The Ano4 channel in the AP is required for orexigenic action of asprosin

About This Grant

PROJECT SUMMARY A recent study involving whole-exome sequencing of 640, 000 human subjects showed that variant of anoctamin (ANO4) gene is linked with human obesity. Our lab revealed that Ano4, a calcium-activated chloride channel, is highly expressed in the ventromedial hypothalamic nucleus glucose-inhibited neurons but minimal in glucose- excited neurons. Furthermore, Ano4-mediated currents are functionally required for their activation in response to low glucose. In a brain-wide mapping of Ano4-expressing neurons, I found that many area postrema (AP) neurons express Ano4 (APAno4 neurons). In a pilot study, I found that genetic deletion of Ano4 specifically in the AP results in decreased body weight and low blood glucose levels. Additionally, chemogenetic activation of APAno4 neurons promotes feeding and increases blood glucose levels. Asprosin is a hunger-induced glucogenic and centrally acting orexigenic hormone, and protein tyrosine phosphatase receptor δ (Ptprd) serves as the asprosin receptor in the brain. My preliminary data showed that APAno4 neurons express Ptprd, and asprosin can activate APAno4 neurons, but the effect is largely abolished by the Ano blocker CaCC(inh)-A01. Here I put forward a general hypothesis that the Ano4 channel in the AP is required for orexigenic action of asprosin. In the Aim 1 of the proposal, I will continues to probe the physiological functions of APAno4 neurons in the contexts of type 1 diabetes and diet-induced obesity - whether loss-of-function of Ano4 would alleviate hyperglycemia and obesity. Ano blocker CaCC(inh)-A01 was show to attenuate diet-induced obesity, but whether the effect is specifically mediated by APAno4 neurons is still unknown. Thus, I will test the effect the CaCC(inh)-A01 when APAno4 neurons are activated. Since APAno4 neurons express Ptprd, in the Aim 2, I will characterize the metabolic phenotypes of mice with deletion of Ptprd in APAno4 neurons. Asprosin can activate APAno4 neurons during brain slice recording, but it is not known if Ano4 in the AP is required for asprosin’s action in vivo. Toward this, I will test the effect of asprosin in mice when Ano4 are deleted in the AP. Furthermore, I will also characterize the cellular functions of APAno4 neurons (e.g., Ano currents, sEPSC and sIPSC) in response to asprosin when Ptprd or Ano4 is deleted. Overall, these proposed studies will reveal Ano4 in the AP as a potential target for treating obesity and associated complications, and further unravel the role of Ano4 in mediating asprosin’s action. In addition, this project will provide an ideal training opportunity to prepare me for an independent research career focusing on the central regulation of energy and glucose homeostasis, in particular on the circulating hormones and chemicals regulating neuronal activity and their roles in metabolic control.