CX3Ckemokineja

CX3C chemokines are a small family of chemokines defined by the presence of three amino acids (X) separating the first two cysteine residues, yielding a C-X3-C motif. They are chemokines involved in leukocyte trafficking and cell adhesion. The prototypical member in humans is CX3CL1, also known as fractalkine.

CX3CL1 is unusual among chemokines in that it exists as both a membrane-bound protein and a soluble chemokine. The membrane form is produced by a type I transmembrane protein with a mucin-like stalk that presents the chemokine domain on the cell surface; proteolytic cleavage releases a soluble form that can function as a chemoattractant.

The receptor for CX3CL1 is CX3CR1, a G protein-coupled receptor expressed on subsets of monocytes, NK cells, cytotoxic T cells, and certain brain cells. Binding of CX3CL1 to CX3CR1 activates signaling pathways that regulate leukocyte adhesion, migration, and survival.

Physiological roles include immune surveillance, inflammation, vascular biology, and neuroimmune communication. In the CNS, fractalkine signaling modulates microglia-neuron interactions and participates in neuroinflammation and neurodegenerative disease processes. Altered CX3CR1-CX3CL1 signaling has been implicated in conditions such as atherosclerosis, inflammatory diseases, and pain.

Therapeutic interest centers on modulating CX3CR1 signaling to control inflammation or neurodegeneration. Regulation occurs at the level of transcription, proteolytic shedding, and receptor signaling, with ongoing research in animal models and clinical studies.