RESUMO
Metabolic changes are critical in the regulation of Ca2+ influx in central and peripheral neuroendocrine cells. To study the regulation of L-type Ca2+ channels by AMPK we used biochemical reagents and ATP/glucose-concentration manipulations in rat chromaffin cells. AICAR and Compound-C, at low concentration, significantly induce changes in L-type Ca2+ channel-current amplitude and voltage dependence. Remarkably, an overlasting decrease in the channel-current density can be induced by lowering the intracellular level of ATP. Accordingly, Ca2+ channel-current density gradually diminishes by decreasing the extracellular glucose concentration. By using immunofluorescence, a decrease in the expression of CaV1.2 is observed while decreasing extracellular glucose, suggesting that AMPK reduces the number of functional Ca2+ channels into the plasma membrane. Together, these results support for the first time the dependence of metabolic changes in the maintenance of Ca2+ channel-current by AMPK. They reveal a key step in Ca2+ influx in secretory cells.
Assuntos
Proteínas Quinases Ativadas por AMP , Aminoimidazol Carboxamida , Canais de Cálcio Tipo L , Células Cromafins , Glucose , Animais , Células Cromafins/metabolismo , Células Cromafins/efeitos dos fármacos , Canais de Cálcio Tipo L/metabolismo , Proteínas Quinases Ativadas por AMP/metabolismo , Ratos , Glucose/metabolismo , Glucose/farmacologia , Aminoimidazol Carboxamida/análogos & derivados , Aminoimidazol Carboxamida/farmacologia , Trifosfato de Adenosina/metabolismo , Ribonucleotídeos/farmacologia , Pirimidinas/farmacologia , Cálcio/metabolismo , Pirazóis/farmacologia , Células Cultivadas , Ratos Wistar , Ativação do Canal Iônico/efeitos dos fármacosRESUMO
Neuronal control of the energy homeostasis requires the arcuate nucleus of the hypothalamus. This structure integrates peripheral and central signals concerning the energy state of the body. It comprises two populations of neurons releasing anorexigenic and orexigenic peptides, among others. Both populations are regulated by leptin, an anorexigenic hormone, released by white adipose tissue. Voltage-gated calcium entry is critical to promote neurotransmitter and hormone release. It is already known that calcium channel current is inhibited by leptin in orexigenic neurons. However, fine-tuning details of calcium channel regulation in arcuate nucleus by leptin remain to be elucidated. This work aimed to investigate whether 5' adenosine monophosphate-activated protein kinase (AMPK) underlies the leptin-induced inhibition of calcium channels. By using patch-clamping methods, immunocytochemical, and biochemical reagents, we recorded calcium channel currents in orexigenic neuropeptide Y neurons of the arcuate nucleus of rats. Consistently, leptin inhibition of the calcium channel current was not only prevented by AMPK inhibition with Compound C but also hampered with 5-aminoimidazole-4-carboxamide ribonucleoside. Furthermore, leptin selectively inhibited L-type calcium channel current amplitude without major changes in voltage dependence or current kinetics. These results support for the first time the key role of AMPK in the maintenance and regulation of voltage-gated calcium channels. Together, they advance our understanding of the regulation of calcium channels in the central nervous system and emerging questions concerning food intake and energy balance.NEW & NOTEWORTHY Our results readily support the hypothesis that AMPK is responsible for the maintenance of the calcium current and mediates the fine-tuning modulation of the leptin response. The novelty of these results strengthens the critical role of AMPK in the general energy balance and homeostasis.
