"Identification and characterization of the signaling pathways controlling Pi(4,5)P2 cell homeostasis."

磷脂酰肌醇(PI)是一种膜结合的信号分子，调节多种细胞功能。PIS在细胞膜上产生，影响许多细胞过程，如细胞分裂和迁移。特定PI的空间限制和稳态水平是通过激酶、磷酸酶和磷脂酶的作用来调节的，这些酶和磷脂酶特异性地定位于不同的亚细胞间。因此，磷脂酰肌醇在不同膜上的分离参与了膜结构的异质性，并创建了具有独特物理和生物性质的离散结构域。大部分PI(4，5)P2在细胞膜上富含，参与几乎所有涉及细胞表面的事件，包括细胞分裂和迁移。然而，对调节细胞皮质PI(4，5)P2(PI(4，5)P2稳态)的信号网络知之甚少。我们最近发现了一种果蝇肌醇5-磷酸酶，dOCRL，它控制PI(4，5)P2动态平衡(Ben El Kadhi等人，当代生物学，2011年)。我们证明了dOCRL与内体有关，它使内膜上的PI(4，5)P2去磷酸化，从而限制该磷脂酰肌醇在质膜上的作用。我们证明这一功能对于细胞质分裂的保真度是必要的。虽然PI(4，5)P2的动态平衡对质膜上的许多功能是重要的，但它的调节在很大程度上仍不清楚。在这里，我们的目标是确定和表征控制PI(4，5)P2细胞动态平衡的信号通路。具体地说，我们的目标是(I)确定控制肌醇磷脂循环的哪种酶与dOCRL合作来控制PI(4，5)P2的动态平衡。(Ii)研究调节PI(4，5)P2稳态的dOCRL/Arf6功能相互作用。这项研究将为更好地理解PI(4，5)P2的动态平衡是如何控制的。我们的中长期目标是整合PI(4，5)P2稳态研究产生的知识，以进一步了解需要维持PI(4，5)P2稳态的细胞功能，如细胞分裂和细胞迁移，这两个功能我们在实验室中进行了深入的研究。

Phosphoinositides (PI) are membrane-bound signaling molecules that regulate a wide variety of cellular functions. PIs are produced at cellular membranes and influence a number of cellular processes such as cell division and migration. The spatial restriction and steady-state levels of specific PIs are regulated through the actions of kinases, phosphatases and phospholipases, which are specifically localized in different sub-cellular compartments. Therefore, phosphoinositide segregation on different membranes participates to membrane structural heterogeneity and creates discrete domains with unique physical and biological properties. Majority of the PI(4,5)P2 is enriched at the plasma membrane where it participates in nearly all events that involve the cell surface including cell division and migration. However little is known about the signaling network that regulates enrichment of PI(4,5)P2 at the cellular cortex (Pi(4,5)P2 homeostasis). We have recently identified a Drosophila inositol 5-phosphatase, dOCRL, that controls Pi(4,5)P2 homeostasis (Ben El Kadhi et al., Current biology 2011). We demonstrated that dOCRL is associated with endosomes and that it dephosphorylates PI(4,5)P2 on internal membranes to restrict this phosphoinositide at the plasma membrane. We showed that this function was necessary for the fidelity of cytokinesis. While Pi(4,5)P2 homeostasis is important for numerous function occurring at the plasma membrane, its regulation remains largely unknown. Here, we aim to identify and characterize the signaling pathways controlling Pi(4,5)P2 cell homeostasis. Specifically our goals are to (i) To identify which of the enzyme controlling the phosphoinositide cycle collaborates with dOCRL to control Pi(4,5)P2 homeostasis. (ii) To characterize dOCRL / Arf6 functional interactions for the regulation of Pi(4,5)P2 homeostasis. This study will provide a better understanding on how PI(4,5)P2 homeostasis is controlled. Our mid/long-term objective is to integrate the knowledge generated by the study of PI(4,5)P2 homeostasis to further understand cellular functions that require the maintenance of PI(4,5)P2 homeostasis such as cell division and cell migration, two functions we study intensively in the laboratory.