Vinexin, CAP/Ponsin, Argbp2: a Novel Adaptor Protein Family Regulating Cytoskeletal Organization and Signal Transduction

Vinexin, CAP/ponsin, ArgBP2: a Novel Adaptor Protein Family Regulating Cytoskeletal Organization and Signal Transduction

Noriyuki Kioka∗, Kazumitsu Ueda, and Teruo Amachi Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606- 8502, Japan

ABSTRACT. Adaptor proteins, composed of two or more protein-protein interacting modules without enzymatic activity, regulate various cellular functions. Vinexin, CAP/ponsin, and ArgBP2 constitute a novel adaptor protein family. They have a novel conserved region homologous to the active peptide sorbin, as well as three SH3 (src homology 3) domains. A number of proteins binding to this adaptor family have been identified. There is accumulating evidence that this protein family regulates cell adhesion, cytoskeletal organization, and growth factor signaling. This review will summarize the structure and the function of proteins in this family.

Key words: SH3/sorbin/anchorage-dependence/insulin/vinexin

Adaptor proteins are known to regulate numerous cellular SoHo (sorbin homology) domain and three SH3 (src homol- events, including cell adhesion, migration, proliferation, ogy 3) domains. We refer to this protein family as the survival and cell cycle, both spatially and temporally vinexin family in this review. (Buday, 1999; Flynn, 2001; Pawson and Scott, 1997). These proteins are composed of two or more protein-protein (or protein-lipid) interacting modules without enzymatic Structural features of the vinexin family activity. They link appropriate proteins to other proteins (or Vinexin family proteins share one SoHo domain in their membrane), form large signaling complexes, and specify N-terminal region and three SH3 domains in the C-terminal the subcellular localization of specific molecules. They con- region (Fig. 1). The molecular architecture of this family is tribute to the specificity of cellular responses, the efficiency highly conserved. The SoHo domain was thus named be- of the responses, and where specific events occur. Grb2 and cause this region shows a high degree of similarity to the bi- Crk were first recognized as adaptor proteins to link two ologically active peptide sorbin (Charpin et al., 1992). Sorb- or more signaling molecules only about ten years ago. Pro- in is a 153-amino acid polypeptide originally purified from teins in this class are growing and it is now obvious that porcine intestine as an active peptide stimulating absorption adaptor proteins regulate not only growth factor signaling of water and electrolytes in the guinea pig gall bladder but also cytoskeletal organization (Buday, 1999; Flynn, (Charpin et al., 1992). The gene encoding porcine sorbin 2001; Pawson and Scott, 1997). has not been identified and its relationship to vinexin family In this review, we will focus on a novel adaptor protein proteins remains to be determined. Porcine sorbin and hu- family, including vinexin, CAP (c-Cbl associated protein)/ man ArgBP2 show an extremely high degree of identity ponsin and ArgBP2 (Arg-binding protein 2). Proteins in this (95% identity in the central 139 amino acids of sorbin) family are involved in both signal transduction and actin (Charpin et al., 1992; Wang et al., 1997), and no other simi- cytoskeletal organization. All of these proteins contain a lar genes have been found in the human genome to date. Thus, the sorbin peptide is likely to be a proteolytic frag- *To whom correspondence should be addressed: Noriyuki Kioka, Ph.D., ment or an alternative splicing variant of a porcine ortholog Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan. of ArgBP2. The function of SoHo domain has not been Tel: +81–75–753–6106, Fax: +81–75–753–6104 clearly defined, but one observation suggested that the E-mail: [email protected] SoHo domain of CAP/ponsin binds to the membrane Abbreviations: ArgBP2, Arg-binding protein 2; CAP, c-Cbl associated protein; ERK2, extracellular signal-regulated kinase 2; FA, focal adhesion; protein flotillin (see below) (Kimura et al., 2001). PAK, p21-activated kinase; PI3K, phosphatidylinositol-3-OH kinase; SH3, All vinexin family proteins found to date have three SH3 src homology 3; SoHo, sorbin homology.

