Anti-Spa1 antibodies are used in antigen-specific immunodetection in biological samples. The target Spa1 is a known alias name of the protein signal-induced proliferation-associated 1, encoded by the SIPA1 gene in humans. This 1042-amino acid residue protein is known to be a GTPase activator for the nuclear Ras-related regulatory proteins Rap1 and Rap2 in vitro, converting them to the putatively inactive GDP-bound state. It is localized to the membrane, nucleus, and cytoplasm of the cell. In terms of tissue expression, it is reported to be expressed in fetal as well as in adult tissues.