Discrete expression of insulin receptor substrate-4 mRNA in adult rat brain

The insulin receptor substrate (IRS) proteins are a family of important regulatory adapters that mediate the coupling between receptor-associated tyro sine kinases and downstream effecters including phosphatidylinositol-3'-kinases (PI-3 - Ks). In the present study, the distribution of IRS-4 mRNA was determined in rat brain by in situ hybridization. IRS-4 mRNA was widely expressed throughout the hypothalamus, with the most dense labeling observed in the medial preoptic nucleus, ventromedial hypothalamus, and arcuate nucleus. In contrast, and unlike IRS-1 or IRS-2, expression of IRS-4 mRNA in other forebrain and midbrain regions was much more restricted. The expression of IRS-4 mRNA in the hypothalamus suggests a specific role for this factor in the signaling of one or more receptors involved hypothalamic functions including feeding, lactation, sexual and parental behaviors. (C) 1999 Elsevier Science B.V. All rights reserved.