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Fig. 1. Schematic representation of the domain structure of vinexin family proteins. Amino acid lengths of each protein are shown at the right side of each protein. The percentages of sequence identity with mouse vinexin α in each domain are indicated at the amino acid level. One representative splicing variant each is shown for CAP/ponsin, ArgBP2 and rexin. The filled triangle indicates the site at which exon I of CAP/ponsin would be inserted. Arrowheads indi- cate the possible core sequences (PXXP) for SH3 ligands. domains in their C-terminal region. The SH3 domain is known to bind to proline-rich sequences containing the Proteins belong to vinexin family PXXP core sequence (P, proline; X, any amino acid). Inter- Three mammalian proteins of vinexin family were isolat- actions of the SH3 domain to proline-rich ligands usually ed by their binding ability to target proteins. Vinexin was show broad specificity, and each SH3 domain has several originally isolated as a vinculin binding protein by yeast target proteins (Buday, 1999; Li et al., 2001; Mayer, 2001). two-hybrid screening using the proline-rich hinge region of Similar to other SH3 domain-containing adaptor molecules, vinculin (Kioka et al., 1999). The vinexin gene is composed including Grb2 and Nck, SH3 domains of vinexin family of at least 22 exons, distributed over a distance of about 30 proteins also have multiple binding partners (Table I). These kb in human chromosome 8. Vinexin is transcribed into at proteins include signaling molecules such as c-Abl, c-Arg, least two isoforms, vinexin α and β (Fig. 1) (Kioka et al., Sos, and c-Cbl, and cytoskeletal molecules such as vinculin 1999) (several other splicing variants can be found in the and afadin. Interestingly, vinexin family proteins also con- GenBank EST database). Both isoforms contain a common tain proline-rich sequences that possibly function as SH3 C-terminal sequence containing three SH3 domains, but binding sequences. One of these PXXP sequences of CAP/ vinexin β does not include the N-terminal region of vinexin ponsin was shown to bind Grb4 SH3 domains (Cowan and α containing the SoHo domain. Vinexin α and β expression Henkemeyer, 2001). Thus, vinexin family proteins function are differently regulated. Northern blotting analysis showed as SH3 domain-mediated adaptors or scaffolding molecules. that vinexin α is expressed at high levels in skeletal muscle

Table I. SoHo PROTEINS

Localization Tissue distribution Binding proteins ubiquitous, heart, skeletal muscle Vinexin α/β FA, cell-cell vinculin, Sos, flotillin (retina, gonad, outflow tract)* c-Cbl, insulin receptor, stress fibers, CAP/ponsin ubiquitous, heart, adipocyte Sos, vinculin, afadin FA, cell-cell, nucleus flotillin, Grb4, ataxin7 c-Arg, c-Abl vinculin, ArgBP2 (nArgBP2) stress fibers, nucleus ubiquitous, heart, brain SAPAP, afadin *expression in mouse embryos

2 Vinexin, CAP/ponsin, ArgBP2: a Novel Adaptor Family and at low levels in other tissues, and that vinexin β is ex- postsynaptic densities (Kawabe et al., 1999). nArgBP2 is pressed ubiquitously but at high levels in the heart (Kioka et expressed exclusively in the brain and is co-localized with al., 1999). The combined expression patterns of vinexin α SAPAP at postsynaptic densities (Kawabe et al., 1999). This and β are similar to that of their binding partner vinculin, variant has a 606-amino acid insertion not included in other implying that vinexin and vinculin function in coordination splicing variants, and the insertion contains a zinc finger with each other. Vinexin α and β expression in embryonic motif, suggesting that it may have specific functions in development are also regulated in a different manner. In neurons. situ hybridization showed that vinexin β is expressed Vinexin family proteins have been found not only in ubiquitously at 10.5 dpc (Kawauchi et al., 2001). In con- mammals but also in other multicellular organisms (Fig. 1). trast, vinexin α is expressed in a highly tissue-specific man- Whole genome analysis demonstrated that Drosophila ner. At 10.5 dpc, vinexin α is expressed only in the dorsal melanogaster and Caenorhabditis elegans have at least half of the retinal pigment epithelium and in the outflow one vinexin family protein, rexin (accession number tract and atrioventricular canal of the heart (Kawauchi et al., BAB62019) and yk22a10 (accession number AL021492), 2001). At 12.5 dpc, vinexin α is also expressed in the gonad respectively. These proteins show a high degree