Department of Bioinformatics and Molecular Neuropathology, Meiji Pharmaceutical University, 2-522-1, Noshio, Kiyose-shi 204-8588, Japan.
Department of RNA Pathobiology and Therapeutics, Meiji Pharmaceutical University, 2-522-1, Noshio, Kiyose-shi 204-8588, Japan.
Cells. 2023 Feb 13;12(4):602. doi: 10.3390/cells12040602.
Genetic variations of have been implicated as a susceptibility factor of Alzheimer's disease (AD). A polymorphism on exon 2 of , rs12459419, affects the alternative splicing of this exon. The minor allele is associated with a reduced risk of AD and promotes the skipping of exon 2 to produce a shorter CD33 isoform lacking the extracellular ligand-binding domain, leading to decreased suppressive signaling on microglial activity. Therefore, factors that regulate the splicing of exon 2 may alter the disease-associated properties of CD33. Herein, we sought to identify the regulatory proteins of CD33 splicing. Using a panel of RNA-binding proteins and a human CD33 minigene, we found that exon 2 skipping of was promoted by HNRNPA1. Although the knockdown of HNRNPA1 alone did not reduce exon 2 skipping, simultaneous knockdown of HNRNPA1 together with that of HNRNPA2B1 and HNRNPA3 promoted exon 2 inclusion, suggesting functional redundancy among HNRNPA proteins. Similar redundant regulation by HNRNPA proteins was observed in endogenous of THP-1 and human microglia-like cells. Although mouse showed a unique splicing pattern of exon 2, we confirmed that HNRNPA1 promoted the skipping of this exon. Collectively, our results revealed novel regulatory relationships between CD33 and HNRNPA proteins.
的遗传变异被认为是阿尔茨海默病（AD）的易感因素。位于外显子 2 上的 rs12459419 多态性影响该外显子的选择性剪接。次要等位基因与 AD 风险降低相关，并促进外显子 2 的跳过，产生缺乏细胞外配体结合域的较短 CD33 同工型，从而降低对小胶质细胞活性的抑制信号。因此，调节外显子 2 剪接的因素可能会改变 CD33 的疾病相关特性。在此，我们试图确定 CD33 剪接的调节蛋白。使用一组 RNA 结合蛋白和人类 CD33 基因外显子 2 缺失突变体，我们发现 HNRNPA1 促进了 CD33 的外显子 2 跳过。尽管单独敲低 HNRNPA1 本身不会减少外显子 2 跳过，但同时敲低 HNRNPA1 与 HNRNPA2B1 和 HNRNPA3 会促进外显子 2 的包含，表明 HNRNPA 蛋白之间存在功能冗余。在 THP-1 和人源小胶质细胞样细胞的内源性 CD33 中也观察到 HNRNPA 蛋白的类似冗余调节。尽管小鼠 CD33 显示出独特的外显子 2 剪接模式，但我们证实 HNRNPA1 促进了该外显子的跳过。总之，我们的结果揭示了 CD33 和 HNRNPA 蛋白之间的新的调节关系。
