Suppresses the insulin receptor and EGFR-transduced MAPK signaling pathway, but does not inhibit MAPK activation by a constitutively active mutant Ras (PubMed:12027893). Probably impairs the formation of GTP-Ras (PubMed:12027893). Inhibits Ras-independent, but not Ras-dependent, activation of RAF1 (PubMed:12717443). Represses integrin-mediated cell spreading via inhibition of TESK1-mediated phosphorylation of cofilin (PubMed:15584898). Interacts (via C-terminus) with TESK1 (via both C- and N-termini); the interaction inhibits TESK1 kinase activity (PubMed:12027893, PubMed:15584898). Interacts with RAF1 (PubMed:12717443). Interacts with CAV1 (via C-terminus) (By similarity). Found in the cytoplasm in unstimulated cells but is translocated to the membrane ruffles in cells stimulated with EGF (epidermal growth factor) (By similarity). Colocalizes with TESK1 in vesicular spots in the cytoplasm (PubMed:15584898). The Cys-rich domain is responsible for the localization of the protein to the membrane ruffles. The disease is caused by variants affecting distinct genetic loci, including the gene represented in this entry. Some patients carrying mutations in SPRY4 also have a heterozygous mutation in another HH-associated gene including DUSP6 and FGFR1 (PubMed:23643382). Belongs to the sprouty family.