of similari- and in the ventral part of the pons (Kawauchi et al., 2001). ty (40%–70%) in SoHo and SH3 domains, but low levels of Although common features of these tissues expressing similarity in other regions. It is noteworthy that no orthologs vinexin α are not clear, endothelial cells in the outflow tract or paralogs of vinexin family proteins have been found and atrioventricular canal are known to transform to in the genome of the unicellular eukaryotic organism mesenchymal cells, implying that vinexin α may be Saccharomyces cerevisiae, which is similar to other cyto- involved in this transformation and tissue development. skeletal or cell adhesion molecules, including vinculin and CAP/ponsin (Fig. 1) was first identified as an SH3 do- integrins. These observations implied that vinexin family main-containing protein by functional screening for binding proteins may play roles in intercellular communication. to SH3 ligand, and was named SH3P12 (Sparks et al., 1996). This protein was then reported to be a binding protein for c-Cbl and afadin by different groups and named Roles of vinexin family proteins in cell adhesion CAP and ponsin, respectively (Mandai et al., 1999; Ribon et and cytoskeletal organization al., 1998a; Ribon et al., 1998b) (referred to in this review as Vinculin, a cytoskeletal protein, is likely to be one of the CAP/ponsin). Northern blotting analysis using full-length most important binding partners for vinexin family proteins cDNA showed that CAP/ponsin is expressed ubiquitously (Table I), as all three mammalian proteins of vinexin family but at high levels in the heart (Mandai et al., 1999; Ribon et bind to vinculin (Kawabe et al., 1999; Kioka et al., 1999; al., 1998b). This gene is transcribed into at least 13 splicing Mandai et al., 1999). Vinculin is an actin-binding cytoskele- variants (Lebre et al., 2001; Mandai et al., 1999), which tal protein, localized at cell-extracellular matrix (ECM) and could be expressed in a tissue-specific manner. Although cell-cell adhesion sites. Vinexins and CAP/ponsin are also differences in function or tissue distribution between localized at cell-ECM and cell-cell adhesion sites and are splicing variants have not been determined in detail, tissue- co-localized with vinculin (Fig. 2) (Kioka et al., 1999; Man- specific expression pattern of one exon, exon I, has been dai et al., 1999; Ribon et al., 1998a). ArgBP2 is co-local- determined (Lebre et al., 2001). Exon I of CAP/ponsin is ized with actin stress fibers and in the nucleus (Wang et al., expressed at high levels in the heart and at moderate levels 1997). Exogenous expression of vinexin α and CAP/ponsin in skeletal muscle and brain as determined by full-length in fibroblast cells stimulates formation of actin stress fibers cDNA, but is not expressed in the kidney, where moderate and focal adhesions (Kioka et al., 1999; Ribon et al., expression of full-length CAP/ponsin was detected. 1998a). Furthermore, exogenous expression of vinexin β in The third member of the mammalian vinexin family is C2C12 myoblasts enhanced cell spreading (Kioka et al., ArgBP2 (Fig. 1). ArgBP2 was isolated as a binding protein 1999). It is worth noting that the exogenous expression of for c-Abl and c-Arg, non-receptor type tyrosine kinases vinculin enhances cell spreading and formation of actin (Wang et al., 1997). ArgBP2 is expressed ubiquitously stress fibers and focal adhesions (Geiger et al., 1992), in a but at high levels in the heart, in a manner similar to CAP/ similar way to vinexin family proteins. Therefore, coopera- ponsin (Wang et al., 1997). Interestingly, ArgBP2 and CAP/ tive function between vinculin and vinexin family proteins ponsin have another homologous region in addition to SoHo may play an important role in stimulating the formation or and SH3 domains. This region is not found in other vinexin the stabilization of focal contacts and actin stress fibers. family proteins including vinexin, suggesting that ArgBP2 Intramolecular interactions between head and tail do- and CAP/ponsin are closely related. ArgBP2 has also been mains of vinculin regulate its binding activity for actin and reported to have alternative splicing variants. One splicing other cytoskeletal proteins, talin and VASP (Huttelmaier et variant, nArgBP2 (neural ArgBP2), was isolated by virtue al., 1998; Johnson and Craig, 1994; Johnson and Craig, of its binding to SAPAP (SAP90/PSD95-associated pro- 1995). Disruption of the head-tail interaction is believed to tein), a SAP90/PSD95 binding protein localized at neuronal be one of the key events in focal adhesion complex forma-

