PtdIns(3,4,5)P3 binding is necessary for WAVE2-induced formation of lamellipodia

Abstract

Polarized cell movement is triggered by the development of a PtdIns(3,4,5)P(3) gradient at the membrane, which is followed by rearrangement of the actin cytoskeleton. The WASP family verprolin homologous protein (WAVE) is essential for lamellipodium formation at the leading edge by activating the Arp2/3 complex downstream of Rac GTPase. Here, we report that WAVE2 binds to PtdIns(3,4,5)P(3) through its basic domain. The amino-terminal portion of WAVE2, which includes the PtdIns(3,4,5)P(3)-binding sequence, was localized at the leading edge of lamellipodia induced by an active form of Rac (RacDA) or by treatment with platelet-derived growth factor (PDGF). Production of PtdIns(3,4,5)P(3) at the cell membrane by myristoylated phosphatidylinositol-3-OH kinase (PI(3)K) is sufficient to recruit WAVE2 in the presence of dominant-negative Rac and latrunculin, demonstrating that PtdIns(3,4,5)P(3) alone is able to recruit WAVE2. Expression of a full-length mutant of WAVE2 that lacks the lipid-binding activity inhibited proper formation of lamellipodia induced by RacDA. These results suggest that one of the products of PI(3)K, PtdIns(3,4,5)P(3), recruits WAVE2 to the polarized membrane and that this recruitment is essential for lamellipodium formation at the leading edge.

The Endoplasmic Reticulum Is a Reservoir for WAVE/SCAR Regulatory Complex Signaling in the Arabidopsis Leaf

“…This is because, in nonplant species, a significant fraction of cellular W/SRC is cytosolic (Eden et al, 2002;Bogdan and Klämbt, 2003). In addition, biochemical studies that employ soluble vertebrate WAVE/SCAR proteins or fully assembled W/SRC detect specific binding to phospholipids that is consistent with a cytosolic recruitment model (Oikawa et al, 2004;Steffen et al, 2004;Lebensohn and Kirschner, 2009). However, in many motile cell types, including neurons, NAP1 has a striking punctate or perinuclear localization pattern that may reflect the general importance of multiple organelles in the cellular cycles of W/SRC activation and use (Bogdan and Klämbt, 2003;Steffen et al, 2004;Millius et al, 2009).…”

“…In mammalian cells that crawl on a solid substrate, current models propose that a cytosolic pool of inactive WAVE/ SCAR proteins and W/SRC is locally recruited and activated at specific plasma membrane surfaces in response to signals from some unknown Rac guanine nucleotide-exchange factor (GEF), protein kinase, and/ or lipid kinase (Oikawa et al, 2004;Lebensohn and Kirschner, 2009;Chen et al, 2010). However, in Drosophila melanogaster neurons (Bogdan and Klämbt, 2003) and cultured human melanoma cells (Steffen et al, 2004), there are large pools of W/SRC with a perinuclear or organelle-like punctate localization that has no obvious relationship to cell shape or motility, raising uncertainty about the cellular mechanisms of W/SRC activation and the importance of different subcellular pools of the complex.…”

Essential role for Abi1 in embryonic survival and WAVE2 complex integrity

“…The Abi1-mediated tyrosine phosphorylation of WAVE2 by Abl regulates WAVE2 complex activity either by regulating conformation of the complex, as suggested (22), or by regulating interactions among the complex components or with other cellular targets (10,23,24). The interaction of Abi1 with p85 (24) might modulate PI3 kinase activity (10); this activity would be consistent with coincident modulation of WAVE complex activity by its interaction with PIP3, or PIP3-mediated membrane recruitment of WAVE2 (25).…”

Activation of Arp2/3 complex-dependent actin polymerization by plant proteins distantly related to Scar/WAVE

“…The basic region of human WAVE2 has recently been shown to bind to PtdIns(3,4,5)P 3 and mediate recruitment of WAVE2 to the plasma membrane in response to growth factor stimulation (26). Thus, the basic regions of AtSCAR proteins may also function to mediate their interaction with membranes.…”