The prolactin receptor from the brushtail possum (Trichosurus vulpecula): cDNA cloning, expression and functional analysis

A full length, prolactin receptor cDNA clone has been isolated from the bru shtail possum (Trichosurus vulpecula). This clone encodes a 625 amino acid protein which shares 60-70 and 54% sequence identity with prolactin recepto r (long form) sequences from mammalian and avian species, respectively. Seq uence similarity was highest in the extra-cellular, hormone-binding domain and in specific regions of the intracellular domain which regulates prolact in receptor signalling in cells. Prolactin receptor mRNA was detected in a wide range of possum tissues and in the mammary gland the PRL-R gene was di fferentially expressed during lactation with peak mRNA levels being detecte d during the first 6 days of lactation and after day 115 throughout late la ctation. This pattern of PRL-R mRNA expression in the mammary gland is simi lar to that observed for circulating prolactin in the lactating possum. In CHO cells transiently transfected with the possum prolactin receptor, expre ssion of a beta-lactoglobulin promoter/reporter gene construct was increase d 3-fold by adding prolactin. The possum prolactin receptor is therefore ca pable of binding ovine prolactin and activating the Jak2/Stat5 signalling c ascade. This provides evidence for the highly conserved nature of the prola ctin signalling pathway in mammalian evolution. (C) 1999 Elsevier Science I reland Ltd. All rights reserved.