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Fig. 2. Schematic diagram showing the functions of the vinexin family. Vxn, vinexin; C/P, CAP/ponsin; AB2, ArgBP2; Vinc, vinculin; α-cat, α-catenin; β-cat, β-catenin; Flt, flotillin; Ata7, ataxin-7; IR, insulin receptor; GFR, growth factor receptor. tion. Although phosphatidylinositol-4,5-bisphosphate, prob- (Mandai et al., 1999). Vinculin is known to localize at adhe- ably induced downstream of activated Rho GTPases, has rens junctions and form the complex with cadherin-catenin been shown to disrupt the head-tail interaction and stimulate cell adhesion system through binding to α-catenin (Watabe- the binding ability of vinculin to talin (Gilmore and Burr- Uchida et al., 1998; Weiss et al., 1998). Afadin interacts idge, 1996; Weekes et al., 1996), the existence of other fac- with the cytoplasmic domain of the cell adhesion molecule tor(s) that disrupt head-tail interaction has also been sug- nectin through its PDZ domain (Ikeda et al., 1999; Mandai gested (Steimle et al., 1999). Vinexin and CAP/ponsin bind et al., 1997; Takahashi et al., 1999). The nectin-afadin cell to the vinculin proline-rich hinge region linking head and adhesion system is localized at adherens junctions and re- tail domains (Kioka et al., 1999; Mandai et al., 1999). Anal- cruits the cadherin-catenin cell adhesion system. Although ysis of the crystal structure of the vinculin tail suggested CAP/ponsin is suggested to be dispensable for recruiting the that the hinge region is exposed to the surface of the mole- cadherin-catenin-vinculin system to nectin-afadin system cule (Bakolitsa et al., 1999). It is interesting to determine (Tachibana et al., 2000), it may have some functions in link- whether interaction of vinexin family protein is also regulating these two adhesion systems. ed by intramolecular interaction of vinculin, or whether vinexin family proteins regulate the interaction of head and tail domains of vinculin and its binding ability to actin and talin. Regulation of growth factor-induced signal The function of vinexin family proteins at cell-cell adhe- transduction by vinexin family proteins sion sites has not been fully elucidated. Mandai et al. sug- All vinexin family proteins contain three SH3 domains gested that CAP/ponsin is localized at adherens junction with no enzymatic activity, suggesting that they function as and binds not only to vinculin but also to afadin (Fig. 2) adaptor molecules or scaffolding molecules in signal trans-

4 Vinexin, CAP/ponsin, ArgBP2: a Novel Adaptor Family duction pathways. Especially, vinexin β is composed of zation is similar to that of the binding partner c-Abl, which only three SH3 domains and linker regions of 10–100 ami- has been shown to shuttle between stress fibers and the cell no acids (i.e., it does not contain a SoHo domain) (Fig. 1) nucleus and to integrate the cell adhesion and cell cycle sig- (Kioka et al., 1999). Vinexins and CAP/ponsin bind to Sos, nals (Lewis et al., 1996; Van Etten et al., 1989). Interesting- a guanine nucleotide exchange factor for Ras and Rac, ly, PSORT II (http://psort.nibb.ac.jp/), a computer program through the third SH3 domain (Fig. 2) (Akamatsu et al., for the prediction of protein localization sites in cells, pre- 1999; Ribon et al., 1998b). Interestingly, addition of growth dicted that all vinexin family proteins, including yk22a10 factors (including epidermal growth factor (EGF), platelet- and rexin, would show nuclear localization with probabili- derived growth factor and serum) to serum-starved NIH3T3 ties of 50%–80%. This program identified at least one nu- cells induce the phosphorylation of Sos, leading to the clear localization signal (monopartite signal: 4-residue pat- dissociation of vinexin-Sos interaction (Akamatsu et al., tern composed of 4 basic amino acids (K or R), or of three 1999). This regulation of vinexin-Sos interaction by basic amino acids (K or R) and H) in each vinexin family phosphorylation is very similar to those of other adaptor protein. Indeed, vinexin localizes in the nucleus under some molecules including Grb2 and Nck (Cherniack et al., 1995; conditions (Kioka et al., 1999). Immunostaining using anti- Okada and Pessin, 1996; Waters et al., 1995). Furthermore, CAP/ponsin antibody showed some signals in the nucleus exogenous expression of vinexin β enhanced the EGF- (Cowan and Henkemeyer, 2001; Mandai et al., 1999). induced JNK (c-jun N-terminal kinase) activation (possibly