共查询到20条相似文献,搜索用时 31 毫秒
1.
Pia A. Elustondo Matthew Nichols George S. Robertson Evgeny V. Pavlov 《Journal of bioenergetics and biomembranes》2017,49(1):113-119
Calcium (Ca2+) plays diverse roles in all living organisms ranging from bacteria to humans. It is a structural element for bones, an essential mediator of excitation-contraction coupling, and a universal second messenger in the regulation of ion channel, enzyme and gene expression activities. In mitochondria, Ca2+ is crucial for the control of energy production and cellular responses to metabolic stress. Ca2+ uptake by the mitochondria occurs by the uniporter mechanism. The Mitochondrial Ca2+ Uniporter (MCU) protein has recently been identified as a core component responsible for mitochondrial Ca2+ uptake. MCU knockout (MCU KO) studies have identified a number of important roles played by this high capacity uptake pathway. Interestingly, this work has also shown that MCU-mediated Ca2+ uptake is not essential for vital cell functions such as muscle contraction, energy metabolism and neurotransmission. Although mitochondrial Ca2+ uptake was markedly reduced, MCU KO mitochondria still contained low but detectable levels of Ca2+. In view of the fundamental importance of Ca2+ for basic cell signalling, this finding suggests the existence of other currently unrecognized pathways for Ca2+ entry. We review the experimental evidence for the existence of alternative Ca2+ influx mechanisms and propose how these mechanisms may play an integral role in mitochondrial Ca2+ signalling. 相似文献
2.
Bucking C Wood CM 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2007,177(3):349-360
A diet containing an inert marker (ballotini beads, quantified by X-radiography) was used to quantify the transport of two
essential minerals, Ca2+ and Mg2+ from the diet during the digestion and absorption of a single meal of commercial trout food (3% ration). Initially, net uptake
of Ca2+ was observed in the stomach followed by subsequent Ca2+ fluxes along the intestine which were variable, but for the most part secretory. This indicated a net secretion of Ca2+ along the intestinal tract resulting in a net assimilation of dietary Ca2+ of 28%. Similar handling of Ca2+ and Mg2+ was observed along the gastrointestinal tract (GI), although net assimilation differed substantially between the cations,
with Mg2+ assimilation being close to 60%, mostly a result of greater uptake by the stomach. The stomach displayed the highest net
uptake rates for both cations (1.5 and 1.3 mmol kg−1 fish body mass for Ca2+ and Mg2+, respectively), occurring within 2 h following ingestion of the meal. Substantial secretions of both Ca2+ and Mg2+ were observed in the anterior intestine, which were attributed to bile and other intestinal secretions, while fluxes in the
mid and posterior intestine were small and variable. The overall patterns of Ca2+ and Mg2+ handling in the GI tract were similar to those observed for Na+ and K+ (but not Cl−) in a previous study. Overall, these results emphasize the importance of dietary electrolytes in ionoregulatory homeostasis. 相似文献
3.
M. Yu. Skorkina 《Journal of Evolutionary Biochemistry and Physiology》2012,48(2):147-151
The kinetics of cell osmoregulatory reactions under conditions of activation and blockade of Ca2+-channels was studied on a model of frog polyfunctional nucleated erythrocytes. Both activation and blockade of Ca2+-channels has been established to promote swelling of nuclei and an increase of the nucleocytoplasmic ratios under conditions of hypotonic exposure. The osmoregulatory cell reactions after activation of Ca2+-channels are manifested as a decrease of the cell volume. The blocker of Ca2+-channels verapamil produces a transitory increase and decrease of the erythrocyte volume with time intervals of 30 and 60 s. The clearly expressed functional activity of the nuclear membrane in response to the hypotonic action under conditions of activation and blockade of Ca2+-channels indicates participation of Ca2+ ions in mechanisms of the nucleocytoplasmic transfer. 相似文献
4.
