[Interactions between prolactin with its receptor].

Abstract

The prolactin (PRL) receptor has recently been sequenced. The rat PRL receptor is a linear glycosylated polypeptide of 291 amino-acids. The major part of the molecule is located on the external part of the cellular membrane. Recently, a larger form of the receptor has been evidenced in rabbit, and man, which presents some partial structural homology with the sequence of the growth hormone receptor. The PRL receptor, distributed in various tissues, is located in equivalent quantities in the peripheral and internal membranes of the cells. The transduction mechanism(s) from the activated receptor to the genes controlling the expression of different prolactin-induced-proteins is not yet well understood. Prolactin is the main hormone involved sequentially in the down and up-regulation of the PRL receptors number. Such a long-term induction of receptors by PRL is evidenced under physiological conditions such as pregnancy and lactation. The recent demonstration of different molecular forms of PRL generated after the transduction of the hormone (glycosylated PRL, cleaved PRL, 16K fragment) introduces the hypothesis that the interaction between the hormone and its receptor is probably more complex. These different prolactins are still capable of binding to the receptor and their biological activities are more or less conserved. The physiological or pathological significance of such an heterogeneity of the PRL molecule needs to be further confirmed.