scholarly journals Estrogen Regulation of Genes Important for K+ Channel Signaling in the Arcuate Nucleus

Endocrinology ◽  
2007 ◽  
Vol 148 (10) ◽  
pp. 4937-4951 ◽  
Author(s):  
Troy A. Roepke ◽  
Anna Malyala ◽  
Martha A. Bosch ◽  
Martin J. Kelly ◽  
Oline K. Rønnekleiv
Keyword(s):  
Protein Kinase ◽  
Guinea Pig ◽  
Arcuate Nucleus ◽  
Neuronal Excitability ◽  
Estradiol Benzoate ◽  
K Channel ◽  
Pcr Analysis ◽  
Estrogen Regulation ◽  
K Channels ◽  
Channel Function

Estrogen affects the electrophysiological properties of a number of hypothalamic neurons by modulating K+ channels via rapid membrane actions and/or changes in gene expression. The interaction between these pathways (membrane vs. transcription) ultimately determines the effects of estrogen on hypothalamic functions. Using suppression subtractive hybridization, we produced a cDNA library of estrogen-regulated, brain-specific guinea pig genes, which included subunits from three prominent K+ channels (KCNQ5, Kir2.4, Kv4.1, and Kvβ1) and signaling molecules that impact channel function including phosphatidylinositol 3-kinase (PI3K), protein kinase Cε (PKCε), cAMP-dependent protein kinase (PKA), A-kinase anchor protein (AKAP), phospholipase C (PLC), and calmodulin. Based on these findings, we dissected the arcuate nucleus from ovariectomized guinea pigs treated with estradiol benzoate (EB) or vehicle and analyzed mRNA expression using quantitative real-time PCR. We found that EB significantly increased the expression of KCNQ5 and Kv4.1 and decreased expression of KCNQ3 and AKAP in the rostral arcuate. In the caudal arcuate, EB increased KCNQ5, Kir2.4, Kv4.1, calmodulin, PKCε, PLCβ4, and PI3Kp55γ expression and decreased Kvβ1. The effects of estrogen could be mediated by estrogen receptor-α, which we found to be highly expressed in the guinea pig arcuate nucleus and, in particular, proopiomelanocortin neurons. In addition, single-cell RT-PCR analysis revealed that about 50% of proopiomelanocortin and neuropeptide Y neurons expressed KCNQ5, about 40% expressed Kir2.4, and about 60% expressed Kv4.1. Therefore, it is evident that the diverse effects of estrogen on arcuate neurons are mediated in part by regulation of K+ channel expression, which has the potential to affect profoundly neuronal excitability and homeostatic functions, especially when coupled with the rapid effects of estrogen on K+ channel function.

Modulation of K channels by coexpressed human alpha1C-adrenoceptor in Xenopus oocytes

1997 ◽  
Vol 272 (3) ◽  
pp. H1275-H1286
Author(s):  
G. N. Tseng ◽  
J. A. Yao ◽  
J. Tseng-Crank
Keyword(s):  
Protein Kinase ◽  
Model System ◽  
K Channel ◽  
K Channels ◽  
Channel Modulation ◽  
Channel Function ◽  
Adrenergic Modulation ◽  
Intracellular Ca ◽  
Dependent Protein ◽  
Multiple Receptor

alpha1-Adrenoceptors participate in the regulation of inotropy and chronotropy in the heart. Modulation of cardiac K-channel function plays an important role in these alpha1-adrenergic functions. Studies of the mechanisms of K-channel modulation by alpha1-adrenoceptors are hampered by the coexistence of multiple receptor and channel subtypes in the heart. We therefore used a model system of coexpressing a specific receptor (human alpha1c-adrenoceptor) and a K-channel clone (hIsK, rKv1.2, or rKv1.4) in oocytes. alpha1c-Adrenoceptor stimulation caused a rapid upregulation of hIsK by elevating the intracellular Ca concentration. At least part of this effect was due to an activation of calmodulin and Ca/calmodulin-dependent protein kinase II. On the other hand, alpha1c-adrenoceptor stimulation caused a slow downregulation of rKv1.2 and rKvl.4 by activating protein kinase C. The differential modulation of K channels by alpha1c-adrenoceptors demonstrated in our experiments corroborates the complexity of alpha1-adrenergic functions in the heart. Our results indicate that the oocyte model system can be a useful approach in studying alpha1-adrenergic modulation of ion-channel function and signal transduction.