Hongzhong Chen Liwen Wang Tetsuo Takano Shenkui Liu Xinxin Zhang 《Acta Physiologiae Plantarum》2016,38(4):94
Cation/H+ exchangers (CAXs) are membrane proteins that transport Ca2+ and other cations using the H+ gradient generated by H+-ATPase or H+-pyrophosphatase. This study reports the characterization of CAX2 from Puccinellia tenuiflora with respect to molecular and functional properties. PutCAX2 was cloned from a cDNA library of P. tenuiflora seedlings. The expression of PutCAX2 in shoots and roots was induced by Ca2+ and Ba2+ treatments. A green fluorescent protein (GFP) marker revealed that PutCAX2 was located on the endoplasmic reticulum (ER) membrane. Four yeast transformants were created using GFP fusion PutCAX2 and truncated PutCAX2s, and their growth in the presence of various cations (Fe3+, Al3+, Mn2+, Cu2+, Co2+, Ni2+, Mg2+, Zn2+, Na+, Li+, Ca2+, and Ba2+) was analyzed. The N-terminally truncated PutCAX2 (GFP-ΔNPutCAX2) and the N and C-terminally truncated PutCAX2 (GFP-ΔNCPutCAX2) transformants grew well in the presence of 100 and 150 mM Ca2+ or 8 and 20 mM Ba2+, whereas the GFP-PutCAX2 and C-terminally truncated PutCAX2 (GFP-ΔCPutCAX2) transformants did not show any tolerance to Ca2+ or Ba2+. The Ba2+ content in whole yeast cells expressing GFP-ΔNPutCAX2 or GFP-ΔNCPutCAX2 was lower than that in other yeast transformants. Moreover, the efflux experiment showed that the Ba2+ efflux rate of yeast cells expressing GFP-ΔNPutCAX2 and GFP-ΔNCPutCAX2 was higher than that of other yeast cells. To our knowledge, this is the first report on the molecular and functional characterization of a novel ER-localized CAX protein from a wild halophyte plant; the results suggest that the N-terminus of PutCAX2 acts as an auto-inhibitory domain, which affects the Ca2+ and Ba2+ tolerance of yeast. 相似文献
5.
We have previously characterized the “RCA” channel (root Ca2+ channel), a voltage-dependent, Ca2+-permeable channel found in plasma membrane-enriched vesicles from wheat roots incorporated into artificial planar lipid bilayers.
Earlier work indicated that this channel was insensitive to 1,4-dihydropyridines (DHPs, such as nifedipine and 202–791). However,
the present study shows that this channel is sensitive to DHPs, but only with submillimolar Ca2+, when the probability of channel opening is reduced, with flickery closures becoming increasingly evident as Ca2+ activity decreases. Under these ionic conditions, addition of nanomolar concentrations of (+) 202–791 or nifedipine caused
an increase in both the probability of channel opening and the unitary conductance. It is proposed that there is a competitive
interaction between Ca2+ and DHPs at one of the Ca2+-binding sites involved in Ca2+ permeation and that binding of a DHP to one of the Ca2+-permeation sites facilitates movement of other calcium ions through the channel. The present study shows that higher plant
Ca2+-permeable channels can be greatly affected by very low concentrations of DHPs and that channel sensitivity may vary with
the ionic conditions of the experiment. The results also indicate interesting structural and functional differences between
plant and animal Ca2+-permeable channels. 相似文献
6.
Powered by the mitochondrial membrane potential, Ca2+ permeates the mitochondria via a Ca2+ channel termed Ca2+ uniporter and is pumped out by a Na+/Ca2+ exchanger, both of which are located on the inner mitochondrial membrane. Mitochondrial Ca2+ transients are critical for metabolic activity and regulating global Ca2+ responses. On the other hand, failure to control mitochondrial Ca2+ is a hallmark of ischemic and neurodegenerative diseases. Despite their importance, identifying the uniporter and exchanger remains elusive and their inhibitors are non-specific. This review will focus on the mitochondrial exchanger, initially describing how it was molecularly identified and linked to a novel member of the Na+/Ca2+ exchanger superfamily termed NCLX. Molecular control of NCLX expression provides a selective tool to determine its physiological role in a variety of cell types. In lymphocytes, NCLX is essential for refilling the endoplasmic reticulum Ca2+ stores required for antigendependent signaling. Communication of NCLX with the store-operated channel in astroglia controls Ca2+ influx and thereby neuro-transmitter release and cell proliferation. The refilling of the Ca2+ stores in the sarcoplasmic reticulum, which is controlled by NCLX, determines the frequency of action potential and Ca2+ transients in cardiomyocytes. NCLX is emerging as a hub for integrating glucose-dependent Na+ and Ca2+ signaling in pancreatic β cells, and the specific molecular control of NCLX expression resolved the controversy regarding its role in neurons and β cells. Future studies on an NCLX knockdown mouse model and identification of human NCLX mutations are expected to determine the role of mitochondrial Ca2+ efflux in organ activity and whether NCLX inactivation is linked to ischemic and/or neurodegenerative syndromes. Structure-function analysis and protein analysis will identify the NCLX mode of regulation and its partners in the inner membrane of the mitochondria. 相似文献
7.
