Abstract
CISD (CDGSH iron-sulfur domain) is a subtype of iron and sulfur cluster binding domain, which is highly conserved in prokaryotes and eukaryote; however, the biological functions are largely unclear. In human and mice, there are three CISD proteins, including CISD1, CISD2 and CISD3. In mice, it has been reported that Cisd1-null mice demonstrate a reduced oxidative capacity of mitochondria; Cisd2 knockout mice led to mitochondrial defect and an increased autophagy accompany by premature aging; Cisd3 is unclear yet. In this study, we identified that CG1458 and C3420 are CISD proteins by alignment CDGSH domain sequence in Drosophila. CG1458 contains a CDGSH domain in C-terminal region. The sequence of CG1458 is similar to those of Cisd1 and Cisd2 in mice. In Drosophila, we found that CG1458 is located on or within the mitochondria, and that it increases in abundance with aging. Using a daughterless-GAL4 driver, overexpression of CG1458 fly line was found to reduce the mean lifespan to 41% compared to that of wild-type Drosophila. The hypomorphic allele, EPG6528 mutant increased the mean lifespan of male flies by 29%, compared to that of wild-type flies. CG1458 likely is a mitochondria-associated protein, thus we use muscle tissue which has the highest energy needs and are therefore the most dependent on mitochondrial function as the tissue model. We found that aging causes protein degradation declines and accumulation of polyubiquitinated proteins, thus we proposed that overexpression of CG1458 results in loss of climbing activity due to the dysfunctional proteins cannot be degraded properly. Using ectopically express CG1458 by Mef2-Gal4 in thoracic muscle, we observed that the mitochondria were swollen, enlarged and fusion-like phenotype in flies in which CG1458 was overexpressed. By contrast, flies in which the expression of CG1458 was knocked down using Mef2-Gal4 driven micro-shRNA were found that mitochondrial morphology became fragmented and atypical round-shaped, were called fission-like phenotype. We also showed that expression of mouse Cisd1 caused the fission-like mitochondria; and expression of mouse Cisd2 caused elongated mitochondria. However, there were no significant differences of mitochondrial morphology between knockdown of CG1458 and expression of Cisd1/Cisd2 in knockdown of CG1458 background. These results indicated that CG1458 may be a regulator of mitochondrial dynamics in Drosophila. Beside aging and mitochondrial dynamics, CG1458 plays an important role in cell death way in Drosophila. In our study, we show that CG1458 involve in Rpr- and Grim-induced cell death, but not Hpo-triggered Hid-induced cell death, additionally, CG1458 may be a component to assist Rpr-dependent cell death against dBruce. The balance between of pro-apoptotic proteins and anti-apoptotic proteins is crucial for cell death regulation. These results showed that CG1458 is an upstream gene of DIAP1. On the other hand, we also focus on caspase-independent cell death and found that CG1458 might be involved in this cell death pathway. In summary, CG1458 plays important roles in aging, mitochondrial dynamics and cell death. Yet, the more detail molecular mechanism of CG1458 need to be investigated. Mostly important, we propose a novel concept that CG1458 is a bridge to link these three fields together.