Ca-associated Triphasic PH Changes in Mitochondria During Brown Adipocyte Activation

Overview

Journal Mol Metab

Specialty Cell Biology

Date 2017 Jul 29

PMID 28752044

Citations 11

Authors

Yanyan Hou

Tetsuya Kitaguchi

Rokus Kriszt

Yu-Hua Tseng

Michael Raghunath

Madoka Suzuki

Affiliations

Soon will be listed here.

Abstract

Objective: Brown adipocytes (BAs) are endowed with a high metabolic capacity for energy expenditure due to their high mitochondria content. While mitochondrial pH is dynamically regulated in response to stimulation and, in return, affects various metabolic processes, how mitochondrial pH is regulated during adrenergic stimulation-induced thermogenesis is unknown. We aimed to reveal the spatial and temporal dynamics of mitochondrial pH in stimulated BAs and the mechanisms behind the dynamic pH changes.

Methods: A mitochondrial targeted pH-sensitive protein, mito-pHluorin, was constructed and transfected to BAs. Transfected BAs were stimulated by an adrenergic agonist, isoproterenol. The pH changes in mitochondria were characterized by dual-color imaging with indicators that monitor mitochondrial membrane potential and heat production. The mechanisms of pH changes were studied by examining the involvement of electron transport chain (ETC) activity and Ca profiles in mitochondria and the intracellular Ca store, the endoplasmic reticulum (ER).

Results: A triphasic mitochondrial pH change in BAs upon adrenergic stimulation was revealed. In comparison to a thermosensitive dye, we reveal that phases 1 and 2 of the pH increase precede thermogenesis, while phase 3, characterized by a pH decrease, occurs during thermogenesis. The mechanism of pH increase is partially related to ETC. In addition, the pH increase occurs concurrently with an increase in mitochondrial Ca. This Ca increase is contributed to by an influx from the ER, and it is further involved in mitochondrial pH regulation.

Conclusions: We demonstrate that an increase in mitochondrial pH is implicated as an early event in adrenergically stimulated BAs. We further suggest that this pH increase may play a role in the potentiation of thermogenesis.

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