Figure 2.

SUMO1 conjugates remain nuclear during increased amyloid burden. (a) Western blot analysis of subcellular fractions of 36‐week‐old KI/WT and KI/AD mouse brain using anti‐HA antibody (upper two panels) and antibodies to GluN1 (a marker of the postsynaptic compartment) and Synaptophysin (a marker of the presynaptic compartment) to validate the fractionation procedure (lower two panels). H, homogenate; P1, nuclear pellet; S1, supernatant after P1 sedimentation; P2, crude synaptosomal pellet; S2, supernatant after P2 sedimentation; LP1, lysed synaptosomal membranes; LS1, supernatant after LP1 sedimentation; LP2, pellet after LS1 sedimentation, SPM, synaptic plasma membranes. Bracket indicates the anti‐HA signal representing SUMOylation, arrow indicates RanGAP1, stars indicate nonspecific signal detected by the anti‐HA antibody. (b) Brain sagittal sections of aged (36 weeks old) KI/AD (left panels) and WT/AD (right panels) mice were immunostained using antibodies directed against HA (red, labels HA‐HA conjugates), MAP2 (green, labels neuronal somata and dendrites), and Synapsin1 (Syn1, magenta, labels synapses). The images show triple‐labeled neurons of hippocampal subiculum (b), cortical layer 5 (c), and proximal apical dendrite from hippocampal CA3 (d). The white line shows the orientation of the line‐scan used to generate the image stack shown in the bottom side view. Scale bar: 10 μm. Note that the anti‐HA immunosignal is mainly located in neuronal nuclei, only background staining is observed in WT/AD mice. Little anti‐HA signal is observed along MAP2‐positive structures and does not colocalize with Synapsin1