scholarly journals Depolarization-induced Calcium Responses in Sympathetic Neurons: Relative Contributions from Ca2+ Entry, Extrusion, ER/Mitochondrial Ca2+ Uptake and Release, and Ca2+ Buffering

2006 ◽  
Vol 129 (1) ◽  
pp. 29-56 ◽  
Author(s):  
Michael Patterson ◽  
James Sneyd ◽  
David D. Friel
Keyword(s):  
Plasma Membrane ◽  
Voltage Clamp ◽  
Diffusion Model ◽  
Time Course ◽  
Sympathetic Neurons ◽  
Cell Types ◽  
Specific Cell ◽  
Modeling Studies ◽  
Uniform Model ◽  
Uptake And Release

Many models have been developed to account for stimulus-evoked [Ca2+] responses, but few address how responses elicited in specific cell types are defined by the Ca2+ transport and buffering systems that operate in the same cells. In this study, we extend previous modeling studies by linking the time course of stimulus-evoked [Ca2+] responses to the underlying Ca2+ transport and buffering systems. Depolarization-evoked [Ca2+]i responses were studied in sympathetic neurons under voltage clamp, asking how response kinetics are defined by the Ca2+ handling systems expressed in these cells. We investigated five cases of increasing complexity, comparing observed and calculated responses deduced from measured Ca2+ handling properties. In Case 1, [Ca2+]i responses were elicited by small Ca2+ currents while Ca2+ transport by internal stores was inhibited, leaving plasma membrane Ca2+ extrusion intact. In Case 2, responses to the same stimuli were measured while mitochondrial Ca2+ uptake was active. In Case 3, responses were elicited as in Case 2 but with larger Ca2+ currents that produce larger and faster [Ca2+]i elevations. Case 4 included the mitochondrial Na/Ca exchanger. Finally, Case 5 included ER Ca2+ uptake and release pathways. We found that [Ca2+]i responses elicited by weak stimuli (Cases 1 and 2) could be quantitatively reconstructed using a spatially uniform model incorporating the measured properties of Ca2+ entry, removal, and buffering. Responses to strong depolarization (Case 3) could not be described by this model, but were consistent with a diffusion model incorporating the same Ca2+ transport and buffering descriptions, as long as endogenous buffers have low mobility, leading to steep radial [Ca2+]i gradients and spatially nonuniform Ca2+ loading by mitochondria. When extended to include mitochondrial Ca2+ release (Case 4) and ER Ca2+ transport (Case 5), the diffusion model could also account for previous measurements of stimulus-evoked changes in total mitochondrial and ER Ca concentration.

scholarly journals Quantitative Analysis of Mitochondrial Ca2+ Uptake and Release Pathways in Sympathetic Neurons

2000 ◽  
Vol 115 (3) ◽  
pp. 371-388 ◽  
Author(s):  
Stephen L. Colegrove ◽  
Meredith A. Albrecht ◽  
David D. Friel
Keyword(s):  
Plasma Membrane ◽  
Time Course ◽  
Sympathetic Neurons ◽  
Differential Sensitivity ◽  
Rate Equations ◽  
Intact Cells ◽  
Isolated Mitochondria ◽  
Cellular Context ◽  
The Impact ◽  
Uptake And Release

