Figure 3.

TFEBmt reduces lysosomal size, but induces apoptosis in a subset of PD myotubes.

A. Immunostaining of non-infected cells (day 13 in differentiation medium) and cells infected with a mutant form of TFEB (TFEBmt) with LAMP1 (red) and Flag (green). Ad-TFEBmt was added to the myotubes for 72 h on day 10 in differentiation medium. Ad-TFEBmt-infected cells show massive accumulation of TFEB in the nuclei and significant reduction in lysosomal size, similar to that seen with TFEB.

B. Western blot of cell lysates confirms the presence of TFEB in the nuclear fraction; the different intensities of the two bands corresponding to LAMP1 protein in untreated and TFEBmt-treated samples may reflect the differences in the glycosylation pattern.

C. Western blot of protein lysates from untreated, Ad-null, TFEB, and TFEBmt-treated myotubes with anti-caspase-3 antibody. No activated (cleaved) products are detected in any condition. α-Tubulin was used as a loading control.

D. TUNEL assay shows the presence of some apoptotic cells in Ad-TFEB-infected cultures, but not in control cultures infected with adenovirus alone (n = 3). Bar: 10 µm for all panels.