Based on the provided reference, "RAC" refers to Rac GTPases, which are small G-proteins widely implicated in tumorigenesis and metastasis. While the provided reference touches on cancer biology, it doesn't directly focus on broader immunology concepts. Therefore, defining "RAC" solely within immunology requires a broader understanding.
Let's break down the role of Rac GTPases, and then place them in an immunological context:
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Rac GTPases: Molecular Switches: These proteins act as molecular switches, cycling between an inactive (GDP-bound) and an active (GTP-bound) state. This cycling is tightly regulated by guanine nucleotide exchange factors (GEFs), GTPase-activating proteins (GAPs), and guanine nucleotide dissociation inhibitors (GDIs).
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Signaling Pathways: When activated, Rac GTPases initiate downstream signaling cascades. According to the reference, they transduce signals from tyrosine-kinase, G-protein-coupled receptors (GPCRs), and integrins.
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Cellular Functions: These signaling cascades control critical cellular functions, including:
- Motility: Cell movement, important for immune cell trafficking.
- Adhesion: How cells stick to each other or the extracellular matrix.
- Proliferation: Cell growth and division, vital for immune responses.
RAC in the Immune System
In immunology, Rac GTPases play crucial roles in various immune cell functions:
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T Cell Activation: Rac GTPases are essential for T cell receptor (TCR) signaling and activation. They regulate the formation of the immunological synapse, the contact zone between a T cell and an antigen-presenting cell (APC). Rac activation is critical for proper T cell activation and effector function.
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B Cell Activation: Similarly, Rac proteins participate in B cell receptor (BCR) signaling and B cell activation. They influence B cell migration to lymphoid follicles and antibody production.
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Neutrophil Function: Neutrophils, a type of phagocytic immune cell, rely heavily on Rac GTPases for chemotaxis (movement towards a chemical signal), phagocytosis (engulfing pathogens), and the generation of reactive oxygen species (ROS) to kill microbes.
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Macrophage Function: Macrophages utilize Rac GTPases for similar functions as neutrophils, including phagocytosis and migration. Rac also regulates macrophage polarization (M1 vs. M2 phenotypes), influencing the type of immune response.
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Dendritic Cell Migration: Dendritic cells (DCs) are antigen-presenting cells that bridge the innate and adaptive immune systems. Rac GTPases are vital for DC migration from peripheral tissues to lymph nodes, where they present antigens to T cells and initiate adaptive immunity.
Summary Table
| Immune Cell Type | Function | Rac GTPase Role |
|---|---|---|
| T Cells | Activation, Effector Function | TCR signaling, immunological synapse formation |
| B Cells | Activation, Antibody Production | BCR signaling, migration to lymphoid follicles |
| Neutrophils | Chemotaxis, Phagocytosis, ROS Production | Cell movement, engulfing pathogens, generating reactive oxygen species |
| Macrophages | Phagocytosis, Migration, Polarization | Engulfing pathogens, cell movement, influencing M1/M2 phenotypes |
| Dendritic Cells | Migration, Antigen Presentation | Migration to lymph nodes, initiating adaptive immunity |
