The Skap-hom dimerization and PH domains comprise a 3'-phosphoinositide-gated molecular switch.
PH domains, by binding to phosphoinositides, often serve as membrane-targeting modules. Using crystallographic, biochemical, and cell biological approaches, we have uncovered a mechanism that the integrin-signaling adaptor Skap-hom uses to mediate cytoskeletal interactions. Skap-hom is a homodimer containing an N-terminal four-helix bundle dimerization domain, against which its two PH domains pack in a conformation incompatible with phosphoinositide binding. The isolated PH domains bind PI[3,4,5]P(3), and mutations targeting the dimerization domain or the PH domain's PI[3,4,5]P(3)-binding pocket prevent Skap-hom localization to ruffles. Targeting is retained when the PH domain is deleted or by combined mutation of the PI[3,4,5]P(3)-binding pocket and the PH/dimerization domain interface. Thus, the dimerization and PH domain form a PI[3,4,5]P(3)-responsive molecular switch that controls Skap-hom function.
Swanson
Kenneth D
KD
Cancer Biology Program, Division of Hematology-Oncology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA 02115, USA.
Tang
Yong
Y
Ceccarelli
Derek F
DF
Poy
Florence
F
Sliwa
Jan P
JP
Neel
Benjamin G
BG
Eck
Michael J
MJ
D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D019281:Dimerization; D049452:Green Fluorescent Proteins / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010716:Phosphatidylinositols / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017354:Point Mutation; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012190:Retroviridae / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D014161:Transduction, Genetic
D048868:Adaptor Proteins, Signal Transducing; D010716:Phosphatidylinositols; D049452:Green Fluorescent Proteins