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

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.

Viral disruption of the blood–brain barrier

“…Nectin-4, an adherens junction protein, was recently identified as an epithelial cell receptor for measles virus [85,86]. Some proteins were first identified as viral receptors and subsequently shown to be components or possible regulators of tight junctions, including CAR [87] and the receptor for human hepatitis A virus, respectively [88]. Why viruses use tight junction proteins as attachment or entry receptors is poorly understood [79].…”

Regulation of T cell trafficking by the T cell immunoglobulin and mucin domain 1 glycoprotein

“…TIM-1 and TIM-4 are highly glycosylated, and several TIM-TIM homotypic and heterotypic interactions may take place on the vascular bed with a potential role in the secondary tethering of circulating immune cells. Recently, TIM-1 was also detected in human umbilical vein endothelial cells (HUVECs) at the tight junction level, suggesting it may function as an adhesive receptor on the vascular bed by favoring leukocyte adhesion and transmigration [116]. In addition to interacting with P-selectin on endothelial cells, TIM-1 on the surface of T cells may also interact with P-selectin presented by adhered platelets or their microparticle fragments, further contributing to the efficacy of T cell trafficking [5].…”

Targeting the therapeutic effects of exercise on redox‐sensitive mechanisms in the vascular endothelium during tumor progression

“…The activation of these pathways in vascular endothelial cells leads to mobilization, rearrangement of the cytoskeleton, and tubular formation (31,37). In addition to vascularization, ROS can stimulate small GTPase signaling pathways, leading to cellular rearrangement and alterations in the vascular endothelial cells which may promote tumor cell invasion (7,36,38).…”

“…As the central nervous system does not have any lymphatic vessels, the only method of entry for tumor cells is the blood stream. Once inside the brain microvasculature tumor cells must cross the blood-brain barrier (BBB), which is reinforced with TJs (7). The mechanism of tumor cell extravasation into the brain is not well understood; however, one hypothesis involves the activation of redox-sensitive pathways, which compromise TJ protein integrity, leading to tumor cell invasion (40).…”

“…These processes are of particular consequence in the brain endothelium where TJ protein complexes form an additional barrier that limits passage into the cerebrospinal environment. Activation of redox-sensitive small GTPases can lead to the disruption of TJs and promote tumor cell extravasation (7). There is evidence that exercise can alter the oxidation status of the microvasculature and thereby may offer protection against tumor cell invasion into the brain (8).…”