Seven-transmembrane receptors (7TMRs) comprise a large family of membrane-bound proteins that share a unifying signal transduction mechanism (i.e., upon activation, these receptors signal through G proteins). These receptors are involved in a vast variety of physiological functions, including neurotransmission, function of exocrine and endocrine glands, smell, taste, vision, chemotaxis, embryogenesis, development, human immunodeficiency virus (HIV) infection, oncogenesis, cell growth, and differentiation. More recent studies indicate that these receptors are also associated with and signal through other molecules (1). Therefore, it is more appropriate to use the term 7TMR than G protein-coupled receptors (GPCRs).