and RyR pathways as revealed by the differential sensitivity to actin perturbation. 相似文献
10.
Considerable insight into intracellular Ca2+ responses has been obtained through the development of whole cell models that are based on molecular mechanisms, e.g., single channel kinetics of the inositol 1,4,5-trisphosphate (IP3) receptor Ca2+ channel. However, a limitation of most whole cell models to date is the assumption that IP3 receptor Ca2+ channels (IP3Rs) are globally coupled by a “continuously stirred” bulk cytosolic [Ca2+], when in fact open IP3Rs experience elevated “domain” Ca2+ concentrations. Here we present a 2N+2-compartment whole cell model of local and global Ca2+ responses mediated by N=100,000 diffusely distributed IP3Rs, each represented by a four-state Markov chain. Two of these compartments correspond to bulk cytosolic and luminal Ca2+ concentrations, and the remaining 2N compartments represent time-dependent cytosolic and luminal Ca2+ domains associated with each IP3R. Using this Monte Carlo model as a starting point, we present an alternative formulation that solves a system of advection-reaction equations for the probability density of cytosolic and luminal domain [Ca2+] jointly distributed with IP3R state. When these equations are coupled to ordinary differential equations for the bulk cytosolic and luminal [Ca2+], a realistic but minimal model of whole cell Ca2+ dynamics is produced that accounts for the influence of local Ca2+ signaling on channel gating and global Ca2+ responses. The probability density approach is benchmarked and validated by comparison to Monte Carlo simulations, and the two methods are shown to agree when the number of Ca2+ channels is large (i.e., physiologically realistic). Using the probability density approach, we show that the time scale of Ca2+ domain formation and collapse (both cytosolic and luminal) may influence global Ca2+ oscillations, and we derive two reduced models of global Ca2+ dynamics that account for the influence of local Ca2+ signaling on global Ca2+ dynamics when there is a separation of time scales between the stochastic gating of IP3Rs and the dynamics of domain Ca2+. 相似文献
11.
The subcellular localization of membrane Ca2+ channels is crucial for their functioning, but is difficult to study because channels may be distributed more closely than the resolution of conventional microscopy is able to detect. We describe a technique, stochastic channel Ca2+ nanoscale resolution (SCCaNR), employing Ca2+-sensitive fluorescent dyes to localize stochastic openings and closings of single Ca2+-permeable channels within <50 nm, and apply it to examine the clustered arrangement of inositol trisphosphate receptor (IP3R) channels underlying local Ca2+ puffs. Fluorescence signals (blips) arising from single functional IP3Rs are almost immotile (diffusion coefficient <0.003 μm2 s−1), as are puff sites over prolonged periods, suggesting that the architecture of this signaling system is stable and not subject to rapid, dynamic rearrangement. However, rapid stepwise changes in centroid position of fluorescence are evident within the durations of individual puffs. These apparent movements likely result from asynchronous gating of IP3Rs distributed within clusters that have an overall diameter of ∼400 nm, indicating that the nanoscale architecture of IP3R clusters is important in shaping local Ca2+ signals. We anticipate that SCCaNR will complement superresolution techniques such as PALM and STORM for studies of Ca2+ channels as it obviates the need for photoswitchable labels and provides functional as well as spatial information. 相似文献
12.
Anna M. Hagenston Noam D. Rudnick Christine E. Boone Mark F. Yeckel 《Cell calcium》2009,45(3):310-317
Calcium ions (Ca2+) released from inositol trisphosphate (IP3)-sensitive intracellular stores may participate in both the transient and extended regulation of neuronal excitability in neocortical and hippocampal pyramidal neurons. IP3 receptor (IP3R) antagonists represent an important tool for dissociating these consequences of IP3 generation and IP3R-dependent internal Ca2+ release from the effects of other, concurrently stimulated second messenger signaling cascades and Ca2+ sources. In this study, we have described the actions of the IP3R and store-operated Ca2+ channel antagonist, 2-aminoethoxydiphenyl-borate (2-APB), on internal Ca2+ release and plasma membrane excitability in neocortical and hippocampal pyramidal neurons. Specifically, we found that a dose of 2-APB (100 μM) sufficient for attenuating or blocking IP3-mediated internal Ca2+ release also raised pyramidal neuron excitability. The 2-APB-dependent increase in excitability reversed upon washout and was characterized by an increase in input resistance, a decrease in the delay to action potential onset, an increase in the width of action potentials, a decrease in the magnitude of afterhyperpolarizations (AHPs), and an increase in the magnitude of post-spike afterdepolarizations (ADPs). From these observations, we conclude that 2-APB potently and reversibly increases neuronal excitability, likely via the inhibition of voltage- and Ca2+-dependent potassium (K+) conductances. 相似文献
13.
