| Summary: | 碩士 === 國立清華大學 === 分子與細胞生物研究所 === 93 === Eosinophil cationic protein (ECP) is a major component of eosinophil granule protein that is used as a clinical bio-marker for asthma and allergic inflammatory diseases. It has been reported that ECP displays many biological activities including cytotoxicity, immunomodulation, regulation of fibroblast activity, and induction of airway mucus secretion. In the previous study, we found that chimeric protein fused with the signal peptide of ECP (ECPsp) inhibited the growth of E. coli, S. cerevisiae, and P. pastoris, but not mammalian cell line A431 due to lack of human signal peptide peptidase (hSPP), a protease located on the endoplasmic reticulum (ER) membrane in mammalian cells. The ECPsp can be digested by signal peptidase and SPP sequentially in ER to generate two polypeptide fragments, ECPspM1-G17 (ECPsp1-17) and ECPspL18-A27 (ECPsp18-27), which may be released from ER membrane. In this study, the chimeric enhanced green fluorescence protein (eGFP) fused with ECPsp, ECPspG17L, ECPsp1-17, and ECPsp18-27 were respectively expressed in A431, Beas-2B, and HL60 cells. It was found that the ECPspG17L chimera inhibited the cell growth, and the same phenomenon was also observed in the cells expressing ECPsp in the presence of siRNA specificially designed for hSPP, implicating that the ECPsp was a toxic signal peptide, and that the expression of hSPP protected the cells from growth inhibition. Moreover, we have recently discovered that ECPsp1-17 induced the expression of transforming growth factor alpha (TGF-��) in all three cell lines examined, suggesting that ECPsp1-17 possessed a novel function that contributed to the proliferation of epithelial cells and was possibly involved in mechanisms of airway remodelling related to asthma.
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