Autophagy plays beneficial effect on diabetic encephalopathy in type 2 diabetes: studies in vivo and in vitro.

OBJECTIVES: The hypothalamus regulates metabolism and feeding behavior by perceiving the levels of peripheral insulin. However, little is known about the hypothalamic changes after aberrant metabolism. In this study, we investigated the changes of insulin and autophagy relevant signals of hypothalamus under diabetes mellitus. METHODS: C57B/L mice were injected with low-dose streptozotocin (STZ) and fed with high-fat diet to induce type 2 diabetes mellitus. In vitro, PC12 cells were treated with oleic acid to mimic lipotoxicity. RESULTS: Results showed that the cholesterol level in the hypothalamus of the diabetic mice was higher than that of the normal mice. The expression of insulin receptors and insulin receptor substrate-1 were downregulated and the number of Fluoro-Jade C positive cells significantly increased in the hypothalamic arcuate nucleus of the diabetic mice. Furthermore, Upregulation of mammalian target of rapamycin (mTOR) and downregulation of LC 3II were obvious in the hypothalamus of the diabetic mice. In vitro, results showed that high-lipid caused PC12 cell damage and upregulated LC3 II expression. Pretreatment of cells with 3-methyladenine evidently downregulated LC3 II expression and aggravated PC12 cell death under high lipid conditions. By contrast, pretreatment of cells with rapamycin upregulated LC3 II expression and ameliorated PC12 cell death caused by lipotoxicity. CONCLUSION: These results demonstrate that autophagy activation confers protection to neurons under aberrant metabolism and that autophagy dysfunction in the hypothalamus occurs in the chronic metabolic disorder such as T2DM.

pVHL mediates K63-linked ubiquitination of nCLU.

pVHL, product of von Hippel-Lindau (VHL) tumor suppressor gene, functions as the substrate recognition component of an E3-ubiquitin ligase that targets proteins for ubiquitination and proteasomal degradation. Hypoxia-inducible factor α (HIFα) is the well-known substrate of pVHL. Besides HIFα, pVHL also binds to many other proteins and has multiple functions. In this manuscript, we report that the nuclear clusterin (nCLU) is a target of pVHL. We found that pVHL had a direct interaction with nCLU. nCLU bound to pVHL at pVHL's ß domain, the site for recognition of substrate, indicating that nCLU might be a substrate of pVHL. Interestingly, pVHL bound to nCLU but did not lead to nCLU destruction. Further studies indicated that pVHL mediated K63-linked ubiquitination of nCLU and promoted nCLU nuclear translocation. In summary, our results disclose a novel function of pVHL that mediates K63-linked ubiquitination and identify nCLU as a new target of pVHL.

Prolyl hydroxylase domain protein 3 targets Pax2 for destruction.

Prolyl hydroxylase domain proteins (PHDs) hydroxylate HIFα in the presence of oxygen, leading to HIFα proteasomal destruction. The PHDs family comprises PHD1, 2, and 3. Recent studies indicate that, in addition to HIFα, PHDs have other substrates. Paired box (Pax) 2, a transcription factor, was found aberrantly expressed in a variety of cancers. However, the underlying mechanisms remain unknown. Here we demonstrate that PHD3 is a negative regulator of expression of Pax2. We found that PHD3 bound to Pax2 and mediated Pax2 destruction directly. Inhibition of PHD3 hydroxylase activity led to upregulation of Pax2 protein but not mRNA level. We found that Pax2 protein was increased and PHD3 protein was decreased in colorectal cancer, and the increased Pax2 was associated with decreased PHD3. Our results suggest that PHD3 targets Pax2 for destruction. The findings may disclose a mechanism for the regulation of Pax2 expression in cancer cells.

Discrepancy of biologic behavior influenced by bone marrow derived cells in lung cancer.

Disseminated cancer cells may initially require local nutrients and growth factors to thrive and survive in bone marrow. However, data on the influence of bone marrow derived cells (BMDC, also called bone stromal cells in some publications) on lung cancer cells is largely unexplored. This study explored the mechanism of how bone stromal factors contribute to the bone tropism in lung cancer. The difference among lung cancer cell lines in their abilities to metastasize to bone was found using the SCID animal model. Supernatant of bone marrow aspiration (BM) and condition medium from human bone stromal cells (BSC) were used to study the activity of bone stromal factors. We found bone stromal factors significantly increased the proliferation, invasion, adhesion and expression of angiogenosis-related factors, and inhibited the apoptosis for high bone metastasis H460 lung cancer cells. These biologic effects were not seen in SPC-A1 or A549 cells, which are low bone metastasis lung cancer cells. Adhesion of H460 cells to surface coated with bone stromal cells can activate some signal transduction pathways, and alter the expression of adhesion associated factors, including integrin ß 3 and ADAMTS-1, two potential targets related with bone metastasis. We concluded that bone marrow derived cells had a profound effect on biological behavior of lung cancers, therefore favoring the growth of lung cancer cells in bone.