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1.
Senin II Tikhomirova NK Churumova VA Grigoriev II Kolpakova TA Zinchenko DV Philippov PP Zernii EY 《Biochemistry. Biokhimii?a》2011,76(3):332-338
Antibodies AB60–72 and AB80–92 against two immune-dominant epitopes of photoreceptor Ca2+-binding protein recoverin, 60-DPKAYAQHVFRSF-72 and 80-LDFKEYVIALHMT-92, which can be exposed in a Ca2+-dependent manner, were obtained. The presence of AB60–72 or AB80–92 results in a slight increase in Ca2+-affinity of recoverin and does not affect significantly a Ca2+-myristoyl switch mechanism of the protein. However in the presence of AB60–72 or AB80–92 recoverin loses its ability to interact with rhodopsin kinase and consequently to perform a function of Ca2+-sensitive inhibitor of rhodopsin phosphorylation in photoreceptor cells. 相似文献
2.
Elizabeth Zubrzycka-Gaarn Glen MacDonald Laurie Phillips Annelise O. Jorgensen David H. MacLennan 《Journal of bioenergetics and biomembranes》1984,16(5-6):441-464
In order to determine whether polymorphic forms of the Ca2+ + Mg2+-dependent ATPase exist, we have examined the cross-reactivity of five monoclonal antibodies prepared against the rabbit skeletal muscle sarcoplasmic reticulum enzyme with proteins from microsomal fractions isolated from a variety of muscle and nonmuscle tissues. All of the monoclonal antibodies cross-reacted in immunoblots against rat skeletal muscle Ca2+ + Mg2+-dependent ATPase but they cross-reacted differentially with the enzyme from chicken skeletal muscle. No cross-reactivity was observed with the Ca2+ + Mg2+-dependent ATPase of lobster skeletal muscle. The pattern of antibody cross-reactivity with a 100,000 dalton protein from sarcoplasmic reticulum and microsomes isolated from various muscle and nonmuscle tissues of rabbit demonstrated the presence of common epitopes in multiple polymorphic forms of the Ca2+ + Mg2+-dependent ATPase. One of the monoclonal antibodies prepared against the purified Ca2+ + Mg2+-dependent ATPase of rabbit skeletal muscle sarcoplasmic reticulum was found to cross-react with calsequestrin and with a series of other Ca2+-binding proteins and their proteolytic fragments. Its cross-reactivity was enhanced in the presence of EGTA and diminished in the presence of Ca2+. Its lack of cross-reactivity with proteins that do not bind Ca2+ suggests that it has specificity for antigenic determinants that make up the Ca2+-binding sites in several Ca2+-binding proteins including the Ca2+ + Mg2+-dependent ATPase.This paper is dedicated to the memory of Dr. David E. Green. 相似文献
3.
Visinin-like protein (VILIP-1) belongs to the neuronal Ca2+ sensor family of EF-hand Ca2+-binding proteins that regulate a variety of Ca2+-dependent signal transduction processes in neurons. It is an interaction partner of α4β2 nicotinic acetylcholine receptor
(nAChR) and increases surface expression level and agonist sensitivity of the receptor in oocytes. Nicotine stimulation of
nicotinic receptors has been reported to lead to an increase in intracellular Ca2+ concentration by Ca2+-permeable nAChRs, which in turn might lead to activation of VILIP-1, by a mechanism described as the Ca2+-myristoyl switch. It has been postulated that this will lead to co-localization of the proteins at cell membranes, where
VILIP-1 can influence functional activity of α4-containing nAChRs.
In order to test this hypothesis we have investigated whether a nicotine-induced and reversible Ca2+-myristoyl switch of VILIP-1 exists in primary hippocampal neurons and whether pharmacological agents, such as antagonist
specific for distinct nAChRs, can interfere with the Ca2+-dependent membrane localization of VILIP-1.
Here we report, that only α7- but not α4-containing nAChRs are able to elicit a Ca2+-dependent and reversible membrane-translocation of VILIP-1 in interneurons as revealed by employing the specific receptor
antagonists dihydro-beta-erythroidine and methylallylaconitine.
The nAChRs are associated with processes of synaptic plasticity in hippocampal neurons and they have been implicated in the
pathology of CNS disorders, including Alzheimer’s disease and schizophrenia. VILIP-1 might provide a novel functional crosstalk
between α4- and α7-containing nAChRs. 相似文献
4.
