Evolution of Gab family adaptor proteins Tetteh Abbeyquaye a , Juan Riesgo-Escovar b , Thomas Raabe c , Justin R. Thackeray a, * a Biology Department, Clark University, 950 Main Street, Worcester, MA 01610, USA b Neurobiology Institute, UNAM, Quere ´taro 76230, Mexico c Institute of Medical Radiation and Cell Research, University of Wu ¨rzburg, 97078 Wu ¨rzburg, Germany Received 4 October 2002; received in revised form 26 February 2003; accepted 6 March 2003 Received by M. Schartl Abstract The Gab/dos/Soc-1 proteins form a family of multi-adaptor/scaffolding proteins involved in receptor tyrosine kinase signaling. To further understanding of the Gab family and the Drosophila Dos protein in particular, we isolated a dos homolog from both Drosophila pseudoobscura and Drosophila virilis and compared their gene structures and protein sequences with the rest of the Gab family. The presence of two conserved introns confirmed that the dos and gab genes are orthologous, but the Caenorhabditis elegans soc-1 gene had no unambiguously conserved introns with either dos or gab. However, phylogenetic analysis suggests that soc-1 probably represents a divergent member of the Gab family. Apart from the PH domain, which is well conserved in all Gab family members, the proteins show a low level of sequence conservation. Two tyrosines that probably bind to the Src Homology 2 (SH2) domains of a tyrosine phosphatase in all Gab family members are conserved at the C-terminal end; two other potential SH2-binding sites in Dos were also identified, as well as several proline rich sequences that might bind to SH3 or EVH1 domains in other proteins. A major partner for mammalian Gab is phospholipase C-g (PLC-g); genetic and biochemical tests for a PLC-g-SH3::Dos interaction were negative, indicating that if Drosophila PLC-g binds to Dos, it must do so indirectly or through an SH2-phosphotyrosine interaction. q 2003 Elsevier Science B.V. All rights reserved. Keywords: Dos; Soc-1; Phosphotyrosine- Src Homology 2 (SH2) interaction; SH3-proline rich domain interaction; Conserved introns 1. Introduction The daughter of sevenless (dos) gene encodes an adaptor/scaffolding protein in Drosophila that is a member of the Grb2-associated binder (Gab) family. This family includes the mammalian proteins Gab1, Gab2 and Gab3, as well as Soc-1 of Caenorhabditis elegans (reviewed by Liu and Rohrschneider, 2002). Proteins in the Gab family are characterized by the presence of an N-terminal pleckstrin homology (PH) domain, as well as several tyrosines and proline-rich sequences (PRS) that serve as binding sites for other proteins with Src Homology 2 (SH2) or Src Homology 3 (SH3) domains, respectively. Gab family members are thought to mediate receptor tyrosine kinase (RTK) signaling by organizing a cluster of downstream components at the activated receptor, such as Grb-2, phospholipase C-g (PLC-g), and the protein tyrosine phosphatase, Shp-2 (Holgado-Madruga et al., 1996; Gual et al., 2000). Dos was first identified in a screen for suppressors of an activated form of the RTK Sevenless (Raabe et al., 1996), and as a molecule that immunoprecipitated with an inactive form of the protein tyrosine phosphatase Corkscrew (Csw) (Herbst et al., 1996). Sev is required for development of the R7 photoreceptor and genetic analysis has shown that Dos acts between the receptor and Ras (Raabe et al., 1996). In common with many other RTKs, activation of Sev results in autophosphorylation of several tyrosine residues on the cytoplasmic side of the receptor, each of which serves as a specific docking site for signaling molecules that contain SH2 or other phosphotyrosine binding domains. Following Sev activation, Dos becomes phosphorylated on at least two tyrosines, Y801 and Y854, generating binding sites for the two SH2 domains in Csw (Herbst et al., 1996, 1999; Allard et al., 1998). A major unresolved question about Dos function is to what extent its function mirrors its mammalian counterpart, 0378-1119/03/$ - see front matter q 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0378-1119(03)00505-5 Gene 311 (2003) 43–50 www.elsevier.com/locate/gene * Corresponding author. Tel.: þ 1-508-793-7539; fax: þ1-508-793-8861. E-mail address: jthackeray@clarku.edu (J.R. Thackeray). Abbreviations: bp, base pair(s); kb, kilobase pair(s); ORF, open reading frame; Mya, million years ago.