Identification of a Dynamic Mitochondrial Protein Complex Driving Cholesterol Import, Trafficking, and Metabolism to Steroid Hormones
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Bibliographic record
Abstract
Steroid hormones are critical for organismal development and health. The rate-limiting step in steroidogenesis is the transport of cholesterol from the outer mitochondrial membrane (OMM) to the cytochrome P450 enzyme CYP11A1 in the inner mitochondrial membrane (IMM). Cholesterol transfer occurs through a complex termed the "transduceosome," in which cytosolic steroidogenic acute regulatory protein interacts with OMM proteins translocator protein and voltage-dependent anion channel (VDAC) to assist with the transfer of cholesterol to OMM. It has been proposed that cholesterol transfer from OMM to IMM occurs at specialized contact sites bridging the two membranes composed of VDAC and IMM adenine nucleotide translocase (ANT). Blue native PAGE of Leydig cell mitochondria identified two protein complexes that were able to bind cholesterol at 66- and 800-kDa. Immunoblot and mass spectrometry analyses revealed that the 800-kDa complex contained the OMM translocator protein (18-kDa) and VDAC along with IMM CYP11A1, ATPase family AAA domain-containing protein 3A (ATAD3A), and optic atrophy type 1 proteins, but not ANT. Knockdown of ATAD3A, but not ANT or optic atrophy type 1, in Leydig cells resulted in a significant decrease in hormone-induced, but not 22R-hydroxycholesterol-supported, steroid production. Using a 22-phenoxazonoxy-5-cholene-3-beta-ol CYP11A1-specific probe, we further demonstrated that the 800-kDa complex offers the microenvironment needed for CYP11A1 activity. Addition of steroidogenic acute regulatory protein to the complex mobilized the cholesterol bound at the 800-kDa complex, leading to increased steroid formation. These results identify a bioactive, multimeric protein complex spanning the OMM and IMM unit that is responsible for the hormone-induced import, segregation, targeting, and metabolism of cholesterol.
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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 | 0.000 | 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 it