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Molecular and Cellular Biology, September 2000, p. 6518-6536, Vol. 20, No. 17
The Beatson Institute for Cancer research,
CRC Beatson Laboratories, Bearsden, Glasgow G61 1BD, United Kingdom
Received 6 April 2000/Accepted 17 May 2000
The v-Src oncoprotein is translocated to integrin-linked focal
adhesions, where its tyrosine kinase activity induces adhesion disruption and cell transformation. We previously demonstrated that the
intracellular targeting of Src is dependent on the actin cytoskeleton,
under the control of the Rho family of small G proteins. However, the
assembly of v-Src into focal adhesions does not require its catalytic
activity or myristylation-dependent membrane association. Here, we
report that the SH3 domain is essential for the assembly of focal
adhesions containing the oncoprotein by mediating a switch from a
microtubule-dependent, perinuclear localization to actin-associated focal adhesions; furthermore, v-Src translocation to focal adhesions requires myosin activity, at least under normal conditions when the
actin cytoskeleton is being dynamically regulated. Although the SH3
domain of v-Src is also necessary for its association with focal
adhesion kinase (FAK), which is often considered a likely candidate
mediator of focal adhesion targeting via its carboxy-terminal targeting
sequence, we show here that binding to FAK is not essential for the
targeting of v-Src to focal adhesions. The p85 regulatory subunit of
phosphatidylinositol (PI) 3-kinase also associates with v-Src in an
SH3-dependent manner, but in this case inhibition of PI 3-kinase
activity suppressed assembly of focal adhesions containing the
oncoprotein. Thus, the Src SH3 domain, which binds PI 3-kinase and
which is necessary for activation of Akt downstream, is required for
the actin-dependent targeting of v-Src to focal adhesions.
0270-7306/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
The SH3 Domain Directs Acto-Myosin-Dependent
Targeting of v-Src to Focal Adhesions via Phosphatidylinositol
3-Kinase
*
Corresponding author. Mailing address: The Beatson
Institute for Cancer Research, CRC Beatson Laboratories, Garscube
Estate, Switchback Rd., Bearsden, Glasgow G61 1BD, United Kingdom.
Phone: 0141-330-3953. Fax: 0141-942-6521. E-mail:
m.frame{at}beatson.gla.ac.uk.
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