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Laporte, Ste´phane A.,Miller, William E.,Kim, Kyeong-Man,Caron, Marc G. 전남대학교 약품개발연구소 2002 약품개발연구지 Vol.11 No.-
β-Arrestins, proteins involved in the turn-off of G protein-coupled receptor (GPCR) activation, bind to the β_2-adaptin subunit of the clathrin adaptor AP-2. The interaction of β_2-adaptin with β-Arrestin involves critical arginine residues in the C-terminal domain of β-Arrestin and plays an important role in initiating clathrin-mediated endocytosis of the β_2-adrenergic receptor(β_2AR) (Laporte, S. A., Oakley, R. H., Holt, J. A., Barak, L. S., and Caron, M. G. (2000) J. Biol. Chem. 276, 23120-23126). However, the β-arrestin-binding site in β_2-adaptin has not been identified, and little is known about the role of β-arrestin/AP-2 interaction in the endocytosis of other GPCRs. Using in vitro binding assays, we have identified two glutamate residues (Glu-849 and Glu-902) in β_2-adaptin that are important in β-arrestin binding. These residues are located in the platform subdomain of the C terminus β_2-adaptin, where accessory/adapter endocytic proteins for other classes of receptors interact, distinct from the main site where clathrin interact. The functional significance of the β-arrestin/AP-2/clathrin complex in the endocytosis of GPCRs such as the β_2AR and vasopressin type Ⅱ receptor was evaluated using mutant constructs of the β_2-adaptin C terminus containing either the clathrin and the β-arrestin binding domains or the β-arrestin-binding domain alone. When expressed in human embryonic kidney 293 cells, both constructs acted as dominant negatives inhibiting the agonist-induced internalization of the β_2AR and the vasopressin type Ⅱ receptor. In addition, although the β_2-adaptin construct containing both the clathrin and β-arrestin binding domains was able to block the endocytosis of transferrin receptors, a β_2-adaptin construct capable of assoociating with β-arrestin but lacking its high affinity clathrin interaction did not interfere with transferrin receptor endocytosis. These results suggest that the interaction of β-arrestin with β_2-adaptin represents a selective endocytic trigger for several members of the GPCR family.
Nanoscopic wear behavior of face centered cubic metals
Ko, H.E.,Park, H.W.,Jiang, J.Z.,Caron, A. Elsevier 2018 ACTA MATERIALIA Vol.147 No.-
<P><B>Abstract</B></P> <P>The wear behavior of three face centered cubic metals (Au, Ag and Ni) have been investigated by friction force microscopy. Depending on the applied normal load two tribological mechanisms can be distinguished: shearing and ploughing. Our experimental shearing friction data can be well described by the Johnson-Kendal-Roberts model. Our results show a positive correlation between the shear strength and the surface energy of the investigated metals. Further, ploughing is confirmed to be determined by the resistance of a metal to be plastically deformed, i.e. its hardness. We find that the ploughing friction coefficient and the wear volume inversely scale with the hardness.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>