NPRL2, also known as nitrogen permease regulator-like 2, is a critical component of the GATOR1 complex. GATOR1 functions as a negative regulator of the mammalian target of rapamycin complex 1 (mTORC1) kinase when intracellular amino acids are low, thus playing a significant role in the mTORC1 signaling pathway which is involved in multiple biological processes like cell growth, metabolism, and autophagy [1,2,3,4,5]. Genetic models, such as gene knockout (KO) mouse models, are valuable for studying its functions.

In KO mouse models, loss of NPRL2 expression in mouse excitatory glutamatergic neurons causes seizures before death, similar to sudden unexpected death of epileptics (SUDEP) in humans. It also increases mTORC1-dependent signal transduction, alters brain amino acid homeostasis, reduces dendritic branching, and increases the strength of action potentials due to elevated expression of epilepsy-linked voltage-gated sodium channels [1]. In hepatocellular carcinoma, down-regulation of NPRL2 using siRNA and shRNA in HepG2 cells enhances cell proliferation, migration, and colony formation in vitro, and increases tumor growth in mouse xenograft models. This is associated with increased Rag GTPases and mTOR activation and inhibited autophagy [2].

In conclusion, NPRL2 plays a crucial role in regulating mTORC1 signaling, which impacts various biological processes. Studies using KO mouse models have revealed its significance in epilepsy-related phenotypes and cancer development, providing insights into the underlying mechanisms and potential therapeutic targets for these disease areas.

References:

1. Hui, Jeremy B, Silva, Jose Cesar Hernandez, Pelaez, Mari Carmen, Sephton, Chantelle F, Dutchak, Paul A. 2022. NPRL2 Inhibition of mTORC1 Controls Sodium Channel Expression and Brain Amino Acid Homeostasis. In eNeuro, 9, . doi:10.1523/ENEURO.0317-21.2022. https://pubmed.ncbi.nlm.nih.gov/35165201/

2. Wang, Ya-Chin, Tsai, Ming-Chao, Chen, Yaw-Sen, Yu, Ming-Lung, Lin, Chih-Wen. 2022. NPRL2 down-regulation facilitates the growth of hepatocellular carcinoma via the mTOR pathway and autophagy suppression. In Hepatology communications, 6, 3563-3577. doi:10.1002/hep4.2019. https://pubmed.ncbi.nlm.nih.gov/36321403/

3. Chen, Zhixiong, Jiang, Qilong, Zhu, Pingyu, Jiang, Li, Tang, Wei. 2018. NPRL2 enhances autophagy and the resistance to Everolimus in castration-resistant prostate cancer. In The Prostate, 79, 44-53. doi:10.1002/pros.23709. https://pubmed.ncbi.nlm.nih.gov/30178500/

4. Zhang, Jia, Shen, Yajun, Yang, Zuozhen, Chen, Wanlin, Gan, Jing. 2021. A splicing variation in NPRL2 causing familial focal epilepsy with variable foci: additional cases and literature review. In Journal of human genetics, 67, 79-85. doi:10.1038/s10038-021-00969-z. https://pubmed.ncbi.nlm.nih.gov/34376795/

5. Chuang, Jing-Yuan, Kuo, Hsiao-Hui, Wang, Pei-Han, Su, Chih-Jou, Yih, Ling-Huei. 2024. NPRL2 is required for proliferation of oncogenic Ras-transformed bronchial epithelial cells. In Cell division, 19, 22. doi:10.1186/s13008-024-00126-w. https://pubmed.ncbi.nlm.nih.gov/38915098/