TPH1 Knockout HK-2 Cell Line

The TPH1 Knockout HK-2 Cell Line is a CRISPR/Cas9-edited knockout model derived from the human HK-2 proximal tubule epithelial cell line, featuring targeted disruption of the TPH1 gene. This stable loss-of-function cell line provides a consistent system for investigating tryptophan hydroxylase 1 function and serotonin-mediated signaling in a renal epithelial context. By abrogating TPH1 expression, the knockout line offers a reliable platform for studying peripheral serotonin biosynthesis and for screening pathway modulators.

HK-2 cells are an immortalized human proximal tubule epithelial line originally derived from normal adult kidney cortex. These cells retain key characteristics of proximal tubular cells, including polarized morphology and functional transport activities, making them a relevant model for renal physiology, drug transport, and nephrotoxicity studies. Their human origin and well-characterized phenotype support gene knockout analyses of tubular epithelial signaling.

TPH1 encodes tryptophan hydroxylase 1, the rate-limiting enzyme in peripheral serotonin synthesis. It hydroxylates tryptophan to 5-hydroxytryptophan, which is subsequently decarboxylated to serotonin (5-HT). TPH1 activity requires tetrahydrobiopterin (BH4) and Fe2+ as cofactors and is regulated by phosphorylation via cAMP-dependent protein kinase (PKA) and calcium/calmodulin-dependent kinase, as well as by glucocorticoids. Interactions with 14-3-3 proteins modulate enzyme stability. Produced serotonin activates 5-HT receptors (HTR1-7) and is cleared by the serotonin transporter SLC6A4, mediating diverse physiological effects in peripheral tissues.

In the kidney, TPH1-derived serotonin may influence proximal tubule functions such as ion transport, cellular proliferation, and fibrotic responses. This knockout model enables dissection of endogenous serotonin’s role in these processes, separating local from systemic effects. It is particularly valuable for studying serotonin??s contribution to renal fibrosis and for exploring crosstalk with other signaling pathways in proximal tubule cells.

Applications include quantitative PCR and Sanger sequencing for knockout confirmation, Western blot for protein analysis, ELISA or HPLC for serotonin and metabolite quantification, immunofluorescence for localization, calcium flux assays for receptor activation, and proliferation/apoptosis assays. The cell line supports drug screening and mechanistic studies of serotonin pathway modulators, with utility in renal fibrosis research. For further information, please contact Ascent Research.