Activity of beta3-beta4 loop of the PH domain is required for the membrane targeting of SWAP-70.
SWAP-70 translocates to the plasma membrane in a phosphoinositide 3-kinase (PI 3-kinase)-dependent manner and contributes to membrane ruffling. It binds to phosphatidylinositol trisphosphate (PtdIns(3,4,5)P(3)) through its PH domain, which is essential for the membrane translocation after EGF stimulation. We examined the behavior of the SWAP-70s which have mutations in the beta3/beta4 loop of the PH domain. The two mutants fused to green fluorescent protein (GFP) carrying the mutations failed to translocate to the plasma membrane. The sole PH domains carrying the same mutations behaved similarly. The PtdIns(3,4,5)P(3) binding activity of two mutants was comparable to that of the wild-type protein. These results suggest that translocation of SWAP-70 largely depends on the activity of the PH domain, and that not only PtdIns(3,4,5)P(3) binding activity, but also some additional activity of the PH domain is required for the translocation.
Fukui
Yasuhisa
Y
Division of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan. ayfukui@mail.ecc.u-tokyo.ac.jp
Wakamatsu
Isamu
I
Tachikawa
Hiroyuki
H
Okamura
Yoshihiko
Y
Tanaka
Takayuki
T
Ihara
Sayoko
S
D000818:Animals; D019556:COS Cells; D002462:Cell Membrane / Q000378:metabolism; D002522:Chlorocebus aethiops; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000502:physiology*; D021381:Protein Transport / Q000502:physiology
D004268:DNA-Binding Proteins; D020662:Guanine Nucleotide Exchange Factors; D009687:Nuclear Proteins; D018129:Phosphatidylinositol Phosphates; C060974:phosphatidylinositol 3,4,5-triphosphate