Figure 3.

Truncated GPC4 Proteins Are Unstable and Degraded by the UPS

(A) HEK293 cells transfected with constructs encoding N-terminally tagged WT and truncated GPC4 were grown in the absence or presence of 10 μM MG-132 for 14 hours. Total protein was isolated and analyzed by SDS-PAGE and immunoblotting with antibodies directed against V5 (46-0705, ThermoFisher Scientific, 1:5000) and β-actin (A5441, Sigma; 1:20,000). A representative image is shown, and approximate sizes in kDa are indicated (MultiMark Standard, Invitrogen).

(B) Quantification of three independent experiments performed in triplicate. The immunoreactive signals were quantified with a LAS4000 imager. Steady-state protein amounts are expressed as the ratio of GPC4/β-actin, which is the loading control for normalization.

An asterisk denotes p ≤ 0.05; statistical comparisons were made with a two-tailed t test; error bars represent mean ± SEM.