Host factors that have been shown to be essential for HCV replication include cyclophilin A, heat shock protein 90 (Hsp90), the vesicle-associated membrane protein–associated proteins A and B, and the protein Ku-0059436 cost kinase Akt. Knockdown

of the expression of these genes or application of inhibitors such as cyclosporin A to inhibit cyclophilin A, geldanamycin to antagonize Hsp90 activity,3 or triciribine to suppress the constitutive Akt activity observed in the presence of HCV4 resulted in impaired HCV replication (reviewed in Bode et al.5). Apart from this, members of the Src protein tyrosine kinase family (SFK) have been reported to be important for viral replication or production and release of infectious particles of different viruses, such as human immunodeficiency virus or hepatitis B virus.5

SFKs mediate intracellular signals of many different cellular receptors that control a diverse spectrum of biological activities. This kinase family consists of eight members—namely Lyn, Hck, Lck, Blk, c-Src, Fyn, Yes, and Fgr—that show similar modes of regulation but differ with respect to cell type specificity and function. Thus, Src, Fyn, and Yes are expressed in most tissues, whereas Rucaparib research buy the other SFK members are primarily found in hematopoietic cells, with the exception of Lck and Lyn, which have also been detected in neurons (reviewed in Parsons and Parsons6 and Okutani et al.7). Although there are some conflicting reports indicating that

NS5A interacts with SFK members and that they may influence viral replication,8, 9 the role of SFKs for HCV replication and the interaction of HCV with SFKs are not well understood. The present study addresses the interrelationship between HCV and c-Src and provides evidence that c-Src is important for complex formation of NS5A and NS5B—a complex known to be required for viral RNA replication.10 DMSO, dimethyl sulfoxide; GAPDH, glyceraldehyde 3-phosphate dehydrogenase; GST, glutathione S-transferase; HCV, hepatitis C virus; Hsp90, heat shock protein 90; PBS, phosphate-buffered saline; PCR, polymerase chain reaction; SDS-PAGE, sodium dodecyl sulfate–polyacrylamide gel electrophoresis; Thiamet G SFK, Src family kinase; siRNA, small interfering RNA. The antibody specific for c-Src was purchased from Millipore (Schwalbach, Germany), for glutathione S-transferase (GST) from Cell Signaling (Danvers, MA), for NS3 from Abcam (Cambridge, UK), and for NS5A and NS5B were obtained from Alexis (San Diego, CA). The c-Src inhibitor herbimycin A was purchased from Calbiochem (Schwalbach, Germany). The human hepatoma cells Huh 7 wild-type and Huh 7.5 as well as the Huh 5-15, Huh 9-13, and Huh 11-7 cell lines harboring the HCV replicase complex2 were cultivated in Dulbecco’s modified Eagle’s medium/nutrient mix F-12 (Invitrogen, Karlsruhe, Germany) supplemented with 10% (vol/vol) heat-inactivated fetal bovine serum (Perbio, Bonn, Germany).