Rate equations for mitochondrial Ca2+ uptake and release and plasma membrane Ca2+ transport were determined from the measured fluxes in the preceding study and incorporated into a model of Ca2+ dynamics. It was asked if the measured fluxes are sufficient to account for the [Ca2+]i recovery kinetics after depolarization-evoked [Ca2+]i elevations. Ca2+ transport across the plasma membrane was described by a parallel extrusion/leak system, while the rates of mitochondrial Ca2+ uptake and release were represented using equations like those describing Ca2+ transport by isolated mitochondria. Taken together, these rate descriptions account very well for the time course of recovery after [Ca2+]i elevations evoked by weak and strong depolarization and their differential sensitivity to FCCP, CGP 37157, and [Na+]i. The model also leads to three general conclusions about mitochondrial Ca2+ transport in intact cells: (1) mitochondria are expected to accumulate Ca2+ even in response to stimuli that raise [Ca2+]i only slightly above resting levels; (2) there are two qualitatively different stimulus regimes that parallel the buffering and non-buffering modes of Ca2+ transport by isolated mitochondria that have been described previously; (3) the impact of mitochondrial Ca2+ transport on intracellular calcium dynamics is strongly influenced by nonmitochondrial Ca2+ transport; in particular, the magnitude of the prolonged [Ca2+]i elevation that occurs during the plateau phase of recovery is related to the Ca2+ set-point described in studies of isolated mitochondria, but is a property of mitochondrial Ca2+ transport in a cellular context. Finally, the model resolves the paradoxical finding that stimulus-induced [Ca2+]i elevations as small as ∼300 nM increase intramitochondrial total Ca2+ concentration, but the steady [Ca2+]i elevations evoked by such stimuli are not influenced by FCCP.

Segmental specialization of calcium-activated potassium conductances in an identified leech neuron

1995 ◽  
Vol 73 (3) ◽  
pp. 957-963 ◽  
Author(s):  
D. C. Merz
Keyword(s):  
Voltage Clamp ◽  
Action Potentials ◽  
Time Course ◽  
Cell Types ◽  
Reproductive Organs ◽  
Resting Membrane Potential ◽  
Potassium Conductances ◽  
K Current ◽  
High Concentrations ◽  
X Cells

1. Retzius (R) neurons of the fifth and sixth segmental ganglia of the leech, called R(5,6) neurons are specialized to innervate the adjacent reproductive organs and are morphologically and functionally distinct from R neurons of standard ganglia [R(x) cells]. In this study the electrical properties of the R(x) and R(5,6) neurons were compared under current-clamp and voltage-clamp conditions. 2. The action-potential waveforms of R(x) and R(5,6) cells were similar except for the presence in the R(5,6) cells of a long afterhyperpolarization (AHP) following action potentials arising from the resting membrane potential but not from more depolarized potentials. Its role may thus be to inhibit firing of the R(5,6) neurons at rest or in response to weak depolarizing stimuli. 3. In the presence of the Ca2+ channel blocker Cd2+, the long AHP of the R(5,6) was abolished, and the action potentials of all R cells were identical. 4. Under voltage clamp, current kinetics and densities were similar between R(x) and R(5,6) cells for Ca2+ currents, delayed and inward rectifier K+ currents, and a rapid Ca(2+)-activated K+ current (IKc) that is common to the two cell types. The R(5,6) cells, however, expressed a second Ca(2+)-activated K+ current that was not observed in the R(x) cells. This current, called IKAHP, activated and inactivated more slowly than IKC, with a time course similar to that of the AHP observed under physiological conditions. 5. Neither IKC nor IKAHP was blocked by high concentrations of charybdotoxin or apamin, which block vertebrate Ca(2+)-activated K+ channels.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals The 'lipid raft' microdomain proteins reggie-1 and reggie-2 (flotillins) are scaffolds for protein interaction and signalling.

2005 ◽  
Vol 72 ◽  
pp. 109-118 ◽  
Author(s):  
Claudia A. O. Stuermer ◽  
Helmut Plattner
Keyword(s):  
Plasma Membrane ◽  
Lipid Raft ◽  
Ganglion Cells ◽  
Single Cells ◽  
Cell Types ◽  
Cellular Prion Protein ◽  
Surface Proteins ◽  
Current View ◽  
Specific Cell ◽  
Rna Knockdown

