共查询到20条相似文献,搜索用时 31 毫秒
1.
Chaloux B Caron AZ Guillemette G 《Biology of the cell / under the auspices of the European Cell Biology Organization》2007,99(7):379-388
Background information. In endocrine cells, IP3R (inositol 1,4,5‐trisphosphate receptor), a ligand‐gated Ca2+ channel, plays an important role in the control of intracellular Ca2+ concentration. There are three subtypes of IP3R that are distributed differentially among cell types. RINm5F cells express almost exclusively the IP3R‐3 subtype. The purpose of the present study was to investigate the effect of PKA (protein kinase A) on the activity of IP3R‐3 in RINm5F cells. Results. We show that immunoprecipitated IP3R‐3 is a good substrate for PKA. Using a back‐phosphorylation approach, we show that endogenous PKA phosphorylates IP3R‐3 in intact RINm5F cells. [3H]IP3 (inositol 1,4,5‐trisphosphate) binding affinity and IP3‐induced Ca2+ release activity were enhanced in permeabilized cells that were pre‐treated with forskolin or PKA. The PKA‐induced enhancement of IP3R‐3 activity was also observed in intact RINm5F cells stimulated with carbachol and epidermal growth factor, two agonists that use different receptor types to activate phospholipase C. Conclusion. The results of the present study reveal a converging step where the cAMP and the Ca2+ signalling systems act co‐operatively in endocrine cell responses to external stimuli. 相似文献
2.
Joon-Chul Kim Min-Jeong Son Krishna P. Subedi Do Han Kim Sun-Hee Woo 《Molecules and cells》2010,29(4):387-395
HL-1 cells are the adult cardiac cell lines available that continuously divide while maintaining an atrial phenotype. Here
we examined the expression and localization of inositol 1,4,5-trisphosphate receptor (IP3R) subtypes, and investigated how pattern of IP3-induced subcellular local Ca2+ signaling is encoded by multiple IP3R subtypes in HL-1 cells. The type 1 IP3R (IP3R1) was expressed in the perinucleus with a diffuse pattern and the type 2 IP3R (IP3R2) was expressed in the cytosol with a punctate distribution. Extracellular ATP (1 mM) elicited transient intracellular Ca2+ releases accompanied by a Ca2+ oscillation, which was eliminated by the blocker of IP3Rs, 2-APB, and attenuated by ryanodine. Direct introduction of IP3 into the permeabilized cells induced Ca2+ transients with Ca2+ oscillations at ⩾ 20 μM of IP3, which was removed by the inhibition of IP3Rs using 2-APB and heparin. IP3-induced local Ca2+ transients contained two distinct time courses: a rapid oscillation and a monophasic Ca2+ transient. The magnitude of Ca2+ oscillation was significantly larger in the cytosol than in the nucleus, while the monophasic Ca2+ transient was more pronounced in the nucleus. These results provide evidence for the molecular and functional expression
of IP3R1 and IP3R2 in HL-1 cells, and suggest that such distinct local Ca2+ signaling may be correlated with the punctate distribution of IP3R2s in the cytosol and the diffuse localization of IP3R1 in the peri-nucleus. 相似文献
3.
Fujimoto T Machida T Tsunoda T Doi K Ota T Kuroki M Shirasawa S 《Biochemical and biophysical research communications》2011,(2):214-217
KRAS-induced actin-interacting protein (KRAP) was originally characterized as a filamentous- actin-interacting protein. We have recently found that KRAP is an associated molecule with inositol 1,4,5-trisphosphate (IP3) receptor (IP3R) and is responsible for the proper subcellular localization of IP3R. Since it remains unknown whether KRAP regulates the IP3R-mediated Ca2+ signaling, we herein examined the effects of KRAP on the IP3R-mediated Ca2+ release by Ca2+ imagings in the cultured HEK293 or MCF7 cells. Reduction of KRAP protein by KRAP-specific siRNA diminishes ATP-induced Ca2+ release and the ATP-induced Ca2+ release is completely quenched by the pretreatment with the IP3R inhibitor but not with the ryanodine receptor inhibitor, indicating that KRAP regulates IP3R-mediated Ca2+ release. To further reveal mechanistic insights into the regulation of IP3R-mediated Ca2+ release by KRAP, we examined the effects of the KRAP-knockdown on the releasable Ca2+ content of intracellular Ca2+ stores. Consequently, reduction of KRAP does not affect the amount of ionophore- or Ca2+-ATPase inhibitor-induced Ca2+ release in the HEK293 cells, indicating that releasable Ca2+ content of intracellular Ca2+ stores is not altered by KRAP. Thus, KRAP is involved in the proper regulation of IP3R-mediated Ca2+ release. 相似文献
4.