The inositol 1,4,5-trisphosphate receptor/channel (IP3R) is a major regulator of intracellular Ca2+ signaling, and liberates Ca2+ ions from the endoplasmic reticulum in response to binding at cytosolic sites for both IP3 and Ca2+. Although the steady-state gating properties of the IP3R have been extensively studied and modeled under conditions of fixed [IP3] and [Ca2+], little is known about how Ca2+ flux through a channel may modulate the gating of that same channel by feedback onto activating and inhibitory Ca2+ binding sites. We thus simulated the dynamics of Ca2+ self-feedback on monomeric and tetrameric IP3R models. A major conclusion is that self-activation depends crucially on stationary cytosolic Ca2+ buffers that slow the collapse of the local [Ca2+] microdomain after closure. This promotes burst-like reopenings by the rebinding of Ca2+ to the activating site; whereas inhibitory actions are substantially independent of stationary buffers but are strongly dependent on the location of the inhibitory Ca2+ binding site on the IP3R in relation to the channel pore. 相似文献
14.
Száva Bánsághi Tünde Golenár Muniswamy Madesh Gy?rgy Csordás Satish RamachandraRao Kumar Sharma David I. Yule Suresh K. Joseph Gy?rgy Hajnóczky 《The Journal of biological chemistry》2014,289(12):8170-8181
Reactive oxygen species (ROS) stimulate cytoplasmic [Ca2+] ([Ca2+]c) signaling, but the exact role of the IP3 receptors (IP3R) in this process remains unclear. IP3Rs serve as a potential target of ROS produced by both ER and mitochondrial enzymes, which might locally expose IP3Rs at the ER-mitochondrial associations. Also, IP3Rs contain multiple reactive thiols, common molecular targets of ROS. Therefore, we have examined the effect of superoxide anion (O2⨪) on IP3R-mediated Ca2+ signaling. In human HepG2, rat RBL-2H3, and chicken DT40 cells, we observed [Ca2+]c spikes and frequency-modulated oscillations evoked by a O2⨪ donor, xanthine (X) + xanthine oxidase (XO), dose-dependently. The [Ca2+]c signal was mediated by ER Ca2+ mobilization. X+XO added to permeabilized cells promoted the [Ca2+]c rise evoked by submaximal doses of IP3, indicating that O2⨪ directly sensitizes IP3R-mediated Ca2+ release. In response to X+XO, DT40 cells lacking two of three IP3R isoforms (DKO) expressing either type 1 (DKO1) or type 2 IP3Rs (DKO2) showed a [Ca2+]c signal, whereas DKO expressing type 3 IP3R (DKO3) did not. By contrast, IgM that stimulates IP3 formation, elicited a [Ca2+]c signal in every DKO. X+XO also facilitated the Ca2+ release evoked by submaximal IP3 in permeabilized DKO1 and DKO2 but was ineffective in DKO3 or in DT40 lacking every IP3R (TKO). However, X+XO could also facilitate the effect of suboptimal IP3 in TKO transfected with rat IP3R3. Although in silico studies failed to identify a thiol missing in the chicken IP3R3, an X+XO-induced redox change was documented only in the rat IP3R3. Thus, ROS seem to specifically sensitize IP3Rs through a thiol group(s) within the IP3R, which is probably inaccessible in the chicken IP3R3. 相似文献
15.
