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Articles by F Zhu
Total Records ( 3 ) for F Zhu
  Q Qiu , G Liu , W Li , Q Shi , F Zhu and G. Lu

Glycerol-3-phosphate acyltransferase (GPAT) catalyzes the first committed step of de novo triacylglycerol synthesis by converting glycerol-3-phosphate to lysophosphatidic acid (LPA). LPA is a mitogen that mediates multiple cellular processes including cell proliferation. Four GPAT isoforms have been cloned to date. GPAT4 is strongly expressed in the mouse testis. Reverse transcription–polymerase chain reaction (PCR), real-time PCR, and in situ hybridization (ISH) were used to analyze the GPAT4 expression and to localize the expressing cell types in the mouse testis during postnatal development. GPAT4 cDNA was inserted into pcDNA4/His to construct a recombinant vector, which was transfected into a mouse spermatogonial cell line (GC-1spg). GPAT4 was first expressed in mice at 2 weeks postnatally. Expression was abundant from the third week, plateaued at week 5–6 and then maintained at a high level in the adult. ISH revealed that GPAT4 gene was expressed abundantly in spermatocytes and around spermatids during meiosis but not in elongated spermatids during later spermiogenesis. GC-1spg cells showed a marked increase in proliferation after transfection with GPAT4; cell cycle analysis showed a decrease in the percentage of cells in the G0/G1 phase and an increase in the S phase. Thus, GPAT4 might play an important role in spermatogenesis, especially in mid-meiosis.

  J. H Shim , Z. Y Su , J. I Chae , D. J Kim , F Zhu , W. Y Ma , A. M Bode , C. S Yang and Z. Dong

Green tea is a highly popular beverage globally. Green tea contains a number of polyphenol compounds referred to as catechins, and (–)-epigallocatechin gallate (EGCG) is believed to be the major biologically active compound found in green tea. EGCG has been reported to suppress lung cancer, but the molecular mechanisms of the inhibitory effects of EGCG are not clear. We found that EGCG interacted with the Ras–GTPase-activating protein SH3 domain-binding protein 1 (G3BP1) with high binding affinity (Kd = 0.4 µmol/L). We also showed that EGCG suppressed anchorage-independent growth of H1299 and CL13 lung cancer cells, which contain an abundance of the G3BP1 protein. EGCG was much less effective in suppressing anchorage-independent growth of H460 lung cancer cells, which express much lower levels of G3BP1. Knockdown shG3BP1-transfected H1299 cells exhibited substantially decreased proliferation and anchorage-independent growth. shG3BP1 H1299 cells were resistant to the inhibitory effects of EGCG on growth and colony formation compared with shMock-transfected H1299 cells. EGCG interfered with the interaction of G3BP1 and the Ras–GTPase-activating protein and further suppressed the activation of Ras. Additional results revealed that EGCG effectively attenuated G3BP1 downstream signaling, including extracellular signal-regulated kinase and mitogen-activated protein kinase/extracellular signal-regulated kinase kinase, in wild-type H1299 and shMock H1299 cells but had little effect on H460 or shG3BP1 H1299 cells. Overall, these results strongly indicate that EGCG suppresses lung tumorigenesis through its binding with G3BP1. Cancer Prev Res; 3(5); 670–9. ©2010 AACR.

  P Wang , F Zhu and K. Konstantopoulos

Elevated levels of prostaglandin (PG)E2 and interleukin (IL)-6 have been reported in the cartilage and synovial fluid from patients with arthritic disorders. PGE2 regulates IL-6 production in numerous different cells including macrophages and synovial fibroblasts. Although PGE2 stimulates IL-6 expression in human chondrocytes, the underlying signaling pathway of this process has yet to be delineated. Here, we investigate the mechanism of IL-6 induction in human T/C-28a2 chondrocytes treated with exogenously added PGE2. PGE2 induces IL-6 mRNA and protein expression via a cAMP-dependent pathway, reaching maximal levels after 60 min of stimulation before declining to baseline levels at 6 h. Forskolin, an adenylyl cyclase activator, also stimulates IL-6 expression in human chondrocytes in a dose- and time-dependent fashion. Inhibition of downstream effectors of cAMP activity such as protein kinase A (PKA) or phosphatidylinositol 3 kinase (PI3K) blocks PGE2- and forskolin-induced IL-6 upregulation. Simultaneous inhibition of PKA and PI3K reduces IL-6 expression in stimulated chondrocytes well below the basal levels of untreated cells. Gel shift, supershift, and chromatin immunoprecipitation assays reveal the activation and binding of the nuclear factor (NF)-B p65 subunit to the IL-6 promoter, which is markedly suppressed by selective PI3K or PKA pharmacological inhibitors. p65 knockdown completely abrogates IL-6 mRNA synthesis in PGE2- and forskolin-primed chondrocytes. Cumulatively, our data show that PGE2 and forskolin induce IL-6 expression in human chondrocytes via cAMP/PKA and PI3K-dependent pathways, which in turn regulate the activation and binding of p65 to the IL-6 promoter.

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