The heptahelical receptors for corticotropin-releasing factor (CRF), CRFR1 and CRFR2, display different specificities for CRF family ligands: CRF and urocortin I bind to CRFR1 with high affinity, whereas urocortin II and III bind to this receptor with very low affinities. In contrast, all the urocortins bind with high affinities, and CRF binds with lower affinity to CRFR2. The first extracellular domain (ECD1) of CRFR1 is important for ligand recognition. Here, we characterize a bacterially expressed soluble protein, ECD1-CRFR2␤, corresponding to the ECD1 of mouse CRFR2␤. The Corticotropin-releasing factor (CRF) 1 (1) is the major neuroregulator of the hypothalamic-pituitary-adrenal axis and, among other roles, serves to integrate the endocrine, autonomic, and behavioral responses to stress. In addition to its central nervous system actions, CRF and its related ligands also affect the cardiovascular, reproductive, gastrointestinal, skin, and immune systems (2). The CRF ligand family includes (frog) sauvagine, (fish) urotensins, mammalian urocortin I (3, 4), and the 38 amino acid peptides from the newly recognized genes urocortin II (5) and urocortin III (6), also known as stresscopin-related peptide and stresscopin (7).The actions of CRF ligands are initiated by binding to their receptors, whose activation results in an increase of intracellular cAMP, hydrolysis of phosphoinositol, activation of mitogen-activated protein (MAP) kinases (8, 9), and other signaling pathways (10). In mammals, two receptor types, CRFR1 and CRFR2, have been cloned (11-17); orthologous receptors have also been identified in many other species including chicken (18), fish (19), and Xenopus (20). A third receptor, CRFR3, with a high level of sequence identity to CRFR1, has been cloned in catfish (19). CRF receptors have been characterized in the central nervous system and various peripheral sites including pituitary, gastrointestinal tract, epididymis, heart, gonad, adrenal, skin, and skeletal muscle.The CRF receptors are 7-transmembrane domain proteins with relatively large first extracellular domains (ECD1s). Both CRFR1 and CRFR2 exist as multiple splice variants and belong to the type B receptor family that includes receptors for growth hormone-releasing factor, secretin, calcitonin, vasoactive intestinal peptide, glucagon, glucagon-like peptide (GLP), and parathyroid hormone (2).The ligand specificities in binding to CRFR1 and CRFR2 are markedly different. Although both CRF and urocortin I bind with equally high affinities to CRFR1, the affinity of CRF for CRFR2 is at least 10 times lower than that of urocortin I. There is no high affinity interaction of either urocortin II or urocortin III with CRFR1, whereas their affinities for CRFR2 are in the subnanomolar range. The agonist, sauvagine, and the peptide antagonist, astressin, have equally high affinities for both types of receptors (5,6,21).The majority of differences between the sequences of the two receptors are found in their ECD1s. Mutagenesis studies have identified regions o...

The CRF receptors are members of a 7-transmembrane receptor family that includes GH-releasing hormone (GRF), calcitonin, vasoactive intestinal peptide (VIP), secretin, and PTH receptors. To determine the structural features of the CRF receptor that may influence ligand recognition, a series of mutant receptors was analyzed for binding to astressin, a CRF antagonist, and to urocortin, a CRF agonist. Mutant receptors included chimeras between the CRF-R1 and GRF-R or Activin IIB-R, a single membrane spanning receptor serine/threonine kinase. Binding to the mutant receptors was assessed using 125I-[DTyr1] astressin (Ast*) and 125I-[Tyr0]-rat urocortin (Ucn*). There was no binding to a chimeric receptor in which the first extracellular domain (E1c) (i.e. the N-terminal region) of the CRF-R1 was replaced by that of the GRF-R. The complementary chimera in which E1 domain of the GRF-R was replaced by that of the CRF-R1 bound astressin and urocortin with Ki values approximately 10 nM, compared with inhibitory binding dissociation constant (Ki) values of approximately 2-4 nM for the wild-type CRF-R1. The chimera in which E1 of the activin IIB receptor was replaced by E1 of the CRF-R1 bound astressin with a Ki approximately 4 nM. A chimera in which both the first and fourth extracellular domains of the CRF-R1 replaced the corresponding domains of the GRF-R bound astressin with Ki approximately 4 nM and urocortin with a Ki approximately 2 nM. A chimera in which all four extracellular domains of the CRF receptor replaced those of the GRF-R bound astressin and urocortin with Ki values approximately 4 nM and approximately 1 nM, respectively. In conclusion, the major determinants for high affinity binding of CRF agonists and antagonists to CRF-R1 are found in the first extracellular domain of the receptor.

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Major outer membrane protein sequences, determined from Chlamydia-positive eye swab samples collected in 2 Egyptian villages, were used to analyze the epidemiology of trachoma in an endemic setting. Samples were collected during the 1999 Azithromycin in Control of Trachoma trial, in which residents of villages were mass treated with either oral azithromycin or topical tetracycline and were followed up for nearly 2 years. Three genovar families (A, Ba, and C) and 12 genovars were detected, with 2 genovars (A1 and Ba1) comprising almost 75% of the samples. The presence of >1 genovar within households was common, with > or =24% of households having >1 genovar. Evidence consistent with reinfection and persistence as mechanisms of communitywide continued presence of trachoma was provided by data for individuals infected with rare genovars.

Legalization of oral contraceptives in Japan has led to an urgent need to educate both men and women on the inability of the pill to protect against STDs, including HIV Policymakers and providers need to recognize the importance of encouraging dual method use in Japan.