This volume and its companion, Volume 339, supplement Volumes 176, 177, 239, and 261. Chapters are written with a "hands-on" perspective. That is, practical applications with critical evaluations of methodologies and experimental considerations needed to design, execute, and interpret NMR experiments pertinent to biological molecules.

Chemokines are involved in cell migration and activation during routine immune surveillance, inflammation and even cancer metastasis. The migration of chemokine receptor-bearing cells, including leukocytes and tumor cells, occurs in response to the secretion of chemokines, which accumulate on cell surfaces through interaction with glycosaminoglycans (GAGs) where they effectively serve as traffic signals to guide cell movement. Engagement of chemokines with their receptors subsequently causes the activation of signaling pathways that result in firm adhesion and extravasation of the cell into tissue, and in the case of leukocytes, activation of defense mechanisms. However, in cancer cells, the signaling pathways can be exploited or redirected, resulting in responses like survival, growth and proliferation. Herein, a structural and functional approach was used to address specific questions about the interactions of chemokines (i) with GAGs and (ii) with chemokine receptors in the context of cancer. Technically, the use of mass spectrometry has been a strong theme throughout these studies. In Chapter 2, a novel application of hydroxyl radical footprinting coupled with mass spectrometry was used to characterize the GAG binding specificity of the chemokine, MCP-3/CCL7. Potential GAG binding epitopes, identified by mass spectrometry, were then validated by mutagenesis and functional assays. In Chapter 3 and 4, a phosphoproteomic mass spectrometry strategy was used to elucidate CXCL12-mediated survival signaling through the receptor, CXCR4, in cells from patients with chronic lymphocytic leukemia (CLL). While signaling cascades involved in chemokine-mediated migration are well established, pathways involved in cell survival and proliferation in cancer, are not. Methods developed for phosphopeptide enrichment, and subsequent analysis via mass spectrometry are described in Chapter 3, and interesting/novel phosphoproteins, potentially involved in CXCL12-mediated CLL survival are described in Chapter 4. In Chapter 5, a functional approach was taken to elucidate the roles of receptors CXCR4 and CXCR7 in breast cancer growth and metastasis. The data show that CXCR7 affects the functional activity of CXCR4 in vitro, and decreases the extent of lung metastases in vivo, without inhibiting primary tumor growth. Overall, these studies serve to better understand some of the regulatory mechanisms that control chemokine function in normal physiology and in cancer.

The understanding of chemokines, the proteins that control the migration of cells, and their receptors, is critical to the study of causes and therapies for a wide range of human diseases and infections, including certain types of cancer, inflammatory diseases, HIV, and malaria. This volume, focusing on chemokine structure and function, as well as signaling, and its companion volume (Methods in Enzymology volume 461, focusing on chemokines as potential targets for disease intervention) provide a comprehensive overview and time-tested protocols in this field, making it an essential reference for researchers in the area. - Along with its companion volume, provides a comprehensive overview of chemokine methods, specifically as related to potential disease therapy - Gathers tried, tested, and trusted methods and techniques from top players in chemokine research - Provides an essential reference for researchers in the field

It has been shown that the amino terminus and second extracellular loop (EC2) of CXCR2 are crucial for ligand binding and receptor activation. The lack of an ionic lock motif in the third intracellular loop of CXCR2 focuses an investigation of the mechanism by which these two extracellular regions contribute to receptor recognition and activation. The first objective of this investigation was to predict the structure of CXCR2 based on known structures of crystallized GPCRs. Rhodopsin, [beta]2- adrenergic receptor, CXCR4 were used for homology modeling of CXCR2 structure. Highly conserved motifs found in sequence alignments of the template GPCRs were helpful to generate CXCR2 models. We also studied solvent accessibility of residues in the EC2 of CXCR2 in the inactive state. Most of the residues in the EC2 were found to be solvent accessible in the inactive state, suggesting the residues might be involved in ligand recognition. Second, we studied the role of charged residues in the EC2 of CXCR2 in ligand binding and receptor activation using constitutively active mutants (CAM) of CXCR2, D9K and D9R. Combinatorial mutations consisting of the CAM in the amino terminus and single mutations of charged residues in the EC2 were generated to study two concepts including "attraction" and "repulsion" models. The mutant receptors were used to test their effects on cell surface expression, ligand binding, receptor activation through PLC-[beta]3, and cellular transformation. All the mutations in the repulsion model result in CXCR2 receptors that are unable to bind ligand, suggesting that each of the Arg residues in the EC2 are important for ligand recognition. Interestingly, mutations in the attraction model partially inhibited receptor activation by the CAM D9K, suggesting that Glu198 and Asp199 residues in the EC2 are associated with receptor activation. Furthermore, a novel CAM, E198A/D199A, was identified in this study. These negatively charged residues are very close to a conserved disulfide bond linking the EC2 and the third transmembrane. In this sense, these current discoveries concerning the structural basis of CXCR2 and interdisciplinary approaches would provide new insights to investigate unknown mechanisms of interaction with its cognate ligands and receptor activation.

Chemokine receptors belong to the G protein-coupled receptor (GPCR) family of proteins and are critical mediators of the directed migration of leukocytes in innate and adaptive immune responses. Understanding the behavior of chemokine receptors under basal and agonist-stimulated conditions is essential to developing effective therapeutics for inflammatory and autoimmune diseases. For the first time, the constitutive activity of the C-C chemokine receptor type 1 (CCR1) is uncovered through ligand-independent cellular migration, constitutive phosphorylation and association with [beta]-arrestin-2, and continual internalization followed by recycling back to the plasma membrane. Initial data suggests that CCR1 can act as a scavenging receptor to sequester chemokines intracellularly without canonical G protein signaling, thereby providing biological relevance to receptor constitutive activity. A Ser/Thr-rich cluster in the distal carboxy-terminal tail of CCR1 is identified as the major site of basal phosphorylation and fulfills a necessary, but not sufficient, role in pre-coupling to [beta]-arrestin-2. Site-directed mutagenesis of receptor transmembrane domains and conserved DRY motif has identified residues important for stabilizing CCR1 in a constitutively active state. Activation of CCR1 primarily leads to a conformational rearrangement with [beta]-arrestin-2, while endogenous chemokines induce this change with differential potency and efficacy. Lastly, small metal ion chelator molecules are able to activate desensitization and down-modulation of CCR1 with similar efficacy to natural ligands. Taken together, the work presented herein underlies the complexity of CCR1 function in the presence and absence of ligand and provides new avenues for therapeutic targeting.