New Insights into Ligand-Receptor Pairing and Coevolution of Relaxin Family Peptides and Their Receptors in Teleosts
Figure 4
Ligand-receptor pairings of the Rln/Insl peptides and their Rxfp receptors putatively associated with (a) reproductive and (b) neuroendocrine processes in teleosts as hypothesized based on mammalian pairings and on their gene duplication history (see Figures 1 and 3). Few tetrapods (reptiles, frog, and opposum) and zebrafish have been found to possess the receptor rxfp2-like, which is phylogenetically more closely related to rxfp2 than rxfp1, but still of ancient origin [2]. However, the lack of insl3 in the reptiles, that also harbour rxfp2-like (data from [2]), suggests that Rln may be an alternate ligand. +Zebrafish retained two 3R paralogs of rxfp2, rxfp2a, and rxfp 2b, while the remaining teleosts appear to have lost one copy. *In zebrafish, the rxfp4 gene was lost and possibly replaced by rxfp3-3a3 (see Figures 3 and 4). Images of receptors and peptides adopted with permission from the publisher for Halls et al. [5] and Kong et al. [6].
