Interaction of Neuronal Calcium Sensor-1 (NCS-1) with Phosphatidylinositol 4-Kinase β Stimulates Lipid Kinase Activity and Affects Membrane Trafficking in COS-7 Cells
Bibliographic record
Abstract
Phosphatidylinositol 4-kinases (PI4K) catalyze the first step in the synthesis of phosphatidylinositol 4,5-bisphosphate, an important lipid regulator of several cellular functions. Here we show that the Ca(2+)-binding protein, neuronal calcium sensor-1 (NCS-1), can physically associate with the type III PI4Kbeta with functional consequences affecting the kinase. Recombinant PI4Kbeta, but not its glutathione S-transferase-fused form, showed enhanced PI kinase activity when incubated with recombinant NCS-1, but only if the latter was myristoylated. Similarly, in vitro translated NCS-1, but not its myristoylation-defective mutant, was found associated with recombinant- or in vitro translated PI4Kbeta in PI4Kbeta-immunoprecipitates. When expressed in COS-7 cells, PI4Kbeta and NCS-1 formed a complex that could be immunoprecipitated with antibodies against either proteins, and PI 4-kinase activity was present in anti-NCS-1 immunoprecipitates. Expressed NCS-1-YFP showed co-localization with endogenous PI4Kbeta primarily in the Golgi, but it was also present in the walls of numerous large perinuclear vesicles. Co-expression of a catalytically inactive PI4Kbeta inhibited the development of this vesicular phenotype. Transfection of PI4Kbeta and NCS-1 had no effect on basal PIP synthesis in permeabilized COS-7 cells, but it increased the wortmannin-sensitive [(32)P]phosphate incorporation into phosphatidylinositol 4-phosphate during Ca(2+)-induced phospholipase C activation. These results together indicate that NCS-1 is able to interact with PI4Kbeta also in mammalian cells and may play a role in the regulation of this enzyme in specific cellular compartments affecting vesicular trafficking.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| 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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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 source (direct Gemma or distilled Codex), 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".