Inhibits neurite branching, arbor length and neurite complexity (PubMed:26089202). Inhibits EGF-mediated p42/44 ERK signaling (PubMed:16877379). Negatively regulates the MAPK cascade, resulting in a reduction of extracellular matrix protein accumulation (By similarity). May function as an antagonist of fibroblast growth factor (FGF) pathways and may negatively modulate respiratory organogenesis (By similarity). Interacts with TESK1 (By similarity). Interacts with USP11 (By similarity). Interacts with CAV1 (via C-terminus) (PubMed:16877379). Expressed in the brain with expression the highest in Purkinje cell bodies and projections in the cerebellum (at protein level) (PubMed:26089202). Also expressed in central and peripheral nervous system ganglion cells, superior cervical ganglion and dorsal root ganglion (at protein level) (PubMed:26089202). Expressed in the retinal ganglion cell layer and the inner nuclear layer (at protein level) (PubMed:26089202). By FGF signaling. Belongs to the sprouty family.