Biological activities of Bv8 analogues

1. The small protein Bv8, secreted by the skin of the frog Bombina variegata, belongs to a novel family of secreted proteins whose orthologues have been identified in snakes (MIT) and in mammals (prokineticins (PKs)). A characteristic feature of this protein family is the same N-terminal sequence, AVITGA, and the presence of 10 cysteines with identical spacing in the C-terminal domain. Two closely related G protein-coupled receptors that mediate signal transduction of Bv8/PKs have been cloned (PK-R1 and PK-R2). In mammals, the Bv8/PK protein family is involved in a number of biological activities such as ingestive behaviours, circadian rhythms, angiogenesis and pain sensitization. 2. In an attempt to identify the structural determinants required for the pronociceptive activity of Bv8, we prepared Bv8 derivatives lacking one (des-Ala-Bv8) or two (des-Ala-Val-Bv8) residues from the N-terminus. 3. des-Ala-Bv8 displayed a receptor affinity five times lower than that of Bv8, it was five times less potent in inducing [Ca(2+)](i) transients and in causing p42/p44 MAPK phosphorylation in CHO-cells expressing PK-R1 and PK-R2. Moreover, dA-Bv8 was about 20 times less potent than Bv8 in inducing hyperalgesia in rats. 4. The deletion of the first two amino acids of Bv8 abolished any biological activity both ‘in vitro' and ‘in vivo'; however, des-AlaVal-Bv8 is able to antagonize the Bv8-induced hyperalgesia, binding the PK-Rs on peripheral and central projections of the primary sensitive neurons