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. 2021 Nov 2;14:757278. doi: 10.3389/fnmol.2021.757278

FIGURE 5.

FIGURE 5

SUMOylation of Kv4.2g at K579 increases surface expression. SUMOylation was (+) or was not (–) increased in HEK cells expressing wild-type TC, TC K437R, or TC K579R. Surface proteins were biotinylated, cells were lysed, and surface expressed fractions (SE) were isolated using NeutrAvidin resin. Proteins that did not bind to the NeutrAvidin resin were considered to be the intracellular fraction (I). (A,C,E) Western blots containing SE and I from one representative experiment for each treatment group. The upper portion of the blot (above 50 kD) was used to visualize Kv4.2g with anti-GFP; it was then stripped and re-probed with anti-Na+/K+-ATPase. The lower portion of the blot (below 50 kD) was probed for actin. (B,D,F) Bar graphs showing the mean ± SEM Kv4.2g surface expression [SE Kv4.2g OD/SE Na+/K+-ATPase OD]. Each dot is one independent experiment. Asterisk, significantly different. TC: control, 1.0 ± 0.1 vs. SUMO2 + Ubc9, 1.3 ± 0.1, t-test p = 0.046; TC K437R: control, 0.9 ± 0.1 vs. SUMO2 + Ubc9, 1.4 ± 0.2, t-test p = 0.037; TC K579R: control, 1.0 ± 0.1 vs. SUMO2 + Ubc9, 0.9 ± 0.1, t-test p = 0.528.