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Phenotypic Differences Among Mice with Induced Cardiomyocyte‐Restricted Ablation of Cops5, Cops8, or Both
Author(s) -
Lewno Megan,
Wang Xuejun
Publication year - 2021
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.2021.35.s1.05216
Subject(s) - conditional gene knockout , biology , necroptosis , genetically modified mouse , transgene , tamoxifen , ubiquitin , phenotype , medicine , andrology , endocrinology , microbiology and biotechnology , apoptosis , genetics , cancer , programmed cell death , gene , breast cancer
Background‐ Within a large subset of heart failure, the ubiquitin proteasome system has shown to be inadequate or even causative. The COP9 signalosome (CSN) holocomplex, a vital ubiquitination regulator, directly regulates Cullin‐RING ligases (CRLs) via Cullin deneddylation. This holocomplex is formed by 8 unique subunits (COPS1~COPS8), where the deneddylase activity resides in COPS5. Our lab has shown in the past that cardiomyocyte‐restricted knockout (CKO) of the Cops8 gene causes cardiomyocyte necroptosis, dilated cardiomyopathy, and shortened lifespan in mice. This study tests whether the protection against necroptosis by Cops8 is deneddylation‐dependent or Cops8‐specific, possibly alluding to subunit‐specific functions independent of the holocomplex. Methods and Results‐ CKO of Cops8 , Cops5, or both in adult mice was achieved using a tamoxifen‐inducible Cre‐LoxP system. Echocardiography performed 21 days after tamoxifen withdrawal showed no significant difference between MerCreMer (MCM) transgenic and Cops8‐floxed/Cops5‐floxed control groups. Compared with either control group, all CKO groups developed dilated cardiomyopathy, but the severity in the Cops5‐CKO and the Cops8+Cops5 double CKO (dCKO) groups was greater than that in the Cops8‐CKO group. Kaplan‐Meier survival analyses revealed shortened lifespans for all CKO groups, compared with the MCM group. The post‐tamoxifen lifespans of Cops5‐CKO and dCKO mice were comparable (median 42 days vs. 42 days; p=0.66) but significantly shorter than that of the Cops8‐CKO (81 days, p<0.0001). In Cops5‐CKO and dCKO mice, we observed an increased number of cardiomyocytes positive for Evan's blue dye uptake and increased myocardial CD45 proteins compared to Cops8‐CKO. All CKO myocardium showed increases in full‐length caspase 8 but decreased cleaved caspase 8, indicating suppression of caspase 8 activation by defective CSN. Conclusions (1)Cops5‐CKO and dCKO are similarly detrimental but are more so than Cops8‐CKO; (2) the primary defect caused by Cops8‐CKO results from impaired CSN holocomplex formation and thereby loss of Cullin deneddylation.