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. 2005 Nov 23;25(47):10884–10893. doi: 10.1523/JNEUROSCI.2909-05.2005

Figure 5.

Figure 5.

Transport of IGF-I across the choroid plexus. A, Megalin in rat choroid plexus cells interacts with IGF-I. Blots, Reciprocal coimmunoprecipitation of megalin with IGF-I after adding the latter to choroid plexus cultures. Photomicrographs, Megalin (green) and IGF-I (red) colocalize in cultured choroid plexus epithelial cells. Scale bar, 10 μm. B, Rat choroid plexus cells expressing siMegalin translocate significantly less IGF-I from the lower to the upper culture chamber (see Fig. 1 E). **p < 0.01 versus HIV-infected cells by Student's t test. C, When rat choroid plexus cells express miniMegalin, the amount of translocated IGF-I is significantly increased. **p < 0.01 by Student's t test. D, Rats infected with HIV-siMeg in the choroid plexus translocate significantly less Dig-IGF-I from the blood into the CSF. Representative blot and quantitative histograms are shown. *p < 0.05 versus HIV-infected rats by Student's t test (n = 4). E, In rats expressing siMeg in the choroid plexus, intracarotid injection of IGF-I (10 μg per rat) results in significantly lower stimulation of Akt in brain parenchyma (hippocampus) 1 h later. Representative blots and quantitation histograms are shown. Total Akt remained unchanged. F, Rats expressing a KR IGF-IR in choroid plexus (HIV-KR rats) did not translocate Dig-IGF-I from the blood into the CSF. The blot shows Dig-IGF-I in CSF of HIV (control) and HIV-KR rats. Two rats per treatment are shown (n = 5). G, Megalin is not required for IGF-I-induced activation of Akt in rat choroid plexus. After infection of choroid plexus with HIV-siMeg, intracarotid IGF-I is still able to stimulate phosphorylation of Akt in choroid plexus. H, Inhibition of PKC with bisindolylamine (Bis), but not of PI3K/Akt with wortmannin (Wort) or MAPK with PD98059 (PD), abrogates passage of Dig-IGF-I across a rat choroid plexus epithelial monolayer. Representative blots are shown. At least three independent invitro experiments were run for each condition. IP, Immunoprecipitation; siMeg, siMegalin; miniMeg, miniMegalin; p, phosphorylated.