Fig. 1.

Expression of TDP-43 and shorter alternative splicing isoform, TDP-S6, in HEK-293 cells. A, TDP-43 consists of six exons that encode a protein of 414 amino acids. RRM1 spans exons 3 and 4, RRM2 spans exons 5 and 6, and the glycine-rich C-terminal domain lies within exon 6. TDP-S6 is generated by an additional splicing event resulting in a reading frameshift after amino acid 277. Thus, TDP-S6 contains 18 unique amino acids (278–295) on its C terminus (grey) corresponding to residual intron RNA included during an alternative splicing event. B, Western blotting (WB) analysis of transfected control (mock plasmid), HA-tagged TDP-43, or TDP-S6. C, loss of TDP-43 phosphorylation during phosphatase treatment. The HA-TDP-43-transfected total cell lysate was incubated for 2.5 h with the addition of an increasing concentration of alkaline phosphatase followed by Western analysis. Phosphorylated TDP-43 isoforms are indicated by asterisks.