Figure 10.

Effect of phosphorylation at Ser-13 and/or Ser-16 on the internalization of WT (22Q) Httex1 PFFs in striatal neurons. Primary rat striatal neurons treated with 0.5 μm unmodified or PTM Q₂₂ PFFs were immunostained using the MW8 anti-total Htt antibody. Staining for MAP2 and Hoechst-33342 was also performed to reveal neuronal cell bodies and nuclei, respectively. A, low magnification imaging showing that the MW8 antibody equivalently detected unmodified and PTM Q₂₂ Httex1 PFFs, in contrast to the untreated condition. B, high magnification confocal imaging of individual neurons showing that while unmodified Q₂₂ PFFs are mostly not internalized, some neurons treated with pSer-13-Q₂₂, pSer-16-Q₂₂, and pSer-13/pSer-16-Q₂₂ Httex1 PFFs exhibit prominent internalization of PFFs, as established by orthogonal projection of z-stacks (Orth. Projection, rightmost lane). Orthogonal projections of all imaged channels of the same neurons are presented in Fig. S3A.