Blockers of voltage-gated K channels inhibit proliferation of cultured brown fat cells

1993 ◽  
Vol 264 (4) ◽  
pp. C1014-C1019 ◽  
Author(s):  
P. A. Pappone ◽  
S. I. Ortiz-Miranda
Keyword(s):  
Cell Proliferation ◽  
Potassium Channels ◽  
Potassium Channel ◽  
Culture Conditions ◽  
Brown Fat ◽  
Neonatal Rat ◽  
Channel Blockers ◽  
Continuous Exposure ◽  
Fat Cells ◽  
Voltage Gated

Cultured brown fat cells have both voltage- and Ca(2+)-activated potassium channels. We tested whether potassium channel activity is necessary for brown fat proliferation by growing adipocytes and preadipocytes from neonatal rat brown fat in the presence of potassium channel blockers. Whole cell patch-clamp experiments showed that verapamil, nifedipine, and quinine block the voltage-gated potassium current (IK,V) with micromolar affinity. Ca(2+)-activated currents (IK,NE) could be activated by micromolar intracellular Ca2+ concentrations and were blocked by nanomolar concentrations of apamin. Both IK,V and IK,NE are blocked by millimolar concentrations of tetraethylammonium (TEA). Under standard culture conditions, the number of cells showing the multilocular morphology characteristic of brown fat cells doubled in 3-5 days. Continuous exposure to 100 nM norepinephrine had no effect on this process. Cell proliferation was inhibited by TEA, quinine, or verapamil. The inhibition was dose dependent, with concentrations for half-block of cell proliferation similar to the Kd values for block of IK,V. Apamin, which selectively blocks IK,NE, had no effect on cell growth. These results suggest that functional voltage-gated potassium channels, but not Ca(2+)-activated potassium channels, may be necessary for the normal proliferation of brown fat cells in culture.

Potassium channel block does not affect metabolic responses of brown fat cells

1992 ◽  
Vol 262 (3) ◽  
pp. C678-C681 ◽  
Author(s):  
P. A. Pappone ◽  
M. T. Lucero
Keyword(s):  
Potassium Channels ◽  
Metabolic Response ◽  
Brown Fat ◽  
Neonatal Rat ◽  
K Channel ◽  
Fat Cells ◽  
Adrenergic Stimulation ◽  
K Channels ◽  
Voltage Gated ◽  
Calcium Activated Potassium Channels

Hormonally stimulated brown fat cells are capable of extremely high metabolic rates, making them an excellent system in which to examine the role of plasma membrane ion channels in cell metabolism. We have previously shown that brown fat cell membranes have both voltage-gated and calcium-activated potassium channels (Voltage-gated potassium channels in brown fat cells. J. Gen. Physiol. 93: 451-472, 1989; Membrane responses to norepinephrine in cultured brown fat cells. J. Gen. Physiol. 95: 523-544, 1990). Currents through both the voltage-activated potassium channels, IK,V, and the calcium-activated potassium channels, IK,Ca, can be blocked by the membrane-impermeant K channel blocker tetraethylammonium (TEA). We used microcalorimetric measurements from isolated neonatal rat brown fat cells to assess the role these potassium conductances play in the metabolic response of brown fat cells to adrenergic stimulation. Concentrations of TEA as high as 50 mM, sufficient to block approximately 95% of IK,V and 100% of IK,Ca, had no effect on norepinephrine-stimulated heat production. These results show that neither voltage-gated nor calcium-activated K channels are necessary for a maximal thermogenic response in brown fat cells and suggest that K channels are not involved in maintaining cellular homeostasis during periods of high metabolic activity.

Adrenergic modulation of intracellular pH in isolated brown fat cells from hamster and rat

1994 ◽  
Vol 267 (2) ◽  
pp. C349-C356 ◽  
Author(s):  
S. C. Lee ◽  
J. S. Hamilton ◽  
T. Trammell ◽  
B. A. Horwitz ◽  
P. A. Pappone
Keyword(s):  
Intracellular Ph ◽  
Uncoupling Protein ◽  
Cell Types ◽  
Brown Fat ◽  
Neonatal Rat ◽  
Fat Cells ◽  
Adrenergic Stimulation ◽  
Regulatory Systems ◽  
Ratio Imaging ◽  
Free Media

