A Canonical EF‐Loop Directs Ca<sup>2+</sup>‐Sensitivity in Phospholipase C‐η2
Bibliographic record
Abstract
Phospholipase C-η (PLCη) enzymes are a class of phosphatidylinositol 4,5-bisphosphate-hydrolyzing enzymes involved in intracellular signaling. PLCη2 can sense Ca(2+) (stimulated by ∼1 µM free Ca(2+) ) suggesting that it can amplify transient Ca(2+) signals. PLCη enzymes possess an EF-hand domain composed of two EF-loops; a canonical 12-residue loop (EF-loop 1) and a non-canonical 13-residue loop (EF-loop 2). Ca(2+) -binding to synthetic peptides corresponding to EF-loops 1 and 2 of PLCη2 and EF-loop 1 of calmodulin (as a control) was examined by 2D-[(1) H,(1) H] TOCSY NMR. Both PLCη2 EF-loop peptides bound Ca(2+) in a similar manner to that of the canonical calmodulin EF-loop 1, particularly at their N-terminus. A molecular model of the PLCη2 EF-hand domain, constructed based upon the structure of calmodulin, suggested both EF-loops may participate in Ca(2+) -binding. To determine whether the EF-hand is responsible for Ca(2+) -sensing, inositol phosphate accumulation was measured in COS7 cells transiently expressing wild-type or mutant PLCη2 proteins. Addition of 70 µM monensin (a Na(+) /H(+) antiporter that increases intracellular Ca(2+) ) induced a 4- to 7-fold increase in wild-type PLCη2 activity. In permeabilized cells, PLCη2 exhibited a ∼4-fold increase in activity in the presence of 1 µM free Ca(2+) . The D256A (EF-loop1) mutant exhibited a ∼10-fold reduction in Ca(2+) -sensitivity and was not activated by monensin, highlighting the involvement of EF-loop 1 in Ca(2+) -sensing. Involvement of EF-loop 2 was examined using D292A, H296A, Q297A, and E304A mutants. Interestingly, the monensin responses and Ca(2+) -sensitivities were largely unaffected by the mutations, indicating that the non-canonical EF-loop 2 is not involved in Ca(2+) -sensing.
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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 | 0.000 |
| 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".