研究内容

10　詳細

2005年4月〜 東京大学大学院薬学系研究科 薬化学教室 助教 > 投稿論文(共同研究)
Adaptive thermogenesis in brown adipose tissue involves activation of pannexin-1 channels
Subramanian Senthivinayagam, Vlad Serbulea, Clint M. Upchurch, Renata Polanowska- Grabowska, Suresh K. Mendu, Srabani Sahu, Prathiba Jayaguru, Kevin W. Aylor, Mahendra D. Chordia, Limor Steinberg, Nathaniel Oberholtzer, Seichii Uchiyama, Noriko Inada, Ulrike M. Lorenz, Thurl E. Harris, Susanna R. Keller, Akshaya K. Meher, Alexandra Kadl, Bimal N. Desai, Bijoy K. Kundu, Norbert Leitinger
Mol. Metab., 2021, 44, 101130

■　Abstract
Objective:
Brown adipose tissue (BAT) is specialized in thermogenesis. The conversion of energy into heat in brown adipocytes proceeds via stimulation of β-adrenergic receptor (βAR)-dependent signaling and activation of mitochondrial uncoupling protein 1 (UCP1). We have previously demonstrated a functional role for pannexin-1 (Panx1) channels in white adipose tissue; however, it is not known whether Panx1 channels play a role in the regulation of brown adipocyte function. Here, we tested the hypothesis that Panx1 channels are involved in brown adipocyte activation and thermogenesis.

Methods:
In an immortalized brown pre-adipocytes cell line, Panx1 currents were measured using patch-clamp electrophysiology. Flow cytometry was used for assessment of dye uptake and luminescence assays for adenosine triphosphate (ATP) release, and cellular temperature measurement was performed using a ratiometric fluorescence thermometer. We used RNA interference and expression plasmids to manipulate expression of wild-type and mutant Panx1. We used previously described adipocyte-specific Panx1 knockout mice (Panx1 Adip-/-) and generated brown adipocyte-specific Panx1 knockout mice (Panx1 BAT-/-) to study pharmacological or cold-induced thermogenesis. Glucose uptake into brown adipose tissue was quantified by positron emission tomography (PET) analysis of 18F-fluorodeoxyglucose (18F-FDG) content. BAT temperature was measured using an implantable telemetric temperature probe.

Results:
In brown adipocytes, Panx1 channel activity was induced either by apoptosis-dependent caspase activation or by β3AR stimulation via a novel mechanism that involves Gβγ subunit binding to Panx1. Inactivation of Panx1 channels in cultured brown adipocytes resulted in inhibition of β3AR-induced lipolysis, UCP-1 expression, and cellular thermogenesis. In mice, adiponectin-Cre-dependent genetic deletion of Panx1 in all adipose tissue depots resulted in defective β3AR agonist- or cold-induced thermogenesis in BAT and suppressed beigeing of white adipose tissue. UCP1-Cre-dependent Panx1 deletion specifically in brown adipocytes reduced the capacity for adaptive thermogenesis without affecting beigeing of white adipose tissue and aggravated diet-induced obesity and insulin resistance.

Conclusions:
These data demonstrate that Gβγ-dependent Panx1 channel activation is involved in b 3AR-induced thermogenic regulation in brown adipocytes. Identification of Panx1 channels in BAT as novel thermo-regulatory elements downstream of β3AR activation may have therapeutic implications.

■　内容・ひとこと
2015年に報告したレシオ型蛍光性温度センサーの応用論文です．褐色脂肪細胞の熱産生に対するパネキシンチャンネルの役割を調べました．この論文への貢献は，細胞レベルの熱産生実験のために，蛍光性温度センサーを提供した「だけ」ですが，それでも自分の開発した蛍光プローブが広く使われていくのは素直に嬉しく感じます．そろそろ自分が開発した蛍光性温度センサーの応用例も10に届きそうですが，そのほとんどが褐色脂肪細胞の熱産生をテーマにしているのが興味深いです．これは化学一筋の自分には想像できない使い道でした．