Zeatin riboside attenuates mutant Htt aggregations through increasing proteasome activity.

<p>(A) With or without 1 µM MG 132 pretreatment for 30 min and following the presence or absence of zeatin riboside for 24 h, pHtt-25Q-mKate- or pHtt-109Q-mKate-transfected and pZsProSensor-co-transfected cells were subjected to a confocal microscopic analysis. Bar represents 5 µm. In each group, the mKate-aggregated cells in proportion to the transfected cells were counted (100∼150 cells). Data points represent the mean ± SEM. *<i>p</i><0.05, compared to the mutant Htt control group. #<i>p</i><0.05, compared to the MG 132-treated mutant Htt group. (B) With or without 1 µM MG 132 pretreatment for 30 min, pHtt-109Q-mKate-transfected cells were treated with or without zeatin riboside for 24 h and subjected to a filter retardation assay and Western blot analysis. The relative optical density of the bands were quantified by densitometry relative to actin and normalized to the levels under the Htt-109Q-overexpressed control condition which was set as 1.0. Data points represent the mean ± SEM. *<i>p</i><0.05, compared to the mutant Htt control group. AU represents arbitrary unit. (C) pHtt-25Q-mKate-transfected cells were treated with or without zeatin riboside or 1 µM MG 132. pHtt-109Q-mKate-transfected cells were pretreated with or without 1 µM ZM for 30 min and then supplemented with or without zeatin riboside or 1 µM MG 132 for 24 h and subjected to a proteasome activity assay. *<i>p</i><0.05, compared to the Htt-25Q control group. #<i>p</i><0.05, compared to the Htt-109Q control group. These data represent one out of three independent experiments that gave similar results.