Table 1.
Individual GPCR and cilia parameters: low frame rate (3–5 fps) tracking
CiliumaTracking time Cilium length GPCR densitybGPCRs on ciliumcAmdDaxeDmfMIgfcshMSDinti
 min μm μm−2  % μm2/s μm2/s   μm2 
R1 10.5 3.7 269.2 932 0.24 0.074 0.148 0.77 1.0 0.079 
R2 3.0 4.2 1,487.5 5,833 1.34 0.026 0.051 0.35 0.7 0.020 
R3 4.0 1.9 4,965.2 8,735 4.47 0.035 0.069 0.78 1.0 0.020 
R4 17.1 3.7 2,790.7 9,721 2.51 0.135 0.270 0.50 1.0 0.079 
R5 (1) 12.0 2.9 1,653.2 4,592 1.49 0.015 0.030 0.61 1.0 0.009 
R5 (2) 12.0     0.081 0.163 0.34 1.0 0.049 
R6 8.4 3.8 1,607.6 5,795 1.45 0.030 0.059 0.42 0.9 0.018 
R7 4.5 4.3 30.5 123 0.03 0.145 0.290 0.26 1.0 0.070 
R8 9.7 2.4 873.2 1,969 0.79 0.095 0.189 0.70 1.0 0.056 
Mean R  3.6 1,744.9 4,713 1.54 0.071 0.141 0.53 0.96 0.045 
SEM R  0.3 512.5 1,172 0.47 0.016 0.032 0.07 0.03 0.009 
S1 11.9 5.6 557.5 2,947 0.50 0.085 0.170 0.39 1.0 0.027 
S2 (1) 12.7 4.8 10,676.0 48,368 9.61 0.167 0.334 0.62 1.0 0.099 
S2 (2) 12.7     0.180 0.361 0.55 1.0 0.099 
S3 (1) 9.2 7.4 6,534.6 45,267 5.88 0.063 0.126 0.63 1.0 0.037 
S3 (2) 9.2     0.032 0.065 0.62 1.0 0.020 
S4 28.3 7.0 7,292.1 47,937 6.56 0.079 0.157 0.21 0.7 0.047 
S5 14.7 8.1 1,591.5 12,077 1.43 0.141 0.282 0.28 1.0 0.079 
S6 7.5 10.0 1,761.3 16,631 1.59 0.075 0.149 0.50 0.8 0.064 
S7 14.8 4.7 2,591.2 11,404 2.33 0.109 0.217 0.44 1.0 0.075 
S8 4.1 8.2 2,612.2 20,191 2.35 0.121 0.242 0.39 0.9 0.096 
S9 5.2 6.4 1,461.0 8,748 1.31 0.086 0.172 0.19 0.3 0.010 
S10 6.3 7.2 2,412.5 16,257 2.17 0.138 0.276 0.49 1.0 0.099 
S11 (1) 16.0 7.3 1,487.1 10,205 1.34 0.129 0.258 0.46 1.0 0.056 
S11 (2) 16.0     0.111 0.222 0.56 1.0 0.056 
Mean S  7.2 3,543.4 21,821 3.19 0.108 0.216 0.45 0.91 0.062 
SEM S  0.5 1,061.4 5,640 0.86 0.011 0.022 0.04 0.05 0.008 
CiliumaTracking time Cilium length GPCR densitybGPCRs on ciliumcAmdDaxeDmfMIgfcshMSDinti
 min μm μm−2  % μm2/s μm2/s   μm2 
R1 10.5 3.7 269.2 932 0.24 0.074 0.148 0.77 1.0 0.079 
R2 3.0 4.2 1,487.5 5,833 1.34 0.026 0.051 0.35 0.7 0.020 
R3 4.0 1.9 4,965.2 8,735 4.47 0.035 0.069 0.78 1.0 0.020 
R4 17.1 3.7 2,790.7 9,721 2.51 0.135 0.270 0.50 1.0 0.079 
R5 (1) 12.0 2.9 1,653.2 4,592 1.49 0.015 0.030 0.61 1.0 0.009 
R5 (2) 12.0     0.081 0.163 0.34 1.0 0.049 
R6 8.4 3.8 1,607.6 5,795 1.45 0.030 0.059 0.42 0.9 0.018 
R7 4.5 4.3 30.5 123 0.03 0.145 0.290 0.26 1.0 0.070 
R8 9.7 2.4 873.2 1,969 0.79 0.095 0.189 0.70 1.0 0.056 
Mean R  3.6 1,744.9 4,713 1.54 0.071 0.141 0.53 0.96 0.045 
SEM R  0.3 512.5 1,172 0.47 0.016 0.032 0.07 0.03 0.009 
S1 11.9 5.6 557.5 2,947 0.50 0.085 0.170 0.39 1.0 0.027 
S2 (1) 12.7 4.8 10,676.0 48,368 9.61 0.167 0.334 0.62 1.0 0.099 
S2 (2) 12.7     0.180 0.361 0.55 1.0 0.099 
S3 (1) 9.2 7.4 6,534.6 45,267 5.88 0.063 0.126 0.63 1.0 0.037 
S3 (2) 9.2     0.032 0.065 0.62 1.0 0.020 
S4 28.3 7.0 7,292.1 47,937 6.56 0.079 0.157 0.21 0.7 0.047 
S5 14.7 8.1 1,591.5 12,077 1.43 0.141 0.282 0.28 1.0 0.079 
S6 7.5 10.0 1,761.3 16,631 1.59 0.075 0.149 0.50 0.8 0.064 
S7 14.8 4.7 2,591.2 11,404 2.33 0.109 0.217 0.44 1.0 0.075 
S8 4.1 8.2 2,612.2 20,191 2.35 0.121 0.242 0.39 0.9 0.096 
S9 5.2 6.4 1,461.0 8,748 1.31 0.086 0.172 0.19 0.3 0.010 
S10 6.3 7.2 2,412.5 16,257 2.17 0.138 0.276 0.49 1.0 0.099 
S11 (1) 16.0 7.3 1,487.1 10,205 1.34 0.129 0.258 0.46 1.0 0.056 
S11 (2) 16.0     0.111 0.222 0.56 1.0 0.056 
Mean S  7.2 3,543.4 21,821 3.19 0.108 0.216 0.45 0.91 0.062 
SEM S  0.5 1,061.4 5,640 0.86 0.011 0.022 0.04 0.05 0.008 
a

Individual cilia: R, Rhoi3S; S, SSTR3. Numbers in parentheses identify individual Qdot-GPCR for cilia in which more than one was labeled.

b

GPCR density was estimated by calibration of the optical system with recombinant EGFP of known concentrations. Confinement of the EGFP label to the ciliary membrane and the sampling by the optical system were accounted for as described previously (Peet et al., 2004).

c

Total number of GPCRs within the given cilium.

d

Membrane area fraction occupied by the expressed GPCRs.

e

Dax is the 1D axial diffusion coefficient estimated from the initial slope of the MSD(τ) plot for an individual Qdot-GPCR.

f

Effective membrane diffusion coefficient: Dm ≈ 2Dax. Dax underestimates the true 2D membrane diffusion coefficient approximately twofold. Note the similarity of the mean microscopic Rhoi3S diffusion coefficient in ciliary membranes, Dm, reported here to the mean macroscopic lateral diffusion coefficient estimated for rhodopsin within discrete lobules of photoreceptor disc membranes, Dlat = 0.130 ± 0.012 µm2/s (Najafi et al., 2012a).

g

Mobility index (see text).

h

Fraction of cilium length sampled by the indicated GPCR.

i

MSD value at the y-intercept of the linear regression of the first two MSD(τ) points.

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