Figure 9.

Batten disease mutations interfering with lysosomal targeting motifs. (A) CLN3 proteins carrying mutations that mimic two naturally occurring Batten disease-causing mutations, either introduction of a stop codon after E399 (stop) or a frameshift after G424 (fs), were transiently expressed in HeLa cells. Cells were fixed with PFA, permeabilized with Triton X-100, labeled with antibodies to CLN3 and PDI, and analyzed by epifluorescence microscopy. Both mutated proteins were retained in the ER (a and c, respectively), judged by colocalization with PDI (b and d). (B) Immunoblotting of cell lysates with a CLN3 specific antiserum 3326. Wt CLN3 occurs as a 43/46-kDa doublet, whereas the mutations resulted in proteins of 39 kDa (stop) and 50 kDa (fs), respectively.