Intersectin Can Regulate the Ras/MAP Kinase Pathway Independent
of Its Role in Endocytosis*
Received for publication, May 15, 2000, and in revised form, June 30, 2000
Published, JBC Papers in Press, July 13, 2000, DOI 10.1074/jbc.M004096200
Xin-Kang Tong‡, Natasha K. Hussain‡§, Anthony G. Adams¶, John P. O’Bryan¶,
and Peter S. McPherson‡i
From the ‡Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University,
Montreal, Quebec H3A 2B4, Canada and the ¶Laboratory of Signal Transduction, National Institute of
Environmental Health Sciences, Research Triangle Park, North Carolina 27709
We previously identified intersectin, a multiple EH
and SH3 domain-containing protein, as a component of
the endocytic machinery. Overexpression of the SH3 do-
mains of intersectin blocks transferrin receptor endocy-
tosis, possibly by disrupting targeting of accessory pro-
teins of clathrin-coated pit formation. More recently, we
identified mammalian Sos, a guanine-nucleotide ex-
change factor for Ras, as an intersectin SH3 domain-
binding partner. We now demonstrate that overexpres-
sion of intersectin’s SH3 domains blocks activation of
Ras and MAP kinase in various cell lines. Several stud-
ies suggest that activation of MAP kinase downstream of
multiple receptor types is dependent on endocytosis.
Thus, the dominant-negative effect of the SH3 domains
on Ras/MAP kinase activation may be indirectly medi-
ated through a block in endocytosis. Consistent with
this idea, incubating cells at 4 °C or with phenylarsine
oxide, treatments previously established to inhibit EGF
receptor endocytosis, blocks EGF-dependent activation
of MAP kinase. However, under these conditions, Ras
activity is unaffected and overexpression of the SH3
domains of intersectin is still able to block Ras activa-
tion. Thus, intersectin SH3 domain overexpression can
effect EGF-mediated MAP kinase activation directly
through a block in Ras, consistent with a functional role
for intersectin in Ras activation.
Src homology 3 (SH3)1 domains