Chemotaxis is mediated by?
**Core Concept**
Chemotaxis is the movement of cells in response to chemical signals, playing a crucial role in various physiological processes such as inflammation, wound healing, and immune response. It involves the detection of chemical gradients by specialized receptors on the cell surface, triggering a series of signaling events that ultimately lead to cell migration.
**Why the Correct Answer is Right**
Chemotaxis is primarily mediated by G-protein coupled receptors (GPCRs) that are activated by chemokines, a family of small cytokines that bind to specific receptors on the surface of immune cells. The binding of chemokines to their receptors triggers a signaling cascade that activates downstream effectors, including phospholipase C (PLC), which ultimately leads to the reorganization of the actin cytoskeleton and cell movement. The chemokine receptors are specifically expressed on the surface of immune cells, such as T cells and neutrophils, allowing them to respond to specific chemokine gradients.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because chemokines, not chemotaxis, are the primary molecules involved in mediating cell movement.
**Option B:** This option is incorrect because although GPCRs are involved in chemotaxis, they are not the sole mediators of this process. Other signaling pathways, such as those involving phosphoinositide 3-kinase (PI3K), also play critical roles.
**Option C:** This option is incorrect because while actin cytoskeleton reorganization is a critical step in chemotaxis, it is not the primary mediator of this process.
**Clinical Pearl / High-Yield Fact**
Chemokines and their receptors are critical in the pathogenesis of various inflammatory and autoimmune diseases, such as rheumatoid arthritis and multiple sclerosis, making them important targets for therapeutic intervention.
**Correct Answer:** C. G-protein coupled receptors (GPCRs)