PubMed · 13639669
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W A MULLER. 1959-02-20. Uropepsinogen.. https://doi.org/10.1055/s-0028-1113617
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PSGL-1, the optimal selectin ligand demonstrated by in vivo studies to date, is an essential adhesive molecule mediating the rolling of leukocytes on the endothelial cells and the recruitment of leukocytes to the inflamed tissue. Recent studies demonstrated, in addition to its direct role in capture of leukocytes from the bloodstream, PSGL-1 also functions as a signal-transducing receptor and initiates a series of intracellular signal events during the activation of leukocytes. Our present work showed antibody engagement of PSGL-1 upregulated the transcriptional activity of CSF-1 promotor and increased the endogenous expression of CSF-1 mRNA in Jurkat cell. Overexpression of wild-typed non-receptor tyrosine kinase Syk, but not kinase dead mutant of Syk, promoted the upregulation of the transcriptional activity of CSF-1 promoter caused by antibody engagement of PSGL-1. Additionally, special inhibitor of Syk Piceatannol suppressed the increase of CSF-1 mRNA caused by the engagement of PSGL-1. The results suggest that signal transducted by PSGL-1 upregulate the transcriptional activity of CSF-1, and non-receptor tyrosine kinase Syk participates in this pathway.
Structural flexibility plays a crucial role in protein function. To assess whether specific structural changes are associated with the binding of an immunoreceptor tyrosine-based activation motif (ITAM) to the tandem Src homology-2 domains (tSH2) of the spleen tyrosine kinase [EC 2.7.7.112] (Syk), we used an approach based on protein hydrogen/deuterium exchange in the presence and absence of the diphosphorylated ITAM peptide. The protein deuterium uptake by the intact Syk protein was monitored in time by electrospray mass spectrometry, which revealed a dramatic relative decrease in deuterium uptake when the protein was bound to the ITAM peptide, suggesting an overall change in protein dynamics. Subsequently, the deuterium incorporation of individual segments of the protein was investigated using proteolysis and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) peptide mass-analysis, which revealed that several regions of Syk tSH2 are significantly more protected from exchange in the presence of the ITAM peptide. Four protected regions encompass the phosphotyrosine and hydrophobic binding sites on the SH2 domains, whereas two other protected regions are located in the inter-SH2 linker motif and do not make any direct contacts with the peptide. Interestingly, our data suggest that binding of the ITAM peptide to Syk tSH2 induces distal structural effects on the protein that stabilize the inter-SH2 linker region, possibly by raising the degree of helical structure upon binding.
OBJECTIVE: To detect protein expression of MMPs and TIMPs in various salivary gland neoplasms and to investigate their roles in invasion and metastasis of the malignant salivary gland tumors. METHODS: Immunohistochemistry and Gelatin zymography analyses for MMP-2, MMP-9, MT1-MMP, TIMP-1 and TIMP-2 were performed in 26 malignant and 28 benign salivary gland tumors. RESULTS: The expression of MMP-2 and MMP-9 was significantly higher in carcinomas than in adenomas (P < 0.05). The MMP-2/TIMP-1 and MMP-2/TIMP-2 was also significantly higher in carcinomas than in adenomas (P < 0.05). There was a cooperated effect among MMP-2, MT1-MMP and TIMP-2. The expression of active MMP-2, proMMP-9 and active MMP-9 was significantly higher in malignant tumors than in benign tumors (P < 0.05). CONCLUSION: MMP-2 and MMP-9 may play important roles in invasion of malignant salivary gland tumors. A disturbed balance between MMP-2, MMP-9, TIMP-1 and TIMP-2 in malignant salivary gland tumors was detected. It was the absolute increase of MMP-2 and MMP-9 to induce the unbalance.