Pyruvate dehydrogenase has a major role in mast cell function, and its activity is regulated by mitochondrial microphthalmia transcription factor.

Background: We have recently observed that oxidative phosphorylation-mediated ATP production is essential for mast cell function. Pyruvate dehydrogenase (PDH) is the main regulator of the Krebs cycle and is located upstream of the electron transport chain. However, the role of PDH in mast cell function has not been described. Microphthalmia transcription factor (MITF) regulates the development, number, and function of mast cells. Localization of MITF to the mitochondria and its interaction with mitochondrial proteins has not been explored.

Objective: We sought to explore the role played by PDH in mast cell exocytosis and to determine whether MITF is localized in the mitochondria and involved in regulation of PDH activity.

Methods: Experiments were performed in vitro by using human and mouse mast cells, as well as rat basophil leukemia cells, and in vivo in mice. The effect of PDH inhibition on mast cell function was examined. PDH interaction with MITF was measured before and after immunologic activation. Furthermore, mitochondrial localization of MITF and its effect on PDH activity were determined.

Results: PDH is essential for immunologically mediated degranulation of mast cells. After activation, PDH is serine dephosphorylated. In addition, for the first time, we show that MITF is partially located in the mitochondria and interacts with PDH. This interaction is dependent on the phosphorylation state of PDH. Furthermore, mitochondrial MITF regulates PDH activity.

Conclusion: The association of mitochondrial MITF with PDH emerges as an important regulator of mast cell function. Our findings indicate that PDH could arise as a new target for the manipulation of allergic diseases.