Mechanism of luminal Ca<Superscript>2+</Superscript> and Mg<Superscript>2+</Superscript> action on the vacuolar slowly activating channels 总被引:2,自引:0,他引:2
The non-selective slow vacuolar (SV) channel can dominate tonoplast conductance, making it necessary to tightly control its activity. Applying the patch-clamp technique to vacuoles from sugar beet (Beta vulgaris L.) taproots we studied the effect of divalent cations on the vacuolar side of the SV channel. Our results show that the SV channel has two independent binding sites for vacuolar divalent cations, (i) a less selective one, inside the channel pore, binding to which impedes channel conductance, and (ii) a Ca2+-selective one outside the membrane-spanning part of the channel protein, binding to which stabilizes the channels closed conformations. Vacuolar Ca2+ and Mg2+ almost indiscriminately blocked ion fluxes through the open channel pore, decreasing measured single-channel current amplitudes. This low-affinity block displays marked voltage dependence, characteristic of a permeable blocker. Vacuolar Ca2+—with a much higher affinity than Mg2+—slows down SV channel activation and shifts the voltage dependence to more (cytosol) positive potentials. A quantitative analysis results in a model that exactly describes the Ca2+-specific effects on the SV channel activation kinetics and voltage gating. According to this model, multiple (approximately three) divalent cations bind with a high affinity at the luminal interface of the membrane to the channel protein, favoring the occupancy of one of the SV channels closed states (C2). Transition to another closed state (C1) diminishes the effective number of bound cations, probably due to mutual repulsion, and channel opening is accompanied by a decrease of binding affinity. Hence, the open state (O) is destabilized with respect to the two closed states, C1 and C2, in the presence of Ca2+ at the vacuolar side. The specificity for Ca2+ compared to Mg2+ is explained in terms of different binding affinities for these cations. In this study we demonstrate that vacuolar Ca2+ is a crucial regulator to restrict SV channel activity to a physiologically meaningful range, which is less than 0.1% of maximum SV channel activity.Abbreviation SV Slow vacuolar 相似文献
8.
Recent evidence highlights the functional importance of the Golgi apparatus (GA) in neurological diseases. The functions of
the mammalian GA, in addition to the processing and transport of cargo, also include ionic homeostasis. Besides Ca2+-release channels which serves GA as an agonist-sensitive intracellular Ca2+ store, and Ca2+-binding proteins, the GA contains Ca2+-uptake mechanisms consisting of the well-known sarco-endoplasmic reticulum Ca2+-transport ATPases and the much less characterized secretory-pathway Ca2+-transport ATPases (SPCA). SPCA can transport both Ca2+ and Mn2+ into the Golgi lumen and therefore is involved in the cytosolic and intra-Golgi Ca2+ and Mn2+ homeostasis. It has shown that both of the mRNA and protein of SPCAs are highly expressed in brain. In addition, brain is
the region with the highest activity of SPCA isoforms, which may be related to the involvement of Ca2+ and Mn2+ homeostasis in neural functions. In this review, we compile some recent findings showing that the SPCA isoform plays a much
more important role in intracellular ionic homeostasis than previously anticipated and illustrating the involvement of SPCA
isoforms in certain neurophysiological or neuropathological process. We are interested in gaining insight into the intricate
role of the SPCA pumps to explain the GA-specific functions in neurological disorders. 相似文献
9.
