Lewis K E, O'Day D H
Department of Zoology, Erindale College, University of Toronto, Mississauga, Ontario, Canada.
Cell Signal. 1994 Feb;6(2):217-22. doi: 10.1016/0898-6568(94)90079-5.
A unique aspect of phagocytosis during the sexual cycle of Dictyostelium discoideum is the ability of the zygote giant cell (ZGC) to attract and engulf hundreds of amoebae of the same species. The work presented here is one of two initial attempts to understand the signal transduction pathways that are involved during this event. Our data indicate that the uptake of amoebae by the ZGCs is negatively modulated by 5'-AMP and adenosine (ADO). The hierarchical inhibition of phagocytosis by the ADO analogues, N-ethylcarboxyadiadenosine and phenyl isopropyl adenosine, argue that the phagocytosis of amoebae by ZGCs is mediated by an ADO receptor, which is similar to the purinogenic class of receptor, A2. As with the A2 receptor, stimulation of cells by ADO binding causes an up-regulation of cAMP synthesis thereby increasing the intracellular levels of cAMP. During the phagocytic phase of sexual development, 5'-AMP and ADO undergo marked and successive increases in amounts supporting their natural role in modulating phagocytosis. This negative modulation of phagocytosis by ADO is similar to that found in mammalian macrophages and may represent an evolutionary precursor to that regulatory process. Furthermore, the slowing of phagocytosis has important implications to sexual development of D. discoideum.
盘基网柄菌有性生殖周期中吞噬作用的一个独特方面是合子巨细胞（ZGC）能够吸引并吞噬数百个同种变形虫。本文所呈现的工作是最初尝试理解此过程中涉及的信号转导途径的两项研究之一。我们的数据表明，ZGC对变形虫的摄取受到5'-AMP和腺苷（ADO）的负调控。ADO类似物N-乙基羧基二腺苷和苯基异丙基腺苷对吞噬作用的分级抑制表明，ZGC对变形虫的吞噬作用是由一种ADO受体介导的，该受体类似于嘌呤能受体A2类。与A2受体一样，ADO结合刺激细胞会导致cAMP合成上调，从而增加细胞内cAMP水平。在有性发育的吞噬阶段，5'-AMP和ADO的量显著且持续增加，这支持了它们在调节吞噬作用中的天然作用。ADO对吞噬作用的这种负调控与在哺乳动物巨噬细胞中发现的情况类似，可能代表了该调节过程的进化前身。此外，吞噬作用的减慢对盘基网柄菌的有性发育具有重要意义。
