Plays a role in the generation of neuronal polarity formation and axon growth (PubMed:17439943). Implicated in the formation of a single axon by developing neurons (PubMed:17439943). May inhibit the formation of additional axons by inhibition of PI3K in minor neuronal processes (PubMed:17439943). Plays a role in the formation of F-actin-enriched protrusive structures at the cell periphery (By similarity). Plays a role in cytoskeletal organization by regulating the subcellular localization of FSCN1 and DBN1 at axonal growth cones (By similarity). Promotes gastric cancer cell migration and invasion in a PAK1-dependent manner (By similarity). Interacts with PIK3CA and PIK3R1 (PubMed:17439943). Interacts with PAK1 (By similarity). Interacts (via C-terminus) with Ras-related Rab-5 proteins (By similarity). Interacts (via C-terminus) with Ras-related Rap-2 proteins (By similarity). Interacts (via N-terminus) with FSCN1; this interaction induces neuron axon development (By similarity). Interacts with DBN1 (By similarity). Localized in F-actin-enriched filopodia and lamellipodia at axonal growth cones (PubMed:17439943). Colocalizes with PAK1, F-actin, myosins and integrins in invadopodia at the cell periphery (By similarity). Colocalized with Ras-related Rab-5 proteins in cytoplasmic vesicles (By similarity). Accumulates in axon growth cones in a F-actin-dependent manner (By similarity). Colocalized with FSCN1 and F-actin at filipodia and lamellipodia of axonal growth cones (By similarity). Colocalized with DBN1 and F-actin at transitional domain of the axonal growth cone (By similarity). Expressed in brain (at protein level) (PubMed:17439943). Low level expression in brain up to E15, higher level expression from E18 to P14 with highest level around P4 (PubMed:17439943). Low level expression in adult brain (PubMed:17439943). Low level expression in hippocampal neurons up to stage 2 in culture (PubMed:17439943). Higher level from stage 3 with highest level of isoform 1 on day 7 in vitro (DIV7) (PubMed:17439943). Phosphorylated isoform 1 from DIV7 with high level up to DIV28, isoform 2 detectable from stage 3 to DIV7 (PubMed:17439943). Up-regulated during neuronal polarization (PubMed:17439943). Isoform 1 is partially phosphorylated (PubMed:17439943). Phosphorylated by PAK1 (By similarity). Hippocampal neurons with reduced levels of RUFY3 show an increase in formation of additional axons (PubMed:17439943). This effect is suppressed in the presence of the PI3K inhibitor LY294002 and enhanced by overexpression of SHTN1 (PubMed:17439943). Overexpression of RUFY3 suppresses additional axons formed upon overexpression of SHTN1 (PubMed:17439943).