Díaz D Bartolo R Delgadillo DM Higueldo F Gomora JC 《The Journal of membrane biology》2005,207(2):91-105
Inorganic ions have been used widely to investigate biophysical properties of high voltage-activated calcium channels (HVA:
Cav1 and Cav2 families). In contrast, such information regarding low voltage-activated calcium channels (LVA: Cav3 family) is less documented. We have studied the blocking effect of Cd2+, Co2+ and Ni2+ on T-currents expressed by human Cav3 channels: Cav3.1, Cav3.2, and Cav3.3. With the use of the whole-cell configuration of the patch-clamp technique, we have recorded Ca2+ (2 mM) currents from HEK−293 cells stably expressing recombinant T-type channels. Cd2+ and Co2+ block was 2- to 3-fold more potent for Cav3.2 channels (EC50 = 65 and 122 μM, respectively) than for the other two LVA channel family members. Current-voltage relationships indicate
that Co2+ and Ni2+ shift the voltage dependence of Cav3.1 and Cav3.3 channels activation to more positive potentials. Interestingly, block of those two Cav3 channels by Co2+ and Ni2+ was drastically increased at extreme negative voltages; in contrast, block due to Cd2+ was significantly decreased. This unblocking effect was slightly voltage-dependent. Tail-current analysis reveals a differential
effect of Cd2+ on Cav3.3 channels, which can not close while the pore is occupied with this metal cation. The results suggest that metal cations
affect differentially T-type channel activity by a mechanism involving the ionic radii of inorganic ions and structural characteristics
of the channels pore. 相似文献
10.
Jiayu Liu Yufan Niu Jingjing Zhang Yuqing Zhou Zheng Ma Xuan Huang 《Plant Cell, Tissue and Organ Culture》2018,132(3):413-424
Calcium (Ca2+) signals are essential transducers and regulators in many adaptive and developmental processes in plants. Protective responses of plants to a variety of environmental stress factors are mediated by transient changes of Ca2+ concentration in plant cells. Ca2+ ions are quickly transported by channel proteins present on the plasma membrane. During responses to external stimuli, various signal molecules are transported directly from extracellular to intracellular compartments via Ca2+ channel proteins. Three types of Ca2+ channels have been identified in plant cell membranes: voltage-dependent Ca2+-permeable channels (VDCCs), which is sorted to depolarization-activated Ca2+-permeable channels (DACCs) and hyperpolarization-activated Ca2+-permeable channels (HACCs), voltage-independent Ca2+-permeable channels (VICCs). They make functions in the abiotic stress such as TPCs, CNGCs, MS channels, annexins which distribute in the organelles, plasma membrane, mitochondria, cytosol, intracelluar membrane. This review summarizes recent advances in our knowledge of many types of Ca2+ channels and Ca2+ signals involved in abiotic stress resistance and responses in plant cells. 相似文献
11.
The mitochondrial permeability transition pore was originally described in the 1970’s as a Ca2+ activated pore and has since been attributed to the pathogenesis of many diseases. Here we evaluate how each of the current models of the pore complex fit to what is known about how Ca2+ regulates the pore, and any insight that provides into the molecular identity of the pore complex. We also discuss the central role of Ca2+ in modulating the pore’s open probability by directly regulating processes, such as ATP/ADP balance through the tricarboxylic acid cycle, electron transport chain, and mitochondrial membrane potential. We review how Ca2+ influences second messengers such as reactive oxygen/nitrogen species production and polyphosphate formation. We discuss the evidence for how Ca2+ regulates post-translational modification of cyclophilin D including phosphorylation by glycogen synthase kinase 3 beta, deacetylation by sirtuins, and oxidation/ nitrosylation of key residues. Lastly we introduce a novel view into how Ca2+ activated proteolysis through calpains in the mitochondria may be a driver of sustained pore opening during pathologies such as ischemia reperfusion injury. 相似文献
12.
