Figure 11.

Effect of phosphorylation at Ser-13 and/or Ser-16 on the internalization of mutant (Q₄₂) Httex1 PFFs in striatal neurons. Primary rat striatal neurons treated with 0.5 μm unmodified or PTM Q₄₂ PFFs were immunostained using the MW8 anti-total Htt antibody. MAP2 and Hoechst-33342 staining were also performed to reveal neuronal cell bodies and nuclei, respectively. A, low-magnification imaging showing that the MW8 antibody equivalently detected unmodified and PTM Q₄₂ PFFs in contrast to the untreated condition. B, high-magnification confocal imaging of individual neurons showing that whereas unmodified-Q₄₂ PFFs are mostly not internalized, some neurons treated with pSer-13-Q₄₂, pSer-16-Q₄₂, and pSer-13/pSer-16-Q₄₂ 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. S3B.