Chapter 4.1 - Constitutive Roles for SDF-1/CXCR4 and Fractalkine/CX3CR1 in the CNS

Abstract

This chapter discusses the roles for chemokines in fundamental neurophysiological processes. Two chemokine systems, namely SDF-1 (CXCL12) and fractalkine (CX3CL1) and their respective receptors CXCR4 and CX3CR1, are prominently and constitutively expressed in the central nervous system (CNS). This expression pattern suggests that these chemokine ligand–receptor pairs exhibit fundamental roles in neurophysiology. Functional insights into the specific capacities of these chemokine receptor systems in neurophysiology have also been suggested. A specific intercellular communication network, between neurons and microglia, is suggested by the predominant expression of fractalkine on neurons and CX3CR1 on microglia. Many signal transduction pathways are activated by fractalkine in cultured nervous system cells, including microglia, astrocytes, and neurons. The relative abundance of SDF-1 and CXCR4 in the CNS suggests fundamental roles for this chemokine system in neurophysiology. Pleiotropic roles for SDF-1 in the CNS seem likely given the expression pattern of this chemokine and its receptor, CXCR4, on cells of the CNS.