Sprouty-4 (also known as SPRY4) is an inhibitor of the insulin receptor and EGFR-transduced mitogen-activated protein kinase (MAPK) signaling pathway downstream of FGF and EGF receptor tyrosine kinase activation. It is positioned upstream of RAS activation and impairs the formation of active GTP-RAS. SPRY4 is widely expressed, with different isoforms. The protein consists of 322 amino acids, with a cysteine-rich region, Src homology 3 binding regions, proline-rich regions, and a PEST sequence. It is expressed predominantly in the cytoplasm. Northern results show bands across most tissues, with strongest expression in heart, brain, placenta, lung, and intestine.