001 by Fisher’s PLSD post hoc analysis; Figure 6D) and rTgWT neurons (∗p < 0.05 and ∗∗p < 0.01 by Fisher's PLSD post hoc analysis; Figure 6D). As reported previously, (Liao et al., 1999), synaptic GluR1 receptor expression detected on fixed neurons (Figure 6A) strongly corresponded to

surface N-GluR1 receptor expression detected on living neurons (Figure 5D). Labeling of total NR1 receptors with a rabbit polyclonal antibody against the N terminus of NR1 (Liao et al., 1999) in fixed neurons cultured from these three lines of mice revealed a similar pattern of expression (Figure 6C). In TgNeg and rTgWT neurons, NR1 receptors are clustered in spines as identified by the strong overlap between PSD95 and NR1 expression (small arrows in upper panels of Figure 6C). In contrast, the large arrows in the lower panels of Figure 6C indicate the reduced colocalization of ABT 199 PSD95 and NR1 in rTgP301L neurons. Normalization of www.selleckchem.com/products/ve-822.html NR1 fluorescence intensity in spines to that in the dendritic shafts demonstrated that the synaptic expression of NR1 receptors are decreased in rTgP301L mice compared to TgNeg and rTgWT neurons (∗∗∗p < 0.001 by Fisher's PLSD post hoc analysis; Figure 6D). Our results indicate that tau mislocalization to dendritic spines damages

these spines profoundly by disrupting the synaptic targeting or anchoring of both AMPA and NMDA receptors. We postulated that the mislocalization of tau in spines depends upon abnormal htau hyperphosphorylation, which occurs to a greater extent in rTgP301L than rTgWT mice (Figure 7). Tau consists

Adenosine of at least three structurally distinct regions, including an amino-terminal projection domain and a carboxyl-terminal domain that contains repetitive microtubule-binding motifs flanked by proline-rich regions (Buée et al., 2000 and Avila et al., 2004). Hyperphosphorylation of htau at the 14 serine (S) and threonine (T) residues that can be phosphorylated by proline (P)-directed S/T kinases has been shown to modulate tau neurotoxicity, control tau binding to F-actin and regulate the effect of htau on the viability of retinal neurons in the fruit fly (Fulga et al., 2007, Steinhilb et al., 2007a and Steinhilb et al., 2007b). The neurons of fruit flies, like other lower organisms, lack dendritic spines (Hering and Sheng, 2001). Therefore, the relevance of this finding to mammalian neurons, where F-actin concentrates in dendritic spines, has not been established. To validate that P301L htau is hyperphosphorylated in vitro on SP/TP residues previously implicated in tau neurotoxicity, we examined htau phosphorylation levels in our rat neuron cultures expressing WT or P301L htau. Changes in tau phosphorylation underlying tau pathology have a temporally specific sequence (Maurage et al., 2003, Luna-Muñoz et al., 2007 and Bertrand et al.