Protein expression levels of membrane proteins in isolated mouse brain capillaries
The quantitative expression level of membrane proteins in brain capillary endothelial cells isolated from wild-type, Mdr1a/b(−/−) (P-gp knockout), Bcrp1(−/−) (Bcrp knockout), and Mdr1a/b(−/−)Bcrp1(−/−) (P-gp/Bcrp combined knockout) mice is shown. Whole tissue lysates of brain capillaries were digested with trypsin as described under Materials and Methods. The protein expression amounts were measured by subjecting the digests to LC/MS/MS with internal standard peptides. The data represent mean ± S.E.M. (three independent measurements were done on three separate aliquots from the pooled capillary homogenate from 10 mice of each genotype). There was no statistically significant difference in expression of all the tested ABC and SLC transporters between the wild-type, P-gp knockout, Bcrp knockout, and P-gp/Bcrp combined knockout mice (p > 0.05).
| Molecular Names | Protein Expression Level | |||
|---|---|---|---|---|
| Wild Type | Mdr1a/b(−/−) | Bcrp1(−/−) | Mdr1a/b(−/−)Bcrp1(−/−) | |
| fmol/μg protein | ||||
| ABC transporters | ||||
| Abca1 | 0.397 ± 0.065 | 0.499 ± 0.041 | 0.358 ± 0.027 | 0.392 ± 0.056 |
| Abca2 | N.D. | N.D. | N.D. | N.D. |
| Mdr1a (Abcb1a) | 16.3 ± 0.8 | N.D. | 17.0 ± 0.3 | N.D. |
| Mdr1b (Abcb1b) | N.D. | N.D. | N.D. | N.D. |
| Mrp1 (Abcc1) | N.D. | N.D. | N.D. | N.D. |
| Mrp2 (Abcc2) | N.D. | N.D. | N.D. | N.D. |
| Mrp3 (Abcc3) | N.D. | N.D. | N.D. | N.D. |
| Mrp4 (Abcc4) | 2.18 ± 0.13 | 2.31 ± 0.15 | 1.79 ± 0.09 | 1.98 ± 0.10 |
| Mrp5 (Abcc5) | N.D. | N.D. | N.D. | N.D. |
| Mrp6 (Abcc6) | N.D. | N.D. | N.D. | N.D. |
| Bcrp (Abcg2) | 3.53 ± 0.21 | 4.20 ± 0.18 | N.D. | N.D. |
| Mrp7 (Abcc7) | N.D. | N.D. | N.D. | N.D. |
| SLC transporters | ||||
| Glut1 (Slc2a1) | 110 ± 5 | 121 ± 6 | 115 ± 6 | 114 ± 5 |
| Lat1 (Slc7a5) | 1.80 ± 0.32 | 2.03 ± 0.42 | 1.89 ± 0.41 | 1.71 ± 0.45 |
| 4F2 hc (Slc3a2) | 17.1 ± 1.0 | 20.5 ± 0.9 | 17.6 ± 0.7 | 18.6 ± 0.6 |
| Mct1 (Slc16a1) | 25.2 ± 2.5 | 27.8 ± 1.9 | 27.5 ± 1.8 | 23.5 ± 0.7 |
| Oatp2 (Slco1a1) | 1.55 ± 0.31 | 2.01 ± 0.12 | 1.92 ± 0.45 | 0.648 ± 0.155 |
| Oatp14 (Slco161) | 1.70 ± 0.1 | 1.84 ± 0.09 | 1.68 ± 0.08 | 1.57 ± 0.17 |
| Oat3 (Slc22a8) | 1.74 ± 0.18 | 1.75 ± 0.08 | 1.75 ± 0.27 | 1.47 ± 0.29 |
| Ent1 (Slc29a1) | 1.18 ± 0.40 | 0.887 ± 0.151 | 1.15 ± 0.33 | 1.06 ± 0.30 |
| Pmat | N.D. | N.D. | N.D. | N.D. |
| Rlip76 | N.D. | N.D. | N.D. | N.D. |
| Receptors | ||||
| Insr | 0.797 ± 0.096 | 0.911 ± 0.039a | 0.837 ± 0.083a | 0.482 ± 0.019 |
| Lrp1 | 1.02 ± 0.20a | 0.883 ± 0.008 | 1.01 ± 0.06a | 0.400 ± 0.001 |
| Tfr1 | 5.16 ± 0.44 | 5.49 ± 0.42 | 4.91 ± 0.34 | 3.98 ± 0.40 |
| Claudin-5 | 8.05 ± 1.73 | 9.16 ± 1.21 | 8.96 ± 1.15 | 6.40 ± 1.70 |
| Cd147 | 21.3 ± 0.80 | 22.9 ± 0.80 | 23.3 ± 1.40 | 18.4 ± 1.60 |
| Housekeeping genes | ||||
| Na+/K+ ATPase | 39.1 ± 1.4 | 41.0 ± 1.2 | 41.8 ± 1.2 | 44.5 ± 1.8 |
| γ-gtp | 3.25 ± 0.30 | 3.34 ± 0.38 | 3.10 ± 0.26 | 3.16 ± 0.24 |
N.D., not detected.
↵a Among the receptors that were studied, Insr and Lrp1 expression was trended lower in the P-gp/Bcrp combined knockout mice (p < 0.05 compared with P-gp/Bcrp combined knockout mice).