The Hepatitis A Virus Cellular Receptor, HAVcR-1, Reduces the Integrity of Human Endothelial Tight Junctions.

Abstract

Abstract Background: Disruption of Tight Junctions (TJ's) in endothelial cells can cause a leaky vascular bed and may therefore lead to vascular spread of cancer cells. Hepatitis A virus (HAV) cellular receptor HAVcR-1, also known as KIM-1/TIM-1, is the cellular receptor for the hepatotropic picornavirus that causes acute hepatitis-A in humans. Although HAVcR-1 is expressed in every human organ, the natural function of HAVcR-1 remains unknown. In the current study, we investigated the location, association and possible functionality of HAVcR-1 in human endothelial cells.Methods: HAVcR-1 protein in human endothelial cells was visualised using immunohistochemistry and mRNA transcript by RT-PCR. A hammerhead ribozyme transgene that specifically targeted human HAVcR-1 was constructed and used to knockdown endogenously expressed HAVcR-1 (HECVHKD); moreover, forced expression was obtained by insertion of a transgene into wild type endothelial cells (HECVHEX).TJ function was assessed using trans-endothelial resistance (TER) and paracellular permeability assays under the influence of HGF (40ng/ml) a cytokine we have previously shown to modulate TJs in human endothelial cells.Results: Human endothelial cells expressed HAVcR-1 at low levels. The location of both endogenous and forcibly expressed HAVcR-1 was at the cell-cell junction, at the region of the TJ. In this study, one of the first to examine the location and binding partners of HAVcR-1, expression of this receptor was targeted to the vicinity of intercellular junctions, via ZO-1, which further was demonstrated to be at the site of the TJ by its co-localisation with ZO-2. This was true of both endogenously and forcibly expressed protein. Moreover, HAVcR-1 was co-precipitated with the regulatory factor Rho C. Although there was no change in function of HECVHEX cells, the TJ function of the HECVHKD cells exhibited significantly reduced response to HGF over 2h (p<0.01). Interestingly, there was no concurrent response in PCP.Conclusion: These results demonstrate for the first time that HAVcR-1 may have a previously undiscovered role in the regulation of TJ integrity in human endothelial cells. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2158.