Secreted proteins, 8-11 kDa with C’ a-helix, 3 anti-parallel b-strands, and activate GPCR and GAG
Alpha or CXC: first two conserved cysteines separated, active mainly on neutrophils
Beta or CC: first two conserved cysteines adjacent; active on monocytes, lymphocytes, basophils.
Chemokine Receptors are 7 transmembrane glycoproteins
Variable N’ determines chemokine specificity. Variable C’ determines interactions with molecules.
Chemokine receptors are specific (one che mokine), shared (several chemokines of same branch) or
promiscuous (multiple chemok ines across branches)
Fractalkine: chemoattractant AND adhesion molecule
Found on activated endothelium. Surface for m is a cell adhesion molecule that induces cell activation.
Soluble form attracts monocytes, NK cells, and CD8+ T lymphocyte.
FKN induces leukocyte capture since monocytes, CD8+ T cells, and NK cells adhere to FKN
Mouse Cardiac Allotransplantation rejection
Rejected grafts were harvested; immuno-stained using anti-FKN Ab and compared to isograft controls.
Anti-CX3CR1 treatment prolongs cardiac allograft survival.
Fractalkine expression is increased in acute renal allograft rejection.
Fractalkine and CX3CR1 in Atherosclerosis
FKN-/- and CX3CR1-/- mice have less atherogenesis
Human CX3CR1 polymorphisms protect against cardiovascular disease.
Where is FKN expressed in cells?
FKN-GFP is expressed in PM and in juxtanuclear compartment that overlaps but is not identical to RE.
Cell surface FKN is internalized and FKN co-localizes with AP-2 and clathrin
Inhibition of dynamin-1 or Clathrin siRNA prevents internalization of FKN.
Disruption of AP-2-binding cytoplasmic tail of FKN prevents internalization of chemokine?
Deletion of the cytoplasmic tail of FKN prevents internalization of the chemokine
Disruption of both AP-2-binding motifs decreases internalization of FKN.
Constitutive endocytosis of FKN prevents its degradation by cell surface metalloproteases
In steady state, internalized FKN cycles back to the plasma membrane.
Cell surface FKN undergoes clathrinmediated endocytosis.
The juxtanuclear compartment represents a specialized recycling compartment.
Traff ic of internalized FKN back to PM is mediated by SNARE protein, VAMP-3 and syntaxin-13.
TP stimulation leads to FKN shedding, mobilizes PM FKN, increase FKN-dependent leukocyte adhesion whereby
FKN clusters at sites of contact with adherent leukocytes that enhances the avidity.
Slit and Robo: Neuronal Guidance Cues