Mitochondrial cAMP prevents apoptosis modulating Sirt3 protein level and OPA1 processing in cardiac myoblast cells

Abstract

Mitochondria, responding to a wide variety of signals, including oxidative stress, are critical in regulating apoptosis that plays a key role in the pathogenesis of a variety of cardiovascular diseases. A number of mitochondrial proteins and pathways have been found to be involved in the mitochondrial dependent apoptosis mechanism, such as optic atrophy 1 (OPA1), sirtuin 3 (Sirt3), deacetylase enzyme and cAMP signal. In the present work we report a network among OPA1, Sirt3 and cAMP in ROS-dependent apoptosis. Rat myoblastic H9c2 cell lines, were treated with tert-butyl hydroperoxide (t-BHP) to induce oxidative stress-dependent apoptosis. FRET analysis revealed a selective decrease of mitochondrial cAMP in response to t-BHP treatment. This was associated with a decrease of Sirt3 protein level and proteolytic processing of OPA1. Pretreatment of cells with permeant analogous of cAMP (8-Br-cAMP) protected the cell from apoptosis preventing all these events. Using H89, inhibitor of the protein kinase A (PKA), and protease inhibitors, evidences have been obtained that ROS-dependent apoptosis is associated with an alteration of mitochondrial cAMP/PKA signal that causes degradation/proteolysis of Sirt3 that, in turn, promotes acetylation and proteolytic processing of OPA1.

Mitochondrial Dynamics of Proximal Tubular Epithelial Cells in Nephropathic Cystinosis

“…Our recent studies have shown in CTNS−/− ciPTEC a higher mitochondrial fragmentation index associated with lower mitochondrial potential and mitochondrial cyclic AMP levels, rescued by 24 h treatment with 100 µM cysteamine or with the cell-permeant analogue of cyclic AMP, 8-Br-cAMP [8]. cAMP, in fact, is one of the major regulators of mitochondrial function [28][29][30] and dynamics [31]. In this contest, it should be noted that MEA has been found to improve mitochondrial function in mitochondrial respiratory chain diseases [32].…”

“…The protein expression levels of OPA1 were not significantly changed in mutated cells, compared to control ciPTEC cells (data not shown). However, the activity of OPA1 is also controlled at the post-translational level by proteolytic and acetylation changes [31]. Various stress conditions, including apoptotic stimulation, trigger the complete conversion of L-OPA1 into S-OPA1.…”

Mitochondrial Quality Control in Cardiomyocytes: A Critical Role in the Progression of Cardiovascular Diseases

“…OPA1 is hyperacetylated under pathological stress and its GTPase activity is suppressed, whereas SIRT3, a NAD-dependent protein deacetylase (Onyango et al, 2002), can deacetylate OPA1 at Lys926 and Lys931 and restore its GTPase activity in vivo (Samant et al, 2014). These changes are accompanied by altered mitochondrial cAMP/PKA signaling (Signorile et al, 2017). Additionally, acetylation participates in regulation of mitophagy.…”

PBMC of Multiple Sclerosis Patients Show Deregulation of OPA1 Processing Associated with Increased ROS and PHB2 Protein Levels

“…Interesting, PHB2 has been found up-regulated in lymphocytes of MS patients [26]. OPA1 processing is also modulated by its acetylation status mediated by SIRT3 enzyme, a mitochondrial deacetylase that also plays an important role in apoptosis [20]. In this work we have analyzed the protein level, and proteolytic processing of OPA1 and its stress-associated regulators, OMA1, SIRT3, and PHB2 in PBMCs of MS patients.…”

“…Various stress conditions, including apoptotic stimulation are associated with the conversion of L-OPA1 into S-OPA1. The processing and activity of OPA1 is regulated by mitochondrial proteases, such as OMA1, cellular energetic condition [19], post-translational modification, such as acetylation status [20,21], and oxidative stress [20,22]. OMA1-mediated processing of OPA1 is a cellular stress response, in fact, although OMA1 is constitutively active, it display strongly enhanced activity in response to OS [23].…”