O. V. Kozlova S. Yu. Egorov F. G. Kupriyanova-Ashina Nick Rid G. I. El’-Registan 《Microbiology》2004,73(6):629-634
Using the mutant strain Aspergillus awamori 66A, producing the recombinant Ca2+-dependent photosensitive protein aequorin, the dynamics of Ca2+ was studied for the first time in the cytosol of micromycetes exposed to stressful factors, such as an increase in extracellular Ca2+ to 50 mM, hypoosmotic shock, and mechanical shock. The cell response to stress proved to involve an increase in the Ca2+ concentration in the cytosol, which was determined from the amplitude of aequorin luminescence and the time of the amplitude enhancement and relaxation. The level of the Ca2+ response depended on the physiological stimulus. Inhibitory analysis with various agents that block Ca2+ channels and with agonists that specifically enhance the activity of the channels suggested that (1) the level of Ca2+ in the cytosol of micromycetes increases in response to stress because of the ion influx from both the growth medium and intracellular reservoirs and (2) potential-dependent transport systems play the major role in the Ca2+ influx into the cytosol of the micromycete cells.Translated from Mikrobiologiya, Vol. 73, No. 6, 2004, pp. 734–740.Original Russian Text Copyright © 2004 by Kozlova, Egorov, Kupriyanova-Ashina, Rid, El-Registan. 相似文献
5.
Mironova GD Belosludtsev KN Belosludtseva NV Gritsenko EN Khodorov BI Saris NE 《Journal of bioenergetics and biomembranes》2007,39(2):167-174
Earlier we found that in isolated rat liver mitochondria the reversible opening of the mitochondrial cyclosporin A-insensitive
pore induced by low concentrations of palmitic acid (Pal) plus Ca2+ results in the brief loss of Δψ [Mironova et al., J Bioenerg Biomembr (2004), 36:171–178]. Now we report that Pal and Ca2+, increased to 30 and 70 nmol/mg protein respectively, induce a stable and prolonged (10 min) partial depolarization of the
mitochondrial membrane, the release of Ca2+ and the swelling of mitochondria. Inhibitors of the Ca2+ uniporter, ruthenium red and La3+, as well as EGTA added in 10 min after the Pal/Ca2+-activated pore opening, prevent the release of Ca2+ and repolarize the membrane to initial level. Similar effects can be observed in the absence of exogeneous Pal, upon mitochondria
accumulating high [Sr2+], which leads to the activation of phospholipase A2 and appearance of endogenous fatty acids. The paper proposes a new model of the mitochondrial Ca2+ cycle, in which Ca2+ uptake is mediated by the Ca2+ uniporter and Ca2+ efflux occurs via a short-living Pal/Ca2+-activated pore. 相似文献
6.
O. V. Kozlova F. G. Kupriyanova-Ashina S. Yu. Egorov G. I. El’-Registan 《Microbiology》2004,73(6):635-642
The microbial alkylhydroxybenzenes (AHB), which are anabiosis autoinducers also termed d1 factors, participate in the stress response of mycelial fungi, as determined from changes in intracellular Ca2+ concentration. By using the genetically modified strain Aspergillus awamori 66A, which produces the recombinant Ca2+-dependent protein aequorin, the dynamics of Ca2+ was studied in the cytosol of cells exposed to mechanical shock in the presence of protective doses (0.001–0.01% w/vol) of a chemical AHB analogue, 4-n-hexylresorcinol. As under stressful conditions, Ca2+ concentration increases in the cell cytosol in response to an enhanced AHB level in a growing fungal culture; thus, AHB is perceived by cells as a stress signal. The level of cell response, which was determined from the amplitude of luminescence dependent on the Ca2+ concentration in the cytosol, was related to the physiological age of the cells and the AHB concentration. Micromycete preincubation with AHB was found to protect cells from subsequent stress; this was reflected in the Ca2+ response. The protective AHB effect was manifested as (1) a significant decrease in the amplitude of luminescence and, thus, in Ca2+ accumulation in the cytosol during subsequent mechanical stress (as compared to the control—mechanical stress only); (2) development of a secondary Ca2+ response, which was not observed in the control; and (3) a high level of Ca2+ retained in the cytosol for a long time in the presence of AHB (as compared to the control without preincubation with AHB). The mechanisms underlying the AHB effect on Ca2+ transport systems are discussed.Translated from Mikrobiologiya, Vol. 73, No. 6, 2004, pp. 741–750.Original Russian Text Copyright © 2004 by Kozlova, Kupriyanova-Ashina, Egorov, El-Registan. 相似文献
7.