The anoxia-dependent elevation of cytosolic Ca2+ concentration, [Ca2+]cyt, was investigated in plants differing in tolerance to hypoxia. The [Ca2+]cyt was measured by fluorescence microscopy in single protoplasts loaded with the calcium-fluoroprobe Fura 2-AM. Imposition of
anoxia led to a fast (within 3 min) significant elevation of [Ca2+]cyt in rice leaf protoplasts. A tenfold drop in the external Ca2+ concentration (to 0.1 mM) resulted in considerable decrease of the [Ca2+]cyt shift. Rice root protoplasts reacted upon anoxia with higher amplitude. Addition of plasma membrane (verapamil, La3+ and EGTA) and intracellular membrane Ca2+-channel antagonists (Li+, ruthenium red and cyclosporine A) reduced the anoxic Ca2+-accumulation in rice. Wheat protoplasts responded to anoxia by smaller changes of [Ca2+]cyt. In wheat leaf protoplasts, the amplitude of the Ca2+-shift little depended on the external level of Ca2+. Wheat root protoplasts were characterized by a small shift of [Ca2+]cyt under anoxia. Plasmalemma Ca2+-channel blockers had little effect on the elevation of cytosolic Ca2+ in wheat protoplasts. Intact rice seedlings absorbed Ca2+ from the external medium under anoxic treatment. On the contrary, wheat seedlings were characterized by leakage of Ca2+. Verapamil abolished the Ca2+ influx in rice roots and Ca2+ efflux from wheat roots. Anoxia-induced [Ca2+]cyt elevation was high particularly in rice, a hypoxia-tolerant species. In conclusion, both external and internal Ca2+ stores are important for anoxic [Ca2+]cyt elevation in rice, whereas the hypoxia-intolerant wheat does not require external sources for [Ca2+]cyt rise. Leaf and root protoplasts similarly responded to anoxia, independent of their organ origin. 相似文献
13.
Derek R. Laver 《Biophysical reviews》2018,10(4):1087-1095
Ryanodine receptors (RyRs) are the Ca2+ release channels in the sarcoplasmic reticulum in striated muscle which play an important role in excitation-contraction coupling and cardiac pacemaking. Single channel recordings have revealed a wealth of information about ligand regulation of RyRs from mammalian skeletal and cardiac muscle (RyR1 and RyR2, respectively). RyR subunit has a Ca2+ activation site located in the luminal and cytoplasmic domains of the RyR. These sites synergistically feed into a common gating mechanism for channel activation by luminal and cytoplasmic Ca2+. RyRs also possess two inhibitory sites in their cytoplasmic domains with Ca2+ affinities of the order of 1 μM and 1 mM. Magnesium competes with Ca2+ at these sites to inhibit RyRs and this plays an important role in modulating their Ca2+-dependent activity in muscle. This review focuses on how these sites lead to RyR modulation by Ca2+ and Mg2+ and how these mechanisms control Ca2+ release in excitation-contraction coupling and cardiac pacemaking. 相似文献
14.
Intracellular Ca2+ is vital for cell physiology. Disruption of Ca2+ homeostasis contributes to human diseases such as heart failure, neuron-degeneration, and diabetes. To ensure an effective
intracellular Ca2+ dynamics, various Ca2+ transport proteins localized in different cellular regions have to work in coordination. The central role of mitochondrial
Ca2+ transport mechanisms in responding to physiological Ca2+ pulses in cytosol is to take up Ca2+ for regulating energy production and shaping the amplitude and duration of Ca2+ transients in various micro-domains. Since the discovery that isolated mitochondria can take up large quantities of Ca2+ approximately 5 decades ago, extensive studies have been focused on the functional characterization and implication of ion
channels that dictate Ca2+ transport across the inner mitochondrial membrane. The mitochondrial Ca2+ uptake sensitive to non-specific inhibitors ruthenium red and Ru360 has long been considered as the activity of mitochondrial
Ca2+ uniporter (MCU). The general consensus is that MCU is dominantly or exclusively responsible for the mitochondrial Ca2+ influx. Since multiple Ca2+ influx mechanisms (e.g. L-, T-, and N-type Ca2+ channel) have their unique functions in the plasma membrane, it is plausible that mitochondrial inner membrane has more than
just MCU to decode complex intracellular Ca2+ signaling in various cell types. During the last decade, four molecular identities related to mitochondrial Ca2+ influx mechanisms have been identified. These are mitochondrial ryanodine receptor, mitochondrial uncoupling proteins, LETM1
(Ca2+/H+ exchanger), and MCU and its Ca2+ sensing regulatory subunit MICU1. Here, we briefly review recent progress in these and other reported mitochondrial Ca2+ influx pathways and their differences in kinetics, Ca2+ dependence, and pharmacological characteristics. Their potential physiological and pathological implications are also discussed. 相似文献
15.
