1B). HBVpreS/2-48myr-K-FITC inhibited HBV infection in PHH like HBVpreS/2-48myr, as measured by secreted HBeAg. HBVpreS/2-48myr(D11,13)-K-FITC was inactive, confirming the requirement of the 9-NPLGFFP-15 sequence. HBVpreS/1-48-K-FITC showed only marginal activity. To examine whether the differences in infection inhibition reflect specific binding properties to susceptible cells, we incubated differentiated HepaRG cells with the three peptides (200 nM) and analyzed cell association by confocal microscopy. As depicted in Fig. 1C, HBVpreS/2-48myr-K-FITC
was localized at the PM of HepaRG cells (upper right). Incubation of cells with HBVpreS/2-48myr(D11,13)-K-FITC (lower left) or HBVpreS/1-48-K-FITC (lower right) did not result in significant PM staining, demonstrating https://www.selleckchem.com/products/Fulvestrant.html the dependency of binding on the sequence integrity and the presence of the myristic acid.
The specific peptide signal could clearly be discriminated from the punctuated cellular autofluorescence detected in the absence of peptide (upper left). HBVpreS/2-48myr-K-FITC binding was observed only in the hepatic clusters of HepaRG cells but not in biliary cells (data not shown). Besides Fludarabine supplier HepaRG cells, HBV infects PHH28 and PTH8 and is blocked by acylated HBVpreS-derived lipopeptides.20, 24 We therefore tested PHH and PTH for their ability to bind HBVpreS/2-48myr-K-FITC. We detected a sequence-specific and myristoyl-dependent association of the wildtype but not the control peptide with the PM of PHH (Fig. 2A). Specific binding of HBVpreS/2-48myr-K-FITC to PHH could also be detected in suspended cells by flow cytometry (Fig. 2B). Significant binding, visible by a shift
of the cell population towards an approximately 10-fold higher fluorescence signal, was observed only for cells incubated with HBVpreS/2-48myr-K-FITC, but not Cyclin-dependent kinase 3 with HBVpreS/2-48myr(D11,13)-K-FITC (Fig. 2B, dark green line versus orange line). Binding was prevented by an excess of the nonlabeled peptide HBVpreS/2-48myr (blue line) but not with the respective mutant HBVpreS/2-48myr(D11,13) (red line). This substantiates the high specificity of HBVpreS-receptor interaction in PHH. Consistently, PTH bound HBVpreS/2-48myr-K-FITC with comparable efficacy as PHH. Again, binding was prevented by unlabeled HBVpreS/2-48myr but not by the mutant HBVpreS/2-48myr(D11,13) (Fig. 2C). To investigate if HBVpreS1-receptor expression is restricted to hepatocytes from HBV susceptible hosts, we performed binding studies using PMH that are not susceptible to HBV infection.29 Unexpectedly, we observed the same sequence specific and myristoyl-dependent binding of HBVpreS/2-48myr-K-FITC to the PMH surface as for PHH, PTH, and HepaRG cells (Fig. 3A). Specific binding to PMH was confirmed by flow cytometry (data not shown). Binding was also detected in primary rat hepatocytes (PRH) (Fig. 3B).