title: Mammalian son of sevenless Guanine nucleotide exchange factors: old concepts and new perspectives.
abstract: The Son of Sevenless (Sos) factors were originally discovered 2 decades ago as specialized Ras activators in signaling pathways controlling the process of R7 cell development in the eye of Drosophila melanogaster. The 2 known members of the mammalian Sos family (Sos1 and Sos2) code for ubiquitously expressed, highly homologous (69% overall) proteins involved in coupling signals originated by cell surface receptor tyrosine kinases (RTKs) to downstream, Ras-dependent mitogenic signaling pathways. Mechanistically, the Sos proteins function as enzymatic factors interacting with Ras proteins in response to upstream stimuli to promote guanine nucleotide exchange (GDP/GTP) and subsequent formation of the active Ras-GTP complex. In this review, we summarize current knowledge on structural, regulatory, and functional aspects of the Sos family, focusing on specific aspects of Sos biology such as structure-function relationship, crosstalk with different signaling pathways, and in vivo functional significance as deduced from phenotypic characterization of Sos knockout mice and human genetic syndromes caused by germline hSos1 mutations.
authors.affiliation: Unidad de Biología Celular, Área de Biología Celular y del Desarrollo, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Madrid, Spain.
authors.forename: José M
authors.initials: JM
authors.lastname: Rojas
authors.forename: José Luis
authors.initials: JL
authors.lastname: Oliva
authors.forename: Eugenio
authors.initials: E
authors.lastname: Santos