I. V. Shemarova V. P. Nesterov 《Journal of Evolutionary Biochemistry and Physiology》2007,43(2):135-144
The review considers Ca2+-messenger systems in primitive multicellulars (sponges and hydrozoa organisms). Analysis is performed of Ca2+ participation in regulation of early development of the organisms, their mobility, metamorphosis, chemoreception, and some other functions. 相似文献
16.
Nicotinic acid dinucleotide phosphate (NAADP) is unique amongst Ca2+ mobilizing messengers in that its principal function is to mobilize Ca2+ from acidic organelles. Early studies indicated that it was likely that NAADP activates a novel Ca2+ release channel distinct from the well characterized Ca2+ release channels on the (sarco)-endoplasmic reticulum (ER), inositol trisphosphate and ryanodine receptors. In this review,
we discuss the emergence of a novel family of endolysosomal channels, the two-pore channels (TPCs), as likely targets for
NAADP, and how molecular and pharmacological manipulation of these channels is enhancing our understanding of the physiological
roles of NAADP as an intracellular Ca2+ mobilizing messenger. 相似文献
17.
E. I. Khoroshavina M. V. Dubinin A. V. Khokhlov V. N. Samartsev 《Biochemistry (Moscow) Supplemental Series A: Membrane and Cell Biology》2018,12(2):128-136
The effect of bile acids as inducers of Ca2+ efflux from the matrix was studied on isolated rat liver mitochondria. Mitochondria in the presence of cyclosporin A (CsA) were energized by succinate, then loaded with Ca2+ and after the addition of the calcium uniporter inhibitor ruthenium red were de-energized by malonate. It was shown that under these conditions hydrophobic bile acids lithocholic and chenodeoxycholic at concentrations of 10 and 30 μM respectively and hydrophilic bile acids ursodeoxycholic and cholic at a concentration of 400 μM induce Ca2+ efflux from the mitochondrial matrix. It is noted that the efflux of these ions is not associated with damage of the inner mitochondrial membrane by bile acids, since it is accompanied by the generation of Δψ, i.e., the formation of the diffusion potential. It is assumed that along with induction of calcium efflux from the matrix, bile acids are also capable of transporting hydrogen and potassium ions in the opposite direction, i.e., perform H+/Ca2+ and K+/Ca2+ exchange. It was found that ruthenium red added to Ca2+-loaded energized mitochondria prevents the return of these ions to the matrix and weakens the effect of chenodeoxycholic acid as an inducer of the CsA-sensitive mitochondrial pore and the effect of ursodeoxycholic acid as an inducer of CsA-insensitive permeability of the inner mitochondrial membrane. We conclude that in the conditions of the calcium uniporter activity decrease, Ca2+ efflux from the matrix induced by bile acids can be considered as one of the mechanisms reducing their effectiveness as inducers of the Ca2+-dependent CsA-sensitive pore and CsA-insensitive permeability transition in mitochondria. 相似文献
18.
The clustering of cardiac RyR mutations, linked to sudden cardiac death (SCD), into several regions in the amino acid sequence
underlies the hypothesis that these mutations interfere with stabilising interactions between different domains of the RyR2.
SCD mutations cause increased channel sensitivity to cytoplasmic and luminal Ca2+. A synthetic peptide corresponding to part of the central domain (DPc10:2460G–P2495) was designed to destabilise the interaction of the N-terminal and central domains of wild-type RyR2 and mimic the effects
of SCD mutations. With Ca2+ as the sole regulating ion, DPc10 caused increased channel activity which could be reversed by removal of the peptide whereas
in the presence of ATP DPc10 caused no activation. In support of the domain destablising hypothesis, the corresponding peptide
(DPc10-mut) containing the CPVT mutation R2474S did not affect channel activity under any circumstances. DPc10-induced activation
was due to a small increase in RyR2 sensitivity to cytoplasmic Ca2+ and a large increase in the magnitude of luminal Ca2+ activation. The increase in the luminal Ca2+ response appeared reliant on the luminal-to-cytoplasmic Ca2+ flux in the channel, indicating that luminal Ca2+ was activating the RyR2 via its cytoplasmic Ca2+ sites. DPc10 had no significant effect on the RyR2 gating associated with luminal Ca2+ sensing sites. The results were fitted by the luminal-triggered Ca2+ feed-through model and the effects of DPc10 were explained entirely by perturbations in cytoplasmic Ca2+-activation mechanism. 相似文献
19.
