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Activation of Mitochondrial Calpain 1 Leads to Degradation of PDH
Author(s) -
Chen Qun,
Thompson Jeremy,
Hu Ying,
Hollander John,
Lesnefsky Edward
Publication year - 2018
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2018.32.1_supplement.543.7
Subject(s) - mitochondrion , calpain , oxidative phosphorylation , pyruvate dehydrogenase complex , calcium , knockout mouse , protein subunit , cytosol , chemistry , biochemistry , microbiology and biotechnology , biology , receptor , enzyme , gene , organic chemistry
INTODUCTION Calpain 1 (CPN1) is a ubiquitous calpain including one large subunit and a small regulatory subunit (calpain 4, CPN4). Genetic removal of CPN4 eliminates the CPN1 activity. CPN1 exists in both cytosol and mitochondria. Activation of CPN1 contributes to mitochondrial damage and cardiac injury during ischemia (ISC)‐reperfusion (REP). Pyruvate dehydrogenase (PDH) is degraded in mitochondria following ISC‐REP. Since mitochondrial CPN1 (mit‐CPN1) is found in the matrix, we propose that activation of mit‐CPN1 contributes to PDH degradation. Purified heart mitochondria were used to exclude potential cytosolic CPN1 contamination. CPN4 knockout mice were used to eliminate mit‐CPN1. HYPOTHESIS We hypothesize that activation of the mit‐CPN1 impairs oxidative phosphorylation (OXPHOS) through degradation of PDH in isolated mouse heart mitochondria. METHODS Purified cardiac mitochondria were isolated from wild‐type and CPN4 knockout mice. Exogenous calcium (25 uM) was used to activate mit‐CPN1. OXPHOS was determined in mitochondria with or without calcium treatment. Protein content of PDH E1 subunit was assessed by Western blotting. RESULTS In wild type mice, calcium treatment significantly decreased the rate of OXPHOS using pyruvate + malate as complex I substrates compared to non‐calcium‐treated control. Succinate oxidation was also slightly decreased in calcium treated mitochondria from wild type hearts (Table). In contrast, calcium treatment did not affect OXPHOS in mitochondria from CPN4 knockout mice in both substrates. PDH E1 subunit content was decreased in calcium‐treated mitochondria from wild type mice but not from CPN4 knockout mice. A representative image is shown in Figure 1. CONCLUSION Knockout of CPN4 prevents exogenous calcium‐mediated PDH degradation. Inhibition of CPN4 during calcium over load conditions including heart failure and endoplasmic reticulum stress may decrease cardiac injury by protecting mitochondria. Support or Funding Information A Grant‐in‐aid (15GRNT24480123) from the American Heart Association (QC), R21AG054975‐01 (QC), and Merit Review Award (2IO1BX001355‐01, EL) This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .