TABLE 1.
Diffusion coefficients for μ OR and other GPCRs at 37°C, observed by single-molecule techniques at video rate or estimated by FRAP. Data in the timescales >100 ms are listed
|
Deff (μm2/s), mean ± SD‖
|
|||||||
|---|---|---|---|---|---|---|---|
| Reference | GPCR | Cell (N*) | Probe/method | Cold binding‡ | 100 ms | 250 ms | 1.5 s, longer |
| Daumas et al. (2003) | T7-μOR | NRK (?) | Gold/SPT | Yes (45 min) | 0.013 | ND† | 0.0013 (±0.0024) |
| This work | T7-μOR | NRK (57) | Gold/SPT | no | 0.20 (±0.15) | 0.18 (±0.15) | 0.12 (±0.19) |
| This work | T7-μOR | NRK (94) | Gold/SPT | Yes (45 min) | 0.032 (±0.032) | 0.015 (±0.015) | 0.011 (±0.015) |
| This work | μOR | NRK (57) | mGFP/SFVI | NA† | 0.25 (±0.20) | 0.24 (±0.25) | ND |
| This work | μOR | CHO (97) | mGFP/SFVI | NA | 0.14 (±0.10) | 0.10 (±0.09) | ND |
| Daumas et al. (2003) | T7-μOR | CHO (NA) | F-T7-Fab/FRAP§ | NA | ND | ND | 0.005 (±0.002) |
| (No statement on the immobile fraction) | |||||||
|
|
GPCR
|
Cell
|
Probe/method
|
Immobile fraction (%)
|
 mean ± SD
|
||
| Horvat et al. (1999) | LHR¶ | CHO | GFP/FRAP | 57 | 0.16 (±0.035) | ||
| Nelson et al. (1999) | GRHR¶ | CHO | GFP/FRAP | 25 | 0.12 (±0.02) | ||
| Nelson et al. (1999) | GRHR¶ | αT3 | GFP/FRAP | 20 | 0.12 (±0.06) | ||
| Young et al. (2001) | BR¶ | KNRK | GFP/FRAP | 20 | 0.48 (?) | ||
N, number of particles.
NA, not applicable; ND, not determined.
Preincubation of NRK cells with gold probes on ice for 45 min.
FRAP experiments by Daumas et al. were carried out at 22°C.
LHR, luteinizing hormone receptor 3; GRHR, gonadotropin-releasing hormone receptor 2; BR, bombesin receptor 1.
were determined in the MSD-Δt plot (for the trajectories obtained at video rate for 300 frames (10 s)) by linear fitting between the second point and the fourth, 15th, and 90th points, respectively. Note that the diffusion coefficients listed here are mean values, whereas those shown in Fig. 3 are median values. SD (standard deviation) includes true variations in the diffusion coefficient in the membrane and unavoidable statistical variations (Saxton, 1997) as well as experimental errors.