| Summary: | 碩士 === 長庚大學 === 生物醫學研究所 === 98 === Abstract
Human CEP55 (centrosomal protein, 55 kDA) is a coiled-coil
centrosomal protien that locates at loci 10q23.33 and encodes 464 amino acids. Endogenous Cep55 localizes to the mother centriole of interphase cells, appears in the midzone and later translocates to the midbody for
helping cytokinesis completion. Upon mitotic entry, dissociation of Cep55 from centrosome is triggered by Erk2/Cdk1-dependent phosphorylation at Ser425 and Ser428. Ser425 and Ser428 phosphorylation is required for interaction with Plk1 at Cep55 Ser436 site,
whose phosphorylation at the midbody in turn drive cells through cytokinesis. Cells expressing phosphorylation-deficient mutant form of Cep55 may undergo cytokinesis failure.
Cep55 overexpression promotes cell grown in soft agar, in low serum medium and induces tumor formation in nude mice. Overexpression of Cep55 might activate PI3K/AKT pathway and lead to Cep55-elicited cell proliferation and transformation of mammalian cells. Upregulation of
Cep55 was observed in hepatocellular carcinoma (HCC) patient samples.
To study the phosphorylation-dependent regulation of Cep55
expression in vivo, we generate transgenic mice specifically
overexpressing Cep55、the phosphorylation-defected mutant
(S425A,S428A,S436A) and the phosphomimetic mutant (S425E,S428E) in the liver under albumin promoter. We monitored the protein expression in transgenic mice at the early stage by ” in vivo imaging system” analysis, and used RT-PCR in combination with immunofluorescent staining of the liver crytosection for confirming expression of ectopic Cep55 and its mutants.
In general we did not observe gross change in the transgenic livers obtained from Cep55 transgenic mice. However, we noticed abnormal hepatocytes including cellular necrosis and infiltrated inflammation in livers of the alb-myc-Cep55-luci mice, and development failure of liver lobes in the alb-myc-Cep55AAA-luci mice. Careful mounting of these
transgenic mice for liver tumor generation in older age is therefore necessary to gain insight into the effect of Cep55 on cell proliferation in vivo.
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