Non-conventional locations of hormone receptors (binding sites). A review

Recent findings on the noncanonical positions of some well-known extracellular mediators and their receptors are reviewed. Peptide hormones (insulin) and/or their binding sites (cell membrane insulin receptor, nuclear insulin receptor); steroid hormones (corticosteroids and estrogens) and their putative membrane receptors are in the scope of this paper. The possible roles of these unusually located receptors in the intracellular signal propagation and physiological responses are also discussed.