Suppresses the insulin receptor and EGFR-transduced MAPK signaling pathway, but does not inhibit MAPK activation by a constitutively active mutant Ras. Probably impairs the formation of GTP-Ras (By similarity). Inhibits Ras-independent, but not Ras-dependent, activation of RAF1 (By similarity). Represses integrin-mediated cell spreading via inhibition of TESK1-mediated phosphorylation of cofilin (By similarity). Interacts (via C-terminus) with TESK1 (via both C- and N-termini); the interaction inhibits TESK1 kinase activity (PubMed:17974561). Interacts with RAF1 (By similarity). Interacts with CAV1 (via C-terminus) (PubMed:16877379). Found in the cytoplasm in unstimulated cells but is translocated to the membrane ruffles in cells stimulated with EGF (epidermal growth factor). Colocalizes with TESK1 in vesicular spots in the cytoplasm (By similarity). Expressed in the embryo and adult tissues including heart, brain, lung, kidney, and skeletal muscle. At 8 dpc expressed in the lateral plate mesoderm of the primitive streak. At 9.5 and 10.5 dpc expressed in the nasal placodes, maxillary and mandibular processes, posterior part of the hyoid arch and the progress zone of the limb buds and the presomitic mesoderm. At 11.5 dpc expressed in the dorso-lateral region of the somites (mostly in the myotome) and in the otic vesicle. At 11.5 and 12.5 dpc expressed in the distal lung mesenchyme, with a strong expression in the accessory lobe of the lung. By FGF signaling. The Cys-rich domain is responsible for the localization of the protein to the membrane ruffles. Belongs to the sprouty family.