The pro-opiocortin (POMC) molecule is an excellent model with which to investigate questions of processing, differential regulation, and function in diverse mammalian tissues at different points in the life span, and additionally with regard to peptide evolution.
Our Specific Aims are to: I. Determine factors influencing synthesis, processing, and regulation of POMC in diverse tissues. (a) Human anterior pituitary: To delineate more fully cleavage products other than ACTH, Beta-LPH, and Beta-endorphin which may be of potential physiological importance, (b) Rat intermediate lobe: To study neural and peptidergic regulation of POMC and the basis of its glucocorticoid nonsuppressibility. Such studies are also relevant to regulation of brain POMC and to human Cushing's disease (see IV); (c) Brain: To study in vivo in young and old animals neurotransmitter, steroid, and stress regulation of POMC synthesis and processing; (d) Male reproductive tract: To study POMC synthesis and the role of POMC-derived peptides in regulation of reproductive function. II. To determine if POMC present in different tissues and in different organisms is structurally similar to that in anterior pituitary. Studies in Tetrahymena: This will be of evolutionary importance when compared to the known structure of mammalian, rodent, and human forms, while those on human placenta, reproductive tract, and rat brain, when compared to their known pituitary homologues, will add to the very limited information available of sequence similarity or dissimilarity for a given peptide in different tissues. III. To determine if POMC mRNA can be detected in placenta, male reproductive tract, and unicellular organisms. This will provide major confirmation that the detected presence of a given peptide in diverse tissues or organisms represents actual synthesis and would presume a significant physiological role. IV. To delineate disturbances of POMC regulation in Cushing's disease (CD). (a) Studies in the canine model will provide information as to alterations in brain neurotransmitters and CRF regulatory mechanisms that might apply to the pathogenesis of human CD: (b) to assess the role of CRF in the pathogenesis of human CD by studying its mitogenic effect on pituitary corticotrophs; (c) In patients with CD, to characterize plasma forms of POMC peptides and the neuropharmacological regulation of dexamethasone suppressibility so as to establish whether subgroups of CD exist, which should enable design of more appropriate therapeutic approaches.
| Antakly, T; Sasaki, A; Liotta, A S et al. (1985) Induced expression of the glucocorticoid receptor in the rat intermediate pituitary lobe. Science 229:277-9 |
