磷脂酰肌醇（PI）循環在果蠅眼睛視神經光傳導中扮演重要角色。我們先前研究發現，在神經元中二酰基甘油脂肪酶（DAGL / inaE）過表現量或視網膜退化A（rdgA，編碼二酰甘油激酶）和視網膜退化B（rdgB，編碼磷脂酰肌醇轉移蛋白）的表現量降低可以透過減少雷帕黴素的靶標活性(Target of rapamycin, TOR)來延長果蠅壽命，這三種基因都參與磷脂酰肌醇循環。秀麗隱桿線蟲egl-8（磷脂酰肌醇磷脂酶Cβ;PLCβ）被發現突變後可以延長壽命的其他基因。其他磷脂酰肌醇循環基因是否可以調控果蠅的壽命仍然未知。在本篇研究中，我們透過appl-Gal4和elav-Gal4在神經元或da-Gal4全身性降低Lazaro (laza，脂磷酸磷酸酶，也稱為LPP），磷脂酶D（Pld），CDP-DAG合成酶（cdsA），PI激酶（Pi4KII），PLCβ（norpA）基因表現量，並測量它們的壽命變化。在神經元中發現，減少laza，Pld和Pi4KIIα的表現量都顯示壽命的增加，但在cdsA或norpA中沒有看見壽命延長現象。然而，全身性減少基因表現量都沒有顯示出明顯增強的壽命現象，與我們先前的發現一致。透過確認磷酸化S6K蛋白量，在神經元中降低laza，Pld和Pi4KIIα的表現量也伴隨著TOR活性的下降。在我們的研究結果為一些磷脂酰肌醇循環基因如何調控果蠅壽命提供了新的見解。

Phosphatidylinositol (PI) cycle plays an important role in Drosophila phototransduction. Our pervious publications indicate that overexpression of diacylglycerol lipase (DAGL/inaE), or knockdown of retinal degeneration A (rdgA, encoding diacylglycerol kinase) or retinal degeneration B (rdgB, encoding phosphatidylinositol transfer protein) in neurons can extend lifespan via reducing target of rapamycin (TOR) activity in Drosophila, which all three genes participate in PI cycle. C. elegans egl-8 (phosphatidylinositol phospholipase Cβ; PLCβ) is the only other gene reported to enhance lifespan upon mutation. Whether the other PI cycle genes can regulate lifespan in Drosophila remains unknown. Here, we performed systematic knockdown of Lazaro (laza, lipid phosphate phosphatase, also as LPP), Phospholipase D (Pld), CDP-DAG syntase (cdsA), PI kinase (Pi4KII), PLCβ (norpA) genes in neuron by appl-Gal4 and elav-Gal4 or ubiquitously by da-Gal4 and measured their lifespan changes. The results indicate that in neurons knockdown of laza, Pld, and Pi4KII each displays increased lifespan, but not found in cdsA, or norpA. However, none of them by ubiquitous knockdown exhibits any significantly enhanced lifespan, which is consistent with our previous finding. The knockdown of laza, Pld, and Pi4KII in neurons is also accompanied with decreased TOR activity by checking their phosphorylated-S6K protein levels. Our results provide new insights into how some of phosphatidylinositol cycle genes regulate lifespan in Drosophila.

Abstract i
中文摘要 ii
致謝 iii
Table of Content 1
Introduction 2
Materials and methods 5
Fly strains and culture 5
Drosophila lifespan assays 5
RNA extraction and reverse transcription (RT-PCR) 5
Quantitative PCR (Q-PCR) 6
Immunoblotting 6
Results 8
Knockdown of laza in neurons extends lifespan in Drosophila 8
Knockdown of Pld in neurons extends lifespan in Drosophila 9
Knockdown of Pi4KIIa in neurons and ubiquitously can extend lifespan in Drosophila 9
Knockdown of norpA ubiquitously in female decreases and in male increases lifespan in Drosophila 10
Knockdown of cdsA in neurons and ubiquitously does not alter lifespan in Drosophila 10
The longevity flies with the knockdown of laza, Pld and Pi4KIIa show reduced levels of phosphorylated S6 kinase in Drosophila 11
Discussion 12
Figures 15
Tables 33
References 44

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