Besides affecting intracellular calcium signaling, 2‐APB reversibly blocks gap junctional coupling in confluent monolayers, thereby allowing the measurement of single‐cell membrane currents in undissociated cells

Harks, Erik; Camiña, Jesús P.; Peters, P.H.J.; Ypey, Dirk L.; Scheenen, Wim J.J.M.; Zoelen, E.J.J. van; Theuvenet, A.P.R.

doi:10.1096/fj.02-0786fje

Cited by 65 publications

(71 citation statements)

References 40 publications

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“…However, TRP channels have yet to be unequivocally established as the molecular basis for SOCE (74). 2-APB also inhibits the sarco-endoplasmic reticulum Ca 2ϩ ATPase pump (62) and voltage-dependent K ϩ channels (75) and blocks gap junctions, possibly by interfering with the docking interactions of two gap junctional hemi-channels (76).…”

Section: Discussionmentioning

confidence: 99%

Cyclosporin A-insensitive Permeability Transition in Brain Mitochondria

Chinopoulos

Starkov

Fiskum

2003

Journal of Biological Chemistry

123

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The mitochondrial permeability transition pore (PTP) may operate as a physiological Ca 2؉ release mechanism and also contribute to mitochondrial deenergization and release of proapoptotic proteins after pathological stress, e.g. ischemia/reperfusion. Brain mitochondria exhibit unique PTP characteristics, including relative resistance to inhibition by cyclosporin A. In this study, we report that 2-aminoethoxydiphenyl borate blocks Ca 2؉ -induced Ca 2؉ release in isolated, non-synaptosomal rat brain mitochondria in the presence of physiological concentrations of ATP and Mg 2؉ . Ca 2؉ release was not mediated by the mitochondrial Na ؉ /Ca 2؉ exchanger or by reversal of the uniporter responsible for energy-dependent Ca 2؉ uptake. Loss of mitochondrial Ca 2؉ was accompanied by release of cytochrome c and pyridine nucleotides, indicating an increase in permeability of both the inner and outer mitochondrial membranes. Under these conditions, Ca 2؉ -induced opening of the PTP was not blocked by cyclosporin A, antioxidants, or inhibitors of phospholipase A 2 or nitric-oxide synthase but was abolished by pretreatment with bongkrekic acid. These findings indicate that in the presence of adenine nucleotides and Mg 2؉ , Ca 2؉ -induced PTP in non-synaptosomal brain mitochondria exhibits a unique pattern of sensitivity to inhibitors and is particularly responsive to 2-aminoethoxydiphenyl borate.Mitochondria are temporo-spatial modulators of cytosolic [Ca 2ϩ ] through their ability to both sequester and release Ca 2ϩ in concert with Ca 2ϩ transport across the endoplasmic reticulum (1, 2). Physiological mitochondrial Ca 2ϩ efflux, including that caused by Ca 2ϩ -induced Ca 2ϩ release (mCICR), 1 is attributed to either activation of the permeability transition pore (PTP) (3, 4) or to reversal of the Ca 2ϩ uniporter (5). Opening of the PTP has been implicated as a mediator of apoptotic and necrotic cell death as well as a regulator of normal cell Ca 2ϩ homeostasis (4, 6 -12). The characteristic traits of the PTP include reversibility (13), sensitivity to inhibition by cyclosporin A (14), and mitochondrial swelling associated with loss of matrix solutes (15-17). Cyclosporin A is not always effective, however, at inhibiting Ca 2ϩ -induced mitochondrial swelling and loss of ⌬⌿ (18 -22). In addition, the observation that normal intracellular concentrations of adenine nucleotides and Mg 2ϩ partially or completely block PTP activation (23, 24) casts doubt on a physiological role of the PTP.The extent to which mitochondria swell in response to accumulation of large Ca 2ϩ loads also varies considerably with experimental conditions and with mitochondrial tissue type (25-27). Brain mitochondria are particularly resistant to Ca 2ϩ -induced swelling (25, 28); moreover, they represent many cell populations, which may explain their heterogeneous response to large Ca 2ϩ loads and to inhibitors of the PTP, e.g. cyclosporin A (26,29).In this study we report that 2-APB (30) prevents Ca 2ϩ -induced PTP in non-synaptosomal brain mitochondria in the ...

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Section: Discussionmentioning

confidence: 99%

Cyclosporin A-insensitive Permeability Transition in Brain Mitochondria

Chinopoulos

Starkov

Fiskum

2003

Journal of Biological Chemistry

123

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“…After the initial suggestion as a membrane-permeable blocker of inositol 1,4,5-trisphosphate receptors (31), the blocking effects of 2-APB on the various membrane channel proteins, including Ca 2ϩ release-activated calcium channel, gap junction, and sarco/endoplasmic reticulum Ca 2ϩ -ATPase, have been reported (17,(31)(32)(33). On the other hand, depending on the concentration used, 2-APB facilitates the cytosolic regulator of adenylyl cyclase or other Ca 2ϩ -permeable cation channels (18,34,35).…”

Section: Discussionmentioning

confidence: 99%

Membrane-delimited Regulation of Novel Background K+ Channels by MgATP in Murine Immature B Cells

