A Study of the Membrane Anchored Chemokine CX3CL1 and Its Receptor CX3CR1
Abstract: C-X3-C motif
chemokine receptor 1 (CX3CR1) is a G protein-coupled chemokine receptor and a key
regulator of neuroinflammation and response to injury. This GPCR is considered a
putative therapeutic target in diseases associated with inflammation. CX3CR1 is thought
to modulate inflammation in the central nervous system (CNS) and cardiovascular system.
The endogenous ligand for this ... read morereceptor, C-X3-C motif chemokine ligand 1 (CX3CL1; also
known as Fractalkine) has a unique structure compared to other chemokine family members.
CX3CL1 is a 95 kDa protein comprised of a chemokine domain, a glycosylated mucin-like
stalk, a transmembrane domain, and a cytoplasmic domain. In addition to its endogenous
full-length membrane anchored form, CX3CL1 is cleaved at different sites, creating
alternative forms of soluble ligand. The pharmacological properties of such truncated
isoforms and the full-length ligand differ yet have not been well defined. The focus of
our project is to probe the functional role of each CX3CL1 domain. In the Kopin
laboratory, we have utilized the recombinant membrane tethered ligand (MTL) system in
combination with in vitro signaling assays to investigate structure-function properties
of CX3CL1. We have generated and pharmacologically characterized a series of CX3CL1
deletion mutants and domain swaps. The endogenous full-length CX3CL1 (407 amino acids)
activates CX3CR1 without triggering desensitization. In contrast, a tethered chemokine
domain (76 amino acids) construct results in receptor-mediated signaling and induces
receptor desensitization. Notably, a tethered construct which includes both the
chemokine domain and the glycosylated mucin-like stalk results in an intermediate level
of signaling and desensitization. Current studies are underway to further map the
residues which underlie these pharmacological properties. Polymorphisms of CX3CR1 are
also explored. Taken together, our experiments help us better understand the molecular
basis of CX3CL1/CX3CR1 function and lay the groundwork to develop modulators of CX3CR1
as potential treatments for neurological and cardiovascular
Thesis (M.S.)--Tufts University, 2017.
Submitted to the Dept. of Pharmacology & Experimental Therapeutics.
Advisor: Alan Kopin.
Keyword: Pharmacology.read less