HIP-70: a Protein Induced by Estrogen in the Brain and LH-RH in the Pituitary

Estrogen and luteinizing hormone-releasing hormone (LH-RH) interact to influence both behavior and gonadotropin release. However, little is known about the biochemical mechanisms that mediate the effects of these hormones or their interactions. The most prominent protein induced by estrogen in the ventromedial hypothalamus has the same amino-terminal sequence as the most prominent protein induced by LH-RH in the pituitary in vitro and in vivo; these proteins comigrate on two-dimensional gels. Furthermore, the hormonal induction may be caused by modification of a constitutive protein with the same molecular weight (70,000) but a slightly more acidic isoelectric point, whose level is inversely related to the level of the induced form after estrogen treatment. Thus estrogen and LH-RH may interact by additively or synergistically inducing this protein, which is called HIP-70.