Reggie-1 and reggie-2 are two evolutionarily highly conserved proteins which are up-regulated in retinal ganglion cells during regeneration of lesioned axons in the goldfish optic nerve. They are located at the cytoplasmic face of the plasma membrane and are considered to be 'lipid raft' constituents due to their insolubility in Triton X-100 and presence in the 'floating fractions'; hence they were independently named flotillins. According to our current view, the reggies subserve functions as protein scaffolds which form microdomains in neurons, lymphocytes and many other cell types across species as distant as flies and humans. These microdomains are of a surprisingly constant size of less than or equal to 0.1 mm in all cell types, whereas the distance between them is variable. The microdomains co-ordinate signal transduction of specific cell-surface proteins and especially of GPI (glycosylphosphatidylinositol)-anchored proteins into the cell, as is demonstrated for PrPc (cellular prion protein) in T-lymphocytes. These cells possess a pre-formed reggie cap scaffold consisting of densely packed reggie microdomains. PrPc is targeted to the lymphocyte reggie cap when activated by antibody cross-linking, and induces a distinct Ca2+ signal. In developing zebrafish, reggies become concentrated in neurons and axon tracts, and their absence, after morpholino antisense RNA-knockdown, results in deformed embryos with reduced brains. Likewise, defects in Drosophila eye morphogenesis occur upon reggie overexpression in mutant flies. The defects observed in the organism, as well as in single cells in culture, indicate a morphogenetic function of the reggies, with emphasis on the nervous system. This complies with their role as scaffolds for the formation of multiprotein complexes involved in signalling across the plasma membrane.

scholarly journals Transporter-Targeted Nano-Sized Vehicles for Enhanced and Site-Specific Drug Delivery

Cancers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2837 ◽  
Author(s):  
Longfa Kou ◽  
Qing Yao ◽  
Hailin Zhang ◽  
Maoping Chu ◽  
Yangzom D. Bhutia ◽  
...  
Keyword(s):  
Drug Delivery ◽  
Plasma Membrane ◽  
Blood Brain Barrier ◽  
Drug Delivery Systems ◽  
Cell Types ◽  
Delivery Systems ◽  
Target Cells ◽  
Specific Cell ◽  
Site Specific ◽  
Nano Drug Delivery

Nano-devices are recognized as increasingly attractive to deliver therapeutics to target cells. The specificity of this approach can be improved by modifying the surface of the delivery vehicles such that they are recognized by the target cells. In the past, cell-surface receptors were exploited for this purpose, but plasma membrane transporters also hold similar potential. Selective transporters are often highly expressed in biological barriers (e.g., intestinal barrier, blood–brain barrier, and blood–retinal barrier) in a site-specific manner, and play a key role in the vectorial transfer of nutrients. Similarly, selective transporters are also overexpressed in the plasma membrane of specific cell types under pathological states to meet the biological needs demanded by such conditions. Nano-drug delivery systems could be strategically modified to make them recognizable by these transporters to enhance the transfer of drugs across the biological barriers or to selectively expose specific cell types to therapeutic drugs. Here, we provide a comprehensive review and detailed evaluation of the recent advances in the field of transporter-targeted nano-drug delivery systems. We specifically focus on areas related to intestinal absorption, transfer across blood–brain barrier, tumor-cell selective targeting, ocular drug delivery, identification of the transporters appropriate for this purpose, and details of the rationale for the approach.

scholarly journals Taste-Specific Cell Assemblies in a Biologically Informed Model of the Nucleus of the Solitary Tract

2010 ◽  
Vol 104 (1) ◽  
pp. 4-17 ◽  
Author(s):  
Andrew M. Rosen ◽  
Heike Sichtig ◽  
J. David Schaffer ◽  
Patricia M. Di Lorenzo
Keyword(s):  
Time Course ◽  
Single Cells ◽  
Cell Types ◽  
Specific Cell ◽  
Solitary Tract ◽  
Cell Assemblies ◽  
Taste Response ◽  
Electrophysiological Recordings ◽  
Interactive Network ◽  
Time Courses

