BART Inhibits Pancreatic Cancer Cell Invasion by PKCα Inactivation through Binding to ANX7

A novel function for the binder of Arl two (BART) molecule in pancreatic cancer cells is reported. BART inhibits invasiveness of pancreatic cancer cells through binding to a Ca2+-dependent, phosphorylated, guanosine triphosphatase (GTPase) membrane fusion protein, annexin7 (ANX7). A tumor suppressor function for ANX7 was previously reported based on its prognostic role in human cancers and the cancer-prone mouse phenotype ANX7(+/−). Further investigation demonstrated that the BART–ANX7 complex is transported toward cell protrusions in migrating cells when BART supports the binding of ANX7 to the protein kinase C (PKC) isoform PKCα. Recent evidence has suggested that phosphorylation of ANX7 by PKC significantly potentiates ANX7-induced fusion of phospholipid vesicles; however, the current data suggest that the BART–ANX7 complex reduces PKCα activity. Knocking down endogenous BART and ANX7 increases activity of PKCα, and specific inhibitors of PKCα significantly abrogate invasiveness induced by BART and ANX7 knockdown. These results imply that BART contributes to regulating PKCα activity through binding to ANX7, thereby affecting the invasiveness of pancreatic cancer cells. Thus, it is possible that BART and ANX7 can distinctly regulate the downstream signaling of PKCα that is potentially relevant to cell invasion by acting as anti-invasive molecules

Observation of step-induced magnetic domain formation in La1-xSrxMnO3 thin films by photoelectron emission microscopy

科研費報告書収録論文(課題番号:16310081/研究代表者:白井正文/ナノ磁性材料におけるスピン構造とそのダイナミクスに関する理論研究

Import of cytochrome c into mitochondria

The import of cytochrome c into mitochondria can be resolved into a number of discrete steps. Here we report on the covalent attachment of heme to apocytochrome c by the enzyme cytochrome c heme lyase in mitochondria from Neurospora crassa. A new method was developed to measure directly the linkage of heme to apocytochrome c. This method is independent of conformational changes in the protein accompanying heme attachment. Tryptic peptides of [35S]cysteine-labelled apocytochrome c, and of enzymatically formed holocytochrome c, were resolved by reverse-phase HPLC. The cysteine-containing peptide to which heme was attached eluted later than the corresponding peptide from apocytochrome c and could be quantified by counting 35S radioactivity as a measure of holocytochrome c formation. Using this procedure, the covalent attachment of heme to apocytochrome c, which is dependent on the enzyme cytochrome c heme lyase, could be measured. Activity required heme (as hemin) and could be reversibly inhibited by the analogue deuterohemin. Holocytochrome c formation was stimulated 5–10-fold by NADH > NADPH > glutathione and was independent of a potential across the inner mitochondrial membrane. NADH was not required for the binding of apocytochrome c to mitochondria and was not involved in the reduction of the cysteine thiols prior to heme attachment. Holocytochrome c formation was also dependent on a cytosolic factor that was necessary for the heme attaching step of cytochrome c import. The factor was a heat-stable, protease-insensitive, low-molecular-mass component of unknown function. Cytochrome c heme lyase appeared to be a soluble protein located in the mitochondrial intermembrane space and was distinct from the previously identified apocytochrome c binding protein having a similar location. A model is presented in which the covalent attachment of heme by cytochrome c heme lyase also plays an essential role in the import pathway of cytochrome c