Verbert L Lee B Kocks SL Assefa Z Parys JB Missiaen L Callewaert G Fissore RA De Smedt H Bultynck G 《Biology of the cell / under the auspices of the European Cell Biology Organization》2008,100(1):39-49
Background information. The IP3R (inositol 1,4,5‐trisphosphate receptor) is a tetrameric channel that accounts for a large part of the intracellular Ca2+ release in virtually all cell types. We have previously demonstrated that caspase‐3‐mediated cleavage of IP3R1 during cell death generates a C‐terminal fragment of 95 kDa comprising the complete channel domain. Expression of this truncated IP3R increases the cellular sensitivity to apoptotic stimuli, and it was postulated to be a constitutively active channel. Results. In the present study, we demonstrate that expression of the caspase‐3‐cleaved C‐terminus of IP3R1 increased the rate of thapsigargin‐mediated Ca2+ leak and decreased the rate of Ca2+ uptake into the ER (endoplasmic reticulum), although it was not sufficient by itself to deplete intracellular Ca2+ stores. We detected the truncated IP3R1 in different cell types after a challenge with apoptotic stimuli, as well as in aged mouse oocytes. Injection of mRNA corresponding to the truncated IP3R1 blocked sperm factor‐induced Ca2+ oscillations and induced an apoptotic phenotype. Conclusions. In the present study, we show that caspase‐3‐mediated truncation of IP3R1 enhanced the Ca2+ leak from the ER. We suggest a model in which, in normal conditions, the increased Ca2+ leak is largely compensated by enhanced Ca2+‐uptake activity, whereas in situations where the cellular metabolism is compromised, as occurring in aging oocytes, the Ca2+ leak acts as a feed‐forward mechanism to divert the cell into apoptosis. 相似文献
5.
Joon-Chul Kim Krishna P. Subedi Joung Real Ahn 《Progress in biophysics and molecular biology》2010,103(1):59-70
In atrial myocytes lacking t-tubules, action potential triggers junctional Ca2+ releases in the cell periphery, which propagates into the cell interior. The present article describes growing evidence on atrial local Ca2+ signaling and on the functions of inositol 1,4,5-trisphosphate receptors (IP3Rs) in atrial myocytes, and show our new findings on the role of IP3R subtype in the regulation of spontaneous focal Ca2+ releases in the compartmentalized areas of atrial myocytes. The Ca2+ sparks, representing focal Ca2+ releases from the sarcoplasmic reticulum (SR) through the ryanodine receptor (RyR) clusters, occur most frequently at the peripheral junctions in isolated resting atrial cells. The Ca2+ sparks that were darker and longer lasting than peripheral and non-junctional (central) sparks, were found at peri-nuclear sites in rat atrial myocytes. Peri-nuclear sparks occurred more frequently than central sparks. Atrial cells express larger amounts of IP3Rs compared with ventricular cells and possess significant levels of type 1 IP3R (IP3R1) and type 2 IP3R (IP3R2). Over the last decade the roles of atrial IP3R on the enhancement of Ca2+-induced Ca2+ release and arrhythmic Ca2+ releases under hormonal stimulations have been well documented. Using protein knock-down method and confocal Ca2+ imaging in conjunction with immunocytochemistry in the adult atrial cell line HL-1, we could demonstrate a role of IP3R1 in the maintenance of peri-nuclear and non-junctional Ca2+ sparks via stimulating a posttranslational organization of RyR clusters. 相似文献
6.