Alpha-subunit of Gk activates atrial K+ channels of chick, rat, and guinea pig

1988 ◽  
Vol 254 (6) ◽  
pp. H1200-H1205 ◽  
Author(s):  
G. E. Kirsch ◽  
A. Yatani ◽  
J. Codina ◽  
L. Birnbaumer ◽  
A. M. Brown
Keyword(s):  
Guinea Pig ◽  
Single Channel ◽  
Neonatal Rat ◽  
Alpha Subunit ◽  
K Channel ◽  
Muscarinic Agonist ◽  
Guanine Nucleotide Binding Protein ◽  
K Channels ◽  
Open Time ◽  
Guanine Nucleotide Binding

A specific guanine nucleotide-binding protein, Gk, is the link by which muscarinic receptors activate atrial potassium channels (Science Wash. DC 235: 207-211, 1987). In adult guinea pigs, the alpha-subunit at picomolar concentrations mediates the holo-G protein effect (Science Wash. DC 236: 442-445, 1987), but in chick embryo it has been reported that the beta gamma-dimer at nanomolar concentrations rather than the alpha-subunit is the effective mediator (Nature Lond. 325: 321-326, 1987). This difference might have a phylogenetic or ontogenetic basis, and the present experiments tested these possibilities. Preactivated alpha k derived from human red blood cell Gk, when applied to the intracellular surface of inside-out membrane patches from the atria of embryonic chick, neonatal rat, and adult guinea pig activated single K+ channel currents. In each case, the alpha k-activated channels had the same single-channel conductance and mean open time as the muscarinic agonist-activated channels. Half-maximal activation was achieved at alpha k-concentrations of 2.4-13.8 pM. Hence, alpha k-activation of these K+ channels is independent of differences in age or species. The detergent 3-[3-cholamidopropyl)-dimethyammoniol]-1-propanesulfonate (CHAPS), which was used by Logothetis et al. (Nature Lond. 325: 321-326, 1987) at 184 microM to suspend the hydrophobic beta gamma-dimers, activated the same currents. We conclude that the effects of the beta gamma-dimer on these K+ channels is unknown and that as we had proposed earlier (Science Wash. DC 236: 442-445, 1987) it is the alpha-subunit that mediates the Gk effect.

scholarly journals Aging Alters Cerebrovascular Endothelial GPCR and K+ Channel Function: Divergent Role of Biological Sex

2019 ◽  
Vol 75 (11) ◽  
pp. 2064-2073 ◽  
Author(s):  
Md A Hakim ◽  
Phoebe P Chum ◽  
John N Buchholz ◽  
Erik J Behringer
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Old Age ◽  
Purinergic Receptor ◽  
K Channel ◽  
K Channels ◽  
Nitric Oxide Signaling ◽  
Channel Function ◽  
Age Related ◽  
Kir Channel

Abstract Age-related dementia entails impaired blood flow to and throughout the brain due, in part, to reduced endothelial nitric oxide signaling. However, it is unknown whether sex affects cerebrovascular Gq-protein-coupled receptors (GPCRs) and K+ channels underlying endothelium-derived hyperpolarization (EDH) during progressive aging. Thus, we simultaneously evaluated intracellular Ca2+ ([Ca2+]i) and membrane potential (Vm) of intact endothelial tubes freshly isolated from posterior cerebral arteries of young (4–6 mo), middle-aged (12–16 mo), and old (24–28 mo) male and female C57BL/6 mice. Purinergic receptor function (vs. muscarinic) was dominant and enhanced for [Ca2+]i increases in old females versus old males. However, Ca2+-sensitive K+ channel function as defined by NS309-evoked Vm hyperpolarization was mildly impaired in females versus males during old age. This sex-based contrast in declined function of GPCRs and K+ channels to produce EDH may support a greater ability for physiological endothelial GPCR function to maintain optimal cerebral blood flow in females versus males during old age. As reflective of the pattern of cerebral blood flow decline in human subjects, inward-rectifying K+ (KIR) channel function decreased with progressive age regardless of sex. Combined age-related analyses masked male versus female aging and, contrary to expectation, hydrogen peroxide played a minimal role. Altogether, we conclude a sex-based divergence in cerebrovascular endothelial GPCR and K+ channel function while highlighting a previously unidentified form of age-related endothelial dysfunction as reduced KIR channel function.

