Analysis of ubiquitin, deubiquitinating enzymes, and proteasome activity. A, Spinal cord homogenates from control and UbG76V-GFP-Syb2 mice (8 months of age) separated by stepping gel (8% and 12%) and probed with anti-polyubiquitin antibodies. B, Proteasome activity, including ChT-L, trypsin-like, and PGPH activity is similar between control and UbG76V-GFP-Syb2 mice (N = 3 pairs, 8 months of age). C, Spinal cord homogenates from control, GFP-Syb2, and UbG76V-GFP-Syb2 mice (8 months of age) were probed with anti-GFP antibodies and then reprobed with anti-UchL1 antibodies (PGP9.5). UchL1 levels are similar among all three genotypes. D, Spinal cord homogenates from control, GFP-Syb2, and UbG76V-GFP-Syb2 mice (8 months of age) were probed using anti-Usp14 antibodies. Both isoforms of Usp14 are expressed at similar levels in all three genotypes. E–P, Teased thigh muscle fibers from control, GFP-Syb2, and UbG76V-GFP-Syb2 mice (5 months of age) were immunostained with anti-UchL1 antibodies and costained with α-bgt. UchL1 is localized at the NMJs in UbG76V-GFP-Syb2 mice (N), in a pattern similar to that seen in control mice (F) and GFP-Syb2 mice (J). Scale bars: (in P) E–P, 30 μm.