Description

The SLC9A9 Knockout THP-1 Cell Line is a CRISPR/Cas9-edited human monocytic cell line designed for functional analysis of the SLC9A9 gene, encoding the endosomal Na+/H+ exchanger NHE9. This validated knockout model enables loss-of-function studies of endosomal pH regulation in the THP-1 background, suitable for assays spanning immunofluorescence to transcriptomic profiling.

THP-1 is a widely used monocytic leukemia cell line derived from a 1-year-old male with acute monocytic leukemia. It serves as a robust model for monocyte-to-macrophage differentiation, innate immune signaling, and inflammatory responses, particularly upon phorbol ester-induced macrophage polarization. The line??s endosomal and autophagic pathways are highly relevant to immune cell function.

SLC9A9 encodes NHE9, an endosomal Na+/H+ exchanger that finely regulates luminal pH by exchanging luminal H+ for cytosolic Na+. NHE9 activity is controlled by upstream regulators including the nutrient-sensing mTORC1 kinase, the energy sensor AMPK, and the transcription factor TFEB. It interacts with calcineurin B homologous protein (CHP), the vacuolar ATPase (V-ATPase), and ??-arrestin within endosomal sorting complexes. By modulating endosomal acidification, NHE9 influences LC3 lipidation, EGFR recycling, and mTORC1 activation. Loss of NHE9 disrupts endosomal pH homeostasis, leading to aberrant distribution of early endosome markers such as EEA1 and Rab5, impaired Rab7-mediated maturation, and defective autophagic flux evidenced by accumulation of LC3-II and p62/SQSTM1.

In THP-1 cells, SLC9A9 knockout provides a powerful platform to dissect how endosomal pH dysregulation impacts monocyte and macrophage function. NHE9 deficiency impairs phagocytosis, alters cytokine secretion profiles, and disrupts differentiation, processes that are tightly linked to mTORC1-mediated control of autophagy and immune activation. This model is particularly valuable for exploring the molecular links between endosomal trafficking, innate immune signaling, and inflammatory responses, and for studying how endosomal dysfunction contributes to disease states such as glioblastoma and colorectal cancer, where SLC9A9 has been implicated.

Typical applications include quantitative endosomal acidification assays using pHrodo conjugates, autophagic flux monitoring via LC3 and p62 immunoblotting or immunofluorescence, cytokine profiling by ELISA, and transcriptome-wide analysis by RNA-seq. The cell line supports drug screening for compounds that modulate endosomal pH or restore autophagic clearance, and it enables functional studies of SLC9A9-associated neurodevelopmental disorders like autism spectrum disorder and ADHD. For further technical information and support, please contact Ascent Research.