Although the cellular organization of many primary sensory nuclei has been well characterized, questions remain about the functional architecture of the first central relay for gustation, the rostral nucleus of the solitary tract (NTS). Here we used electrophysiological data recorded from single cells in the NTS to inform a network model of taste processing. Previous studies showed that electrical stimulation of the chorda tympani (CT) nerve initiates two types of inhibitory influences with different time courses in separate groups of NTS cells. Each type of inhibition targeted cells with distinct taste response properties. Further analyses of these data identified three NTS cell types differentiated by their latency of evoked response, time course of CT evoked inhibition, and degree of selectivity across taste qualities. Based on these results, we designed a model of the NTS consisting of discrete, reciprocally connected, stimulus-specific “cell” assemblies. Input to the network of integrate-and-fire model neurons was based on electrophysiological recordings from the CT nerve. Following successful simulation of paired-pulse CT stimulation, the network was tested for its ability to discriminate between two “taste” stimuli. Network dynamics of the model produced biologically plausible responses from each unit type and enhanced discrimination between taste qualities. We propose that an interactive network of taste quality specific cell assemblies, similar to our model, may account for the coherence in across-neuron patterns of NTS responses between similar tastants.

Isoform PMCA3 of the plasma membrane calcium pump (ATPase) is localized in the inner plexiform layer of rat retina

1995 ◽  
Vol 53 ◽  
pp. 950-951
Author(s):  
M. C. Antonelli ◽  
T. J. Eakin ◽  
W.L. Stahl
Keyword(s):  
Plasma Membrane ◽  
Plexiform Layer ◽  
Cell Types ◽  
Rat Plasma ◽  
Granule Cell Layer ◽  
System Control ◽  
Specific Cell ◽  
Inner Plexiform Layer ◽  
Transport Molecules

Regulation of cytosolic Ca2+ is of critical importance for maintaining normal cellular function in the nervous system. Control of calcium homeostasis involves the Ca2+-ATPase of plasma membrane (PMCA) and other transporters. The presence of these regulatory molecules may not be a fixed characteristic of cells in a general sense. Rather, each class of cells may utilize a unique combination of transporters to maintain homeostatic control. In addition, unique distributions of transport molecules and their isoforms may exist in individual parts of cells imparting unique transport signatures to specific cell types. PMCA is a major regulator of calcium transport under normal physiological conditions. In order to understand localization of PMCA isoforms in specific cells we have localized specific PMCA mRNAs by in situ hybridization and translated PMCA protein by immunocytochemistry. The present work is focused on localization of PMCA3, an isoform predominantly known to exist in brain and skeletal muscle, but not previously investigated in retina. We previously showed that mRNA encoding rat plasma membrane Ca2+-ATPase isoform PMCA3 was localized in the granule cell layer of the cerebellum.

scholarly journals Molecular Biomarkers for Embryonic and Adult Neural Stem Cell and Neurogenesis

2015 ◽  
Vol 2015 ◽  
pp. 1-14 ◽  
Author(s):  
Juan Zhang ◽  
Jianwei Jiao
Keyword(s):  
Stem Cell ◽  
Neural Stem Cell ◽  
Adult Neurogenesis ◽  
Time Course ◽  
Cell Types ◽  
Molecular Biomarkers ◽  
Specific Cell ◽  
Adult Neural Stem Cell ◽  
Novel Technologies ◽  
Cell Patterns

The procedure of neurogenesis has made numerous achievements in the past decades, during which various molecular biomarkers have been emerging and have been broadly utilized for the investigation of embryonic and adult neural stem cell (NSC). Nevertheless, there is not a consistent and systematic illustration to depict the functional characteristics of the specific markers expressed in distinct cell types during the different stages of neurogenesis. Here we gathered and generalized a series of NSC biomarkers emerging during the procedures of embryonic and adult neural stem cell, which may be used to identify the subpopulation cells with distinguishing characters in different timeframes of neurogenesis. The identifications of cell patterns will provide applications to the detailed investigations of diverse developmental cell stages and the extents of cell differentiation, which will facilitate the tracing of cell time-course and fate determination of specific cell types and promote the further and literal discoveries of embryonic and adult neurogenesis. Meanwhile, via the utilization of comprehensive applications under the aiding of the systematic knowledge framework, researchers may broaden their insights into the derivation and establishment of novel technologies to analyze the more detailed process of embryogenesis and adult neurogenesis.