V. N. Uversky S. E. Permyakov I. I. Senin A. M. Cherskaya S. V. Shulga-Morskoy D. V. Zinchenko A. M. Alekseev A. A. Zargarov V. M. Lipkin P. P. Philippov E. A. Permyakov 《Russian Journal of Bioorganic Chemistry》2000,26(3):152-156
The structural properties of myristoylated forms of recombinant recoverin of the wild type and of its mutants with damaged
second and/or third Ca2+-binding sites were studied by fluorimetry and circular dichroism. The interaction of wild-type recoverin with calcium ions
was shown to induce unusual structural rearrangements in its molecule. In particular, protein binding with Ca2+ ions results in an increase in the mobility of the environment of Trp residues, in hydrophobicity, and in thermal stability
(its thermal transition shifts by 15°C to higher temperatures) but has almost no effect on its secondary structure. Similar
structural changes induced by Ca2+ are also characteristic of the -EF2 mutant of recoverin whose second Ca2+-binding site is modified and cannot bind calcium ions. The structural properties of the -EF3 and -EF2,3 mutants (whose third
or simultaneously second and third Ca2+-binding sites, respectively, are modified and damaged) are practically indifferent to the presence of calcium ions.
For the communication I, see [1]. 相似文献
8.
Effects of intracellular Mg2+ on a native Ca2+-and voltage-sensitive large-conductance K+ channel in cultured human renal proximal tubule cells were examined with the patch-clamp technique in the inside-out mode.
At an intracellular concentration of Ca2+ ([Ca2+]i) of 10−5–10−4 M, addition of 1–10 mM Mg2+ increased the open probability (Po) of the channel, which shifted the Po –membrane potential (Vm) relationship to the negative voltage direction without causing an appreciable change in the gating charge (Boltzmann constant).
However, the Mg2+-induced increase in Po was suppressed at a relatively low [Ca2+]i (10−5.5–10−6 M). Dwell-time histograms have revealed that addition of Mg2+ mainly increased Po by extending open times at 10−5 M Ca2+ and extending both open and closed times simultaneously at 10−5.5 M Ca2+. Since our data showed that raising the [Ca2+]i from 10−5 to 10−4 M increased Po mainly by shortening the closed time, extension of the closed time at 10−5.5 M Ca2+ would result from the Mg2+-inhibited Ca2+-dependent activation. At a constant Vm, adding Mg2+ enhanced the sigmoidicity of the Po–[Ca2+]i relationship with an increase in the Hill coefficient. These results suggest that the major action of Mg2+ on this channel is to elevate Po by lengthening the open time, while extension of the closed time at a relatively low [Ca2+]i results from a lowering of the sensitivity to Ca2+ of the channel by Mg2+, which causes the increase in the Hill coefficient.
M. Kubokawa and Y. Sohma contributed equally to this work. 相似文献
9.
S. E. Permyakov V. N. Uverskii A. M. Cherskaya S. V. Shulga-Morskoy D. V. Zinchenko A. M. Alekseev E. Yu. Zernii A. A. Zargarov I. I. Senin V. M. Lipkin P. P. Philippov E. A. Permyakov 《Russian Journal of Bioorganic Chemistry》2000,26(4):257-261
Unlike wild type recoverin with only two (the second and the third) functioning Ca+2-binding sites out of four potential ones, the +EF4 mutant contains a third active Ca+2-binding site. This site was reconstructed from the fourth potential Ca+2-binding domain by the introduction of several amino acid substitutions in it by site-directed mutagenesis. The effect of
these mutations in the fourth potential Ca+2-binding site of myristoylated recoverin on the structural features and conformational stability of the protein was studied
by fluorimetry and circular dichroism. The apoform of the resulting mutant (free of Ca2+ ions) was shown to have a higher calcium capacity, significantly lower thermal stability, and noticeably different secondary
and tertiary structures as compared with the apoform of wild-type recoverin.
For communication II, see [1]. 相似文献
10.
Makoto Fujisawa Yuko Wada Takahiro Tsuchiya Masahiro Ito 《Archives of microbiology》2009,191(8):649-657
11.
