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Articles by Jianming Liu
Total Records ( 3 ) for Jianming Liu
  Lin Zhang , Jianming Liu , Hongzhou Li and Zhiyong Peng
  Ad hoc On-demand Distance Vector (AODV), Dynamic Source Routing (DSR) and Temporally Ordered Routing Algorithm (TORA) are three on-demand routing protocols for ad hoc networks. This study described the principles of the three protocols. The theoretical models of nodes distribution are then introduced. Finally, the effectiveness of routing protocols in wireless ad hoc networks is discussed based on the model of natural average distribution from a practical point of view. In this experiment, a comparison of performance tests of AODV, DSR and TORA is made by OPNET. From simulation results, it can be found that the performances of the three routing protocols are different and different protocols have different superiority in certain environment. These experimental results are provided as a basis for hardware implementation of wireless ad hoc networks.
  Mili Kapoor , Quansheng Zhou , Francella Otero , Christopher A. Myers , Alison Bates , Rajesh Belani , Jianming Liu , Jiann-Kae Luo , Eleni Tzima , Dong-Er Zhang , Xiang-Lei Yang and Paul Schimmel
  In mammalian cells, specific aminoacyl-transfer RNA (tRNA) synthetases have cytokine functions that require interactions with partners outside of the translation apparatus. Little is known about these interactions and how they facilitate expanded functions that link protein translation to other cellular pathways. For example, an alternative splice fragment of tryptophanyl-tRNA synthetase (TrpRS) and a similar natural proteolytic fragment are potent angiostatic factors that act through the vascular endothelial-cadherin receptor and Akt signaling pathway. Here we demonstrate mobilization of TrpRS for exocytosis from endothelial cells and the potential for plasmin to activate the cytokine function of the extracellular synthetase. Direct physical evidence showed that the annexin II-S100A10 complex, which regulates exocytosis, forms a ternary complex with TrpRS. Functional studies demonstrate that both annexin II and S100A10 regulate trafficking of TrpRS. Thus, complexes of mammalian tRNA synthetases with seemingly disparate proteins may in general be relevant to understanding how their expanded functions are implemented.
  Jianming Liu , Praveen B. Gurpur and Stephen J. Kaufman
  The dystrophin-glycoprotein complex and the α7β1 integrin are trans-sarcolemmal linkage systems that connect and transduce contractile forces between muscle fibers and the extracellular matrix. α7β1 is the major laminin binding integrin in skeletal muscle. Different functional variants of this integrin are generated by alternative splicing and post-translational modifications such as glycosylation and ADP-ribosylation. Here we report a species-specific difference in α7 chains that results from an intra-peptide proteolytic cleavage, by a serine protease, at the 603RRQ605 site. Site-directed mutagenesis of RRQ to GRQ prevents this cleavage. This RRQ sequence in the α7 integrin chain is highly conserved among vertebrates but it is absent in mice. Protein structure modeling indicates this cleavage site is located in an open region between the β-propeller and thigh domains of the α7 chain. Compared with the non-cleavable α7 chain, the cleaved form enhances cell adhesion and spreading on laminin. Cleavage of the α7 chain is elevated upon myogenic differentiation, and this cleavage may be mediated by urokinase-type plasminogen activator. These results suggest proteolytic cleavage is a novel mechanism that regulates α7 integrin functions in skeletal muscle, and that the generation of such cleavage sites is another evolutionary mechanism for expanding and modifying protein functions.
 
 
 
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