《Gene》1997,190(1):151-156
Receptor-stimulated phosphoinositide (PI) hydrolysis is an important and ubiquitous mechanism of intracellular signaling. Inositol 1,4,5-trisphosphate (IP3), generated by phosphoinositide (PI) hydrolysis, binds to and gates an intracellular Ca2+ channel, the IP3 receptor (IP3R), which is therefore a central component of this signaling cascade. Here we describe the development of a baculovirus (BV)/Sf(S. frugiperda) cell system that can be used to look at IP3R function. Agonist-evoked changes in intracellular Ca2+ levels [Ca2+]i were measured (using Fura2) in Sf cells expressing the gene encoding the muscarinic acetylcholine receptor (vmlAchR). Furthermore, we have constructed a recombinant BV (vlP3R), with the core of the IP3R ligand-binding domain from the Drosophila IP3R, under the polyhedrin promoter. The recombinant protein from such a virus was expected to act as a large ligand sink for IP3, generated by stimulation of vmlAchR. Cells coinfected with recombinant BV carrying the potential dominant-negative vIP3R construct and vmlAchR have been used to assay the modulation of IP3R-mediated Ca2+ release, by the ligand sink. 相似文献
16.
Guiling Zhao Zachary P. Neeb M. Dennis Leo Judith Pachuau Adebowale Adebiyi Kunfu Ouyang Ju Chen Jonathan H. Jaggar 《The Journal of general physiology》2010,136(3):283-291
Plasma membrane large-conductance Ca2+-activated K+ (BKCa) channels and sarcoplasmic reticulum inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs) are expressed in a wide variety of cell types, including arterial smooth muscle cells. Here, we studied BKCa channel regulation by IP3 and IP3Rs in rat and mouse cerebral artery smooth muscle cells. IP3 activated BKCa channels both in intact cells and in excised inside-out membrane patches. IP3 caused concentration-dependent BKCa channel activation with an apparent dissociation constant (Kd) of ∼4 µM at physiological voltage (−40 mV) and intracellular Ca2+ concentration ([Ca2+]i; 10 µM). IP3 also caused a leftward-shift in BKCa channel apparent Ca2+ sensitivity and reduced the Kd for free [Ca2+]i from ∼20 to 12 µM, but did not alter the slope or maximal Po. BAPTA, a fast Ca2+ buffer, or an elevation in extracellular Ca2+ concentration did not alter IP3-induced BKCa channel activation. Heparin, an IP3R inhibitor, and a monoclonal type 1 IP3R (IP3R1) antibody blocked IP3-induced BKCa channel activation. Adenophostin A, an IP3R agonist, also activated BKCa channels. IP3 activated BKCa channels in inside-out patches from wild-type (IP3R1+/+) mouse arterial smooth muscle cells, but had no effect on BKCa channels of IP3R1-deficient (IP3R1−/−) mice. Immunofluorescence resonance energy transfer microscopy indicated that IP3R1 is located in close spatial proximity to BKCa α subunits. The IP3R1 monoclonal antibody coimmunoprecipitated IP3R1 and BKCa channel α and β1 subunits from cerebral arteries. In summary, data indicate that IP3R1 activation elevates BKCa channel apparent Ca2+ sensitivity through local molecular coupling in arterial smooth muscle cells. 相似文献
17.
《Channels (Austin, Tex.)》2013,7(4):226-232
Inositol 1,4,5-trisphosphate receptors (IP3Rs) are intracellular Ca2+ channels. Their regulation by both IP3 and Ca2+ allows interactions between IP3Rs to generate a hierarchy of intracellular Ca2+ release events. These can progress from openings of single IP3R, through near-synchronous opening of a few IP3Rs within a cluster to much larger signals that give rise to regenerative Ca2+ waves that can invade the entire cell. We have used patch-clamp recording from excised nuclear membranes of DT40 cells expressing only IP3R3 and shown that low concentrations of IP3 rapidly and reversibly cause IP3Rs to assemble into small clusters. In addition to bringing IP3Rs close enough to allow Ca2+ released by one IP3R to regulate the activity of its neighbors, clustering also retunes the regulation of IP3Rs by IP3 and Ca2+. At resting cytosolic [Ca2+], lone IP3R are more sensitive to IP3 and the mean channel open time (~10ms) is twice as long as for clustered IP3R. When the cytosolic free [Ca2+] is increased to 1µM, to mimic the conditions that might prevail when an IP3R within a cluster opens, clustered IP3R are no longer inhibited and their gating becomes coupled. IP3, by dynamically regulating IP3R clustering, both positions IP3R for optimal interactions between them and it serves to exaggerate the effects of Ca2+ within a cluster. During the course of these studies, we have observed that nuclear IP3R stably express one of two single channel K + conductances (γK ~120 or 200pS). Here we demonstrate that for both states of the IP3R, the effects of IP3 on clustering are indistinguishable. These observations reinforce our conclusion that IP3 dynamically regulates assembly of IP3Rs into clusters that underlie the hierarchical recruitment of elementary Ca2+ release events. 相似文献
18.