Körbel S Bittorf T Siegl E Köllner B 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2004,174(2):121-128
In mammals, erythropoietin regulates the development and differentiation of erythrocytes. Although hematopoietic cells of bony fish correspond in their ontogeneic development, morphology, and function to their mammalian counterparts, an erythropoietin (EPO)-like molecule has not been identified. In this study we present evidence for a mitogenic response of blood and head kidney leukocytes of rainbow trout after stimulation by recombinant human EPO (rhu EPO). The modulation of cellular activities is accompanied by the induction of DNA-binding activities in nuclear extracts of these cells. In addition, flow cytometric analysis of intracellular Ca2+ concentrations revealed a long-lasting and rhu EPO dose-dependent increase, which was shown to be abrogated by cross-aggregation of surface IgM using anti-trout-IgM monoclonal antibodies (mabs). In flow cytometric dual-labeling experiments using rhu EPO/anti-EPO antiserum and mabs specific for trout leukocyte subpopulations, it was shown that a subpopulation of trout B-cells binds rhu EPO. Moreover, in a modified Ca2+ activation assay, it was demonstrated that this blood B-cell subpopulation is the rhu EPO responder population. In conclusion, the data suggest the existence of EPO-binding receptors in trout that are able to trigger Ca2+-independent intracellular signaling in hematopoietic cells of head kidney and Ca2+-dependent activation of a subpopulation of B-lymphocytes.Abbreviations
FSC
forward scatter
-
IFN
interferon
-
IL
interleukin
-
mab
monoclonal antibody
-
PBL
peripheral blood leukocytes
-
PHA
phythemagglutitnin
-
rhu EPO
recombinant human erythropoietin
-
SSC
side scatter
-
TNF
tumor necrosis factor
Communicated by G. Heldmaier 相似文献
12.
Mutoh H Yoshino M 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2004,174(1):21-28
The Ca2+-conducting pathway of myocytes isolated from the cricket lateral oviduct was investigated by means of the whole-cell patch clamp technique. In voltage-clamp configuration, two types of whole cell inward currents were identified. One was voltage-dependent, initially activated at –40 mV and reaching a maximum at 10 mV with the use of 140 mM Cs2+-aspartate in the patch pipette and normal saline in the bath solution. Replacement of the external Ca2+ with Ba2+ slowed the current decay. Increasing the external Ca2+ or Ba2+ concentration increased the amplitude of the inward current and the current–voltage (I–V) relationship was shifted as expected from a screening effect on negative surface charges. The inward current could be carried by Na+ in the absence of extracellular Ca2+. Current carried by Na+ (I
Na) was almost completely blocked by the dihydropyridine Ca2+ channel antagonist, nifedipine, suggesting that the I
Na is through voltage-dependent L-type Ca2+ channels. The other inward current is voltage-independent and its I–V relationship was linear between –100 mV to 0 mV with a slight inward rectification at more hyperpolarizing membrane potentials when 140 mM Cs+-aspartate and 140 mM Na+-gluconate were used in the patch pipette and in the bath solution, respectively. A similar current was observed even when the external Na+ was replaced with an equimolar amount of K+ or Cs+, or 50 mM Ca2+ or Ba2+. When the osmolarity of the bath solution was reduced by removing mannitol from the bath solution, the inward current became larger at negative potentials. The I–V relationship for the current evoked by the hypotonic solution also showed a linear relationship between –100 mV to 0 mV. Bath application of Gd3+ (10 M) decreased the inward current activated by membrane hyperpolarization. These results clearly indicate that the majority of current activated by a membrane hyperpolarization is through a stretch-activated Ca2+-permeable nonselective cation channel (NSCC). Here, for the first time, we have identified voltage-dependent L-type Ca2+ channel and stretch-activated Ca2+-permeable NSCCs from enzymatically isolated muscle cells of the cricket using the whole-cell patch clamp recording technique.Abbreviations
I
Ca
Ca2+ current
-
I
Na
Na+ current
-
I–V
current–voltage
-
NSCC
nonselective cation channel
Communicated by G. Heldmaier 相似文献
13.
