Enables L-aspartate transmembrane transporter activity and L-serine transmembrane transporter activity. Involved in L-aspartate import across plasma membrane. Acts upstream of or within serine import across plasma membrane. Located in intermediate filament. Is expressed in several structures, including central nervous system; dorsal root ganglion; lung; nose; and thymus primordium. Orthologous to human SLC1A4 (solute carrier family 1 member 4). [provided by Alliance of Genome Resources, Apr 2022]