Furthermore, Lebre et al. recently found that one of the through activation of Rac) (Akamatsu et al., 1999). This en- alternative spliced exons of CAP/ponsin, exon I, contains a hancing activity depends on the third SH3 domain. Togeth- bipartite nuclear localization signal (two basic amino acid er, these observations suggest that vinexin β, and possibly clusters separated by 10–12 amino acids) and that the splic- other vinexin family proteins, works as an adaptor molecule ing variant including this exon is localized exclusively in in growth factor signaling. the nucleus (Lebre et al., 2001). They also found that CAP/ Vinexin family proteins are involved in both cell adhe- ponsin binds to ataxin-7, a protein responsible for the sion/cytoskeletal organization and signal transduction as de- neurodegenerative disease spinocerebellar ataxia 7, in the scribed above, suggesting that vinexin family proteins may nucleus. In addition, CAP/ponsin has been shown to bind function as a point of convergence between cell adhesion/ to one of the nuclear receptors, progesterone receptor, cytoskeleton and growth-factor signaling. Therefore, we through its SH3 domain (Boonyaratanakornkit et al., 2001). examined the effects of vinexin expression on anchorage- Therefore, vinexin family proteins may shuttle between dependent ERK2 (extracellular signal-regulated kinase 2) cell-ECM adhesion or cell-cell adhesion sites and the activation. ERK2, one of the MAP kinases required for cell nucleus and integrate the cell adhesion signals and nuclear proliferation, is activated efficiently by EGF stimulation in functions such as transcriptional control and nuclear trans- adherent cells. In contrast, ERK2 activation is minimal if port. cells are in suspension (Cybulsky and McTavish, 1997; Inoue et al., 1996; Johnson and Vaillancourt, 1994; Lin et al., 1997; Marshall, 1995; Miyamoto et al., 1996; Renshaw CAP/ponsin as a regulator of the second signal et al., 1997). This phenomenon is likely to explain the pathway from insulin stimulation to Glut4 trans- mechanisms of anchorage dependence of cell proliferation location at least partially. We found that exogenous expression of Recently, CAP/ponsin has been suggested to be one of vinexin β in NIH3T3 cells allowed ERK2 activation in- the major players regulating the insulin-stimulated signaling duced by EGF even in suspension (Suwa et al.). In contrast, pathway. Insulin stimulates the translocation of insulin-re- expression of vinexin β affected neither the ERK2 activa- sponsive glucose transporter Glut4 from intracellular stor- tion in adherent cells nor ERK2 activity without EGF stimu- age vesicles to the plasma membrane, leading to increases lation. These observations suggested that vinexin β func- in glucose uptake into adipose tissue and muscle. Although tions in regulating the anchorage dependence of ERK2 a number of observations have indicated that activation of activation (Fig. 2). Recently, PAK (p21-activated kinase) phosphatidylinositol-3-OH kinase (PI3K) induced by insu- and PKA (cAMP-dependent kinase) have been reported to lin stimulation plays essential roles in this translocation, it is be involved in regulation of the anchorage dependence of also well known that activation of PI3K alone is not suffi- ERK2 activation (Howe and Juliano, 2000). Interestingly, cient and a second signal independent of PI3K activation is human vinexin α has been reported in the GenBankTM data- required (Alessi and Downes, 1998; Holman and Cushman, base (accession number AF037261) to bind to PAK. There- 1994; Watson and Pessin, 2001). Recent studies indicated fore, it is possible that vinexin cooperates with PAK to regu- that CAP/ponsin enhances insulin-induced phosphorylation late the anchorage dependence of ERK2 activation. of Cbl, and then recruits it to a lipid raft domain, where Vinexin family proteins may also function in the nucleus. many signaling molecules are accumulated (Brown and As described above, ArgBP2 is localized in the nucleus as London, 1998; Simons and Toomre, 2000). The CAP/ well as with stress fibers (Wang et al., 1997). This locali- ponsin-Cbl complex in the raft domain is suggested to acti-

