Hsp90 and Hsp40/Erdj3 are required for the expression and anti-apoptotic function of KSHV K1

Oncogene (2010) 29, 35323544

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ORIGINAL ARTICLE

Hsp90 and Hsp40/Erdj3 are required for the expression and anti-apoptotic function of KSHV K1

KW Wen1,2 and B Damania1,2

1Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, USA and 2Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC, USA

Kaposi sarcoma-associated herpesvirus (KSHV) is a member of the gammaherpesvirus family. It is the etiological agent of three different human cancers, Kaposi sarcoma (KS), primary effusion lymphoma (PEL) and multicentric Castleman disease. The far left end of the KSHV genome encodes a unique transmembrane glyco-protein called K1. K1 possesses the ability to transform rodent broblasts and block apoptosis. K1 has also been shown to activate the PI3K/Akt/mTOR pathway in different cells. Using tandem afnity purication, we identied heat shock protein 90b (Hsp90b) and endoplasmic reticulum-associated Hsp40 (Erdj3/DnaJB11), as cellular binding partners of K1. Interactions of K1 with Hsp90b and Hsp40 were conrmed by co-immuno-precipitation in both directions. Furthermore, K1 also interacted with the Hsp90a isoform. We report that small-interfering RNAs directed against Hsp90 and Hsp40/Erdj3, as well as pharmacological inhibitors of Hsp90, dramatically reduced K1 expression, suggesting that K1 is a client protein of these chaperones. In addition, both Hsp90 and Hsp40/Erdj3 were essential for K1s anti-apoptotic function. Finally, we report that the Hsp90 inhibitors, 17-AAG and 17-DMAG, can suppress the proliferation of KSHV-positive PEL cell lines and exhibited IC50 values of 50 nM and below.

Oncogene (2010) 29, 35323544; doi:http://dx.doi.org/10.1038/onc.2010.124

Web End =10.1038/onc.2010.124 ; published online 26 April 2010

Keywords: KSHV; K1; heat shock proteins; Hsp90;

Hsp40; lytic replication

Introduction

Kaposi sarcoma-associated herpesvirus (KSHV), or human herpesvirus-8, is a gammaherpesvirus. This virus has been implicated as the etiological agent of Kaposi sarcoma (KS) (Chang et al., 1994) and lymphoproliferative diseases of B-cell origin, namely, primary effusion lymphoma (PEL) (Cesarman et al., 1995) and the plasmablastic variant of multicentric Castleman disease (MCD) (Soulier et al., 1995; Gessain et al., 1996).

The rst open-reading frame of KSHV encodes a viral glycoprotein named K1 (Lagunoff and Ganem, 1997). Both K1 transcript and protein have been detected in KS, PEL and MCD, (Samaniego et al., 2001; Bowser et al., 2002; Lee et al., 2003;...