The yin and yang of chemokine receptor activation

Pathogen recognition by sensory neurons: hypotheses on the specificity of sensory neuron signaling

Sensory neurons cooperate with barrier tissues and resident immune cells to form a significant aspect of defensive strategies in concert with the immune system. This assembly of neuroimmune cellular units is exemplified across evolution from early metazoans to mammalian life. As such, sensory neurons possess the capability to detect pathogenic infiltrates at barrier surfaces. This capacity relies on mechanisms that unleash specific cell signaling, trafficking and defensive reflexes. These pathways exploit mechanisms to amplify and enhance the alerting response should pathogenic infiltration seep into other tissue compartments and/or systemic circulation. Here we explore two hypotheses: 1) that sensory neurons' potential cellular signaling pathways require the interaction of pathogen recognition receptors and ion channels specific to sensory neurons and; 2) mechanisms which amplify these sensing pathways require activation of multiple sensory neuron sites. Where possible, we provide references to other apt reviews which provide the reader more detail on specific aspects of the perspectives provided here.

Targeting chemokine receptors from the inside-out: discovery and development of small-molecule intracellular antagonists

Ever since the first biologically active chemokines were discovered in the late 1980s, these messenger proteins and their receptors have been the target for a plethora of drug discovery efforts in the pharmaceutical industry, as well as in academia. Owing to the publication of several chemokine receptor X-ray crystal structures, a highly druggable, intracellular, allosteric binding site which partially overlaps with the G protein binding site was discovered. This intriguing, new approach for chemokine receptor antagonism has captured researchers around the world, pushing the exploration of this intracellular binding site and new antagonists thereof. In this review, we have highlighted the past two decades of research on small-molecule chemokine receptor antagonists that modulate receptor function at the intracellular binding site.

Understanding the mechanisms that facilitate specificity, not redundancy, of chemokine-mediated leukocyte recruitment

Chemokines (chemotactic cytokines) and their receptors are critical to recruitment and positioning of cells during development and the immune response. The chemokine system has long been described as redundant for a number of reasons, where multiple chemokine ligands can bind to multiple receptors and vice versa. This apparent redundancy has been thought to be a major reason for the failure of drugs targeting chemokines during inflammatory disease. We are now beginning to understand that chemokine biology is in fact based around a high degree of specificity, where each chemokine and receptor plays a particular role in the immune response. This specificity hypothesis is supported by a number of recent studies designed to address this problem. This review will detail these studies and the mechanisms that produce this specificity of function with an emphasis on the emerging role of chemokine–glycosaminoglycan interactions.