Martijn Kerkhofs Bruno Seitaj Hristina Ivanova Giovanni Monaco Geert Bultynck Jan B. Parys 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》2018,1865(11):1707-1717
Ca2+ signaling governs a diverse range of cellular processes and, as such, is subject to tight regulation. A main component of the complex intracellular Ca2+-signaling network is the inositol 1,4,5-trisphosphate (IP3) receptor (IP3R), a tetrameric channel that mediates Ca2+ release from the endoplasmic reticulum (ER) in response to IP3. IP3R function is controlled by a myriad of factors, such as Ca2+, ATP, kinases and phosphatases and a plethora of accessory and regulatory proteins. Further complexity in IP3R-mediated Ca2+ signaling is the result of the existence of three main isoforms (IP3R1, IP3R2 and IP3R3) that display distinct functional characteristics and properties. Despite their abundant and overlapping expression profiles, IP3R1 is highly expressed in neurons, IP3R2 in cardiomyocytes and hepatocytes and IP3R3 in rapidly proliferating cells as e.g. epithelial cells. As a consequence, dysfunction and/or dysregulation of IP3R isoforms will have distinct pathophysiological outcomes, ranging from neurological disorders for IP3R1 to dysfunctional exocrine tissues and autoimmune diseases for IP3R2 and -3. Over the past years, several IP3R mutations have surfaced in the sequence analysis of patient-derived samples. Here, we aimed to provide an integrative overview of the clinically most relevant mutations for each IP3R isoform and the subsequent molecular mechanisms underlying the etiology of the disease. 相似文献
7.
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
8.
《Cell calcium》2019
The 5' AMP-activated protein kinase (AMPK) is a nutrient-sensitive kinase that plays a key role in the control of cellular energy metabolism. We have explored here the relationship between AMPK and Ca2+ signaling by looking at the effect of an AMPK activator (A769662) and an AMPK inhibitor (dorsomorphin) on histamine-induced Ca2+-release from the endoplasmic reticulum (ER) in HeLa cells. Our data show that incubation with A769662 (EC50 = 29 μM) inhibited histamine-induced Ca2+-release from the ER in intact cells, as well as inositol-1,4,5-trisphosphate (IP3)-induced Ca2+ release in permeabilized cells. On the contrary, dorsomorphin (EC50 = 0.4 μM) activated both histamine and IP3-induced Ca2+-release and reversed the effect of A769662. These results suggest a direct effect of AMPK regulation on IP3 receptor (IP3R) function. A phosphoproteomic study did not reveal changes in IP3R phosphorylation, but showed significant changes in phosphorylation of proteins placed upstream in the IP3R interactome and in several proteins related with Ca2+ metabolism, which could be candidates to mediate the effects observed. In conclusion, our data suggest that AMPK negatively regulates IP3R. This effect constitutes a novel and very important link between Ca2+ signaling and the AMPK pathway. 相似文献
9.
John G. McCarron Susan Chalmers Debbi MacMillan Marnie L. Olson 《Journal of cellular physiology》2010,224(2):334-344
Smooth muscle responds to IP3‐generating agonists by producing Ca2+ waves. Here, the mechanism of wave progression has been investigated in voltage‐clamped single smooth muscle cells using localized photolysis of caged IP3 and the caged Ca2+ buffer diazo‐2. Waves, evoked by the IP3‐generating agonist carbachol (CCh), initiated as a uniform rise in cytoplasmic Ca2+ concentration ([Ca2+]c) over a single though substantial length (~30 µm) of the cell. During regenerative propagation, the wave‐front was about 1/3 the length (~9 µm) of the initiation site. The wave‐front progressed at a relatively constant velocity although amplitude varied through the cell; differences in sensitivity to IP3 may explain the amplitude changes. Ca2+ was required for IP3‐mediated wave progression to occur. Increasing the Ca2+ buffer capacity in a small (2 µm) region immediately in front of a CCh‐evoked Ca2+ wave halted progression at the site. However, the wave front does not progress by Ca2+‐dependent positive feedback alone. In support, colliding [Ca2+]c increases from locally released IP3 did not annihilate but approximately doubled in amplitude. This result suggests that local IP3‐evoked [Ca2+]c increases diffused passively. Failure of local increases in IP3 to evoke waves appears to arise from the restricted nature of the IP3 increase. When IP3 was elevated throughout the cell, a localized increase in Ca2+ now propagated as a wave. Together, these results suggest that waves initiate over a surprisingly large length of the cell and that both IP3 and Ca2+ are required for active propagation of the wave front to occur. J. Cell. Physiol. 224: 334–344, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
10.