Summary Neuropeptide tachykinins, present within sensory nerves, have been implicated as neurotransmitters involved in nonadrenergic and noncholinergic airway muscle contraction. The signal transduction pathways of tachykinins on muscle contraction and Ca2+ mobilization were investigated in swine trachea. Tachykinins, substance P (SP) and neurokinin A (NKA), concentration (1 nM to 1 μM)-dependently induced contractile responses with removal of epithelium, whereas neurokinin B (NKB) did not alter the muscle tension. The SP- and NKA-evoked muscle contractions were inhibited by NK1-R antagonist L732138, but not by either NK2-R antagonist MDL29913 or NK3-R antagonist SB218795. Consistently, SP-elicited increase in [Ca2+]i was abolished by NK1-R antagonist, neither by NK2-R nor NK3-R antagonists. The SP-induced muscular responses were significantly inhibited by L-type Ca2+ channel blocker verapamil and withdrawal of external Ca2+. Caffeine (10 mM) or ryanodine (50 μM) also partly suppressed the SP-induced muscle responses. Inhibition of inositol 1,4,5-trisphosphate (InsP3) receptor with 2-APB (75 μM) potently attenuated SP-evoked Ca2+ mobilization and muscle contraction, which was further inhibited by 2-APB under Ca2+-free external solution, but not completely. Unexpectedly, simultaneous blockade of InsP3 receptor and ryanodine receptor (RyR) by 2-APB and ryanodine enhanced SP-evoked muscle contraction and Ca2+ mobilization. This potentiation was virtually abolished by removal of external Ca2+, suggesting native Ca2+ channels may contribute to this phenomenon. These results demonstrate that tachykinins produce a potent muscle contraction associated with Ca2+ mobilization via tachykinin NK1- R-dependent activation of multiple signal transduction pathways involving Ca2+ influx and release of Ca2+ from InsP3- and ryanodine-sensitive Ca2+ stores. Blockade of both InsP3 receptor and RyR enhances the Ca2+ influx through native Ca2+ channels in plasma membrane, which is crucial to Ca2+ signaling in response to NK1 receptor activation. 相似文献
20.
Much less attention has been paid to Zn2+ in artificial cerebrospinal fluid (ACSF), i.e., extracellular medium, used for in vitro slice experiments than divalent cations such as Ca2+. Approximately 2 mM Ca2+ is added to conventional ACSF from essentiality of Ca2+ signaling in neurons and glial cells. However, no Zn2+ is added to it, even though the importance of Zn2+ signaling in them is recognizing. On the other hand, synaptic Zn2+ homeostasis is changed during brain slice preparation. Therefore, it is possible that not only neuronal excitation but also synaptic plasticity such as long-term potentiation is modified in ACSF without Zn2+, in which original physiology might not appear. The basal (static) levels of intracellular (cytosolic) Zn2+ and Ca2+ are not significantly different between brain slices prepared with conventional ACSF without Zn2+ and pretreated with ACSF containing 20 nM ZnCl2 for 1 h. In the case of mossy fiber excitation, however, presynaptic activity assessed with FM 4–64 is significantly suppressed in the stratum lucidum of brain slices pretreated with ACSF containing Zn2+, indicating that hippocampal excitability is enhanced in brain slices prepared with ACSF without Zn2+. The evidence suggests that low nanomolar concentration of Zn2+ is necessary for ACSF. Furthermore, exogenous Zn2+ has opposite effect on LTP induction between in vitro and in vivo experiments. It is required to pay attention to extracellular Zn2+ concentration to understand synaptic function precisely. 相似文献