Nam

Woo

Uhm

et al. 2004

Journal of Biological Chemistry

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The initial goal of the present study was to elucidate the effects of 2-APB on membrane currents, which revealed the presence of novel K ؉ channels in WEHI-231 cells. Under whole-cell patch clamp conditions, 2-APB induced background K ؉ current (I K,bg ) and hyperpolarization in WEHI-231 cells. Lowering of intracellular MgATP also induced the I K,bg . The I K,bg was blocked by micromolar concentrations of quinidine but not by tetraethylammonium. In a single channel study, two types of voltage-independent K ؉ channels were found with large (346 picosiemens) and medium conductance (112 picosiemens), named BK bg and MK bg , respectively. The excision of membrane patches (inside-out (i-o) patches) greatly increased the P o of BK bg . In i-o patches, cytoplasmic MgATP (IC 50 ‫؍‬ 0.18 mM) decreased the BK bg activity, although non-hydrolyzable adenosine 5-(␤,␥-imino)-triphosphate had no effect. A pretreatment with Al 3؉ or wortmannin (50 M) blocked the inhibitory effects of MgATP. A direct application of phosphoinositide 4,5-bisphosphate (10 M) inhibited the BK bg activity. Meanwhile, the activity of MK bg was unaffected by MgATP. In cell-attached conditions, the BK bg activity was largely increased by 2-APB. In i-o patches, however, the MgATPinduced inhibition of BK bg was weakly reversed by the addition of 2-APB. In summary, WEHI-231 cells express the unique background K ؉ channels. The BK bg s are inhibited by membrane-delimited elevation of phosphoinositide 4,5-bisphosphate. The activation of BK bg would hyperpolarize the membrane, which augments the calcium influx in WEHI-231 cells.Immune responses are initiated and regulated by the physical interactions of receptors and ligands on lymphocytes and antigen-presenting cells. In addition to the external factors, intrinsic changes of lymphocytes would participate in shaping the ongoing responsiveness of cells. An important intrinsic determinant of responsiveness could be the membrane potential (V m ) that is mainly determined by the potassium permeability of cell membrane and transmembrane gradient of [K ϩ ]. K ϩ channels, besides setting resting V m , play critical roles in various cellular functions (1). Among them, the modulation of calcium signals by providing electrical driving force has been suggested as an essential role of K ϩ channels (1, 2). In human primary T cells, two kinds of K ϩ channels, the voltage-gated K ϩ channels Kv1.3 and the calcium-activated K ϩ channel IKCa1 (hSK4), are found to play such a role; Kv1.3 channels are essential for activation of quiescent cells, and signaling through protein kinase C pathway enhances expression of IKCa1 channels that are required for proliferation (3, 4). Besides V m regulation, K ϩ channels also regulate the loss of intracellular K ϩ , which is a prerequisite step in the normotonic-or the Fas-mediated apoptosis (5, 6). In contrast to the studies in T cells, the characteristics of K ϩ channels and their roles in B cells have been rarely investigated, and the types of reported K ϩ channels are restricted to the v...

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“…The LV component of I Prl is underpinned by the activation of a 2-APB-sensitive MCC To test this hypothesis, Prl (500 nM) was applied to TIDA neurons in the presence of TTX (500 nM) and 2-APB (200 M), a potent blocker of TRPC1, TRPC3, TRPC4, TRPC5, and TRPC6 channels (Clapham et al, 2005); however, it should be noted that 2-APB-dependent inhibitions of IP 3 receptor and gap junction signaling have also been reported (Maruyama et al, 1997;Harks et al, 2003). Under these conditions, the Prl-induced inward current was almost completely abolished (V Hold ϭ Ϫ60 mV; Ϫ1.1 Ϯ 1.0 pA; n ϭ 9; p Ͻ 0.005 vs control), undergoing a 93.6 Ϯ 2.8% reduction (Fig.…”

Section: Prl Activates An Inward Current Composed Of Low-and High-volmentioning

confidence: 99%

Prolactin Regulates Tuberoinfundibular Dopamine Neuron Discharge Pattern: Novel Feedback Control Mechanisms in the Lactotrophic Axis

Lyons

Hellysaz²,

Broberger³

2012

Journal of Neuroscience

127

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Balance in the body's hormonal axes depends on feedback onto neuroendocrine hypothalamic neurons. This phenomenon involves transcriptional and biosynthetic effects, yet less is known about the potential rapid modulation of electrical properties. Here, we investigated this issue in the lactotrophic axis, in which the pituitary hormone prolactin is tonically inhibited by tuberoinfundibular dopamine (TIDA) neurons located in the hypothalamic arcuate nucleus. Whole-cell recordings were performed on slices of the rat hypothalamus. In the presence of prolactin, spontaneously oscillating TIDA cells depolarized, switched from phasic to tonic discharge, and exhibited broadened action potentials. The underlying prolactin-induced current is composed of separate low-and high-voltage components that include the activation of a transient receptor potential-like current and the inhibition of a Ca 2ϩ -dependent BK-type K ϩ current, respectively, as revealed by ion substitution experiments and pharmacological manipulation. The two components of the prolactin-induced current appear to be mediated through distinct signaling pathways as the high-voltage component is abolished by the phosphoinositide 3-kinase blocker wortmannin, whereas the low-voltage component is not. This first description of the central electrophysiological actions of prolactin suggests a novel feedback mechanism. By simultaneously enhancing the discharge and spike duration of TIDA cells, increased serum prolactin can promote dopamine release to limit its own secretion with implications for the control of lactation, sexual libido, fertility, and body weight.

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Besides affecting intracellular calcium signaling, 2‐APB reversibly blocks gap junctional coupling in confluent monolayers, thereby allowing the measurement of single‐cell membrane currents in undissociated cells

Cited by 65 publications

References 40 publications

Cyclosporin A-insensitive Permeability Transition in Brain Mitochondria

Cyclosporin A-insensitive Permeability Transition in Brain Mitochondria

Membrane-delimited Regulation of Novel Background K+ Channels by MgATP in Murine Immature B Cells

Prolactin Regulates Tuberoinfundibular Dopamine Neuron Discharge Pattern: Novel Feedback Control Mechanisms in the Lactotrophic Axis

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