LL5beta directs the translocation of filamin A and SHIP2 to sites of phosphatidylinositol 3,4,5-triphosphate (PtdIns(3,4,5)P3) accumulation, and PtdIns(3,4,5)P3 localization is mutually modified by co-recruited SHIP2.
Phosphatidylinositol 3,4,5-triphosphate (PtdIns(3,4,5)P(3)) accumulates at the leading edge of migrating cells and works, at least partially, as both a compass to indicate directionality and a hub for subsequent intracellular events. However, how PtdIns(3,4,5)P(3) regulates the migratory machinery has not been fully elucidated. Here, we demonstrate a novel mechanism for efficient lamellipodium formation that depends on PtdIns(3,4,5)P(3) and the reciprocal regulation of PtdIns(3,4,5)P(3) itself. LL5beta, whose subcellular localization is directed by membrane PtdIns(3,4,5)P(3), recruits the actin-cross-linking protein Filamin A to the plasma membrane, where PtdIns(3,4,5)P(3) accumulates, with the Filamin A-binding Src homology 2 domain-containing inositol polyphosphate 5-phosphatase 2 (SHIP2). A large and dynamic lamellipodium was formed in the presence of Filamin A and LL5beta by the application of epidermal growth factor. Conversely, depletion of either Filamin A or LL5beta or the overexpression of either an F-actin-cross-linking mutant of Filamin A or a mutant of LL5beta without its PtdIns(3,4,5)P(3)-interacting region inhibited such events in COS-7 cells. Because F-actin initially polymerizes near the plasma membrane, it is likely that membrane-recruited Filamin A efficiently cross-links newly polymerized F-actin, leading to enhanced lamellipodium formation at the site of PtdIns(3,4,5)P(3) accumulation. Moreover, we demonstrate that co-recruited SHIP2 dephosphorylates PtdIns(3,4,5)P(3) at the same location.
Takabayashi
Tetsuji
T
Division of Cell Biology and Neuroscience, Department of Morphological and Physiological Sciences, University of Fukui, Fukui 910-1193, Japan.
Xie
Min-Jue
MJ
Takeuchi
Seiji
S
Kawasaki
Motomi
M
Yagi
Hideshi
H
Okamoto
Masayuki
M
Tariqur
Rahman M
RM
Malik
Fawzia
F
Kuroda
Kazuki
K
Kubota
Chikara
C
Fujieda
Shigeharu
S
Nagano
Takashi
T
Sato
Makoto
M
D000199:Actins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D019556:COS Cells; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology*; D002522:Chlorocebus aethiops; D003285:Contractile Proteins / Q000235:genetics / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000494:pharmacology; D064448:Filamins; D006801:Humans; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D018129:Phosphatidylinositol Phosphates / Q000235:genetics / Q000378:metabolism*; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D011554:Pseudopodia / Q000235:genetics / Q000378:metabolism*
D000199:Actins; D002352:Carrier Proteins; D003285:Contractile Proteins; D064448:Filamins; D008840:Microfilament Proteins; C471180:PHLDB2 protein, human; D018129:Phosphatidylinositol Phosphates; C060974:phosphatidylinositol 3,4,5-triphosphate; D004815:Epidermal Growth Factor; D010744:Phosphoric Monoester Hydrolases; C098706:INPPL1 protein, human; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases