A novel protein encoded by Kaposi's sarcoma-associated herpesvirus open reading frame 36 inhibits cell spreading and focal adhesion kinase activation.
OBJECTIVE
Kaposi's sarcoma-associated herpesvirus (KSHV) is a gamma-herpesvirus implicated in the development of Kaposi's sarcoma, primary effusion lymphoma and some forms of multicentric Castleman's disease. The KSHV open reading frame (ORF) 36 encodes a viral serine/threonine protein kinase. The aim of this study was to characterize the cellular function of the ORF36 protein.


METHODS
The expression kinetics of the ORF36 protein and its localization were determined. The wild-type ORF36 and its mutant proteins were subjected to in vitro kinase assay. Cell morphology change by ORF36 protein was studied. The focal adhesion kinase (FAK) tyrosine phosphorylation and cleavage were determined when ORF36 was expressed.


RESULTS
ORF36 protein expressed in the late phase during the KSHV reactivation. The C-terminal domain of ORF36 protein was important for kinase activity. Moreover, the ORF36 protein altered cell morphology to a round shape, similar to the phenotype of FAK-deficient cells. The kinase activity of ORF36 protein was required for the inhibition of cell spreading. Interestingly, ORF36 protein colocalized with FAK, suppressed its tyrosine phosphorylation and promoted FAK cleavage.


CONCLUSIONS
Our results collectively demonstrate that the KSHV ORF36 protein is a viral protein kinase that inhibits cell spreading and FAK activation.
Park
Junsoo
J
Korea Basic Science Institute, Gwangju, Korea.
Lee
Myung-Shin
MS
Yoo
Seung-Min
SM
Seo
Taegun
T
D002478:Cells, Cultured; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000187:drug effects / Q000378:metabolism*; D019288:Herpesvirus 8, Human / Q000201:enzymology* / Q000235:genetics*; D016366:Open Reading Frames / Q000235:genetics; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism* / Q000494:pharmacology; D014764:Viral Proteins / Q000235:genetics* / Q000378:metabolism
D014764:Viral Proteins; D011494:Protein Kinases; D051416:Focal Adhesion Protein-Tyrosine Kinases