title: Hsp90 and Hsp40/Erdj3 are required for the expression and anti-apoptotic function of KSHV K1.
abstract: 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 glycoprotein called K1. K1 possesses the ability to transform rodent fibroblasts and block apoptosis. K1 has also been shown to activate the PI3K/Akt/mTOR pathway in different cells. Using tandem affinity purification, we identified heat shock protein 90beta (Hsp90beta) and endoplasmic reticulum-associated Hsp40 (Erdj3/DnaJB11), as cellular binding partners of K1. Interactions of K1 with Hsp90beta and Hsp40 were confirmed by co-immunoprecipitation in both directions. Furthermore, K1 also interacted with the Hsp90alpha 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 K1's 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 IC(50) values of 50 nM and below.
authors.affiliation: Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA.
authors.forename: K W
authors.initials: KW
authors.lastname: Wen
authors.forename: B
authors.initials: B
authors.lastname: Damania
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D050956:HSP40 Heat-Shock Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D019288:Herpesvirus 8, Human; D006801:Humans; D054685:Lymphoma, Primary Effusion / Q000473:pathology; D017434:Protein Structure, Tertiary; D034741:RNA, Small Interfering / Q000235:genetics; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: C494648:DNAJB11 protein, human; D050956:HSP40 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; C111600:K1 protein, Human herpesvirus 8; D034741:RNA, Small Interfering; D014764:Viral Proteins