title: The NESH/Abi-3-based WAVE2 complex is functionally distinct from the Abi-1-based WAVE2 complex.
abstract: BACKGROUND
  Abl interactor (Abi) family proteins play significant roles in actin cytoskeleton organization through participation in the WAVE complex. Mammals possess three Abi proteins: Abi-1, Abi-2, and NESH/Abi-3. Abi-1 and Abi-2 were originally identified as Abl tyrosine kinase-binding proteins. It has been disclosed that Abi-1 acts as a bridge between c-Abl and WAVE2, and c-Abl-mediated WAVE2 phosphorylation promotes actin remodeling. We showed previously that NESH/Abi-3 is present in the WAVE2 complex, but neither binds to c-Abl nor promotes c-Abl-mediated phosphorylation of WAVE2.
  
  
  RESULTS
  In this study, we characterized NESH/Abi-3 in more detail, and compared its properties with those of Abi-1 and Abi-2. NESH/Abi-3 was ectopically expressed in NIH3T3 cells, in which Abi-1, but not NESH/Abi-3, is expressed. The expression of NESH/Abi-3 caused degradation of endogenous Abi-1, which led to the formation of a NESH/Abi-3-based WAVE2 complex. When these cells were plated on fibronectin-coated dishes, the translocation of WAVE2 to the plasma membrane was significantly reduced and the formation of peripheral lamellipodial structures was disturbed, suggesting that the NESH/Abi-3-based WAVE2 complex was unable to help produce lamellipodial protrusions. Next, Abi-1, Abi-2, or NESH/Abi-3 was expressed in v-src-transformed NIH3T3 cells. Only in NESH/Abi-3-expressed cells did treatment with an Abl kinase inhibitor, imatinib mesylate, or siRNA-mediated knockdown of c-Abl promote the formation of invadopodia, which are ventral membrane protrusions with extracellular matrix degradation activity. Structural studies showed that a linker region between the proline-rich regions and the Src homology 3 (SH3) domain of Abi-1 is crucial for its interaction with c-Abl and c-Abl-mediated phosphorylation of WAVE2.
  
  
  CONCLUSIONS
  The NESH/Abi-3-based WAVE2 complex is functionally distinct from the Abi-1-based one, and NESH/Abi-3 may be involved in the formation of ventral protrusions under certain conditions.
authors.affiliation: School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, 192-0392, Japan. pupa72040320@yahoo.co.jp.
authors.forename: Saki
authors.initials: S
authors.lastname: Sekino
authors.affiliation: School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, 192-0392, Japan. kashi-vb8.u@ab.auone-net.jp.
authors.forename: Yuriko
authors.initials: Y
authors.lastname: Kashiwagi
authors.affiliation: School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, 192-0392, Japan. hitoshi830213@yahoo.co.jp.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Kanazawa
authors.affiliation: School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, 192-0392, Japan. s096131@toyaku.ac.jp.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Takada
authors.affiliation: School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, 192-0392, Japan. babat@toyaku.ac.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Baba
authors.affiliation: School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, 192-0392, Japan. seisato@igm.hokudai.ac.jp.
authors.forename: Seiichi
authors.initials: S
authors.lastname: Sato
authors.affiliation: School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, 192-0392, Japan. hirokii@toyaku.ac.jp.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Inoue
authors.affiliation: School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, 192-0392, Japan. mkojima@toyaku.ac.jp.
authors.forename: Masaki
authors.initials: M
authors.lastname: Kojima
authors.affiliation: School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, 192-0392, Japan. tani@toyaku.ac.jp.
authors.forename: Katsuko
authors.initials: K
authors.lastname: Tani
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D002465:Cell Movement; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D057809:HEK293 Cells; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D021381:Protein Transport; D011554:Pseudopodia / Q000378:metabolism*; D051300:Wiskott-Aldrich Syndrome Protein Family / Q000378:metabolism*
chemical_list: C513733:ABI1 protein, human; C541989:ABI3 protein, human; C513734:Abi1 protein, mouse; D048868:Adaptor Proteins, Signal Transducing; D003598:Cytoskeletal Proteins; C000605635:Abi-3 protein, mouse; D051300:Wiskott-Aldrich Syndrome Protein Family