Lipotoxic Stress Induces Pancreatic β-Cell Apoptosis through Modulation of Bcl-2 Proteins by the Ubiquitin-Proteasome System

Figure 4

Palmitate and MG132 decrease levels of prosurvival proteins in pancreatic islets and β-cells. ((a)–(c)) MIN6 cells were treated with 0.5 mM palmitate as indicated and expression of prosurvival proteins Bcl-2 (a), Bcl-XL (b), and Mcl-1 (c) was measured by Western blot. Band intensities were quantified and values of the specific time points standardised to β-actin loading controls. Results are the means ± SEM of 3 independent experiments. , , and . ((d)-(e)) MIN6 cells were treated with 10 μM MG132 as indicated and expression of prosurvival proteins Bcl-2 (d), Bcl-XL (e), and Mcl-1 (f) was measured by Western blot. Band intensities were quantified and values of the specific time points standardised to β-actin loading controls. Results are the means ± SEM of 3 independent experiments. ; . ((g)–(i)) Expression of prosurvival Bcl-2 proteins in mouse islets after palmitate treatment. Cell lysates were subjected to Western blotting with antibodies detecting Bcl-2 (g), Bcl-XL (h), and Mcl-1 (i). Quantification of protein bands is indicated at the bottom as a ratio to β-actin loading control. The results are representative of two independent experiments.

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