The activity of the uncoupling protein in brown fat mitochondria is enhanced at alkaline pH, leading to the hypothesis that changes in intracellular pH (pHi) may modulate the thermogenic response to sympathetic stimulation. We employed ratio imaging of the fluorescent dye 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein to measure pHi in acutely isolated single brown fat cells from hamster and neonatal rat and in cultured rat cells. Basal pHi averaged approximately 7.2 in HCO3- media and 0.1-0.15 pH units lower in nominally HCO3(-)-free media in all cell types. In both HCO3- and HCO3(-)-free media, stimulation with norepinephrine (NE) typically caused an alkalinization of approximately 0.05-0.1 pH units, which was followed by a smaller net acidification occurring primarily after NE was removed. Alkalinization seemed to be mediated predominantly by alpha-adrenergic stimulation, while acidification most often followed beta-adrenergic activation. Similar pHi changes were elicited by NE in rat and hamster cells, but responses were more frequent in hamster cells. Assays of recovery from ammonium prepulse-induced acid loads indicated that rat and hamster cells have both Na(+)-H+ and Na(+)- and HCO3(-)-dependent regulatory systems, while hamster cells have, in addition, a Na(+)-independent recovery mechanism activated at acid pHi. We conclude that alpha-adrenergic alkalinization of brown fat may contribute to the control of thermogenesis.

scholarly journals Pandinus imperator scorpion venom blocks voltage-gated potassium channels in GH3 cells.

1988 ◽  
Vol 91 (6) ◽  
pp. 817-833 ◽  
Author(s):  
P A Pappone ◽  
M T Lucero
Keyword(s):  
Potassium Channels ◽  
Potassium Channel ◽  
Potassium Current ◽  
Potassium Currents ◽  
Scorpion Venom ◽  
Gh3 Cells ◽  
Pituitary Cells ◽  
Crude Venom ◽  
Voltage Gated ◽  
Voltage Dependent

We examined the effects of Pandinus imperator scorpion venom on voltage-gated potassium channels in cultured clonal rat anterior pituitary cells (GH3 cells) using the gigohm-seal voltage-clamp method in the whole-cell configuration. We found that Pandinus venom blocks the voltage-gated potassium channels of GH3 cells in a voltage-dependent and dose-dependent manner. Crude venom in concentrations of 50-500 micrograms/ml produced 50-70% block of potassium currents measured at -20 mV, compared with 25-60% block measured at +50 mV. The venom both decreased the peak potassium current and shifted the voltage dependence of potassium current activation to more positive potentials. Pandinus venom affected potassium channel kinetics by slowing channel opening, speeding deactivation slightly, and increasing inactivation rates. Potassium currents in cells exposed to Pandinus venom did not recover control amplitudes or kinetics even after 20-40 min of washing with venom-free solution. The concentration dependence of crude venom block indicates that the toxins it contains are effective in the nanomolar range of concentrations. The effects of Pandinus venom were mimicked by zinc at concentrations less than or equal to 0.2 mM. Block of potassium current by zinc was voltage dependent and resembled Pandinus venom block, except that block by zinc was rapidly reversible. Since zinc is found in crude Pandinus venom, it could be important in the interaction of the venom with the potassium channel. We conclude that Pandinus venom contains toxins that bind tightly to voltage-dependent potassium channels in GH3 cells. Because of its high affinity for voltage-gated potassium channels and its irreversibility, Pandinus venom may be useful in the isolation, mapping, and characterization of voltage-gated potassium channels.

scholarly journals Structure-activity relationship studies of three novel 4-aminopyridine K+ channel blockers

2019 ◽  
Author(s):  
Sofia Rodríguez-Rangel ◽  
Alyssa D. Bravin ◽  
Karla M. Ramos-Torres ◽  
Pedro Brugarolas ◽  
Jorge E. Sánchez-Rodríguez
Keyword(s):  
Multiple Sclerosis ◽  
Potassium Channels ◽  
Symptomatic Treatment ◽  
K Channel ◽  
Channel Blockers ◽  
Rodent Models ◽  
Voltage Gated ◽  
Structure Activity ◽  
Pet Tracer ◽  
Ph Conditions