5 N. Kioka et al. vate TC10, a CDC42 subfamily GTPase, through binding to 35933–35937. the CRKII-C3G complex, then stimulate Glut4 trans- Alessi, D.R. and Downes, C.P. 1998. The role of PI 3-kinase in insulin location in a PI3K-independent manner (Baumann et al., action. Biochim. Biophys. Acta., 1436: 151–164. Bakolitsa, C., de Pereda, J.M., Bagshaw, C.R., Critchley, D.R., and 2000; Chiang et al., 2001; Kanzaki and Pessin, 2001). Fur- Liddington, R.C. 1999. Crystal structure of the vinculin tail suggests a thermore, a single nucleotide polymorphism (SNP) related pathway for activation. Cell, 99: 603–613. to diabetes and obesity was mapped to the CAP/ponsin gene Baumann, C.A., Ribon, V., Kanzaki, M., Thurmond, D.C., Mora, S., on human chromosome 10q23-q24 (Lin et al., 2001). Thus, Shigematsu, S., Bickel, P.E., Pessin, J.E., and Saltiel, A.R. 2000. CAP CAP/ponsin is now a major candidate for the central player defines a second signalling pathway required for insulin-stimulated of the second signaling pathway from insulin stimulation to glucose transport. Nature, 407: 202–207. Glut4 translocation. Bickel, P.E., Scherer, P.E., Schnitzer, J.E., Oh, P., Lisanti, M.P., and Lodish, H.F. 1997. Flotillin and epidermal surface antigen define a new The SoHo domain of CAP/ponsin plays a role in this family of caveolae-associated integral membrane proteins. J. Biol. signaling. Flotillin, a membrane protein localized at caveola Chem., 272: 13793–13802. and/or lipid rafts (Bickel et al., 1997), was found to bind to Boonyaratanakornkit, V., Scott, M.P., Ribon, V., Sherman, L., Anderson, the SoHo domain of CAP/ponsin using two-hybrid screen- S.M., Maller, J.L., Miller, W.T., and Edwards, D.P. 2001. Progesterone ing (Baumann et al., 2000; Kimura et al., 2001). Expression receptor contains a proline-rich motif that directly interacts with SH3 of CAP/ponsin mutants deleting the SoHo domain or SH3 domains and activates c-Src family tyrosine kinases. Mol. Cell, 8: 269– domains inhibited relocation of Cbl to the caveola/raft and 280. Brown, D.A. and London, E. 1998. Functions of lipid rafts in biological Glut4 translocation (Baumann et al., 2000; Kimura et al., membranes. Annu. Rev. Cell Dev. Biol., 14: 111–136. 2001), indicating that SoHo domain-flotillin interaction is Buday, L. 1999. Membrane-targeting of signalling molecules by SH2/SH3 required for translocation. Interestingly, the SoHo domain domain-containing adaptor proteins. Biochim. Biophys. Acta., 1422: of vinexin α has also been reported to bind to flotillin 187–204. (Kimura et al., 2001). These observations indicated that the Charpin, G., Chikh-Issa, A.R., Guignard, H., Jourdan, G., Dumas, C., SoHo domain is a novel protein-protein interacting domain Pansu, D., and Descroix-Vagne, M. 1992. Effect of sorbin on duodenal absorption of water and electrolytes in the rat. Gastroenterology, 103: and that it play roles in signal regulation. 1568–1573. Cherniack, A.D., Klarlund, J.K., Conway, B.R., and Czech, M.P. 1995. Disassembly of Son-of-sevenless proteins from Grb2 during p21ras Conclusions desensitization by insulin. J. Biol. Chem., 270: 1485–1488. In this review, we have focused on a novel adaptor pro- Chiang, S.H., Baumann, C.A., Kanzaki, M., Thurmond, D.C., Watson, tein family containing a SoHo domain and three SH3 do- R.T. Neudauer, C.L., Macara, I.G., Pessin, J.E. and Saltiel, A.R. 2001. mains. There is accumulating evidence that three members Insulin-stimulated GLUT4 translocation requires the CAP-dependent activation of TC10. Nature, 410: 944–948. of this protein family function in regulating cell adhesion/ Cowan, C.A. and Henkemeyer, M. 2001. The SH2/SH3 adaptor Grb4 cytoskeletal organization and signal transduction pathways transduces B-ephrin reverse signals. Nature, 413: 174–179. by recruiting various molecules to critical areas in cells. Cybulsky, A.V. and McTavish, A.J. 1997. Extracellular matrix is required However, the important issue of how they coordinate regu- for MAP kinase activation and proliferation of rat glomerular epithelial lation of cytoskeletal organization and signaling remains to cells. Biochem. Biophys. Res. Commun., 231: 160–166. be resolved. From this point of view, it is interesting that Flynn, D.C. 2001. Adaptor proteins. Oncogene, 20: 6270–6272. all three mammalian proteins of vinexin family bind to Geiger, B., Ayalon, O., Ginsberg, D., Volberg, T., Rodriguez Fernandez, J.L., Yarden, Y., and Ben-Ze'ev, A. 1992. Cytoplasmic control of cell vinculin. One possibility is that the vinculin-vinexin family adhesion. Cold Spring Harb Symp. Quant. Biol., 57: 631–642. protein interaction functions as a switch to transmit the Gilmore, A.P. and Burridge, K. 1996. Regulation of vinculin binding to information from cell adhesion/cytoskeleton to growth fac- talin and actin by phosphatidyl-inositol-4-5-bisphosphate. Nature, 381: tor signals or growth factor signals to cell adhesion/cyto- 