Role of cAMP-dependent protein kinase in cAMP-mediated vasodilation

1992 ◽  
Vol 262 (2) ◽  
pp. H511-H516 ◽  
Author(s):  
J. Haynes ◽  
J. Robinson ◽  
L. Saunders ◽  
A. E. Taylor ◽  
S. J. Strada
Keyword(s):  
Protein Kinase ◽  
Pressor Response ◽  
Platelet Activating Factor ◽  
K Channel ◽  
Dependent Protein Kinase ◽  
K Channels ◽  
Pulmonary Vasodilation ◽  
Camp Dependent Protein Kinase ◽  
Dependent Protein

In this study, the role of adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase A (PKA) in cAMP-dependent relaxation was assessed in the isolated-perfused rat lung using a PKA inhibitor, Rp-cAMPS, 8-bromo-cAMP (8-BrcAMP), and the diterpene activator of adenylate cyclase (AC), forskolin (FSK). A role for K+ channels was also assessed with the nonselective K+ channel blocker, tetraethylammonium (TEA, 10 mM), and an ATP-sensitive K+ channel inhibitor, glibenclamide (GLI, 100 microM). Both 8-BrcAMP (0.1-1.0 mM) and RSK (0.1-10 microM) dose-dependently attenuated the peak pressor response to alveolar hypoxia (HPR). Rp-cAMPS potentiated the HPR and attenuated 8-BrcAMP-mediated vasodilation but had no effect on FSK-mediated vasodilation. FSK-mediated vasodilation was not mimicked by 1,9-dideoxy-FSK, which is biologically inactive on AC but alters K+ channels identically to FSK, nor was it attenuated by the platelet-activating factor antagonist SRI 63-441 or the cyclooxygenase inhibitor indomethacin. TEA, but not GLI, attenuated FSK-mediated vasodilation. Similarly, TEA attenuated 8-BrcAMP-mediated vasodilation. These results support roles for PKA and indirect gating of a non-ATP-sensitive K+ channel in mediating cAMP-dependent pulmonary vasodilation.

scholarly journals Spasmogen action in guinea-pig isolated trachealis: involvement of membrane K+-channels and the consequences of K+-channel blockade

1988 ◽  
Vol 93 (2) ◽  
pp. 319-330 ◽  
Author(s):  
J.P. Boyle ◽  
J.M. Davies ◽  
R.W. Foster ◽  
D.M. Good ◽  
I. Kennedy ◽  
...  
Keyword(s):  
Guinea Pig ◽  
K Channel ◽  
Channel Blockade ◽  
K Channels

scholarly journals Genes Associated with Membrane-Initiated Signaling of Estrogen and Energy Homeostasis

Endocrinology ◽  
2008 ◽  
Vol 149 (12) ◽  
pp. 6113-6124 ◽  
Author(s):  
T. A. Roepke ◽  
C. Xue ◽  
M. A. Bosch ◽  
T. S. Scanlan ◽  
M. J. Kelly ◽  
...  
Keyword(s):  
Weight Gain ◽  
Gene Transcription ◽  
Energy Homeostasis ◽  
Arcuate Nucleus ◽  
Neuronal Excitability ◽  
Body Weight Gain ◽  
Estradiol Benzoate ◽  
The Body ◽  
Gene Microarray ◽  
D 12

