The Critical Role Played by Mitochondrial MITF Serine 73 Phosphorylation in Immunologically Activated Mast Cells.

Lakshmi Bhargavi Paruchuru,Sharmila Govindaraj,Ehud Razin

doi:10.3390/cells11030589

Lakshmi Bhargavi Paruchuru, Sharmila Govindaraj + Show 1 more

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https://doi.org/10.3390/cells11030589

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Journal: Cells	Publication Date: Feb 8, 2022
Citations: 4	License type: CC BY 4.0

Affiliation: Hebrew University of Jerusalem

Abstract

In recent years, growing evidence has indicated the pivotal role of mitochondria in mast cell immunological activation. We have previously reported a decrease in degranulation and cytokine secretion following the inhibition of pyruvate dehydrogenase (PDH) either by CPI-613 (PDH inhibitor/anti-cancer drug) or through its interaction with mitochondrial microphthalmia-associated transcription factor (MITF). In the present study, we further explored the role played by mitochondrial MITF in mast cell exocytosis using rat basophil leukemia cells [RBL], as well as mouse bone marrow-derived mast cells (BMMCs). Here, we report that mast cell degranulation, cytokine secretion and oxidative phosphorylation (OXPHOS) activities were associated with phosphorylation of Serine 73 of mitochondrial MITF, controlled by extracellular signals regulated by protein kinase (ERK1/2) activity. Also, we report here that decreased OXPHOS activity following ERK1/2 inhibition (U0126 treatment) during IgE-Ag activation was mediated by the dephosphorylation of Serine 73 mitochondrial MITF, which inhibited its association with PDH. This led to a reduction in mast cell reactivity. In addition, a phosphorylation-mimicking mitochondrial MITF-S73D positively regulated the mitochondrial activity, thereby supporting mast cell degranulation. Thus, the present research findings highlight the prominence of mitochondrial MITF Serine 73 phosphorylation in immunologically activated mast cells.

Highlights

We recently reported that pyruvate dehydrogenase (PDH), a key player in oxidative phosphorylation and cellular respiration, regulates Mast Cell function controlled by its association with mitochondrial microphthalmia-associated transcription factor (MITF) [1]
The present section of the study was initiated to understand whether prolonged exposure of antigen (Ag)/allergen dinitrophenyl albumin (DNP) on IgE-stimulated cells has any effect on MITF phosphorylation and to identify the changes at the mitochondrial level
We previously reported the association of mitochondrial MITF with PDH, whereby the association-dissociation status was dependent on immunological activation of the mast cell

Summary

Introduction

We recently reported that pyruvate dehydrogenase (PDH), a key player in oxidative phosphorylation and cellular respiration, regulates Mast Cell function controlled by its association with mitochondrial microphthalmia-associated transcription factor (MITF) [1].PDH phosphorylation is one of the fundamental factors determining PDH activity [2]during allergic stimulus. Inhibition of PDH activity by CPI-613, a known anti-cancer agent [3], has been shown to reduce mast cell β-hexosaminidase and cytokine release [1]. Variable factors such as post-translational modifications and protein interactions with MITF influence its transcriptional activity, regulating MITF function in a coordinated manner. Along with mitogen-activated protein kinase (MAPK) activation, mast cell IgE-Ag stimulation activates several kinase pathways [9] This activated signal transduction pathway causes MITF phosphorylation at Serine 73, which enhances its nuclear transcriptional activity [10]. It was previously described that in melanoma cells, MAPK-mediated phosphorylation of MITF at Serine 73 assembles the two coactivators, E1A binding protein p300 and cAMP-response element binding protein (p300/CBP), which together enhance MITF transcriptional activity [11]

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