531–535. skeleton. The similarities and the discrepancies among the Holman, G.D. and Cushman, S.W. 1994. Subcellular localization and traf- three vinexin family proteins in their functions also should ficking of the GLUT4 glucose transporter isoform in insulin-responsive cells. Bioessays, 16: 753–759. be defined, because tissue distributions of these proteins are Howe, A.K. and Juliano, R.L. 2000. Regulation of anchorage-dependent similar and they may have redundant functions. Further signal transduction by protein kinase A and p21-activated kinase. Nat. studies on this protein family will promote our understand- Cell Biol., 2: 593–600. ing of how the loss of control of cell adhesion/cytoskeletal Huttelmaier, S., Mayboroda, O., Harbeck, B., Jarchau, T., Jockusch, organization and signaling cause various diseases. B.M., and Rudiger, M. 1998. The interaction of the cell-contact proteins VASP and vinculin is regulated by phosphatidylinositol-4,5- bisphosphate. Curr. Biol., 8: 479–488. References Ikeda, W., Nakanishi, H., Miyoshi, J., Mandai, K., Ishizaki, H., Tanaka, M., Togawa, A., Takahashi, K., Nishioka, H., Yoshida, H., Mizoguchi, Akamatsu, M., Aota S., Suwa, A., Ueda, K., Amachi, T., Yamada, K.M., A. Nishikawa, S., and Takai, Y. 1999. Afadin: A key molecule essential Akiyama, S.K., and Kioka. N. 1999. Vinexin forms a signaling complex for structural organization of cell-cell junctions of polarized epithelia with Sos and modulates epidermal growth factor-induced c-Jun N-termi- during embryogenesis. J. Cell Biol., 146: 1117–1132. nal kinase/stress-activated protein kinase activities. J. Biol. Chem., 274: Inoue, H., Yamashita, A., and Hakura, A. 1996. Adhesion-dependency of

6 Vinexin, CAP/ponsin, ArgBP2: a Novel Adaptor Family

serum-induced p42/p44 MAP kinase activation is released by retroviral Mayer, B.J. 2001. SH3 domains: complexity in moderation. J. Cell Sci., oncogenes. Virology, 225: 223–226. 114: 1253–1263. Johnson, G.L. and Vaillancourt, R.R. 1994. Sequential protein kinase reac- Miyamoto, S., Teramoto, H., Gutkind, J.S., and Yamada, K.M. 1996. tions controlling cell growth and differentiation. Curr. Opin. Cell Biol., Integrins can collaborate with growth factors for phosphorylation of 6: 230–238. receptor tyrosine kinases and MAP kinase activation: roles of integrin Johnson, R.P. and Craig, S.W. 1994. An intramolecular association be- aggregation and occupancy of receptors. J. Cell Biol., 135: 1633–1642. tween the head and tail domains of vinculin modulates talin binding. J. Okada, S. and Pessin, J.E. 1996. Interactions between Src homology (SH) Biol. Chem., 269: 12611–12619. 2/SH3 adapter proteins and the guanylnucleotide exchange factor SOS Johnson, R.P. and Craig, S.W. 1995. F-actin binding site masked by the are differentially regulated by insulin and epidermal growth factor. J. intramolecular association of vinculin head and tail domains. Nature, Biol. Chem., 271: 25533–25538. 373: 261–264. Pawson, T. and Scott, J.D. 1997. Signaling through scaffold, anchoring, Kanzaki, M. and Pessin, J.E. 2001. Insulin-stimulated GLUT4 transloca- and adaptor proteins. Science, 278: 2075–2080. tion in adipocytes is dependent upon cortical actin remodeling. J. Biol. Renshaw, M.W., Ren, X.D., and Schwartz, M.A. 1997. Growth factor acti- Chem., 276: 42436–42444. vation of MAP kinase requires cell adhesion. EMBO J., 16: 5592–5599. Kawabe, H., Hata, Y., Takeuchi, M., Ide, N., Mizoguchi, A., and Takai, Y. Ribon, V., Herrera, R., Kay, B.K., and Saltiel, A.R. 1998a. A role for 1999. nArgBP2, a novel neural member of ponsin/ArgBP2/vinexin CAP, a novel, multifunctional Src homology 3 domain-containing family that interacts with synapse-associated protein 90/postsynaptic protein in formation of actin stress fibers and focal adhesions. J. Biol. density-95-associated protein (SAPAP). J. Biol. Chem., 274: 30914– Chem., 273: 4073–4080. 