Direct interaction of SOS1 Ras exchange protein with the SH3 domain of phospholipase C-gamma1.
A recent report that microinjection of the SH3 domain of PLC-gamma1 could induce DNA synthesis raised the functional importance of the SH3 domain of PLC-gamma1 in mitogenic signaling. In this report, we provide evidence that SOS1, a p21Ras-specific guanine nucleotide exchange factor, directly binds to the SH3 domain of PLC-gamma1, and that the SH3 domain of PLC-gamma1 is involved in SOS1-mediated p21Ras activation. SOS1 was coprecipitated with the GST-fused SH3 domain of PLC-gamma1 in vitro. The interaction between SOS1 and the PLC-gamma1 SH3 domain is mediated by direct physical interaction. The carboxyl-terminal proline-rich domain of SOS1 is involved in the interaction with the PLC-gamma1 SH3 domain. Moreover, PLC-gamma1 could be co-immunoprecipitated with SOS1 antibody in cell lysates. From transient expression studies, we could demonstrate that the SH3 domain of PLC-gamma1 is necessary for the association with SOS1 in vivo. Intriguingly, overexpression of the SH3 domain of PLC-gamma1, lipase-inactive PLC-gamma1, or wild-type PLC-gamma1 elevated p21Ras activity and ERK activity when compared with vector transfected cells. The PLC-gamma1 mutant lacking the SH3 domain could not activate p21Ras. p21Ras activities in cell lines overexpressing either PLC-gamma1 or the SH2-SH2-SH3 domain of PLC-gamma1 were elevated about 2-fold compared to vector transfected cells. This study is the first to demonstrate that the PLC-gamma1 SH3 domain enhances p21Ras activity, and that the SH3 domain of PLC-gamma1 may be involved in the SOS1-mediated signaling pathway.
Kim
M J
MJ
Department of Life Science and School of Environmental Engineering, Pohang University of Science and Technology, Republic of Korea.
Chang
J S
JS
Park
S K
SK
Hwang
J I
JI
Ryu
S H
SH
Suh
P G
PG
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D019556:COS Cells; D002460:Cell Line; D017931:DNA Primers / Q000235:genetics; D007527:Isoenzymes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D051966:Phospholipase C gamma; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020837:SOS1 Protein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D010738:Type C Phospholipases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D018909:src Homology Domains / Q000235:genetics
D017931:DNA Primers; D007527:Isoenzymes; D011993:Recombinant Fusion Proteins; D020837:SOS1 Protein; D010738:Type C Phospholipases; D051966:Phospholipase C gamma; D016283:Proto-Oncogene Proteins p21(ras)