p66Shc is an apoptotic rheostat whose targeted ROS inhibition improves MI outcomes

Abstract

p66Shc is an oxidoreductase that responds to cell stress by translocating to mitochondria, where p66Shc produces pro-apoptotic reactive oxygen species (ROS). This study identifies ROS-active p66Shc as a monomer that produces superoxide anion independent of metal ions, inhibits cytochrome c peroxidase, and is regulated by environmental condition-induced structural changes. p66Shc anti-apoptotic functions, including: cytochrome c reduction, increased electron transport chain activity, and caspase cascade inhibition were also discovered. This study also demonstrates that p66Shc is a stress-dependent rheostat of apoptosis, regulated by p66Shc-mortalin complexes. These complexes decrease pro-apoptotic ROS production, without blocking p66Shc-mediated cytochrome c reduction. However, stress disrupts p66Shc-mortalin interactions, promoting apoptosis. Tipping p66Shc apoptotic balance toward anti-apoptotic functions by genetic knockdown or p66Shc-selective ROS inhibition decreased pro-apoptotic effects and improved outcomes in zebrafish myocardial infarction models, representing a potential new myocardial infarction treatment with promising results.

p66Shc in Cardiovascular Pathology

“…These results suggest that FLp66Shc conformational dynamics could be regulated by distal CH2 amino acids. Molecular dynamics simulations and in silico structural models supported these findings, indicating that p66Shc has high conformational variability and is intrinsically disordered with interspersed regions of organization [ 182 ].…”

“…Despite p66Shc’s role in cell–cell adhesion and cytoskeletal signaling, which could influence cardiovascular pathologies such as angina perctoris or cardiac arrest, this aspect of p66Shc research is limited in the context of cardiovascular disease. However, it is plausible that p66Shc’s mechanosensory function contributes to atherosceloris, MI, and other pathologies as p66Shc KO improves their outcomes, but these outcomes are also associated with decreased p66Shc-mediated ROS activity and deconvoluting the interactions between p66Shc mechanical and ROS-activating stimuli is difficult [ 118 , 121 , 180 , 181 , 182 ]. p66Shc signaling pathways are summarized in Figure 2 .…”

“…ROS composition differences can therefore govern compartmental and inter-compartmental redox signaling, altering cell fate [ 25 , 26 ]. A variety of functional assays have shown that p66Shc does not directly produce H 2 O 2 , but rather superoxide anion [ 182 ]. Further investigation determined that neither metal cations, nor cyt c, were needed for superoxide anion activity, even though both were previously considered requirements [ 5 , 90 ].…”

“…Several environmental factors regulate p66Shc superoxide anion production during in vitro assays, such as: pH, temperature, shear, and cardiolipin presence. p66Shc ROS production is highest in acidic, warm, cardiolipin-rich environments but is also increased with direct shear (indirect shear on cell membranes also increases p66Shc mitochondrial translocation) [ 2 , 182 ]. Of note, CL is essential for normal electron transport and promotes respiratory complex assembly and could therefore affect structural characteristics of other proteins [ 336 , 337 , 338 ].…”

“…It is prescribed in Europe for mitochondrial diseases with p66Shc associations [ 348 , 349 ]. At high concentrations (40–80 µM), idebenone sensitizes PTP opening and inhibits ETC complex I, but p66Shc-idebenone affinity has a reported Kd of ~229 nM (IC 50 ~ 328 nM) and idebenone’s low concentration mitochondrial mechanism of action has not previously been characterized [ 182 ]. Idebenone has also been shown to improve insulin sensitivity via p52Shc signaling activity [ 350 ].…”