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Apelin-13 enhances arcuate POMC neuron activity via inhibiting M-current.

Lee DK, Jeong JH, Oh S, Jo YH - PLoS ONE (2015)

Bottom Line: This effect is abolished by the apelin (APJ) receptor antagonist.In addition, the effect of apelin is inhibited by the phospholipase C and protein kinase inhibitors.Furthermore, single-cell qPCR analysis shows that POMC neurons express the APJ receptor, PLC-β isoforms, and KCNQ subunits (2, 3 and 5) which contribute to M-type current.

View Article: PubMed Central - PubMed

Affiliation: Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine of Yeshiva University, 1300 Morris Park Avenue, Bronx, NY, 10461, United States of America.

ABSTRACT
The hypothalamus is a key element of the neural circuits that control energy homeostasis. Specific neuronal populations within the hypothalamus are sensitive to a variety of homeostatic indicators such as circulating nutrient levels and hormones that signal circulating glucose and body fat content. Central injection of apelin secreted by adipose tissues regulates feeding and glucose homeostasis. However, the precise neuronal populations and cellular mechanisms involved in these physiological processes remain unclear. Here we examine the electrophysiological impact of apelin-13 on proopiomelanocortin (POMC) neuron activity. Approximately half of POMC neurons examined respond to apelin-13. Apelin-13 causes a dose-dependent depolarization. This effect is abolished by the apelin (APJ) receptor antagonist. POMC neurons from animals pre-treated with pertussis toxin still respond to apelin, whereas the Gβγ signaling inhibitor gallein blocks apelin-mediated depolarization. In addition, the effect of apelin is inhibited by the phospholipase C and protein kinase inhibitors. Furthermore, single-cell qPCR analysis shows that POMC neurons express the APJ receptor, PLC-β isoforms, and KCNQ subunits (2, 3 and 5) which contribute to M-type current. Apelin-13 inhibits M-current that is blocked by the KCNQ channel inhibitor. Therefore, our present data indicate that apelin activates APJ receptors, and the resultant dissociation of the Gαq heterotrimer triggers a Gβγ-dependent activation of PLC-β signaling that inhibits M-current.

No MeSH data available.


Related in: MedlinePlus

Apelin-13 excites POMC neurons via stimulating the Gβγ signaling pathway.(A) Representative recording sample of the whole-cell membrane potential of POMC neurons before, during, and after treatment with apelin-13 with GDP-β-S. GDP-β-S (2 mM) was directly introduced into the cell through patch pipette. Under these conditions, apelin-13 did not excite POMC neurons (n = 8 neurons). (B-C) Sample recording traces showing changes in membrane potential before, during, and after treatment with apelin-13 in animals pre-treated with PTX (B) and in the presence of gallein (C). Application of Apelin-13 (100 nM) effectively depolarized POMC neurons from animals pre-treated with PTX, whereas the same treatment did not change the membrane potential after having blocked Gβγ signaling with gallein. Scale bar: 20 mV, 2 min. (D) Representative recording sample showing that the TRPC channel antagonist 2-APB did not block the effect of apelin-13. Scale bar: 20 mV, 2 min. (E) Summary of the effects of apelin-13 in the presence of Gαi, Gβγ, PLC, PKC and TRPC inhibitors. GDP-β-S, Gallein, U73122, and staurosporin completely blocked the effect. POMC neurons remained to be sensitive to apelin-13 in the presence of PTX and 2-APB. (F) Single-cell qPCR analysis of individual POMC neurons. A representative gel illustrating the expression of the APJ receptor, PLC-β isoforms (1 and 3) and KCNQ subunits (2, 3 and 5) in POMC neurons (L: 100 bp ladder, con: positive control, 1–5: five different APJ receptor-expressing POMC neurons).
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pone.0119457.g002: Apelin-13 excites POMC neurons via stimulating the Gβγ signaling pathway.(A) Representative recording sample of the whole-cell membrane potential of POMC neurons before, during, and after treatment with apelin-13 with GDP-β-S. GDP-β-S (2 mM) was directly introduced into the cell through patch pipette. Under these conditions, apelin-13 did not excite POMC neurons (n = 8 neurons). (B-C) Sample recording traces showing changes in membrane potential before, during, and after treatment with apelin-13 in animals pre-treated with PTX (B) and in the presence of gallein (C). Application of Apelin-13 (100 nM) effectively depolarized POMC neurons from animals pre-treated with PTX, whereas the same treatment did not change the membrane potential after having blocked Gβγ signaling with gallein. Scale bar: 20 mV, 2 min. (D) Representative recording sample showing that the TRPC channel antagonist 2-APB did not block the effect of apelin-13. Scale bar: 20 mV, 2 min. (E) Summary of the effects of apelin-13 in the presence of Gαi, Gβγ, PLC, PKC and TRPC inhibitors. GDP-β-S, Gallein, U73122, and staurosporin completely blocked the effect. POMC neurons remained to be sensitive to apelin-13 in the presence of PTX and 2-APB. (F) Single-cell qPCR analysis of individual POMC neurons. A representative gel illustrating the expression of the APJ receptor, PLC-β isoforms (1 and 3) and KCNQ subunits (2, 3 and 5) in POMC neurons (L: 100 bp ladder, con: positive control, 1–5: five different APJ receptor-expressing POMC neurons).

