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Identification of εPKC targets during cardiac ischemic injury
Grant Budas1, Helio Miranda Costa, Julio Cesar Batista Ferreira
1Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA, USA.
Background:
Epsilon-protein kinase C (εPKC) protects the heart from ischemic injury. However, the mechanism(s) of εPKC cardioprotection is still unclear. Identification of the εPKC targets may aid in elucidating the εPKC-mediated cardioprotective mechanisms. Previous studies, using εPKC transgenic mice and difference in gel electrophoresis, identified proteins involved in glucose metabolism, the expression of which was modified by εPKC. Those studies were accompanied by metabolomic analysis, suggesting that increased glucose oxidation may be responsible for the cardioprotective effect of εPKC. Whether these εPKC-mediated alterations were because of differences in protein expression or phosphorylation was not determined.
Methods And Results:
In the present study, we used an εPKC -specific activator peptide, ψεRACK, combined with phosphoproteomics, to find εPKC targets, and identified that the proteins whose phosphorylation was altered by selective activation of εPKC were mostly mitochondrial proteins. Analysis of the mitochondrial phosphoproteome led to the identification of 55 spots, corresponding to 37 individual proteins, exclusively phosphorylated, in the presence of ψεRACK. The majority of the proteins identified were involved in glucose and lipid metabolism, components of the respiratory chain as well as mitochondrial heat shock proteins.
Conclusions:
The protective effect of εPKC during ischemia involves phosphorylation of several mitochondrial proteins involved in glucose and lipid metabolism and oxidative phosphorylation. Regulation of these metabolic pathways by εPKC phosphorylation may lead to εPKC-mediated cardioprotection induced by ψεRACK.
Insights
Epsilon-protein kinase C (εPKC) protects the heart by phosphorylating mitochondrial proteins involved in metabolism and oxidative phosphorylation. This mechanism enhances glucose oxidation, contributing to cardioprotection during ischemia.
Area of Science:
- Cardiology
- Molecular Biology
- Biochemistry
Background:
- Epsilon-protein kinase C (εPKC) is known to protect the heart against ischemic injury.
- The precise mechanisms underlying εPKC-mediated cardioprotection remain largely unknown.
- Previous research suggested a role for altered glucose metabolism in εPKC's protective effects.
Purpose of the Study:
- To identify specific molecular targets of εPKC activation.
- To elucidate the role of protein phosphorylation in εPKC-induced cardioprotection.
- To investigate the impact of εPKC on mitochondrial function and metabolism.
Main Methods:
- Utilized an εPKC-specific activator peptide (ψεRACK).
- Employed phosphoproteomics to identify εPKC targets.
- Analyzed the mitochondrial phosphoproteome.
Main Results:
- Identified 37 unique mitochondrial proteins exclusively phosphorylated upon εPKC activation with ψεRACK.
- The majority of these proteins are involved in glucose and lipid metabolism.
- Key identified proteins include components of the respiratory chain and mitochondrial heat shock proteins.
Conclusions:
- εPKC-mediated cardioprotection during ischemia involves the phosphorylation of mitochondrial proteins.
- These phosphorylations affect key metabolic pathways, including glucose and lipid metabolism and oxidative phosphorylation.
- Regulation of these pathways by εPKC phosphorylation is a critical mechanism for cardioprotection.
