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