CD150, also known as Signaling Lymphocytic Activation Molecule (SLAM), is a protein found on the surface of immune cells. This protein regulates the immune system, influencing how immune cells communicate and respond to threats. Beyond its immune functions, CD150 has a key role as a gateway for certain viruses to enter cells. Understanding this protein helps explain aspects of immune health and how specific viruses cause disease.
The Identity of CD150
CD150 is a complex glycoprotein, a protein with attached sugar chains, located on the outer surface of various immune cells, including T cells, B cells, and dendritic cells. Its structure has three main parts: an extracellular domain, a transmembrane domain, and a cytoplasmic domain.
The protein is encoded by the SLAMF1 gene on human chromosome 1. This gene is highly similar between humans and mice. Through alternative splicing, the SLAMF1 gene produces several isoforms of the CD150 protein. These isoforms include a membrane-bound form, a secreted form, and a cytoplasmic form, each potentially having distinct functions.
How CD150 Regulates Immune Responses
CD150 regulates the immune system by acting as a co-receptor for lymphocyte activation. Lymphocytes are white blood cells, and their activation is essential for immune responses. When CD150 interacts with other molecules on immune cells, it fine-tunes the signals that determine how these cells become active.
The protein also participates in cell-to-cell adhesion, allowing immune cells to physically interact. These interactions are important for recognizing and responding to foreign invaders or abnormal cells. CD150 mediates intracellular tyrosine phosphorylation signals. This process, involving adding phosphate groups to tyrosine molecules, acts like a switch to turn on or off cellular processes, including immune cell communication and function.
These regulatory roles ensure balanced immune responses, preventing them from being too weak or overactive. For example, CD150 influences the production of signaling molecules by T helper 1 cells and regulates proliferation and antibody production in B cells. Such balanced regulation helps the body effectively fight infections while avoiding damage to its own tissues.
CD150 as a Viral Gateway
CD150 serves as a cellular entry receptor for the measles virus. The measles virus uses its hemagglutinin (H) protein to bind to CD150 on target cells. This binding is the initial step for the virus to enter the cell and begin its replication cycle.
The measles virus’s ability to utilize CD150 explains its infection of immune cells and associated immune suppression during measles infection. Infection of immune cells can weaken the body’s ability to fight off other infections, leading to complications. Studies involving measles virus strains less efficient at recognizing CD150 have shown reduced virulence and disease severity in animal models.
Understanding this interaction is key for developing strategies against measles. Interfering with the binding of the measles virus to CD150 could block viral entry and prevent infection. This knowledge highlights CD150 as a promising target for research into new antiviral therapies or improved vaccine approaches for measles.