I. V. Shemarova S. V. Kuznetsov I. N. Demina V. P. Nesterov 《Journal of Evolutionary Biochemistry and Physiology》2009,45(3):389-399
Earlier we have shown that regulation of rhythm and strength of the frog heart contractions, mediated by transmitters of the autonomic nervous system, is of the Ca2+-dependent character. In the present work, we studied chronoand inotropic effect of verapamil—an inhibitor of Ca2+-channels of the L-type, of nickel chloride-an inhibitor of Ca2+—channels of the T-type and of Na+,Ca2+exchangers as well as of adrenaline and acetylcholine (ACh) after nickel chloride. It has been found that the intracardially administered NiCh2 at a dose of 0.01 μg/kg produced a sharp fall of amplitude of action potential (AP) and an almost twofold deceleration of heart rate (HR). The intracardiac administration of NiCh2 (0.01 μg/kg) on the background of action of verapamil (6 mg/kg, i/m) led as soon as after 3 min to even more prominent HR deceleration and to further fall of the AP amplitude by more than 50% as compared with norm. An intracardiac administration of adrenaline (0.5 mg/kg) partly restored the cardiac activity. However, preservation of the myocardium electrical activity in such animals was brief and its duration did not exceed several minutes. Administration of Ni2+ on the background of acetylcholine (3.6 mg/kg) led to almost complete cessation of cardiac activity. As soon as 3 min after injection of this agent the HR decreased to 2 contractions/min. On electrograms (EG), the 10-fold fall of the AP amplitude was recorded. To elucidate role of extraand intracellular Ca2+ in regulation of strength of heart contractions, isometric contraction of myocardium preparations was studied in response to action of NiCl2 (10–200 μM), verapamil (70 μM), adrenaline (5 μM), and acetylcholine (0.2 μM) after NiCl2. It has been found that Ni2+ causes a dose-dependent increase of the muscle contraction amplitude. Minimal change of the contraction amplitude (on average, by 14.9% as compared with control) was recorded at a Ni2+ concentration of 100 μM. An increase of Ni2+ in the sample to 200 μM increased the cardiac contraction strength, on average, by 41%. The negative inotropic action of verapamil was essentially reduced by 100 μM Ni2+. Adrenaline added to the sample after Ni2+ produced stimulating effect on the cardiac muscle, with an almost twofold rise of the contraction amplitude. ACh (0.2 μM) decreased the cardiac contraction amplitude, on average, by 56.3%, whereas Ni2+ (200 μM) administered after ACh not only restored, but also stimulated partly the myocardial work. Within several parts of percent there was an increase of such isometric contraction parameters as amplitude of the effort developed by muscle, maximal rate, maximal acceleration, time of semirise and semifall. The obtained experimental results indicate that the functional activity of the frog pacemaker and contractile cardiomyocytes is regulated by Ca2+-dependent mechanisms. Structure of these mechanisms includes the potential-controlled Land T-channels of the plasma membrane as well as Na+,Ca2-exchangers characteristic exclusively of contractile cardiomyocytes. The existence of these differences seems to be due to the cardiomyocyte morphological peculiarities that appeared in evolution at the stage of the functional cell specialization. 相似文献
14.
Relevant Ca2+ pools and fluxes in H9c2 cells have been studied using fluorescent indicators and Ca2+-mobilizing agents. Vasopressin produced a cytoplasmic Ca2+ peak with half-maximal effective concentration of 6 nM, whereas thapsigargin-induced Ca2+ increase showed half-maximal effect at 3 nM. Depolarization of the mitochondrial inner membrane by protonophore was also associated with an increase in cytoplasmic Ca2+. Ionomycin induced a small and sustained depolarization, while thapsigargin had a small but transient effect. The thapsigargin-sensitive Ca2+ pool was also sensitive to ionomycin, whereas the protonophore-sensitive Ca2+ pool was not. The vasopressin-induced cytoplasmic Ca2+ signal, which caused a reversible discharge of the sarco-endoplasmic reticulum Ca2+ pool, was sensed as a mitochondrial Ca2+ peak but was unaffected by the permeability transition pore inhibitor cyclosporin A. The mitochondrial Ca2+ peak was affected by cyclosporin A when the Ca2+ signal was induced by irreversible discharge of the intracellular Ca2+ pool, i.e., adding thapsigargin. These observations indicate that the mitochondria interpret the cytoplasmic Ca2+ signals generated in the reticular store. 相似文献
15.