There is substantial evidence that crosstalk between the proliferation and Ca2+-signaling pathways plays a critical role in the regulation of normal physiological functions as well as in the pathogenesis of a variety of abnormal processes. In non-excitable cells, intracellular Ca2+ is mobilized through inositol 1,4,5-trisphosphate sensitive Ca2+ channels (IP3R) expressed on the endoplasmic reticulum. Here we report that mTOR, a point of convergence for signals from mitogenic growth factors, nutrients and cellular energy levels, phosphorylates the IP3R-2, the predominant isoform of IP3R in AR4-2J cells. Pretreatment with the mTOR inhibitor rapamycin, decreased carbachol-induced Ca2+ release in AR4-2J cells. Rapamycin also decreased IP3-induced Ca2+ release in permeabilized AR4-2J cells. We also showed that IGF-1 potentiates carbachol-induced Ca2+ release in AR4-2J cells, an effect that was prevented by rapamycin. Rapamycin also decreased carbachol-induced Ca2+ release in HEK 293A cells in which IP3R-1 and IP3R-3 had been knocked down. These results suggest that mTOR potentiates the activity of IP3R-2 by a phosphorylation mechanism. This conclusion supports the concept of crosstalk between Ca2+ signaling and proliferation pathways and thus provides another way by which intracellular Ca2+ signals are finely encoded. 相似文献
11.
The inositol 1,4,5-trisphosphate receptor (IP3R) is one of two Ca2+ channels that gates Ca2+ release from ER-stores. The ligand IP3, generated upon specific G-protein coupled receptor activation, binds to IP3R to release Ca2+ into the cytosol. IP3R also mediates ER-store Ca2+ release into the mitochondria, under basal as well as stimulatory conditions; an activity that influences cellular bioenergetics and thus, cellular growth and proliferation. In Drosophila neuroendocrine cells expressing a hypomorphic mutant of IP3R, we observed reduced protein translation levels. Here, we discuss the possible molecular mechanism for this observation. We hypothesize that the cellular energy sensor, AMPK connects IP3R mediated Ca2+ release into the mitochondria, to protein translation, via the TOR pathway. 相似文献
12.
《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
13.
Zhou H Nakamura T Matsumoto N Hisatsune C Mizutani A Iesaki T Daida H Mikoshiba K 《Biochemical and biophysical research communications》2008,369(1):213-219
Inositol 1,4,5-trisphosphate receptor (IP3R) plays a crucial role in generating Ca2+ signaling and three subtypes of IP3R have been identified. In spite of a high degree of similarity among these subtypes, their effects on spatio-temporal Ca2+ patterns are specific and diverse; therefore the physiological significance of the differential expression levels of IP3R subtypes in various tissues remains unknown. Here, we examined the relative contribution of the specific subtype of IP3Rs to the agonist-induced Ca2+ signaling and contraction in IP3R-deficient vascular smooth muscle cells and found that IP3R1 deficient cells exclusively showed less sensitivity to the agonist, compared to those from the other genotypes. We also found that IP3R1 dominantly expressed in vascular aortae on a consistent basis, and that phenylephrine (PE)-induced aortic muscle contraction was reduced specifically in IP3R1-deficient aortae. Taken together, we concluded that IP3R1 plays a predominant role in the function of the vascular smooth muscle in vivo. 相似文献
14.
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
15.
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
16.
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
17.
We recently reported key physiologic roles for Ca2+-activated transient receptor potential melastatin 4 (TRPM4) channels in detrusor smooth muscle (DSM). However, the Ca2+-signaling mechanisms governing TRPM4 channel activity in human DSM cells are unexplored. As the TRPM4 channels are activated by Ca2+, inositol 1,4,5-trisphosphate receptor (IP3R)-mediated Ca2+ release from the sarcoplasmic reticulum represents a potential Ca2+ source for TRPM4 channel activation. We used clinically-characterized human DSM tissues to investigate the molecular and functional interactions of the IP3Rs and TRPM4 channels. With in situ proximity ligation assay (PLA) and perforated patch-clamp electrophysiology, we tested the hypothesis that TRPM4 channels are tightly associated with the IP3Rs and are activated by IP3R-mediated Ca2+ release in human DSM. With in situ PLA, we demonstrated co-localization of the TRPM4 channels and IP3Rs in human DSM cells. As the TRPM4 channels and IP3Rs must be located within close apposition to functionally interact, these findings support the concept of a potential Ca2+-mediated TRPM4-IP3R regulatory mechanism. To investigate IP3R regulation of TRPM4 channel activity, we sought to determine the consequences of IP3R pharmacological inhibition on TRPM4 channel-mediated transient inward cation currents (TICCs). In freshly-isolated human DSM cells, blocking the IP3Rs with the selective IP3R inhibitor xestospongin-C significantly decreased TICCs. The data suggest that IP3Rs have a key role in mediating the Ca2+-dependent activation of TRPM4 channels in human DSM. The study provides novel insight into the molecular and cellular mechanisms regulating TRPM4 channels by revealing that TRPM4 channels and IP3Rs are spatially and functionally coupled in human DSM. 相似文献
18.