scholarly journals Differential Regulation of ER Ca2+ Uptake and Release Rates Accounts for Multiple Modes of Ca2+-induced Ca2+ Release

2002 ◽  
Vol 119 (3) ◽  
pp. 211-233 ◽  
Author(s):  
Meredith A. Albrecht ◽  
Stephen L. Colegrove ◽  
David D. Friel
Keyword(s):  
Plasma Membrane ◽  
Sympathetic Neurons ◽  
Surface Membrane ◽  
Central Element ◽  
Differential Regulation ◽  
Transport Systems ◽  
Excitable Cells ◽  
Release Rates ◽  
Multiple Modes ◽  
Uptake And Release

The ER is a central element in Ca2+ signaling, both as a modulator of cytoplasmic Ca2+ concentration ([Ca2+]i) and as a locus of Ca2+-regulated events. During surface membrane depolarization in excitable cells, the ER may either accumulate or release net Ca2+, but the conditions of stimulation that determine which form of net Ca2+ transport occurs are not well understood. The direction of net ER Ca2+ transport depends on the relative rates of Ca2+ uptake and release via distinct pathways that are differentially regulated by Ca2+, so we investigated these rates and their sensitivity to Ca2+ using sympathetic neurons as model cells. The rate of Ca2+ uptake by SERCAs (JSERCA), measured as the t-BuBHQ-sensitive component of the total cytoplasmic Ca2+ flux, increased monotonically with [Ca2+]i. Measurement of the rate of Ca2+ release (JRelease) during t-BuBHQ-induced [Ca2+]i transients made it possible to characterize the Ca2+ permeability of the ER (\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\overline{\mathrm{P}}_{\mathrm{ER}}\) \end{document}), describing the activity of all Ca2+-permeable channels that contribute to passive ER Ca2+ release, including ryanodine-sensitive Ca2+ release channels (RyRs) that are responsible for CICR. Simulations based on experimentally determined descriptions of JSERCA, \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\overline{\mathrm{P}}_{\mathrm{ER}}\) \end{document}, and of Ca2+ extrusion across the plasma membrane (Jpm) accounted for our previous finding that during weak depolarization, the ER accumulates Ca2+, but at a rate that is attenuated by activation of a CICR pathway operating in parallel with SERCAs to regulate net ER Ca2+ transport. Caffeine greatly increased the [Ca2+] sensitivity of \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\overline{\mathrm{P}}_{\mathrm{ER}}\) \end{document}, accounting for the effects of caffeine on depolarization-evoked [Ca2+]i elevations and caffeine-induced [Ca2+]i oscillations. Extending the rate descriptions of JSERCA, \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\overline{\mathrm{P}}_{\mathrm{ER}}\) \end{document}, and Jpm to higher [Ca2+]i levels shows how the interplay between Ca2+ transport systems with different Ca2+ sensitivities accounts for the different modes of CICR over different ranges of [Ca2+]i during stimulation.

scholarly journals Characterization of the cytotoxic effect of extracellular ATP in J774 mouse macrophages

1992 ◽  
Vol 288 (3) ◽  
pp. 897-901 ◽  
Author(s):  
M Murgia ◽  
P Pizzo ◽  
T H Steinberg ◽  
F Di Virgilio
Keyword(s):  
Plasma Membrane ◽  
Membrane Permeability ◽  
Cell Types ◽  
Mouse Cell ◽  
Extracellular Atp ◽  
Cell Swelling ◽  
Specific Cell ◽  
Plasma Membrane Permeability ◽  
Experimental Conditions ◽  
Surface Receptors

