纖維神經促進激素CNTF及環化腺核?單磷酸cAMP對轉?因數AGP/EBP基因表現的調控

Abstract

纖維神經促進激素（ciliary neurotrophic factor CNTF)是維持雞胚副交感纖維神經細胞存活的重要因數。cNTF為一分子量22.8KDa的酸性蛋白質，與IL－6、IL－11、LIF及oncostain M屬於同一家族的細胞激素。此家族的特性是可共用細胞膜訊息傳遞子，gP130，傳遞外來訊息至細胞內。在本篇論文中經由選殖、表現、及親和性管柱層析純化的recombinant CNTF對雞胚纖維神經及小老鼠坐骨神經都有維持存活的生物活性。在人類神經細胞株SK－N－MC中recombinant CNTF可活化細胞質內訊息傳遞子，P－91，轉移至細胞核內，並增加酪氨酸磷酸化，但是其NF－IL6基因不受recombinant CNTF所調控。 （此外CNTF對SK－N－MC細胞以及 cAMP 對急性發炎反應基因AGP/EBP之基因表現也加以研究）。AGP/EBP基因包含兩個ATF可能的核甘酸序列。在本論文研究中證實，AGP/EBP啟動子在－44至－117之間確實有一cAMP調節區。由於AGP/EBP蛋白質本身也可被AMP活化，加上先前已證實轉錄因數NF－κB及AGP/EBP可協同活化AGP/EBP基因的表現，因此cAMP活化AGP/EBP基因的表現可能是經由轉錄因數ATF－1與AGP/EBP相互作用所造成的。CNTF對AGP/EBP在SK－N－MC細胞內的表現則沒什麼作用!

Ciliary neurotrophic factor (CNTF), a 22.8KDa acidic protein, was originally characterized as a survival factor for chick ciliary neurons in vitro. CNTF, interleukin-6 (IL-6), IL-11, leukemia inhibitory factor (LIF) and oncostatin M are a family of cytokines which bind to composite plasma membrane receptors sharing the signal transducing subunit gp-130. In this study, molecular cloning, expression and affinity column purification of recombinant CNTF were described. The purified recombinant CNTF could promote the survival of both chick E8 ciliary ganglia neurons and mouse sciatic neurons in vitro. In human neuroblastoma cell line SK-N-MC, recombinant CNTF stimulated the tyrosine phosphorylation and translocation of p-91 from cytoplasm to the nucleus. CNTF did not affect the expression of NF-IL6, however. The expression of AGP/EBP gene in SK-N-MC cells was also investigated. AGP/EBP promoter region contains two putative cAMP responsive elements (CREs). In this study, we identified a region (-44 to -117) in AGPIEBP promoter that respond to forskolin activation. Thus, in addition to the previously identified synergistic activation of AGPIEBP gene by NF-KB and AGP/EBP protein, it is also activated by cAMP. This latter activation may be through the cooperative action of ATF-1 and AGP/EBP. CNTF has no effect on this AGP/EBP regulation!