Inhibition of protein disulfide isomerase induces differentiation of acute myeloid leukemia cells

Acute myeloid leukemia is a malignant disease of immature myeloid cells. Despite significant therapeutic effects of differentiation-inducing agents in some acute myeloid leukemia subtypes, the disease remains incurable in a large fraction of patients. Here we show that SK053, a thioredoxin inhibitor, induces differentiation and cell death of acute myeloid leukemia cells. Considering that thioredoxin knock-down with short hairpin RNA failed to exert antiproliferative effects in one of the acute myeloid leukemia cell lines, we used a biotin affinity probe-labeling approach to identify potential molecular targets for the effects of SK053. Mass spectrometry of proteins precipitated from acute myeloid leukemia cells incubated with biotinylated SK053 used as a bait revealed protein disulfide isomerase as a potential binding partner for the compound. Biochemical, enzymatic and functional assays using fluorescence lifetime imaging confirmed that SK053 binds to and inhibits the activity of protein disulfide isomerase. Protein disulfide isomerase knockdown with short hairpin RNA was associated with inhibition of cell growth, increased CCAAT enhancer-binding protein α levels, and induction of differentiation of HL-60 cells. Molecular dynamics simulation followed by the covalent docking indicated that SK053 binds to the fourth thioredoxin-like domain of protein disulfide isomerase. Differentiation of myeloid precursor cells requires the activity of CCAAT enhancer-binding protein α, the function of which is impaired in acute myeloid leukemia cells through various mechanisms, including translational block by protein disulfide isomerase. SK053 increased the levels of CCAAT enhancer-binding protein α and upregulated mRNA levels for differentiation-associated genes. Finally, SK053 decreased the survival of blasts and increased the percentage of cells expressing the maturation-associated CD11b marker in primary cells isolated from bone marrow or peripheral blood of patients with acute myeloid leukemia. Collectively, these results provide a proof-of-concept that protein disulfide isomerase inhibition has potential as a therapeutic strategy for the treatment of acute myeloid leukemia and for the development of small-molecule inhibitors of protein disulfide isomerase

Beyond the brain: disrupted in schizophrenia 1 regulates pancreatic β-cell function via glycogen synthase kinase-3β.

Individuals with schizophrenia and their first-degree relatives have higher rates of type 2 diabetes (T2D) than the general population (18-30 vs. 1.2-6.3%), independent of body mass index and antipsychotic medication, suggesting shared genetic components may contribute to both diseases. The cause of this association remains unknown. Mutations in disrupted in schizophrenia 1 (DISC1) increase the risk of developing psychiatric disorders [logarithm (base 10) of odds = 7.1]. Here, we identified DISC1 as a major player controlling pancreatic β-cell proliferation and insulin secretion via regulation of glycogen synthase kinase-3β (GSK3β). DISC1 expression was enriched in developing mouse and human pancreas and adult β- and ductal cells. Loss of DISC1 function, through siRNA-mediated depletion or expression of a dominant-negative truncation that models the chromosomal translocation of human DISC1 in schizophrenia, resulted in decreased β-cell proliferation (3 vs. 1%; P \u3c 0.01), increased apoptosis (0.1 vs. 0.6%; P \u3c 0.01), and glucose intolerance in transgenic mice. Insulin secretion was reduced (0.5 vs. 0.1 ng/ml; P \u3c 0.05), and critical β-cell transcription factors Pdx1 and Nkx6.1 were significantly decreased. Impaired DISC1 allowed inappropriate activation of GSK3β in β cells, and antagonizing GSK3β (SB216763; IC50 = 34.3 nM) rescued the β-cell defects. These results uncover an unexpected role for DISC1 in normal β-cell physiology and suggest that DISC1 dysregulation contributes to T2D independently of its importance for cognition.-Jurczyk, A., Nowosielska, A., Przewozniak, N., Aryee, K.-E., DiIorio, P., Blodgett, D., Yang, C., Campbell-Thompson, M., Atkinson, M., Shultz, L., Rittenhouse, A., Harlan, D., Greiner, D., Bortell, R. Beyond the brain: disrupted in schizophrenia 1 regulates pancreatic β-cell function via glycogen synthase kinase-3β. FASEB J 2016 Feb; 30(2):983-93