Phpt1, also known as Phosphohistidine phosphatase 1 or Protein histidine phosphatase (PHP), is an enzyme in eukaryotes that dephosphorylates proteins and peptides phosphorylated on a histidine residue, and it also has a broader specificity as it can dephosphorylate phospholysine in chemically phosphorylated histone H1 and polylysine [3]. It is implicated in various cellular signaling pathways, and has been linked to disease pathways such as in lung cancer development and brown adipocyte differentiation [1,2].

In lung cancer, Phpt1 is overexpressed, correlating with poor overall survival, especially in EGFR-mutant lung cancer cells. Inhibition of Phpt1 expression in these cells decreases proliferation, clonogenicity, and in vitro tumor growth, and it is required for maintaining erlotinib resistance. FBXO32 acts as an E3 ubiquitin ligase for Phpt1, and knockdown of FBXO32 leads to Phpt1 accumulation, activation of the ERK/MAPK pathway, and promotion of lung cancer cell growth [1]. In brown adipocyte differentiation, the expression level of Phpt1 changes during the process, and knockdown of Phpt1 promotes brown adipocyte differentiation while its ectopic expression suppresses it [2].

In conclusion, Phpt1 is involved in crucial biological processes like lung cancer development and brown adipocyte differentiation. In lung cancer, its overexpression and role in drug resistance make it a potential biomarker and therapeutic target. In brown adipocyte differentiation, its regulation of the process suggests a possible link to obesity and related metabolic diseases. The study of Phpt1 through various functional studies, such as knockdown experiments, helps to understand its role in these disease-related biological processes.

References:

1. Zhang, Ning, Liao, Yifeng, Lv, Weize, Xiao, Mei, Zhang, Hongyu. 2022. FBXO32 targets PHPT1 for ubiquitination to regulate the growth of EGFR mutant lung cancer. In Cellular oncology (Dordrecht, Netherlands), 45, 293-307. doi:10.1007/s13402-022-00669-6. https://pubmed.ncbi.nlm.nih.gov/35411430/

2. Kang, Joo Ae, Kang, Hyun Sup, Bae, Kwang-Hee, Oh, Kyoung-Jin, Kim, Won Kon. . Roles of Protein Histidine Phosphatase 1 (PHPT1) in Brown Adipocyte Differentiation. In Journal of microbiology and biotechnology, 30, 306-312. doi:10.4014/jmb.1909.09003. https://pubmed.ncbi.nlm.nih.gov/31752058/

3. Ek, Pia, Ek, Bo, Zetterqvist, Örjan. 2015. Phosphohistidine phosphatase 1 (PHPT1) also dephosphorylates phospholysine of chemically phosphorylated histone H1 and polylysine. In Upsala journal of medical sciences, 120, 20-7. doi:10.3109/03009734.2014.996720. https://pubmed.ncbi.nlm.nih.gov/25574816/