12, 13 CLDNs are critical components of TJs

that regulate paracellular permeability and polarity and have a tetraspanin topology with four transmembrane domains, two extracellular and one intracellular loops, and N- and C-terminal cytoplasmic domains.14 CLDN1 extracellular loop 1 (EL1) is required for HCV entry9 and is involved in barrier function and contributes to pore formation between polarized cells.15 Mutagenesis studies in nonpolarized 293T cells SP600125 mw demonstrate that CLDN1 enrichment at cell–cell contacts may be important for HCV entry.16 We17, 18 and others16, 19, 20 using a variety of imaging and biochemical techniques reported that CLDN1 associates with CD81. However, due to the lack of neutralizing anti-CLDN1 antibodies targeting extracellular epitopes, the exact role of CLDN1 in the viral entry process is poorly understood. BC, bile canalicular surface; CLDN1, claudin-1; CMFDA, www.selleckchem.com/products/Roscovitine.html 5-chloromethylfluorescein diacetate; EL1 and 2, extracellular loops 1 and 2; FRET, fluorescence resonance energy transfer; HCV, hepatitis C virus; HCVcc, cell culture-derived HCV; HCVpp, HCV pseudoparticles; IgG, immunoglobulin G; PBS, phosphate-buffered saline; SD, standard deviation; SR-BI, scavenger receptor class B type I; TJ, tight junction. Human Huh7,5 Huh7.5.1,21 HepG2,18 293T,5 Bosc,22 Caco-2,23 and rat BRL-3A

cell lines24 were propagated in Dulbecco’s

modified Eagle’s medium/10% fetal bovine serum. 293T/CLDN1 cells were obtained by stable transfection of 293T cells with a pcDNA3.1 vector encoding CLDN1. Dimethyl sulfoxide–mediated differentiation of Huh7.5.1 cells was performed as described.25 Primary human hepatocytes were isolated from liver resections from patients at the RVX-208 Strasbourg University Hospitals with approval from the Institutional Review Board.26, 27 In brief, liver specimens were perfused with calcium-free 4-(2-hydroxyethyl)-1-piperazine ethanesulfonic acid buffer containing 0.5 mM ethylene glycol tetraacetic acid (Fluka) followed by perfusion with 4-(2-hydroxyethyl)-1-piperazine ethanesulfonic acid containing 0.05% collagenase (Sigma) and 0.075% CaCl2 at 37°C. Following washing of cells with phosphate-buffered saline (PBS) and removal of nonviable cells by Percoll (Sigma) gradient centrifugation, freshly isolated hepatocytes (3 × 105 cells/well) were plated in 24-well plates precoated with collagen (Biocoat, BD Biosciences) and allowed to adhere in William’s E medium (Sigma-Aldrich) containing 1% Glutamax (Gibco), 1% insulin transferrin selenium (Gibco), 10−7 M dexamethasone (Sigma), 0.15% bovine serum albumine (Sigma), and 10% fetal bovine serum (PAN Biotec). Anti-CLDN1 antibodies were raised by genetic immunization of Wistar rats using a human CLDN1 complementary DNA expression vector.