Mariggiò Stefania, Sebastià Jordi, Filippi Beatrice Maria, Iurisci Cristiano, Volonté Cinzia, Amadio Susanna, De Falco Valentina, Santoro Massimo, Corda Daniela
Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Via Nazionale 8, 66030 Santa Maria Imbaro, Chieti, Italy.
FASEB J. 2006 Dec;20(14):2567-9. doi: 10.1096/fj.05-5397fje. Epub 2006 Oct 23.
The phosphoinositides have well-defined roles in the control of cellular functions, including cytoskeleton dynamics, membrane trafficking, and cell signaling. However, the interplay among the phosphoinositides and their diffusible derivatives that originate through phospholipase A2 action (the lysophosphoinositides and glycerophosphoinositols) remains to be fully elucidated. Here we demonstrate that in PCCl3 rat thyroid cells, the intracellular levels of glycerophosphoinositol are finely modulated by ATP and norepinephrine through the P2Y metabotropic and alpha-adrenergic receptors, respectively. The enzyme involved here is phospholipase A2 IValpha (PLA2 IValpha), which in these cells specifically hydrolyzes phosphatidylinositol, forming lysophosphatidylinositol, glycerophosphoinositol, and arachidonic acid. This receptor-mediated activation of PLA2 IValpha leads to stimulation of PCCl3 cell growth. The involvement of a PLA2 IValpha-mediated pathway is demonstrated by inhibition of the increase in intracellular glycerophosphoinositol levels and cell proliferation by specific inhibitors, RNA interference, and overexpression of the dominant-negative PLA2 IValpha(1-522). Modulation of PCCl3 cell growth is not seen with inhibitors of arachidonic acid metabolism. In conclusion, these data characterize glycerophosphoinositol as a mediator of the purinergic and adrenergic regulation of PCCl3 cell proliferation, defining a novel regulatory cascade specifically involving this soluble phosphoinositide derivative and widening the involvement of the phosphoinositides in the regulation of cell function.
磷酸肌醇在细胞功能控制中具有明确的作用，包括细胞骨架动力学、膜运输和细胞信号传导。然而，磷酸肌醇及其通过磷脂酶A2作用产生的可扩散衍生物（溶血磷酸肌醇和甘油磷酸肌醇）之间的相互作用仍有待充分阐明。在此，我们证明在PCCl3大鼠甲状腺细胞中，甘油磷酸肌醇的细胞内水平分别通过P2Y代谢型受体和α-肾上腺素能受体，由ATP和去甲肾上腺素进行精细调节。这里涉及的酶是磷脂酶A2 IValpha（PLA2 IValpha），它在这些细胞中特异性水解磷脂酰肌醇，形成溶血磷脂酰肌醇、甘油磷酸肌醇和花生四烯酸。这种受体介导的PLA2 IValpha激活导致PCCl3细胞生长受到刺激。特异性抑制剂、RNA干扰以及显性负性PLA2 IValpha(1-522)的过表达抑制细胞内甘油磷酸肌醇水平的升高和细胞增殖，从而证明了PLA2 IValpha介导途径的参与。花生四烯酸代谢抑制剂未观察到对PCCl3细胞生长的调节作用。总之，这些数据将甘油磷酸肌醇表征为PCCl3细胞增殖的嘌呤能和肾上腺素能调节的介质，定义了一个特别涉及这种可溶性磷酸肌醇衍生物的新型调节级联反应，并拓宽了磷酸肌醇在细胞功能调节中的作用范围。
