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Abp1p and cortactin, new "hand-holds" for actin.

Olazabal IM, Machesky LM - J. Cell Biol. (2001)

Bottom Line: Recently, two new ligands of the Arp2/3 complex have been described that may shed light on the way cells organize complex networks of actin in response to signals.Abp1p, a yeast protein involved in endocytosis, and cortactin, a mammalian src substrate, both enhance the ability of the Arp2/3 complex to assemble branched actin filament networks.

View Article: PubMed Central - PubMed

Affiliation: School of Biosciences, Division of Molecular Cell Biology, University of Birmingham, Birmingham B15 2TT, United Kingdom.

ABSTRACT
Recently, two new ligands of the Arp2/3 complex have been described that may shed light on the way cells organize complex networks of actin in response to signals. Abp1p, a yeast protein involved in endocytosis, and cortactin, a mammalian src substrate, both enhance the ability of the Arp2/3 complex to assemble branched actin filament networks.

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Schematic representation of the sequences of the different Arp2/3 complex activators: WASP, N-WASP, yeast WASP homologues (S. pombe Wsp1 and S. cerevisiae Las17p/Bee1p), Scar/WAVE, ActA, yeast Myosin-I homologue S. pombe Myo1p, Abp1p, and cortactin. All activators contain the A (acidic) sequence to bind to the Arp2/3 complex. The WASP family proteins and ActA all contain one or two WH2 motifs that bind to actin monomer. Myosin I may recruit another molecule that binds actin monomers (such as a WASP homologue). Abp1p and cortactin bind to actin filaments through the actin depolymerizing factor (ADF)-H/C–cofilin homology region and the tandem repeat region, respectively. B, basic; GBD, GTPase binding domain; PPPP, proline-rich region; C, central basic region; SHD, Scar homology domain; WH2*, weaker homology to WASP. Although we have not drawn a basic sequence in yeast WASP, Las17p/Bee1p contains a cluster of basic residues in this region, whereas Wsp1p does not appear to.
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fig1: Schematic representation of the sequences of the different Arp2/3 complex activators: WASP, N-WASP, yeast WASP homologues (S. pombe Wsp1 and S. cerevisiae Las17p/Bee1p), Scar/WAVE, ActA, yeast Myosin-I homologue S. pombe Myo1p, Abp1p, and cortactin. All activators contain the A (acidic) sequence to bind to the Arp2/3 complex. The WASP family proteins and ActA all contain one or two WH2 motifs that bind to actin monomer. Myosin I may recruit another molecule that binds actin monomers (such as a WASP homologue). Abp1p and cortactin bind to actin filaments through the actin depolymerizing factor (ADF)-H/C–cofilin homology region and the tandem repeat region, respectively. B, basic; GBD, GTPase binding domain; PPPP, proline-rich region; C, central basic region; SHD, Scar homology domain; WH2*, weaker homology to WASP. Although we have not drawn a basic sequence in yeast WASP, Las17p/Bee1p contains a cluster of basic residues in this region, whereas Wsp1p does not appear to.

Mentions: Although purified Arp2/3 complex weakly activates actin nucleation, its activity can be dramatically enhanced by cellular activators, including: the WASP family proteins (Machesky and Insall, 1998; Higgs and Pollard, 1999); the Listeria protein ActA (Welch et al., 1998); the type I myosin Myo1p from Schizosaccharomyces pombe (Lee et al., 2000); and recently cortactin and Abp1p. Despite their diversity, each activator interacts with the Arp2/3 complex through a conserved sequence, the acidic “A” domain (Machesky and Insall, 1998). However, the mechanism of stimulation of the Arp2/3 complex differs from some of the activators. All members of the WASP family and ActA appear to require the monomeric actin-binding region (WASP homology [WH]2) (Higgs et al., 1999; Machesky et al., 1999; Rohatgi et al., 1999) (Fig. 1) . However, fungal myosin I's, lack this sequence, but may interact with actin monomer binding proteins such as verprolin or a yeast WASP homologue (Evangelista et al., 2000; Lechler et al., 2000; Lee et al., 2000). Abp1p and cortactin represent a novelty in the mechanism of activation of the Arp2/3 complex, in that they both require a filamentous actin-binding region that consists of an actin depolymerizing factor/cofilin homology domain, or a six to seven–tandem repeat fragment, respectively. Thus, actin monomer binding is not a strict requirement for Arp2/3 complex activation.