30918. Ribon, V., Printen, J.A., Hoffman, N.G., Kay, B.K., and Saltiel, A.R. Kawauchi, T., Ikeya, M., Takada, S., Ueda, K., Shirai, M., Takihara, Y., 1998b. A novel, multifuntional c-Cbl binding protein in insulin receptor Kioka, N., and Amachi, T. 2001. Expression of vinexin α in the dorsal signaling in 3T3-L1 adipocytes. Mol. Cell Biol., 18: 872–879. half of the eye and in the cardiac outflow tract and atrioventricular canal. Simons, K. and Toomre, D. 2000. Lipid rafts and signal transduction. Nat. Mech. Dev., 106: 147–150. Rev. Mol. Cell Biol., 1: 31–39. Kimura, A., Baumann, C.A., Chiang, S.H., and Saltiel, A.R. 2001. The Sparks, A.B., Hoffman, N.G., McConnell, S.J., Fowlkes, D.M., and Kay, sorbin homology domain: a motif for the targeting of proteins to lipid B.K. 1996. Cloning of ligand targets: systematic isolation of SH3 rafts. Proc. Natl. Acad. Sci. USA, 98: 9098–9103. domain-containing proteins. Nat. Biotechnol., 14: 741–744. Kioka, N., Sakata, S., Kawauchi, T., Amachi, T., Akiyama, S.K., Okazaki, Steimle, P.A., Hoffert, J.D., Adey, N.B., and Craig, S.W. 1999. Polyphos- K., Yaen, C., Yamada, K.M., and Aota, S. 1999. Vinexin: a novel phoinositides inhibit the interaction of vinculin with actin filaments. J. vinculin-binding protein with multiple SH3 domains enhances actin Biol. Chem., 274: 18414–18420. cytoskeletal organization. J. Cell Biol., 144: 59–69. Suwa, A., Mitsushima, M., Ito, T., Akamatsu, M., Ueda, K., Amachi, T., Lebre, A.S., Jamot, L., Takahashi, J., Spassky, N., Leprince, C., Ravise, N., and Kioka, N. 2002. Vinexin β regulates anchorage dependence of Zander, C., Fujigasaki, H., Kussel-Andermann, P., Duyckaerts, C., ERK2 activation stimulated by epidermal growth factor. J. Biol. Chem., Camonis, J.H., and Brice, A. 2001. Ataxin-7 interacts with a Cbl-associ- in press. ated protein that it recruits into neuronal intranuclear inclusions. Hum. Tachibana, K., Nakanishi, H., Mandai, K., Ozaki, K., Ikeda, W., Mol. Genet., 10: 1201–1213. Yamamoto, Y., Nagafuchi, A., Tsukita, S., and Takai. Y. 2000. Two Lewis, J.M., Baskaran, R., Taagepera, S., Schwartz, M.A., and Wang. cell adhesion molecules, nectin and cadherin, interact through their J.Y. 1996. Integrin regulation of c-Abl tyrosine kinase activity and cyto- cytoplasmic domain-associated proteins. J. Cell Biol., 150: 1161–1176. plasmic-nuclear transport. Proc. Natl. Acad. Sci. USA, 93: 15174– Takahashi, K., Nakanishi, H., Miyahara, M., Mandai, K., Satoh, K., Satoh, 15179. A., Nishioka, H., Aoki, J., Nomoto, A., Mizoguchi, A., and Takai, Y. Li, W., Fan, J., and Woodley, D.T. 2001. Nck/Dock: an adapter between 1999. Nectin/PRR: an immunoglobulin-like cell adhesion molecule re- cell surface receptors and the actin cytoskeleton. Oncogene, 20: 6403– cruited to cadherin-based adherens junctions through interaction with 6417. Afadin, a PDZ domain-containing protein. J. Cell Biol., 145: 539–549. Lin, T.H., Chen, Q., Howe, A., and Juliano, R.L. 1997. Cell anchorage Van Etten, R.A., Jackson, P., and Baltimore, D. 1989. The mouse type IV permits efficient signal transduction between ras and its downstream c-abl gene product is a nuclear protein, and activation of transforming kinases. J. Biol. Chem., 272: 8849–8852. ability is associated with cytoplasmic localization. Cell, 58: 669–678. Lin, W.H., Chiu, K.C., Chang, H.M., Lee, K.C., Tai, T.Y., and Chuang, Wang, B., Golemis, E.A., and Kruh, G.D. 1997. ArgBP2, a multiple L.M. 2001. Molecular scanning of the human sorbin and SH3-domain- Src homology 3 domain-containing, Arg/Abl-interacting protein, is containing-1 (SORBS1) gene: positive association of the T228A phosphorylated in v-Abl-transformed cells and localized in stress fibers polymorphism with obesity and type 2 diabetes. Hum. Mol. Genet., 10: and cardiocyte Z-disks. J. Biol. Chem., 272: 17542–17550. 1753–1760. Waters, S.B., Yamauchi, K., and Pessin. J.E. 1995. Insulin-stimulated dis- Mandai, K., Nakanishi, H., Satoh, A., Obaishi, H., Wada, M., Nishioka, H., association of the SOS-Grb2 complex. Mol. Cell. Biol., 15: 2791–2799. Itoh, M., Mizoguchi, A., Aoki, T., Fujimoto, T., Matsuda, Y., Tsukita, Watson, R.T. and Pessin. J.E. 2001. Subcellular compartmentalization and S., and Takai, Y. 1997. Afadin: A novel actin filament-binding protein trafficking of the insulin-responsive glucose transporter, GLUT4. Exp. with one PDZ domain localized at cadherin-based cell-to-cell adherens Cell Res., 271: 75–83. junction. J. Cell Biol., 139: 517–528. Weekes, J., Barry, S.T., and Critchley., D.R. 1996. Acidic phospholipids Mandai, K., Nakanishi, H., Satoh, A., Takahashi, K., Satoh, K., Nishioka, inhibit the intramolecular association between the N- and C-terminal H., Mizoguchi, A., and Takai, Y. 1999. Ponsin/SH3P12: An l-afadin- regions of vinculin, exposing actin-binding and protein kinase C and vinculin-binding protein localized at cell-cell and cell-matrix phosphorylation sites. Biochem. J., 314: 827–832. adherens junctions. J. Cell Biol., 144: 1001–1018. Marshall, C.J. 1995. Specificity of receptor tyrosine kinase signaling: tran- (Received for publication, January 29, 2002 sient versus sustained extracellular signal-regulated kinase activation. and accepted, January 30, 2002) Cell, 80: 179–185.