GRIM-19, a Cell Death Regulatory Protein, Is Essential for Assembly and Function of Mitochondrial Complex I

Mitochondria play essential roles in cellular energy production via the oxidative phosphorylation system (OXPHOS) consisting of five multiprotein complexes and also in the initiation of apoptosis. NADH:ubiquinone oxidoreductase (complex I) is the largest complex that catalyzes the first step of electron transfer in the OXPHOS system. GRIM-19 was originally identified as a nuclear protein with apoptotic nature in interferon (IFN)- and all-trans-retinoic acid (RA)-induced tumor cells. To reveal its biological role, we generated mice deficient in GRIM-19 by gene targeting. Homologous deletion of GRIM-19 causes embryonic lethality at embryonic day 9.5. GRIM-19(−/−) blastocysts show retarded growth in vitro and, strikingly, display abnormal mitochondrial structure, morphology, and cellular distribution. We reexamined the cellular localization of GRIM-19 in various cell types and found its primary localization in the mitochondria. Furthermore, GRIM-19 is detected in the native form of mitochondrial complex I. Finally, we show that elimination of GRIM-19 destroys the assembly and electron transfer activity of complex I and also influences the other complexes in the mitochondrial respiratory chain. Our result demonstrates that GRIM-19, a gene product with a specific role in IFN-RA-induced cell death, is a functional component of mitochondrial complex I and is essential for early embryonic development

Mouse DCUN1D1 (SCCRO) is required for spermatogenetic individualization.

Squamous cell carcinoma-related oncogene (SCCRO, also known as DCUN1D1) is a component of the E3 for neddylation. As such, DCUN1D1 regulates the neddylation of cullin family members. Targeted inactivation of DCUN1D1 in mice results in male-specific infertility. Infertility in DCUN1D1-/- mice is secondary to primary defects in spermatogenesis. Time-dam experiments mapped the onset of the defect in spermatogenesis to 5.5 to 6 weeks of age, which temporally corresponds to defects in spermiogenesis. Although the first round of spermatogenesis progressed normally, the number of spermatozoa released into the seminiferous lumen and epididymis of DCUN1D1-/- mice was significantly reduced. Spermatozoa in DCUN1D1-/- mice had multiple abnormalities, including globozoospermia, macrocephaly, and multiple flagella. Many of the malformed spermatozoa in DCUN1D1-/- mice were multinucleated, with supernumerary and malpositioned centrioles, suggesting a defect in the resolution of intercellular bridges. The onset of the defect in spermatogenesis in DCUN1D1-/- mice corresponds to an increase in DCUN1D1 expression observed during normal spermatogenesis. Moreover, consistent with its known function as a component of the E3 in neddylation, the pattern of DCUN1D1 expression temporally correlates with an increase in the neddylated cullin fraction and stage-specific increases in the total ubiquitinated protein pool in wild-type mice. Levels of neddylated Cul3 were decreased in DCUN1D1-/- mice, and ubiquitinated proteins did not accumulate during the stages in which DCUN1D1 expression peaks during spermatogenesis in wild-type mice. Combined, these findings suggest that DCUN1D1-/- mice fail to release mature spermatozoa into the seminiferous lumen, possibly due to unresolved intercellular bridges. Furthermore, the effects of DCUN1D1 on spermatogenesis likely involve its regulation of cullin-RING-ligase (CRL)-type ubiquitin E3 activity during spermiogenesis through its role in promoting Cul3 neddylation. The specific CRLs required for spermiogenesis and their protein targets require identification

SCCRO (DCUN1D1) Is an Essential Component of the E3 Complex for Neddylation*S⃞

Covalent modification of cullins by the ubiquitin-like protein NEDD8 (neddylation) regulates protein ubiquitination by promoting the assembly of cullin-RING ligase E3 complexes. Like ubiquitination, neddylation results from an enzymatic cascade involving the sequential activity of a dedicated E1 (APPBP1/Uba3), E2 (Ubc12), and an ill-defined E3. We show that SCCRO (also known as DCUN1D1) binds to the components of the neddylation pathway (Cullin-ROC1, Ubc12, and CAND1) and augments but is not required for cullin neddylation in reactions using purified recombinant proteins. We also show that SCCRO recruits Ubc12∼NEDD8 to the CAND1-Cul1-ROC1 complex but that this is not sufficient to dissociate or overcome the inhibitory effects of CAND1 on cullin neddylation in purified protein assays. In contrast to findings in cellular systems where no binding is seen, we show that SCCRO and CAND1 can bind to the neddylated Cul1-ROC1 complex in assays using purified recombinant proteins. Although neddylated (not unneddylated) Cul1-ROC1 is released from CAND1 upon incubation with testis lysate from SCCRO+/+ mice, the addition of recombinant SCCRO is required to achieve the same results in lysate from SCCRO–/– mice. Combined, these results suggest that SCCRO is an important component of the neddylation E3 complex that functions to recruit charged E2 and is involved in the release of inhibitory effects of CAND1 on cullin-RING ligase E3 complex assembly and activity

Intravenous application of a primary sevoflurane metabolite improves outcome in murine septic peritonitis: first results

Volatile anesthetics are known to have immunomodulatory effects in conditions of organ injury. A recent study in an experimental sepsis model has shown remarkably improved survival when mice were exposed to volatile anesthetics. In the present study, we show that hexafluoroisopropanol - a water-soluble primary sevoflurane metabolite - has beneficial effects on the overall survival in a murine model of cecal ligation and puncture. Seven-day survival as well as tissue damage markers including transaminases and high mobility group box protein-1 were assessed as measures of end organ damage. In animals undergoing cecal ligation and puncture procedure hexafluoroisopropanol conditioning - but not late postconditioning 24 hours after sepsis induction - significantly increased survival rate (17% vs. 77%, p = 0.037) and attenuated secretion of organ damage markers. This study shows survival benefits by administration of the metabolite of a volatile anesthetic. If successfully translated, hexafluoroisopropanol might offer interesting therapeutic opportunities in the future treatment of abdominal sepsis