Biochemistry and Molecular Biology Laboratory, Brain Research Centre, Department of Zoology, Banaras Hindu University, Varanasi, 221005, India.
CSIR-Institute of Genomics & Integrative Biology, New Delhi, 110025, India.
Sci Rep. 2018 Jul 2;8(1):9928. doi: 10.1038/s41598-018-27640-6.
The multitude of molecular pathways underlying memory impairment in neurological disorders and aging-related disorders has been a major hurdle against therapeutic targeting. Over the years, neuronal growth promoting factors, intracellular kinases, and specific transcription factors, particularly cyclic AMP response element-binding protein (CREB), have emerged as crucial players of memory storage, and their disruption accompanies many cognitive disabilities. However, a molecular link that can influence these major players and can be a potential recovery target has been elusive. Recent reports suggest that extracellular cues at the synapses might evoke an intracellular signaling cascade and regulate memory function. Herein, we report novel function of an extracellular serine protease, kallikrein 8 (KLK8/Neuropsin) in regulating the expression of microtubule associated dendrite growth marker microtubule-associated protein (MAP2)c, dendrite architecture and protein kinase A (PKA)-CREB signaling. Both knockdown of KLK8 via siRNA transfection in mouse primary hippocampal neurons and via intra-hippocampal administration of KLK8 antisense oligonucleotides in vivo reduced expression of MAP2c, dendrite length, dendrite branching and spine density. The KLK8 mediated MAP2c deficiency in turn inactivated PKA and downstream transcription factor phosphorylated CREB (pCREB), leading to downregulation of memory-linked genes and consequent impaired memory consolidation. These findings revealed a protease associated novel pathway of memory impairment in which KLK8 may act as a "regulator of regulators", suggesting its exploration as an important therapeutic target of memory disorders.
在神经紊乱和与衰老相关的紊乱中导致记忆损伤的众多分子途径一直是治疗靶向的主要障碍。多年来，神经元生长促进因子、细胞内激酶和特定转录因子，特别是环 AMP 反应元件结合蛋白（CREB），已成为记忆存储的关键参与者，其破坏伴随着许多认知障碍。然而，一个可以影响这些主要参与者并可能成为潜在恢复目标的分子联系一直难以捉摸。最近的报告表明，突触处的细胞外线索可能会引发细胞内信号级联反应并调节记忆功能。在此，我们报告细胞外丝氨酸蛋白酶激肽释放酶 8（KLK8/神经蛋白酶）在调节微管相关树突生长标记物微管相关蛋白（MAP2）c、树突结构和蛋白激酶 A（PKA）-CREB 信号表达方面的新功能。通过 siRNA 转染在小鼠原代海马神经元中敲低 KLK8 以及体内通过海马内注射 KLK8 反义寡核苷酸都降低了 MAP2c 的表达、树突长度、树突分支和棘密度。KLK8 介导的 MAP2c 缺乏继而使 PKA 和下游转录因子磷酸化 CREB（pCREB）失活，导致记忆相关基因下调和随后的记忆巩固受损。这些发现揭示了一种与蛋白酶相关的记忆损伤新途径，其中 KLK8 可能作为“调节因子的调节剂”发挥作用，提示其作为记忆障碍的重要治疗靶点进行探索。
