Table 2.
FP-based or chemical dye-based sensors for measurement of ion concentration in acidic organelles.
| Ion | Organelle | Cell | Sensor | Class | pKa or Kd (pH or pKa) | Resting pH, or [Ca2+, Zn2+ or Cl−] (pH) | Ref. |
|---|---|---|---|---|---|---|---|
| pH | Endosome | Foreskin keratino-cyte | Cellubrevin-r-pHluorin | Gen a, Single FP-base dual-excitation | 6.9 [61] | Early endosome: 5.9 | [62] |
| HeLa | Tat-E1GFP | Gen, Single FP-base dual-excitation | 6.4–6.7 | Early endosome: 6.8 Endosome: 5.8–6.3 |
[60] | ||
| MIN6 beta-cell | TiVAMP-mKeima | Gen, Single FP-base dual-excitation | 5.8 | Early endosome: 6.3 Late endosome: 5.8 |
[63] | ||
| Synaptic vesicle (SV) | Hippocam-pal neuron | Synaptophysin-mOrange2 | Gen, Single FP-base, intensiometric | 6.5 | GABAergic SV: ~6.4 Glutamatergic SV: ~5.8 |
[64] | |
| Secretory granule | PC12 | Citrine (YFP) used in D1-SG (Ca2+ sensor) | Gen, intensiometric | 5.8 | 5.8 | [65] | |
| PC12 | CgA-ECFP | Gen, Single FP-base, FLIM | N.D. | 5.5 | [66] | ||
| MIN6 | VAMP2-pH.fluorin(e) | Gen, Single FP-base, Intensiometric | N.D. | 6.3 | [67] | ||
| PC12, WSS-1 | NPY-ClopHensor | Gen, Ratiometric (Non-FRET-base) | 6.8 | 5.2 (PC12) 5.6 (WSS1) |
[68] | ||
| Lysosome | HeLa, MCF-7 | Lyso-pH | Chem b, Ratiometric | 5.0 | 4.6 | [69] | |
| Vacuole | A. thaliana | Aleurain-PRpHluorin | Gen, Single FP-base dual-excitation | 6.6 | 5.2 | [70] | |
| A. niger | RaVC (improved version of pHluorin for pH imaging in filamentous fungi) | Gen, Single FP-base dual-excitation | 6.7 (in vitro) 6.9 (in cell) |
6.2–6.5 | [71] | ||
| Ca2+ | Endosome | MIN6 beta-cell | TiVAMP-GEM-GECO1 | Gen, Single FP-base dual-emission | 0.27 (pH 7.5), 0.46 (7.0), 0.68 (6.5), 3.1 (6.0), 17.9 (5.4), 54.2 μM (5.0) | Early endosome: 0.5 (6.3) Late endosome: 2.5 μM (5.8) |
[63] |
| 3T3 Swiss fibroblast | Oregon green 488 BAPTA-5N | Chem, Intensiometric | 20 μM | 3.0 μM (5.7) (30 min incubation) |
[72] | ||
| Pancreatic acinar cell | Oregon green 488 BAPTA-5N | Chem, Intensiometric | 36.5 (pH 7.2), 55.3 (5.9), 116 μM (5.3) | 37 μM (5.9) | [73] | ||
| Secretory granule | PC12 | D1-SG | Gen, FRET-base | 120–190 μM (pH 7.4–5.5) | 69 μM (5.8) | [65] | |
| MIN6 | VAMP2-mut.aequorin | Gen, Intensiometric | 1–10 μM | ~50 μM (6.3) | [67] | ||
| PC12 | Chromogranin-aequorin | Gen, Intensiometric | 3.8 μM [74] | 1.4 μM (~5.5) | [75] | ||
| Sea urchin egg | Fluo-4 | Chem, Intensiometric | 345 nM (pH 7.2) [76] | ~10–100 μM | [77] | ||
| Lysosome | Mouse macrophage | Fura-2 dextran | Chem, Ratiometric | ~200 μM | 600 μM (4.5) | [53] | |
| Mouse macrophage | Oregon green BAPTA-1 dextran | Chem, Intensiometric | ~500 μM | 400 μM (4.5) | [53] | ||
| Human fibroblast | Rhod dextran | Chem, Intensiometric | 551 ± 107 μM | 550 μM (4.5) | [78] | ||
| Cl− | Endosome | J774 cell, CHO cell | BAC-TMR-dextran | Chem, Ratiometric | ~25–50 mM (pH 7.4) | 17→53 mM (6.95→5.30) (J773) 28→73 mM (6.92→5.60) (CHO) |
[79] |
| J774 cell, CHO cell | BAC-dextran-Tf-TMR | Chem, Ratiometric | ~25–50 mM (pH 7.4) | 18→40 mM (6.91→6.05) (J773) 24→46 mM (6.95→6.18) (CHO) |
[80] | ||
| Secretory granule | PC12, WSS-1 | NPY-ClopHensor | Gen, Ratiometric (Non-FRET-base) | 13.1 mM (pKa 6.81) | 110 ± 48 mM (5.2) (PC12) 122 mM (5.6) (WSS1) |
[68] | |
| Lysosome | Venticular myocyte | 6-methoxyquino-linium–dansyl | Chem, Ratiometric | ~15 mM (pH 4.5) | 9.46 mM | [81] | |
| Zn2+ | Secretory granule | INS-1 (832/13) | VAMP2-eZinCh | Gen, Ratiometric (FRET) | 8 (pH 7.1), 260 μM (6.0) | 1–100 μM | [82] |
| Lysosome | NIH 3T3 | DQZn4 | Chem, Ratiometric | 16 nM (pH 5.2) | N.D. | [83] | |
| NSCs, MCF-7, HeLa | LysoZn-1 | Dhem, Ratiometric | ~150 μM (pH 7.2) | N.D. | [84] | ||
| NIH 3T3 | probe 1 (no name) | Chem, Intensiometric | 8.55 μM (pH 5.0) | N.D. | [85] |
a FP-based sensor; b Organic dye-based sensor.