CD172a

CD172a, also known as Signal-Regulatory Protein Alpha (SIRPα), is a transmembrane glycoprotein that belongs to the immunoglobulin superfamily. It is primarily expressed on the surface of myeloid cells, including monocytes, macrophages, granulocytes, and dendritic cells. CD172a plays a crucial role in regulating immune responses and maintaining immune homeostasis.

The CD172a protein consists of three extracellular immunoglobulin-like domains, a transmembrane region, and a cytoplasmic tail. The extracellular domains are responsible for ligand binding, while the cytoplasmic tail contains immunoreceptor tyrosine-based inhibition motifs (ITIMs) that mediate intracellular signaling. Upon ligand binding, CD172a recruits tyrosine phosphatases such as SHP-1 and SHP-2, which negatively regulate cellular activation and signaling pathways.

The primary ligand for CD172a is CD47, a widely expressed membrane protein that acts as a "don't eat me" signal to inhibit phagocytosis. The interaction between CD172a and CD47 is a critical mechanism for self-recognition and immune evasion. In this context, CD172a functions as a receptor for CD47, transmitting inhibitory signals that prevent the phagocytosis of healthy cells. However, this interaction can also be exploited by cancer cells to evade immune surveillance.

CD172a is involved in various physiological and pathological processes, including inflammation, infection, and cancer. Dysregulation of CD172a expression or function has been implicated in autoimmune diseases, chronic infections, and tumor progression. Understanding the role of CD172a in these processes may provide insights into the development of novel therapeutic strategies for immune-related disorders.