E. Y. Zernii D. V. Zinchenko V. I. Vladimirov I. I. Grigoriev E. E. Skorikova V. E. Baksheeva V. M. Lipkin P. P. Philippov I. I. Senin 《Biochemistry (Moscow) Supplemental Series A: Membrane and Cell Biology》2014,8(1):44-49
Recoverin is a Ca2+-binding protein implicated in the Ca2+-dependent regulation of desensitization of visual receptor rhodopsin in vertebrate retinal rods. Here we report that Ca2+ sensitivity of recoverin regulating rhodopsin phosphorylation increases in the presence of the photoreceptor membranes enriched in raft structures. The observed effect is mediated by a key protein component of raft structures caveolin-1. The presence of recombinant fragment Phe81-Arg101 of the caveolin-1 cytoplasmic domain enhances Ca2+ affinity of recoverin, therefore affecting its Ca2+-dependent regulatory activity. 相似文献
16.
Exposure of bovine pulmonary artery smooth muscle plasma membrane suspension with the oxidant H2O2 (1 mM) stimulated Ca2+ATPase activity. We sought to determine the role of matrix metalloprotease-2 (MMP-2) in stimulating Ca2+ATPase activity by H2O2 in the smooth muscle plasma membrane. The smooth muscle membrane possesses a Ca2+-dependent protease activity in the gelatin containing zymogram having an apparent molecular mass of 72 kDa. The 72 kDa protease
activity was found to be inhibited by EGTA, 1: 10-phenanthroline, a2-macroglobulin and tissue inhibitor of metalloprotease-2
(TIMP-2) indicating that the Ca2+-dependent 72 kDa protease is the MMP-2. Western immunoblot studies of the membrane suspension with polyclonal antibodies
of MMP-2 and TIMP-2 revealed that MMP-2 and TIMP-2, respectively, are the ambient matrix metalloprotease and the corresponding
tissue inhibitor of metalloprotease in the membrane.
In addition to increasing the Ca2+ATPase activity, H2O2 also enhanced the activity of the smooth muscle plasma membrane associated protease activity as evidenced by its ability
to degrade14C-gelatin. The protease activity and the Ca2+ATPase activity were prevented by the antioxidant, vitamin E, indicating that the effect produced by H2O2 was due to reactive oxidant species(es). Both basal and H2O2 stimulated MMP-2 activity and Ca2+ATPase activity were inhibited by the general inhibitors of matrix metalloproteases: EGTA, 1: 10-phenanthroline, α2-macroglobulin and also by TIMP-2 (the specific inhibitor of MMP-2) indicating that H2O2 increased MMP-2 activity and that subsequently stimulated Ca2+ATPase activity in the plasma membrane. This was further confirmed by the following observations: (i) adding low doses of
MMP-2 or H2O2 to the smooth muscle membrane suspension caused submaximal increase in Ca2+ATPase activity, and pretreatment with TIMP-2 prevents the increase in Ca2+ATPase activity; (ii) combined treatment of the membrane with low doses of MMP-2 and H2O2 augments further the Ca2+ATPase activity caused by the respective low doses of either H2O2 or MMP-2; and (iii) pretreatment with TIMP-2 prevents the increase in Ca2+ATPase activity in the membrane caused by the combined treatment of MMP-2 and H2O2. 相似文献
17.
We studied store-dependent (activated by depletion of the endoplasmic reticulum, ER, store) entry of Ca2+ from the extracellular medium into neurons of the rat spinal ganglia (small- and medium-sized cells; diameter, 18 to 36 μm).
Activation of ryanodine-sensitive receptors of the ER in the studied neurons superfused by Tyrode solutions containing Ca2+ or with no Ca2+ was provided by application of 10 mM caffeine. The decay phase of caffeine-induced calcium transients in a Ca2+-containing solution was significantly longer than that in a Ca2+-free solution. This fact allows us to suppose that such a phenomenon is determined by Ca2+ entry into the neuron from the extracellular medium activated by caffeine-induced depletion of the ER store. Substitution
of Ca2+-free extracellular solution by Ca2+-containing Tyrode solution, after depletion of the ER stores induced by applications of 100 nM ryanodine, 200 μM ATP, or
1 μM thapsigargin, resulted in increases in the concentration of intracellular Ca2+. These observations allow us to postulate that store-dependent Ca2+ entry into the studied neurons is activated after depletion not only of the inositol trisphosphate-sensitive ER store but
also of the ryanodine-sensitive store. This entry also occurs after blocking of ATPases of the ER by thapsigargin. The kinetic
characteristics of the rising phase of store-dependent Ca2+ entry induced by depletion of the ER stores under the influence of various agents are dissimilar; this can be related to
different mechanisms of activation of such signals and/or to a compartmental organization of the ER.
