Geldanamycin, a Ligand of Heat Shock Protein 90, Inhibits the Replication of Herpes Simplex Virus Type 1 In Vitro

Abstract

Geldanamycin (GA) is an antibiotic targeting the ADP/ATP binding site of heat shock protein 90 (Hsp90).In screening for anti-herpes simplex virus type 1 (HSV-1) candidates, we found GA active against HSV-1. HSV-1 replication in vitro was significantly inhibited by GA with an 50% inhibitory concentration of 0.093 M and a concentration that inhibited cellular growth 50% in comparison with the results seen with untreated controls of 350 M. The therapeutic index of GA was over 3,700 (comparable to the results seen with acyclovir). GA did not inhibit HSV-1 thymidine kinase. Cells infected with HSV-1 demonstrated cell cycle arrest at the G 1 /S transition; however, treatment with GA resulted in a cell cycle distribution pattern identical to that of untreated cells, indicating a restoration of cell growth in HSV-1-infected cells by GA treatment. Accordingly, HSV-1 DNA synthesis was suppressed in HSV-1 ؉ cells treated with GA. The antiviral mechanism of GA appears to be associated with Hsp90 inactivation and cell cycle restoration, which indicates that GA exhibits broad-spectrum antiviral activity. Indeed, GA exhibited activities in vitro against other viruses, including severe acute respiratory syndrome coronavirus. Since GA inhibits HSV-1 through a cellular mechanism unique among HSV-1 agents, we consider it a new candidate agent for HSV-1.Geldanamycin (GA) is a benzoquinone ansamycin and was first isolated as a new entity from the fermentation of Streptomyces hygroscopicus (3). GA binds with a high level of specificity within the ADP/ATP binding pocket of heat shock protein 90 (Hsp90) and inhibits the function of this chaperone (27,36), resulting in inappropriately functioning and rapid degradation of Hsp90-associated client proteins (2, 28). The client proteins are mainly short-lived proteins, including several protein kinases (Raf-1, ErbB-2, and Bcr-Abl), p53, and pRb as well as cyclins and cyclin-dependent kinases (2, 25), which are degraded through the ubiquitin-proteasome pathway but protected by Hsp90 (4,19). As a specific inhibitor of Hsp90 function, GA demonstrated antitumor activity in a multitude of animal models (23) and is now in clinical trial (phase I) in the United States (26). Interference with the function of Hsp90 seems to be the major mechanism of action of GA (29).In a large-scale screening for novel candidates exhibiting activity against herpes simplex virus type 1 (HSV-1), we found (from the fermentation of S. hygroscopicus) a component active against HSV-1 replication. Chemical analysis of the purified compound showed a structure identical to that of GA. A study was then initiated to evaluate the potential of this compound in the treatment of HSV-1 infection. In the present study, the anti-HSV-1 effect of GA was examined in cell cultures. The possible molecular mechanism responsible for its activity against viral infection was also explored. Our investigation showed that the mode of action of GA was closely related to the inactivation of cellular Hsp90 and different from that seen with the vira...

Herpes Simplex Virus Type 1 DNA Polymerase Requires the Mammalian Chaperone Hsp90 for Proper Localization to the Nucleus

“…Geldanamycin is a naturally occurring molecule that specifically binds the ADP/ATP-binding cleft of Hsp90 and destabilizes its interaction with client proteins. We have confirmed the results of Li et al showing that geldanamycin inhibits HSV-1 replication in tissue culture (13). Our results suggest that the viral polymerase may be a client protein of the Hsp90 chaperone machine and that geldanamycin inhibits HSV DNA replication by blocking Hsp90-polymerase interactions required for nuclear targeting.…”

Cellular Stress Rather than Stage of the Cell Cycle Enhances the Replication and Plating Efficiencies of Herpes Simplex Virus Type 1 ICP0 − Viruses

“…Of particular interest is the role of Hsp90. It has been shown that geldanamycin, a specific inhibitor of Hsp90 (34), inhibits the replication of HSV-1 in cell culture (25); therefore, Hsp90 and at least one of its downstream targets are necessary for HSV-1 replication. Geldanamycin also inhibits the replication of (25).…”

“…It has been shown that geldanamycin, a specific inhibitor of Hsp90 (34), inhibits the replication of HSV-1 in cell culture (25); therefore, Hsp90 and at least one of its downstream targets are necessary for HSV-1 replication. Geldanamycin also inhibits the replication of (25). Because Hsp90 is critical for the replication of many viruses and is an important component of the cellular response to stress, which induces HSV-1 reactivation from latency, Hsp90 is a potentially important factor in HSV-1 reactivation.…”

Antiviral evaluation of an Hsp90 inhibitor, gedunin, against dengue virus

“…An antibiotic geldanamycin (GA), which was initially characterized as an anticancer agent, has been reported to exhibit broadspectrum antiviral activity in vitro against several viruses by targeting the ADP/ATP binding site of Hsp90 [21]. The target viruses include herpes simplex virus type-1 (HSV-1) [10], severe acute respiratory syndrome corona virus, vaccinia virus [23], influenza virus, vesicular stomatitis virus [22], hepatitis C virus [24] and ebola virus [11].…”

“…Numerous Hsp90 inhibitors, identified as anticancer agents such as radicicol, geldanamycin (GA), and GA derivatives, block Hsp90 activity by binding to the N-terminal ATP pocket of the protein and inhibiting ATPase activity [9]. Geldanamycin was shown to be active against replication of a range of viruses, including herpes simplex virus type 1 (HSV-1), severe acute respiratory syndrome coronavirus and Zaire EBOV in vitro [10,11].…”