Human SLC10A1 Stable Cell Line - HepG2

CDC42 is a member of the Rho GTPase family responsible for regulating various biological processes, and its activity is frequently hijacked by invading pathogens. Here, researchers discovered that the levels of active CDC42 within hepatocytes correlate positively with the entry efficiency of the Hepatitis B virus (HBV). Mechanistically, CDC42 activation effectively promotes the trafficking of the viral receptor-the sodium taurocholate cotransporting polypeptide (NTCP, also known as SLC10A1)-to the plasma membrane via a Rab11-dependent recycling endosome pathway. NTCP interacts with Rab11, and the activation of the CDC42 signaling pathway enhances this interaction between NTCP and Rab11. The researchers further confirmed that clathrin-mediated endocytosis (CME)-a known entry pathway for HBV-does not depend on CDC42 activity. Notably, they revealed that CDC42-dependent macropinocytosis also serves as an entry pathway for HBV, and its importance for viral infection is no less significant than that of CME. In summary, these findings elucidate novel mechanisms of HBV entry involving previously unrecognized functions of CDC42, while also suggesting that the Rho GTPase signaling pathway holds promise as a potential therapeutic target for antiviral interventions.

Here, researchers established a stable cell line, HepG2-NTCP, in which the viral receptor NTCP was introduced into HepG2 cells, thereby rendering them susceptible to HBV infection. Subsequently, Flag-tagged constitutively active (CA, G12V) and dominant-negative (DN, T17D) mutants of CDC42 were stably expressed in the HepG2-NTCP cells. The results demonstrated that the expression of neither CDC42-CA nor CDC42-DN had any impact on the cellular growth dynamics. Previous studies have indicated that clathrin-mediated endocytosis (CME) serves as a critical pathway for HBV entry into cells. To investigate the relationship between CDC42 and CME, the researchers assessed CME activity in HepG2-NTCP, CDC42-CA, and CDC42-DN cells by quantifying the uptake of fluorescein isothiocyanate (FITC)-labeled transferrin-a constitutive endocytic process mediated by clathrin-dependent pathways. The results revealed no significant differences in CME activity among the HepG2-NTCP control group, the CDC42-CA group, and the CDC42-DN group (Figure 1A, B). Similarly, treating HepG2-NTCP cells with bradykinin or ML141 did not induce any alterations in their CME capacity (Figure 1C, D). These findings indicate that CME activity is not regulated by CDC42.

Figure 1. The effects of CDC42 on HBV internalization is independent of clathrin-mediated endocytosis. (Cui S, et al., 2025)