Neirofiziologiya/Neurophysiology, Vol. 37, No. 3, pp. 277–283, May–June, 2005. 相似文献
18.
In an earlier study, we showed that mitochondria hyperpolarized after short periods of oxygen-glucose deprivation (OGD), and
this response appeared to be associated with subsequent apoptosis or survival. Here, we demonstrated that hyperpolarization
following short periods of OGD (30 min; 30OGD group) increased the cytosolic Ca2+ ([Ca2+]c) buffering capacity in mitochondria. After graded OGD (0 min (control), 30 min, 120 min), rat cultured hippocampal neurons
were exposed to glutamate, evoking Ca2+influx. The [Ca2+]c level increased sharply, followed by a rapid increase in mitochondrial Ca2+ [Ca2+]m. The increase in the [Ca2+]m level accompanied a reduction in the [Ca2+]c level. After reaching a peak, the [Ca2+]c level decreased more rapidly in the 30OGD group than in the control group. This buffering reaction was pronounced in the
30OGD group, but not in the 120OGD group. The enhanced buffering capacity of the mitochondria may be linked to preconditioning
after short-term ischemic episodes. 相似文献
19.
Recoverin, a member of the neuronal calcium sensor (NCS) branch of the calmodulin superfamily, serves as a calcium sensor in retinal rod cells. Ca2+‐induced conformational changes in recoverin promote extrusion of its covalently attached myristate, known as the Ca2+‐myristoyl switch. Here, we present nuclear magnetic resonance (NMR) relaxation dispersion and chemical shift analysis on 15N‐labeled recoverin to probe main chain conformational dynamics. 15N NMR relaxation data suggest that Ca2+‐free recoverin undergoes millisecond conformational dynamics at particular amide sites throughout the protein. The addition of trace Ca2+ levels (0.05 equivalents) increases the number of residues that show detectable relaxation dispersion. The Ca2+‐dependent chemical shifts and relaxation dispersion suggest that recoverin has an intermediate conformational state (I) between the sequestered apo state (T) and Ca2+ saturated extruded state (R): T ? I ? R. The first step is a fast conformational equilibrium ([T]/[I] < 100) on the millisecond time scale (τexδω < 1). The final step (I ? R) is much slower (τexδω > 1). The main chain structure of I is similar in part to the structure of half‐saturated E85Q recoverin with a sequestered myristoyl group. We propose that millisecond dynamics during T ? I may transiently increase the exposure of Ca2+‐binding sites to initiate Ca2+ binding that drives extrusion of the myristoyl group during I ? R. Proteins 2011; © 2011 Wiley‐Liss, Inc. 相似文献
20.
Liang Lu Changsong Wang Xiaohua Gao Peng Xu Jun Wang Qiang Wang Jie Cheng Hang Xiao 《The Journal of membrane biology》2009,227(2):87-94
Low voltage-activated, rapidly inactivating T-type Ca2+ channels are found in a variety of cells, where they regulate electrical activity and Ca2+ entry. In whole-cell patch-clamp recordings from mouse spermatogenic cells, trace element copper (Cu2+) inhibited T-type Ca2+ current (I
T-Ca) with IC50 of 12.06 μM. Inhibition of I
T-Ca by Cu2+ was concentration-dependent and mildly voltage-dependent. When voltage stepped to −20 mV, Cu2+ (10 μM) inhibited I
T-Ca by 49.6 ± 4.1%. Inhibition of I
T-Ca by Cu2+ was accompanied by a shift of −2.23 mV in the voltage dependence of steady-state inactivation. Cu2+ upshifted the current–voltage (I-V) curve. To know the change of the gating kinetics of T-type Ca2+ channels, we analyzed the effect of Cu2+ on activation, inactivation, deactivation and reactivation of T-type Ca2+ channels. Since T-type Ca2+ channels are a key component in capacitation and the acrosome reaction, our data suggest that Cu2+ can affect male reproductive function through T-type Ca2+ channels as a preconception contraceptive material. 相似文献