Abstract4-Aminopyridine (4AP) is a specific blocker of voltage-gated potassium channels (KV1 family) clinically approved for the symptomatic treatment of patients with multiple sclerosis (MS). It has recently been shown that [18F]3F4AP, a radiofluorinated analog of 4AP, also binds to KV1 channels and can be used as a PET tracer for the detection of demyelinated lesions in rodent models of MS. Here, we investigate three novel 4AP derivatives containing methyl (-CH3), methoxy (-OCH3) and trifluoromethyl (-CF3) in the 3 position as potential candidates for PET imaging and/or therapy. We characterized the physicochemical properties of these compounds (pKa and logD) and analyzed their ability to block Shaker K+ channel under different voltage and pH conditions. Our results demonstrate that all three derivatives are able to block voltage-gated potassium channels. Specifically, 3-methyl-4-aminopyridine (3Me4AP) was found to be approximately 7-fold more potent than 4AP, whereas the methoxy (3MeO4AP) and trifluoromethyl (3CF34AP) containing compounds were about 3- to 4-fold less potent than 4AP, respectively. These results suggest that these novel derivatives are potential candidates for therapy and imaging.

scholarly journals Psychiatric presentation of voltage-gated potassium channel antibody-associated encephalopathy

2006 ◽  
Vol 189 (2) ◽  
pp. 182-183 ◽  
Author(s):  
U. D. Parthasarathi ◽  
T. Harrower ◽  
M. Tempest ◽  
J. R. Hodges ◽  
C. Walsh ◽  
...  
Keyword(s):  
Potassium Channels ◽  
Potassium Channel ◽  
Memory Impairment ◽  
Psychiatric Symptoms ◽  
Epileptic Seizures ◽  
Complete Recovery ◽  
Panic Attacks ◽  
Voltage Gated ◽  
With Memory

SummaryVoltage-gated potassium channel antibody encephalopathy, a rare cause of limbic encephalopathy, typically presents with memory impairment and seizures. Psychiatric symptoms have not been emphasised in the literature. Here we describe a 58-year-old man who presented with panic attacks and psychogenic non-epileptic seizures and, later on, developed delusions and hallucinations and then confusion. He was found to have antibodies to voltage-gated potassium channels. Treatment with immuno-modulatory therapy resulted in almost complete recovery.

1,4-Diazabicyclo[2.2.2]octane Derivatives: A Novel Class of Voltage-Gated Potassium Channel Blockers

2005 ◽  
Vol 69 (3) ◽  
pp. 718-726 ◽  
Author(s):  
Earl Gordon ◽  
Jaime-Lee Cohen ◽  
Robert Engel ◽  
Geoffrey W. Abbott
Keyword(s):  
Potassium Channel ◽  
Channel Blockers ◽  
Voltage Gated ◽  
Potassium Channel Blockers

scholarly journals Molecular Proximity of Kv1.3 Voltage-gated Potassium Channels and β1-Integrins on the Plasma Membrane of Melanoma Cells

2002 ◽  
Vol 120 (1) ◽  
pp. 29-37 ◽  
Author(s):  
Vira V. Artym ◽  
Howard R. Petty
Keyword(s):  
Potassium Channels ◽  
Tumor Cell ◽  
Cell Membranes ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
K Channel ◽  
Channel Blockers ◽  
Voltage Gated ◽  
Β1 Integrins ◽  
Kv1.3 Channels

Tumor cell membranes have multiple components that participate in the process of metastasis. The present study investigates the physical association of β1-integrins and Kv1.3 voltage-gated potassium channels in melanoma cell membranes using resonance energy transfer (RET) techniques. RET between donor-labeled anti–β1-integrin and acceptor-labeled anti-Kv1.3 channels was detected on LOX cells adherent to glass and fibronectin-coated coverslips. However, RET was not observed on LOX cells in suspension, indicating that molecular proximity of these membrane molecules is adherence-related. Several K+ channel blockers, including tetraethylammonium, 4-aminopyridine, and verapamil, inhibited RET between β1-integrins and Kv1.3 channels. However, the irrelevant K+ channel blocker apamin had no effect on RET between β1-integrins and Kv1.3 channels. Based on these findings, we speculate that the lateral association of Kv1.3 channels with β1-integrins contributes to the regulation of integrin function and that channel blockers might affect tumor cell behavior by influencing the assembly of supramolecular structures containing integrins.

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