Extracellular ATP (ATPo) is known to be cytotoxic to many cell types through a mechanism which is largely unknown. Very recently this nucleotide has been shown to cause cell death by apoptosis, probably by interacting with specific cell-surface receptors. In the present study we have investigated the mechanism of ATPo-dependent cytotoxicity in the macrophage-like mouse cell line J774. It has been previously reported that in this cell type ATPo activates trans-membrane Ca2+ and Na+ fluxes and a drastic increase in the plasma-membrane permeability to hydrophilic solutes smaller than 900 Da. These changes are followed by cell swelling and lysis. We show in the present study that, although this nucleotide triggers a rise in the cytoplasmic Ca2+ concentration, neither cell swelling nor lysis is Ca(2+)-dependent. Furthermore, cell lysis is not dependent on Na+ influx, as it is not prevented by iso-osmotic replacement of extracellular Na+ with choline or N-methylglucamine. On the contrary, ATPo-dependent cytotoxicity, but not the ATPo-dependent increase in plasma-membrane permeability, is completely abrogated in sucrose medium. Under our experimental conditions ATPo does not cause DNA fragmentation in J774 cells. We conclude from these findings that ATPo does not cause apoptosis of J774 macrophages and promotes a Ca(2+)- and Na(+)-independent colloido-osmotic lysis.

scholarly journals Dissection of Mitochondrial Ca2+ Uptake and Release Fluxes in Situ after Depolarization-Evoked [Ca2+]i Elevations in Sympathetic Neurons

2000 ◽  
Vol 115 (3) ◽  
pp. 351-370 ◽  
Author(s):  
Stephen L. Colegrove ◽  
Meredith A. Albrecht ◽  
David D. Friel
Keyword(s):  
Plasma Membrane ◽  
Initial Phase ◽  
Sympathetic Neurons ◽  
Low Frequency ◽  
Selective Inhibitor ◽  
Atp Production ◽  
Exchange Inhibitor ◽  
Simple Dependence ◽  
Uptake And Release

We studied how mitochondrial Ca2+ transport influences [Ca2+]i dynamics in sympathetic neurons. Cells were treated with thapsigargin to inhibit Ca2+ accumulation by SERCA pumps and depolarized to elevate [Ca2+]i; the recovery that followed repolarization was then examined. The total Ca2+ flux responsible for the [Ca2+]i recovery was separated into mitochondrial and nonmitochondrial components based on sensitivity to the proton ionophore FCCP, a selective inhibitor of mitochondrial Ca2+ transport in these cells. The nonmitochondrial flux, representing net Ca2+ extrusion across the plasma membrane, has a simple dependence on [Ca2+]i, while the net mitochondrial flux (Jmito) is biphasic, indicative of Ca2+ accumulation during the initial phase of recovery when [Ca2+]i is high, and net Ca2+ release during later phases of recovery. During each phase, mitochondrial Ca2+ transport has distinct effects on recovery kinetics. Jmito was separated into components representing mitochondrial Ca2+ uptake and release based on sensitivity to the specific mitochondrial Na+/Ca2+ exchange inhibitor, CGP 37157 (CGP). The CGP-resistant (uptake) component of Jmito increases steeply with [Ca2+]i, as expected for transport by the mitochondrial uniporter. The CGP-sensitive (release) component is inhibited by lowering the intracellular Na+ concentration and depends on both intra- and extramitochondrial Ca2+ concentration, as expected for the Na+/Ca2+ exchanger. Above ∼400 nM [Ca2+]i, net mitochondrial Ca2+ transport is dominated by uptake and is largely insensitive to CGP. When [Ca2+]i is ∼200–300 nM, the net mitochondrial flux is small but represents the sum of much larger uptake and release fluxes that largely cancel. Thus, mitochondrial Ca2+ transport occurs in situ at much lower concentrations than previously thought, and may provide a mechanism for quantitative control of ATP production after brief or low frequency stimuli that raise [Ca2+]i to levels below ∼500 nM.

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