Chemokine Receptors: Cloning Strategies

Chemokines activate leukocytes by binding to G protein-coupled receptors on the cell surface. Cloning DNA that codes for chemokine receptors is important because it can lead rapidly to detailed information about their structure, function, expression, regulation, and evolution, information that often cannot be obtained as readily or as precisely by studying the native protein directly. Many cloning strategies can be used; however, three common elements are required: (i) a library of cloned DNA molecules from an appropriate source; (ii) a gene transfer method for producing the receptor in a naive cell type; and (iii) functional assays to identify relevant clones or to qualify clones identified by other means. A particularly productive cloning strategy has been to isolate from a relevant library those DNA molecules that have sequence similarity to closely related G protein-coupled receptors and then to screen their encoded products with chemokine functional assays. This strategy has been used for five of the six known human leukocyte chemokine receptors, and two herpesvirus-encoded chemokine receptors. The cloning strategy that will lead most rapidly to success cannot be known a priori, since idiosyncratic properties of each receptor can foil even the most rational approach.