APPL2（Adaptor Protein, Phosphotyrosine Interaction, PH Domain and Leucine Zipper Containing 2）是一种衔接蛋白，属于APPL基因家族，该家族还包括APPL1。APPL家族蛋白的共同特点是含有多个功能域，包括PH结构域（pleckstrin homology domain）、PTB结构域（phosphotyrosine-binding domain）和亮氨酸拉链结构域（leucine zipper domain），这些结构域使它们能够参与多种信号通路的调控。APPL2主要通过与细胞膜受体和其他信号分子相互作用，在细胞增殖、代谢、内吞作用和细胞迁移等过程中发挥重要作用。APPL2在多种组织中表达，尤其在脑、心脏和骨骼肌中表达较高。APPL2与胰岛素信号通路密切相关，它能够与AKT和AMPK等关键激酶相互作用，调节葡萄糖代谢和能量平衡。此外，APPL2还参与调控自噬过程，影响细胞的存活和凋亡。APPL2的突变或表达异常可能导致代谢紊乱，如胰岛素抵抗和2型糖尿病。研究表明，APPL2的缺失或功能缺陷会损害胰岛素信号传导，导致血糖调控异常。相反，APPL2的过表达可能增强胰岛素敏感性，但也可能在某些情况下促进肿瘤细胞的生长和迁移，因为它参与调控与癌症相关的信号通路，如PI3K/AKT和MAPK通路。APPL2还与神经系统疾病相关，如阿尔茨海默病，因为它参与调节神经元存活和突触可塑性。在心血管系统中，APPL2的表达水平变化可能影响血管生成和心脏功能。APPL2与APPL1在功能上有部分重叠，但也存在特异性作用，例如APPL2在脂肪代谢和炎症反应中的作用更为突出。总的来说，APPL2是一个多功能的信号调节蛋白，其表达水平的异常可能对代谢、神经和心血管系统产生广泛影响，并与多种疾病的发生发展密切相关。

由该基因编码的蛋白质是小GTP酶RAB5A / Rab5的两种效应，这是参与信号转导途径之一。两个效应包含N-末端滨/ Amphiphysin / RVS（BAR）域，中央pleckstrin同源（PH）结构域和C末端磷酸酪氨酸结合（PTB）结构域，并且它们结合通过BAR域Rab5的。它们与内体膜相关联，并且可以响应于EGF的刺激被易位到细胞核。它们与NURD / MeCP1复合物（核小体重构和脱乙酰/甲基化CpG结合蛋白1复合物）相互作用并需要进行有效的细胞增殖。染色体畸变吨（12; 22）（q24.1; q13.3）涉及该基因与22q13.3缺失综合征的PSAP2基因的结果，也被称为费兰-McDermid综合征。 [由RefSeq的，2011年10月提供]

APPL2 (Adaptor Protein, Phosphotyrosine Interaction, PH Domain and Leucine Zipper Containing 2) is a multifunctional scaffolding protein belonging to the APPL family, which also includes APPL1, characterized by the conserved presence of pleckstrin homology (PH), phosphotyrosine-binding (PTB), and leucine zipper domains that facilitate its integration into diverse cellular signaling networks. By interacting with cell surface receptors and intracellular signaling molecules, APPL2 plays a pivotal role in regulating cell proliferation, migration, endocytosis, and metabolism, with particularly high expression levels observed in the brain, heart, and skeletal muscle. A central function of APPL2 lies in its modulation of the insulin signaling pathway, where it physically associates with key kinases such as AKT and AMPK to coordinate glucose homeostasis and energy balance; consequently, loss-of-function mutations or aberrant expression can impair insulin signal transduction, leading to insulin resistance and type 2 diabetes, whereas enhanced expression may improve insulin sensitivity. Beyond metabolic regulation, APPL2 is implicated in autophagy, influencing cell survival and apoptosis, and it intersects with oncogenic pathways such as PI3K/AKT and MAPK, where its dysregulation can paradoxically promote tumor growth and metastasis. In the nervous system, APPL2 contributes to neuronal survival and synaptic plasticity, linking its dysfunction to neurodegenerative conditions like Alzheimer’s disease, while in the cardiovascular system, its expression levels impact angiogenesis and cardiac function. Although functionally overlapping with APPL1, APPL2 exhibits distinct roles, particularly in lipid metabolism and inflammatory responses, underscoring its critical position as a versatile signal transducer whose dysregulation has broad implications for metabolic, neurological, and cardiovascular health.

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