Alterations of the topological organization of abnormal regions or network-level structural aberrations are still poorly understood for post-traumatic stress disorder (PTSD). Herein, we investigated brain structural networks in recent-onset PTSD patients, all affected by the coalmine-flood disaster. Cortical networks were studied in recent onset PTSD patients (n = 15) and matched healthy controls (n = 25). Cortical networks were constructed by thresholding correlation matrices of 150 regions and quantified using graph theoretical approaches. Contributions of high-degree nodes, and regional and global network measures, including degree and betweenness, were studied. Compared with healthy controls, PTSD patients showed altered quantitative values in global network properties, characterized by shorter path length and higher clustering. Moreover, PTSD patients exhibited decreased connectivity in the right lingual gyrus, parahippocampal gyrus, left supramarginal gyrus, parahippocampal gyrus, bilateral superior and inferior frontal gyrus, superior frontal gyrus, and posterior cingulate gyrus. Nodal centrality decreased predominantly in the occipital regions (lingual gyrus) and default-mode regions, while increased correlations and centralities were observed in the medial temporal lobe and posterior cingulate cortex. PTSD-related networks exhibited a less efficient organization and regional connectivity. According to these findings, we conclude that regional connections involving fear-processing and re-experiential-processing cortex may play a role in maintaining or adapting to PTSD pathology.

SHP-1 is a cytosolic protein-tyrosine phosphatase that behaves as a negative regulator in eukaryotic cellular signaling pathways. To understand its regulatory mechanism, we have determined the crystal structure of the C-terminal truncated human SHP-1 in the inactive conformation at 2.8-A resolution and refined the structure to a crystallographic R-factor of 24.0%. The three-dimensional structure shows that the ligand-free SHP-1 has an auto-inhibited conformation. Its N-SH2 domain blocks the catalytic domain and keeps the enzyme in the inactive conformation, which supports that the phosphatase activity of SHP-1 is primarily regulated by the N-SH2 domain. In addition, the C-SH2 domain of SHP-1 has a different orientation from and is more flexible than that of SHP-2, which enables us to propose an enzymatic activation mechanism in which the C-SH2 domains of SHPs could be involved in searching for phosphotyrosine activators.

The substrate specificity of the catalytic domain of SHP-1, an important regulator in the proliferation and development of hematopoietic cells, is critical for understanding the physiological functions of SHP-1. Here we report the crystal structures of the catalytic domain of SHP-1 complexed with two peptide substrates derived from SIRPalpha, a member of the signal-regulatory proteins. We show that the variable beta5-loop-beta6 motif confers SHP-1 substrate specificity at the P-4 and further N-terminal subpockets. We also observe a novel residue shift at P-2, the highly conserved subpocket in protein- tyrosine phosphatases. Our observations provide new insight into the substrate specificity of SHP-1.

The crystal structures of the protein-tyrosine phosphatase SHP-1 catalytic domain and the complex it forms with the substrate analogue tungstate have been determined and refined to crystallographic R values of 0.209 at 2.5 A resolution and 0.207 at 2.8 A resolution, respectively. Despite low sequence similarity, the catalytic domain of SHP-1 shows high similarity in secondary and tertiary structures with other protein-tyrosine phosphatases (PTPs). In contrast to the conformational changes observed in the crystal structures of PTP1B and Yersinia PTP, the WPD loop (Trp419-Pro428) in the catalytic domain of SHP-1 moves away from the substrate binding pocket after binding the tungstate ion. Sequence alignment and structural analysis suggest that the residues in the WPD loop, especially the amino acid following Asp421, are critical for the movement of WPD loop on binding substrates and the specific activity of protein-tyrosine phosphatases. Our mutagenesis and kinetic measurements have supported this hypothesis.