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The 11 th International Workshop on KSHV & Related Agents, Birmingham, UK
Virus-Cell Interactions II Abstract 62
TARGETING EXTRACELLULAR HSP90 REDUCES KSHV GENE EXPRESSION
DURING DE NOVO INFECTION BY INHIBITING MAPK PATHWAY ACTIVATION
Zhiqiang Qin 1 , Jennifer Isaacs 2 , and Chris Parsons 1,3
Departments of 1 Medicine, 2 Pharmacology and 3 Microbiology/Immunology
Hollings Cancer Center, Medical University of South Carolina
Charleston, SC, USA
Abstract
Heat shock protein 90 (Hsp90) acts as a molecular chaperone orchestrating the folding of
intracellular signaling proteins. Although extracellular (EC) domains for Hsp90 have been
identified, the functional consequences of engaging EC Hsp90 are largely unknown.
Signal transduction induced during KSHV receptor binding and entry is critical for de novo
viral gene expression. Using PCR and immunofluorescence assays, we found that
treatment of HeLa cells with a non-permeable compound targeting EC Hsp90, DNo,
inhibited de novo expression of latent KSHV transcripts and LANA. Pre-treatment of cells
with DNo did not reduce intracellular KSHV DNA content, and DNo maintained an
inhibitory effect when treatment was initiated following viral incubation. In addition, no
effect was observed following KSHV pre-incubation with two soluble Hsp90 protein
isoforms or a mAb targeting a different EC Hsp90 domain. These results suggest that
DNo interferes with post-entry events important for viral gene expression. Immunoblot
analyses of signal transduction intermediates indicated that mitogen-activated protein
kinase kinase (MEK) and extracellular signal-regulated kinase (ERK) phosphorylation
were selectively inhibited in a dose- and time-dependent manner by DNo. Furthermore,
DNo blocked KSHV-mediated induction of MEK and ERK phosphorylation corresponding to
a reduction in LANA expression. Finally, constructs conferring constitutive expression of
P-MEK and P-ERK, but not an ERK dominant negative construct, rescued KSHV gene
expression in DNo-treated cells. These results suggest that EC Hsp90 plays an important
role in KSHV-initiated signal transduction events and viral gene expression and that
strategies targeting EC Hsp90 may have therapeutic benefit for KSHV-related disease.
Presenting author Email: parsonch@musc.edu
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