Veerle Vanderheyden Takuya Wakai Geert Bultynck Humbert De Smedt Jan B. Parys Rafael A. Fissore 《Cell calcium》2009,46(1):56-64
Egg activation and further embryo development require a sperm-induced intracellular Ca2+ signal at the time of fertilization. Prior to fertilization, the egg's Ca2+ machinery is therefore optimized. To this end, during oocyte maturation, the sensitivity, i.e. the Ca2+ releasing ability, of the inositol 1,4,5-trisphosphate receptor type 1 (IP3R1), which is responsible for most of this Ca2+ release, markedly increases. In this study, the recently discovered specific Polo-like kinase (Plk) inhibitor BI2536 was used to investigate the role of Plk1 in this process. BI2536 inactivates Plk1 in oocytes at the early stages of maturation and significantly decreases IP3R1 phosphorylation at an MPM-2 epitope at this stage. Moreover, this decrease in Plk1-dependent MPM-2 phosphorylation significantly lowers IP3R1 sensitivity. Finally, using in vitro phosphorylation techniques we identified T2656 as a major Plk1 site on IP3R1. We therefore propose that the initial increase in IP3R1 sensitivity during oocyte maturation is underpinned by IP3R1 phosphorylation at an MPM-2 epitope(s). 相似文献
19.
《Cell calcium》2020
Type 3 Inositol 1,4,5-trisphosphate (IP3) receptors (IP3R3s) have been identified as anti-oncogenic channels by propelling pro-apoptotic Ca2+ signals to mitochondria. Yet, recent studies (Rezuchova et al, Cell Death Dis, 2019; Ueasilamongkol et al, Hepathology, 2019; Guerra et al, Gut, 2019) revealed that IP3R3 upregulation drives oncogenesis via ER-mitochondrial Ca2+ crosstalk, adding complexity to IP3R3’s role in cancer. 相似文献
20.
《Cell calcium》2018
Intracellular accumulation of oligomeric forms of β amyloid (Aβ) are now believed to play a key role in the earliest phase of Alzheimer's disease (AD) as their rise correlates well with the early symptoms of the disease. Extensive evidence points to impaired neuronal Ca2+ homeostasis as a direct consequence of the intracellular Aβ oligomers. However, little is known about the downstream effects of the resulting Ca2+ rise on the many intracellular Ca2+-dependent pathways. Here we use multiscale modeling in conjunction with patch-clamp electrophysiology of single inositol 1,4,5-trisphosphate (IP3) receptor (IP3R) and fluorescence imaging of whole-cell Ca2+ response, induced by exogenously applied intracellular Aβ42 oligomers to show that Aβ42 inflicts cytotoxicity by impairing mitochondrial function. Driven by patch-clamp experiments, we first model the kinetics of IP3R, which is then extended to build a model for the whole-cell Ca2+ signals. The whole-cell model is then fitted to fluorescence signals to quantify the overall Ca2+ release from the endoplasmic reticulum by intracellular Aβ42 oligomers through G-protein-mediated stimulation of IP3 production. The estimated IP3 concentration as a function of intracellular Aβ42 content together with the whole-cell model allows us to show that Aβ42 oligomers impair mitochondrial function through pathological Ca2+ uptake and the resulting reduced mitochondrial inner membrane potential, leading to an overall lower ATP and increased production of reactive oxygen species and H2O2. We further show that mitochondrial function can be restored by the addition of Ca2+ buffer EGTA, in accordance with the observed abrogation of Aβ42 cytotoxicity by EGTA in our live cells experiments. 相似文献