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
19.
Eva Sammels Benoit Devogelaere Djalila Mekahli Geert Bultynck Ludwig Missiaen Jan B. Parys Yiqiang Cai Stefan Somlo Humbert De Smedt 《The Journal of biological chemistry》2010,285(24):18794-18805
Autosomal dominant polycystic kidney disease is characterized by the loss-of-function of a signaling complex involving polycystin-1 and polycystin-2 (TRPP2, an ion channel of the TRP superfamily), resulting in a disturbance in intracellular Ca2+ signaling. Here, we identified the molecular determinants of the interaction between TRPP2 and the inositol 1,4,5-trisphosphate receptor (IP3R), an intracellular Ca2+ channel in the endoplasmic reticulum. Glutathione S-transferase pulldown experiments combined with mutational analysis led to the identification of an acidic cluster in the C-terminal cytoplasmic tail of TRPP2 and a cluster of positively charged residues in the N-terminal ligand-binding domain of the IP3R as directly responsible for the interaction. To investigate the functional relevance of TRPP2 in the endoplasmic reticulum, we re-introduced the protein in TRPP2−/− mouse renal epithelial cells using an adenoviral expression system. The presence of TRPP2 resulted in an increased agonist-induced intracellular Ca2+ release in intact cells and IP3-induced Ca2+ release in permeabilized cells. Using pathological mutants of TRPP2, R740X and D509V, and competing peptides, we demonstrated that TRPP2 amplified the Ca2+ signal by a local Ca2+-induced Ca2+-release mechanism, which only occurred in the presence of the TRPP2-IP3R interaction, and not via altered IP3R channel activity. Moreover, our results indicate that this interaction was instrumental in the formation of Ca2+ microdomains necessary for initiating Ca2+-induced Ca2+ release. The data strongly suggest that defects in this mechanism may account for the altered Ca2+ signaling associated with pathological TRPP2 mutations and therefore contribute to the development of autosomal dominant polycystic kidney disease. 相似文献
20.
Yun Li Netty G. Santoso Shengqiang Yu Owen M. Woodward Feng Qian William B. Guggino 《The Journal of biological chemistry》2009,284(52):36431-36441
The PKD1 or PKD2 genes encode polycystins (PC) 1 and 2, which are associated with polycystic kidney disease. Previously we demonstrated that PC2 interacts with the inositol 1,4,5-trisphosphate receptor (IP3R) to modulate Ca2+ signaling. Here, we investigate whether PC1 also regulates IP3R. We generated a fragment encoding the last six transmembrane (TM) domains of PC1 and the C-terminal tail (QIF38), a section with the highest homology to PC2. Using a Xenopus oocyte Ca2+ imaging system, we observed that expression of QIF38 significantly reduced the initial amplitude of IP3-induced Ca2+ transients, whereas a mutation lacking the C-terminal tail did not. Thus, the C terminus is essential to QIF38 function. Co-immunoprecipitation assays demonstrated that through its C terminus, QIF38 associates with the IP3-binding domain of IP3R. A shorter PC1 fragment spanning only the last TM and the C-terminal tail also reduced IP3-induced Ca2+ release, whereas another C-terminal fragment lacking any TM domain did not. Thus, only endoplasmic reticulum-localized PC1 can modulate IP3R. Finally, we show that in the polarized Madin-Darby canine kidney cells, heterologous expression of full-length PC1 resulted in a smaller IP3-induced Ca2+ response. Overexpression of the IP3-binding domain of IP3R reversed the inhibitory effect of PC1, suggesting interaction of full-length PC1 (or its cleavage forms) with endogenous IP3R in Madin-Darby canine kidney cells. These results indicate that the behavior of full-length PC1 in mammalian cells is congruent with that of PC1 C-terminal fragments in the oocyte system. These data demonstrate that PC1 inhibits Ca2+ release, perhaps opposing the effect of PC2, which facilitates Ca2+ release through the IP3R. 相似文献