<i>StARD13</i>(<i>Dlc-2</i>) RhoGap Mediates Ceramide Activation of Phosphatidylglycerolphosphate Synthase and Drug Response in Chinese Hamster Ovary Cells
Bibliographic record
Abstract
To identify genes involved in etoposide drug response, we used promoter trap mutagenesis to isolate an etoposide-resistant Chinese hamster ovary (CHO) cell line. This resistant CHO-K1 line, named E91, showed cross-resistance to C(2)-ceramide (N-acetylsphingosine). The promoter trap retrovirus was found integrated into intron 1-2 of the Dlc-2 (Stard13) RhoGap gene. The E91 cells showed elevated guanosine triphosphate (GTP)-bound RhoA levels compared with the parental line, suggesting that retrovirus integration had inactivated one of the Dlc-2 RhoGap alleles. To test whether E91 cells were impaired in an intracellular ceramide-regulated process not directly related to cell killing, we measured mitochondrial phosphatidylglycerolphosphate (PGP) synthase and phospholipase A2 enzyme activities in cells after C(2)-ceramide addition. Parental cells showed elevated enzyme activities after treatment with C(2)-ceramide or tumor necrosis factor alpha, but not the E91 cells. These results suggested that intracellular ceramide signaling was defective in E91 cells due to increased levels of active GTP-bound RhoA. RNA knockdown experiments of the Dlc2 RhoGap resulted in increased GTP-bound RhoA and reduced induction of PGP synthase after C(2)-ceramide addition compared with controls. Expression of a dominant-negative RhoA in the E91 cell line allowed induction of PGP synthase by ceramide. The RNA interference knockdown cell line also showed increased etoposide resistance. This study is the first report for the regulation of a phospholipid biosynthetic enzyme through RhoGap expression.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".