Mentions: The APJ receptor is a G-protein-coupled receptor [28–29]. We intracellularly applied guanosine-5'-O-2-thiodiphosphate (GDP-β-S; 2 mM) into the cell as inclusion of a non-hydrolysable form of GDP through patch pipette prevents G protein-mediated signaling. Under such experimental conditions, POMC neurons did not responded to apelin-13 (Vm: control,- 52.2 ± 3.6 mV, apelin-13,- 52.3 ± 3.6 mV, n = 8 neurons, p > 0.05; Fig. 2A and E), consistent with the fact that this depolarization occurs dependently of G protein signaling.


Apelin-13 enhances arcuate POMC neuron activity via inhibiting M-current.

Lee DK, Jeong JH, Oh S, Jo YH - PLoS ONE (2015)

Apelin-13 excites POMC neurons via stimulating the Gβγ signaling pathway.(A) Representative recording sample of the whole-cell membrane potential of POMC neurons before, during, and after treatment with apelin-13 with GDP-β-S. GDP-β-S (2 mM) was directly introduced into the cell through patch pipette. Under these conditions, apelin-13 did not excite POMC neurons (n = 8 neurons). (B-C) Sample recording traces showing changes in membrane potential before, during, and after treatment with apelin-13 in animals pre-treated with PTX (B) and in the presence of gallein (C). Application of Apelin-13 (100 nM) effectively depolarized POMC neurons from animals pre-treated with PTX, whereas the same treatment did not change the membrane potential after having blocked Gβγ signaling with gallein. Scale bar: 20 mV, 2 min. (D) Representative recording sample showing that the TRPC channel antagonist 2-APB did not block the effect of apelin-13. Scale bar: 20 mV, 2 min. (E) Summary of the effects of apelin-13 in the presence of Gαi, Gβγ, PLC, PKC and TRPC inhibitors. GDP-β-S, Gallein, U73122, and staurosporin completely blocked the effect. POMC neurons remained to be sensitive to apelin-13 in the presence of PTX and 2-APB. (F) Single-cell qPCR analysis of individual POMC neurons. A representative gel illustrating the expression of the APJ receptor, PLC-β isoforms (1 and 3) and KCNQ subunits (2, 3 and 5) in POMC neurons (L: 100 bp ladder, con: positive control, 1–5: five different APJ receptor-expressing POMC neurons).
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getmorefigures.php?uid=PMC4363569&req=5

