Structural mechanisms of autophagy

自噬的结构机制

基本信息

批准号：
8741607
负责人：
James Hurley
金额：
$ 109.88万
依托单位：
NATIONAL INSTITUTE OF DIABETES AND DIGESTIVE AND KIDNEY DISEASES
依托单位国家：
美国
项目类别：
财政年份：
资助国家：
美国
起止时间：
至
项目状态：
未结题

项目摘要

One of the major signaling events in autophagy is when the autophagy-specific class III PI 3-kinase complex synthesizes PI(3)P at the nascent phagophore. The phagophore is the precursor structure to the autophagosome. PI(3)P is recognized by various effector proteins, but the most important are Atg18 in yeast and WIPI 1-4 in mammals. All of these proteins are biochemically competent to bind both PI(3)P and PI(3,5)P2, however, the latter lipid is not known to have a direct role in autophagy. The ability of Atg18 to bind PI(3,5)P2 is important for a second biological function of this protein in vacuole homeostasis. The key autophagic lipid sensors are Atg18 in yeast and the WIPI proteins in mammals. Atg18 and the WIPIs belong to the PROPPIN family of proteins. PROPPINs are seven bladed β-propellers that bind to phosphatidylinositol 3-phosphate (PI(3)P) and phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2). In order to understand how PROPPINs bind phosphoinositides, we have determined the crystal structure of a representative, biochemically tractable PROPPIN, Hsv2 of Kluveromyces lactis. The structure revealed that PROPPINs contain two phosphoinositide binding sites which cooperate with a hydrophobic anchoring loop in membrane binding. These three binding elements cooperate in function, as demonstrated by the incremental loss of function in ATG18 alleles impaired in combinations of the two phosphoinositide binding site and the hydrophobic loop.

自噬中的主要信号传导事件之一是自噬特异性 III 类 PI 3 激酶复合物在新生噬菌体处合成 PI(3)P。吞噬泡是自噬体的前体结构。 PI(3)P 可被多种效应蛋白识别，但最重要的是酵母中的 Atg18 和哺乳动物中的 WIPI 1-4。所有这些蛋白质在生化上都能够结合 PI(3)P 和 PI(3,5)P2，然而，后者脂质在自噬中具有直接作用尚不清楚。 Atg18 结合 PI(3,5)P2 的能力对于该蛋白在液泡稳态中的第二个生物学功能很重要。关键的自噬脂质传感器是酵母中的 Atg18 和哺乳动物中的 WIPI 蛋白。 Atg18 和 WIPI 属于 PROPPIN 蛋白家族。 PROPPIN 是七叶 β 螺旋桨，可与磷脂酰肌醇 3-磷酸 (PI(3)P) 和磷脂酰肌醇 3,5-二磷酸 (PI(3,5)P2) 结合。为了了解 PROPPIN 如何结合磷酸肌醇，我们确定了代表性的、生化上易于处理的 PROPPIN、乳酸克鲁维酵母 Hsv2 的晶体结构。该结构表明，PROPPIN 含有两个磷酸肌醇结合位点，它们与膜结合中的疏水锚定环配合。这三个结合元件在功能上相互配合，两个磷酸肌醇结合位点和疏水环的组合受损的 ATG18 等位基因的功能逐渐丧失就证明了这一点。