Gfpt1, or Glutamine-fructose-6-phosphate transaminase 1, is the first rate-limiting enzyme of the hexosamine biosynthesis pathway (HBP) [2-4, 7, 8]. The HBP produces uridine diphosphate-N-acetyl glucosamine (UDP-GlcNAc), which is crucial for N-or O-linked glycosylation, post-translational modifications that modulate protein activity and expression [2]. Gfpt1 is essential for various biological processes and its study using genetic models, like KO mouse models, has been valuable.

In osteoarthritis (OA), Gfpt1 expression is significantly reduced in OA cartilage compared to normal cartilage. IL-1β stimulation downregulates Gfpt1, but supplementary glutamine can reverse this suppression more effectively than glucosamine. Overexpressing Gfpt1 can restore the anabolic metabolism of cartilage, suggesting it as a potential therapeutic target for OA [1]. In breast cancer, GFPT1 is upregulated and promotes immune escape by enhancing PD-L1 protein stability through O-glycosylation [3]. In cervical cancer, GFPT1 promotes cell proliferation by regulating the ubiquitination and degradation of PTEN [4]. Mutations in GFPT1 can cause congenital myasthenic syndrome (CMS). Muscle-specific lack of Gfpt1 in a knock-in (KI) mouse model led to reduced UDP-HexNAc, CMP-NeuAc and protein O-GlcNAcylation in skeletal muscles, along with abnormal neuromuscular junction structures and elevated markers of the unfolded protein response (UPR) [5]. In another study, knockout of the muscle-specific long isoform of GFPT1 (GFPT1-L) in skeletal muscle affected glucose metabolism and neuromuscular junction formation and maintenance in aged mice [6]. High GFPT1 expression in resectable pancreatic ductal adenocarcinoma is associated with a high risk of lymph node metastasis and unfavorable outcomes [7].

In conclusion, Gfpt1 plays a vital role in the hexosamine biosynthesis pathway and has far-reaching impacts on various biological processes. Studies using KO/CKO mouse models have revealed its significance in diseases such as OA, breast cancer, cervical cancer, CMS, and pancreatic ductal adenocarcinoma. Understanding Gfpt1's functions provides insights into disease mechanisms and potential therapeutic strategies for these conditions.

References:

1. Zhang, Zhao, Li, Xinyu, Guo, Weihua, Huang, Zeyu. 2024. Enhancing GFPT1 expression with glutamine protects chondrocytes in osteoarthritis. In International immunopharmacology, 143, 113427. doi:10.1016/j.intimp.2024.113427. https://pubmed.ncbi.nlm.nih.gov/39426230/

2. Paneque, Alysta, Fortus, Harvey, Zheng, Julia, Werlen, Guy, Jacinto, Estela. 2023. The Hexosamine Biosynthesis Pathway: Regulation and Function. In Genes, 14, . doi:10.3390/genes14040933. https://pubmed.ncbi.nlm.nih.gov/37107691/

3. Tang, Weifang, Gao, Yuan, Hong, Shikai, Wang, Shengying. 2024. GFPT1 accelerates immune escape in breast cancer by modifying PD-L1 via O-glycosylation. In BMC cancer, 24, 1071. doi:10.1186/s12885-024-12811-8. https://pubmed.ncbi.nlm.nih.gov/39210323/

4. Li, Dailing, Guan, Mingmei, Cao, Xiaofei, Lu, Lin, Liu, Guolong. . GFPT1 promotes the proliferation of cervical cancer via regulating the ubiquitination and degradation of PTEN. In Carcinogenesis, 43, 969-979. doi:10.1093/carcin/bgac073. https://pubmed.ncbi.nlm.nih.gov/36040914/

5. Zhang, Ruchen, Farshadyeganeh, Paniz, Ohkawara, Bisei, Masuda, Akio, Ohno, Kinji. 2024. Muscle-specific lack of Gfpt1 triggers ER stress to alleviate misfolded protein accumulation. In Disease models & mechanisms, 17, . doi:10.1242/dmm.050768. https://pubmed.ncbi.nlm.nih.gov/38903011/

6. Farshadyeganeh, Paniz, Nazim, Mohammad, Zhang, Ruchen, Masuda, Akio, Ohno, Kinji. 2023. Splicing regulation of GFPT1 muscle-specific isoform and its roles in glucose metabolisms and neuromuscular junction. In iScience, 26, 107746. doi:10.1016/j.isci.2023.107746. https://pubmed.ncbi.nlm.nih.gov/37744035/

7. Gong, Yitao, Qian, Yunzhen, Luo, Guopei, Wu, Weiding, Liu, Chen. 2021. High GFPT1 expression predicts unfavorable outcomes in patients with resectable pancreatic ductal adenocarcinoma. In World journal of surgical oncology, 19, 35. doi:10.1186/s12957-021-02147-z. https://pubmed.ncbi.nlm.nih.gov/33517899/