During the reproductive cycle, fluctuations in circulating estrogens affect multiple homeostatic systems controlled by hypothalamic neurons. Two of these neuronal populations are arcuate proopiomelanocortin and neuropeptide Y neurons, which control energy homeostasis and feeding. Estradiol modulates these neurons either through the classical estrogen receptors (ERs) to control gene transcription or through a G protein-coupled receptor (mER) activating multiple signaling pathways. To differentiate between these two divergent ER-mediated mechanisms and their effects on homeostasis, female guinea pigs were ovariectomized and treated systemically with vehicle, estradiol benzoate (EB) or STX, a selective mER agonist, for 4 wk, starting 7 d after ovariectomy. Individual body weights were measured after each injection day for 28 d, at which time the animals were euthanized, and the arcuate nucleus was microdissected. As predicted, the body weight gain was significantly lower for EB-treated females after d 5 and for STX-treated females after d 12 compared with vehicle-treated females. Total arcuate RNA was extracted from all groups, but only the vehicle and STX-treated samples were prepared for gene microarray analysis using a custom guinea pig gene microarray. In the arcuate nucleus, 241 identified genes were significantly regulated by STX, several of which were confirmed by quantitative real-time PCR and compared with EB-treated groups. The lower weight gain of EB-treated and STX-treated females suggests that estradiol controls energy homeostasis through both ERα and mER-mediated mechanisms. Genes regulated by STX indicate that not only does it control neuronal excitability but also alters gene transcription via signal transduction cascades initiated from mER activation.

Structural Correlates of K+ Channel Function

Physiology ◽  
1994 ◽  
Vol 9 (4) ◽  
pp. 169-173 ◽  
Author(s):  
M Taglialatela ◽  
AM Brown
Keyword(s):  
Ion Channel ◽  
Ionic Currents ◽  
The Other ◽  
K Channel ◽  
K Channels ◽  
Functional Studies ◽  
Channel Function ◽  
Voltage Dependent ◽  
K Currents

More complementary DNAs have been cloned for Voltage-dependent K+ channels than any other voltage-dependent ion channel. Purely functional studies anticipated this result because K+ currents are far more diverse than voltage-dependent Na+, Ca2+, or Cl currents, the other types of voltage-dependent ionic currents commonly dealt with.

scholarly journals Structural basis of ion permeation gating in Slo2.1 K+ channels

2013 ◽  
Vol 142 (5) ◽  
pp. 523-542 ◽  
Author(s):  
Priyanka Garg ◽  
Alison Gardner ◽  
Vivek Garg ◽  
Michael C. Sanguinetti
Keyword(s):  
Selectivity Filter ◽  
Structural Basis ◽  
K Channel ◽  
Xenopus Laevis Oocytes ◽  
Ion Permeation ◽  
Channel Activation ◽  
K Channels ◽  
Voltage Gated ◽  
Channel Function ◽  
Activation Gate

The activation gate of ion channels controls the transmembrane flux of permeant ions. In voltage-gated K+ channels, the aperture formed by the S6 bundle crossing can widen to open or narrow to close the ion permeation pathway, whereas the selectivity filter gates ion flux in cyclic-nucleotide gated (CNG) and Slo1 channels. Here we explore the structural basis of the activation gate for Slo2.1, a weakly voltage-dependent K+ channel that is activated by intracellular Na+ and Cl−. Slo2.1 channels were heterologously expressed in Xenopus laevis oocytes and activated by elevated [NaCl]i or extracellular application of niflumic acid. In contrast to other voltage-gated channels, Slo2.1 was blocked by verapamil in an activation-independent manner, implying that the S6 bundle crossing does not gate the access of verapamil to its central cavity binding site. The structural basis of Slo2.1 activation was probed by Ala scanning mutagenesis of the S6 segment and by mutation of selected residues in the pore helix and S5 segment. Mutation to Ala of three S6 residues caused reduced trafficking of channels to the cell surface and partial (K256A, I263A, Q273A) or complete loss (E275A) of channel function. P271A Slo2.1 channels trafficked normally, but were nonfunctional. Further mutagenesis and intragenic rescue by second site mutations suggest that Pro271 and Glu275 maintain the inner pore in an open configuration by preventing formation of a tight S6 bundle crossing. Mutation of several residues in S6 and S5 predicted by homology modeling to contact residues in the pore helix induced a gain of channel function. Substitution of the pore helix residue Phe240 with polar residues induced constitutive channel activation. Together these findings suggest that (1) the selectivity filter and not the bundle crossing gates ion permeation and (2) dynamic coupling between the pore helix and the S5 and S6 segments mediates Slo2.1 channel activation.

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