Identification and Characterization of K<sup>+</sup>-Dependent Na<sup>+</sup>-Ca<sup>2+</sup> Exchange Transport in Pigmented MEB4 Cells Mediated by NCKX4
Bibliographic record
Abstract
The SLC24 gene family encodes K(+)-dependent Na(+)-Ca(2+) exchangers or NCKX proteins. The NCKX4 and NCKX5 isoforms have been shown to be important for pigmentation, and single nucleotide polymorphism (SNP) in both alleles of the SLC24a5 gene is the major genetic determinant for light skin in Caucasians. NCKX4 is thought to operate in the surface membrane of cells, whereas NCKX5 is thought to be located in intracellular membranes. However, no functional data have yet been reported to describe either NCKX4 or NCKX5 activity in pigmented cells. In this study, we used the B16 and MEB4 mouse pigmented cell lines to investigate NCKX-mediated Ca(2+) fluxes using (45)Ca uptake experiments and measurements of changes in intracellular free Ca(2+) with the fluorescent Ca(2+)-indicating dye Fluo-4. We used siRNA-mediated knockdown to selectively reduce either NCKX4 or NCKX5 expression. The results show that both B16 and MEB4 cells contain roughly equal amounts of NCKX4 and NCKX5 transcript, but surface membrane NCKX activity is restricted to NCKX4. Intracellular NCKX4 activity was also observed, but we could not unambiguously detect any NCKX5 activity. We were able to demonstrate that NCKX5 is a functional K(+)-dependent Na(+)-Ca(2+) exchanger located in internal membranes after transfection of NCKX5 cDNA in HEK293 cells. We conclude that pigment cells express robust, functional NCKX4 activity, but that the role of NCKX5 remains enigmatic ten years after the discovery of its link to pigmentation.
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".