pone.0119457.g002: Apelin-13 excites POMC neurons via stimulating the Gβγ signaling pathway.(A) Representative recording sample of the whole-cell membrane potential of POMC neurons before, during, and after treatment with apelin-13 with GDP-β-S. GDP-β-S (2 mM) was directly introduced into the cell through patch pipette. Under these conditions, apelin-13 did not excite POMC neurons (n = 8 neurons). (B-C) Sample recording traces showing changes in membrane potential before, during, and after treatment with apelin-13 in animals pre-treated with PTX (B) and in the presence of gallein (C). Application of Apelin-13 (100 nM) effectively depolarized POMC neurons from animals pre-treated with PTX, whereas the same treatment did not change the membrane potential after having blocked Gβγ signaling with gallein. Scale bar: 20 mV, 2 min. (D) Representative recording sample showing that the TRPC channel antagonist 2-APB did not block the effect of apelin-13. Scale bar: 20 mV, 2 min. (E) Summary of the effects of apelin-13 in the presence of Gαi, Gβγ, PLC, PKC and TRPC inhibitors. GDP-β-S, Gallein, U73122, and staurosporin completely blocked the effect. POMC neurons remained to be sensitive to apelin-13 in the presence of PTX and 2-APB. (F) Single-cell qPCR analysis of individual POMC neurons. A representative gel illustrating the expression of the APJ receptor, PLC-β isoforms (1 and 3) and KCNQ subunits (2, 3 and 5) in POMC neurons (L: 100 bp ladder, con: positive control, 1–5: five different APJ receptor-expressing POMC neurons).
Mentions: The APJ receptor is a G-protein-coupled receptor [28–29]. We intracellularly applied guanosine-5'-O-2-thiodiphosphate (GDP-β-S; 2 mM) into the cell as inclusion of a non-hydrolysable form of GDP through patch pipette prevents G protein-mediated signaling. Under such experimental conditions, POMC neurons did not responded to apelin-13 (Vm: control,- 52.2 ± 3.6 mV, apelin-13,- 52.3 ± 3.6 mV, n = 8 neurons, p > 0.05; Fig. 2A and E), consistent with the fact that this depolarization occurs dependently of G protein signaling.

Bottom Line: This effect is abolished by the apelin (APJ) receptor antagonist.In addition, the effect of apelin is inhibited by the phospholipase C and protein kinase inhibitors.Furthermore, single-cell qPCR analysis shows that POMC neurons express the APJ receptor, PLC-β isoforms, and KCNQ subunits (2, 3 and 5) which contribute to M-type current.

View Article: PubMed Central - PubMed

Affiliation: Division of Endocrinology, Department of Medicine, Albert Einstein College of Medicine of Yeshiva University, 1300 Morris Park Avenue, Bronx, NY, 10461, United States of America.

ABSTRACT
The hypothalamus is a key element of the neural circuits that control energy homeostasis. Specific neuronal populations within the hypothalamus are sensitive to a variety of homeostatic indicators such as circulating nutrient levels and hormones that signal circulating glucose and body fat content. Central injection of apelin secreted by adipose tissues regulates feeding and glucose homeostasis. However, the precise neuronal populations and cellular mechanisms involved in these physiological processes remain unclear. Here we examine the electrophysiological impact of apelin-13 on proopiomelanocortin (POMC) neuron activity. Approximately half of POMC neurons examined respond to apelin-13. Apelin-13 causes a dose-dependent depolarization. This effect is abolished by the apelin (APJ) receptor antagonist. POMC neurons from animals pre-treated with pertussis toxin still respond to apelin, whereas the Gβγ signaling inhibitor gallein blocks apelin-mediated depolarization. In addition, the effect of apelin is inhibited by the phospholipase C and protein kinase inhibitors. Furthermore, single-cell qPCR analysis shows that POMC neurons express the APJ receptor, PLC-β isoforms, and KCNQ subunits (2, 3 and 5) which contribute to M-type current. Apelin-13 inhibits M-current that is blocked by the KCNQ channel inhibitor. Therefore, our present data indicate that apelin activates APJ receptors, and the resultant dissociation of the Gαq heterotrimer triggers a Gβγ-dependent activation of PLC-β signaling that inhibits M-current.

No MeSH data available.


Related in: MedlinePlus