Human Signal Regulatory Protein beta 1 (SIRPB1) Protein

Background

Signal regulatory protein beta-1 (SIRPB1) is a transmembrane glycoprotein that is part of the signal regulatory protein (SIRP) family within the immunoglobulin superfamily (IgSF). SIRPB1 is primarily expressed on myeloid cells, such as macrophages, dendritic cells, and granulocytes, and functions as an activating receptor involved in immune regulation, phagocytosis, and cellular signaling. Unlike SIRPA, another family member which interacts with CD47 to deliver inhibitory signals to prevent “self” cell phagocytosis, SIRPB1 typically serves as an activating receptor and does not interact directly with CD47. SIRPB1 plays a role in modulating immune responses, particularly through its association with DAP12 (DNAX activation protein of 12 kDa), an adaptor molecule containing immunoreceptor tyrosine-based activation motifs (ITAMs). Upon activation, SIRPB1 influences signaling cascades that lead to pro-inflammatory cytokine release, phagocytosis, and cellular migration, especially in response to pathogens or tissue injury. Because of its involvement in immune activation, SIRPB1 has become of interest in cancer, infectious diseases, and inflammatory disorders.