Barykin Evgeny P, Yanvarev Dmitry V, Strelkova Maria A, Valuev-Elliston Vladimir T, Varshavskaya Kseniya B, Mitkevich Vladimir A, Makarov Alexander A
Engelhardt Institute of Molecular Biology, Vavilov Str. 32, 119991 Moscow, Russia.
Life (Basel). 2023 Jan 4;13(1):147. doi: 10.3390/life13010147.
Phosphorylation of beta-amyloid peptide (Aβ) at the Ser8 residue affects its neurotoxicity, metal-dependent oligomerisation, amyloidogenicity, and other pathogenic properties. Phosphorylated Aβ (pS8-Aβ) was detected in vivo in AD model mice and in the brains of patients with AD. However, the pS8-Aβ production and the regulation of its levels have not been previously studied in detail. In this paper, immunochemical methods together with radioactive labelling were used to study the Aβ phosphorylation by intracellular and surface protein kinases of HEK293 cells and brain endothelial cells (bEnd.3). It was found that HEK293 robustly phosphorylated Aβ, likely with contribution from casein kinase 2 (CK2), whereas in bEnd.3, the activity of Aβ phosphorylation was relatively low. Further, the study showed that both HEK293 and bEnd.3 could dephosphorylate pS8-Aβ, mainly due to the activity of protein phosphatases PP1 and PP2A. The Aβ dephosphorylation efficiency in bEnd.3 was three times higher than in HEK293, which correlated with the reduced abundance of pS8-Aβ in vascular amyloid deposits of patients with AD compared to senile plaques. These data suggest an important role of CK2, PP1, and PP2A as regulators of Aβ phosphorylation, and point to the involvement of the blood-brain barrier in the control of Aβ modification levels.
β-淀粉样肽（Aβ）丝氨酸8位残基的磷酸化会影响其神经毒性、金属依赖性寡聚化、淀粉样变性及其他致病特性。在AD模型小鼠体内以及AD患者大脑中均检测到了磷酸化Aβ（pS8-Aβ）。然而，此前尚未对pS8-Aβ的产生及其水平调控进行详细研究。本文运用免疫化学方法并结合放射性标记，研究了HEK293细胞和脑内皮细胞（bEnd.3）的细胞内及表面蛋白激酶对Aβ的磷酸化作用。研究发现，HEK293能强烈磷酸化Aβ，可能酪蛋白激酶2（CK2）起到了一定作用，而在bEnd.3中，Aβ磷酸化活性相对较低。此外，研究表明HEK293和bEnd.3均能使pS8-Aβ去磷酸化，这主要归因于蛋白磷酸酶PP1和PP2A的活性。bEnd.3中Aβ的去磷酸化效率比HEK293高3倍，这与AD患者血管淀粉样沉积物中pS8-Aβ丰度低于老年斑的情况相关。这些数据表明CK2、PP1和PP2A作为Aβ磷酸化调节剂具有重要作用，并表明血脑屏障参与了对Aβ修饰水平的控制。