Abp1p and cortactin, new "hand-holds" for actin.

Olazabal IM, Machesky LM - J. Cell Biol. (2001)

Schematic representation of the sequences of the different Arp2/3 complex activators: WASP, N-WASP, yeast WASP homologues (S. pombe Wsp1 and S. cerevisiae Las17p/Bee1p), Scar/WAVE, ActA, yeast Myosin-I homologue S. pombe Myo1p, Abp1p, and cortactin. All activators contain the A (acidic) sequence to bind to the Arp2/3 complex. The WASP family proteins and ActA all contain one or two WH2 motifs that bind to actin monomer. Myosin I may recruit another molecule that binds actin monomers (such as a WASP homologue). Abp1p and cortactin bind to actin filaments through the actin depolymerizing factor (ADF)-H/C–cofilin homology region and the tandem repeat region, respectively. B, basic; GBD, GTPase binding domain; PPPP, proline-rich region; C, central basic region; SHD, Scar homology domain; WH2*, weaker homology to WASP. Although we have not drawn a basic sequence in yeast WASP, Las17p/Bee1p contains a cluster of basic residues in this region, whereas Wsp1p does not appear to.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2196464&req=5

fig1: Schematic representation of the sequences of the different Arp2/3 complex activators: WASP, N-WASP, yeast WASP homologues (S. pombe Wsp1 and S. cerevisiae Las17p/Bee1p), Scar/WAVE, ActA, yeast Myosin-I homologue S. pombe Myo1p, Abp1p, and cortactin. All activators contain the A (acidic) sequence to bind to the Arp2/3 complex. The WASP family proteins and ActA all contain one or two WH2 motifs that bind to actin monomer. Myosin I may recruit another molecule that binds actin monomers (such as a WASP homologue). Abp1p and cortactin bind to actin filaments through the actin depolymerizing factor (ADF)-H/C–cofilin homology region and the tandem repeat region, respectively. B, basic; GBD, GTPase binding domain; PPPP, proline-rich region; C, central basic region; SHD, Scar homology domain; WH2*, weaker homology to WASP. Although we have not drawn a basic sequence in yeast WASP, Las17p/Bee1p contains a cluster of basic residues in this region, whereas Wsp1p does not appear to.
Mentions: Although purified Arp2/3 complex weakly activates actin nucleation, its activity can be dramatically enhanced by cellular activators, including: the WASP family proteins (Machesky and Insall, 1998; Higgs and Pollard, 1999); the Listeria protein ActA (Welch et al., 1998); the type I myosin Myo1p from Schizosaccharomyces pombe (Lee et al., 2000); and recently cortactin and Abp1p. Despite their diversity, each activator interacts with the Arp2/3 complex through a conserved sequence, the acidic “A” domain (Machesky and Insall, 1998). However, the mechanism of stimulation of the Arp2/3 complex differs from some of the activators. All members of the WASP family and ActA appear to require the monomeric actin-binding region (WASP homology [WH]2) (Higgs et al., 1999; Machesky et al., 1999; Rohatgi et al., 1999) (Fig. 1) . However, fungal myosin I's, lack this sequence, but may interact with actin monomer binding proteins such as verprolin or a yeast WASP homologue (Evangelista et al., 2000; Lechler et al., 2000; Lee et al., 2000). Abp1p and cortactin represent a novelty in the mechanism of activation of the Arp2/3 complex, in that they both require a filamentous actin-binding region that consists of an actin depolymerizing factor/cofilin homology domain, or a six to seven–tandem repeat fragment, respectively. Thus, actin monomer binding is not a strict requirement for Arp2/3 complex activation.

Bottom Line: Recently, two new ligands of the Arp2/3 complex have been described that may shed light on the way cells organize complex networks of actin in response to signals.Abp1p, a yeast protein involved in endocytosis, and cortactin, a mammalian src substrate, both enhance the ability of the Arp2/3 complex to assemble branched actin filament networks.

View Article: PubMed Central - PubMed

Affiliation: School of Biosciences, Division of Molecular Cell Biology, University of Birmingham, Birmingham B15 2TT, United Kingdom.

ABSTRACT
Recently, two new ligands of the Arp2/3 complex have been described that may shed light on the way cells organize complex networks of actin in response to signals. Abp1p, a yeast protein involved in endocytosis, and cortactin, a mammalian src substrate, both enhance the ability of the Arp2/3 complex to assemble branched actin filament networks.

Show MeSH
Related in: MedlinePlus