– Synapse-associated protein 1 (SYAP1), also known as PRO3113 and BSTA, belongs to the synapse-associated BSD domain family, featuring three α-helices and two conserved tryptophan and phenylalanine residues located at the C-terminus. Expressed near neuronal Golgi and synaptic regions of cerebellar Purkinje cells, SYAP1 has been linked to intact sensorimotor control and general vesicular trafficking in neurons. SYAP1-deficient mice display impaired locomotor activity. In cultured adipocytes, SYAP1 facilitates mTORC2-mediated phosphorylation of protein kinase Akt1 and adipocyte differentiation. Chromosomal band Xp22.2 houses the human SYAP1 gene, a region associated with developmental delay and autism spectrum disorder. SYAP 1 may be a target for future cancer therapies as it was induced by tamoxifen in breast cancer cells sensitive to tamoxifen growth inhibition.