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Journal of Virology, May 1999, p. 3587-3594, Vol. 73, No. 5
Department of Molecular Pathology, Institute
for Pathology, University of Tübingen, D-72076 Tübingen,
Germany,1 and Department of Pathology
and Laboratory Medicine, University of British Columbia- St. Paul's
Hospital, Vancouver, British Columbia, Canada2
Received 1 September 1998/Accepted 26 January 1999
Recently, we reported on tyrosine phosphorylation of distinct
cellular proteins in the course of enterovirus infections (M. Huber,
H.-C. Selinka, and R. Kandolf, J. Virol. 71:595-600, 1997). These
phosphorylation events were mediated by Src-like kinases and were shown
to be necessary for effective virus replication. That study is now
extended by examination of the interaction of the adapter protein
Sam68, a cellular target of Src-like kinases which has been shown to
interact with the poliovirus 3D polypeptide, with cellular signaling
proteins as well as the function of the latter during infection. Here,
we report that the RNA-binding and protein-binding protein Sam68
associates with the p21ras GTPase-activating
protein RasGAP. Remarkably, RasGAP is cleaved during infections with
different strains of coxsackievirus B3 as well as with echovirus 11 and
echovirus 12, yielding a 104-kDa protein fragment. This cleavage event,
which cannot be prevented by the general caspase inhibitor
benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone, may promote the
activation of the Ras pathway, as shown by the activating dual
phosphorylation of the mitogen-activated protein kinases Erk-1 and
Erk-2 in the late phase of infection. Moreover, downstream targets of
the mitogen-activated protein kinases, i.e., the
p21ras exchange factor Sos-1 and cytoplasmic
phospholipase A2, are phosphorylated with parallel time
courses during infection. Activation or inhibition of cellular
signaling pathways may play a general role in regulating effective
enterovirus replication and pathogenesis, and the results of this study
begin to unravel the molecular cross talk between enterovirus infection
and key cellular signaling networks.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Cleavage of RasGAP and Phosphorylation of Mitogen-Activated
Protein Kinase in the Course of Coxsackievirus B3 Replication

*
Corresponding author. Mailing address: Abteilung fuer
Molekulare Pathologie, Universität Tübingen,
Liebermeisterstr. 8, D-72076 Tübingen, Germany. Phone:
49-7071-2982264. Fax: 49-7071-295334. E-mail:
reinhard.kandolf{at}med.uni-tuebingen.de.
Present address: The Terry Fox Laboratory, British Columbia Cancer
Agency, Vancouver, British Columbia, Canada.
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