PubMed · 6125946
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D T Krieger. 1982. Brain peptides.. https://pubmed.ncbi.nlm.nih.gov/6125946/
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The interrelationship between the hypothalamic-pituitary-adrenal (HPA) activity and expression of central opioids is determined in ischemic Sprague-Dawley rats to support the therapeutic role of naloxone against cerebral ischemia. Two-month old rats received bilateral common carotid artery occlusion plus unilateral (right side) middle cerebral artery occlusion for 90 min under the anesthesia, and followed by reperfusion for various times. The plasma contents of adrenocorticotropin (ACTH) and RNA expression levels of proopiomelanocortin (POMC) were then determined in ischemic rats with or without naloxone treatment. Results showed that ischemia stimulates but reperfusion suppresses the activity of HPA axis. The induced expression of POMC at striatum and cortex areas appears to suppress the release of ACTH from the HPA axis. The suppression on the other hand is prevented by naloxone.
We studied the consequence of taurine release within the supraoptic nucleus (SON) for the hormonal stress response. Rats were chronically implanted with both microdialysis probes in the SON and jugular venous catheters. Three days later the animals received either Ringer's solution or a specific taurine antagonist via retrodialysis directly into the SON during a 10-min forced swimming session, while simultaneously blood samples were collected. Compared to the Ringer's control, treatment with the taurine antagonist significantly attenuated the increase in plasma corticotropin concentration caused by the stressor exposure (P < 0.05, analysis of variance). This finding supports the hypothesis that the hypothalamic-neurohypophysial system is a potent regulator of the hormonal stress response and suggests an important role for taurine in this context.
The biosynthesis of most biologically active peptides involves the action of prohomone convertases, including PC3 (also known as PC1), that catalyze limited proteolysis of precursor proteins. Proteolysis of prohormones occurs mainly in the granules of the regulated secretory pathway. It has been proposed that the targeting of these processing enzymes to secretory granules involves their association with lipid rafts in granule membranes. We now provide evidence for the interaction of the 86 and 64 kDa forms of PC3 with secretory granule membranes. Furthermore, both forms of PC3 were resistant to extraction with TX-100, were floated to low-density fractions in sucrose gradients, and were partially extracted upon cholesterol depletion by methyl-beta-cyclodextrin, indicating that they were associated with lipid rafts in the membranes. Protease protection assays, immunolabeling, and biotinylation of proteins in intact secretory granules identified an approximately 115-residue cytoplasmic tail for 86 kDa PC3. Using two-dimensional gel electrophoresis and a specific antibody, a novel, raft-associated form of 64 kDa PC3 that contains a transmembrane domain consisting of residues 619-638 was identified. This form was designated as 64 kDa PC3-TM, and differs from the 64 kDa mature form of PC3. We present a model of the membrane topology of PC3, where it is anchored to lipid rafts in secretory granule membranes via the transmembrane domain. We demonstrate that the transmembrane domain of PC3 alone was sufficient to target the extracellular domain of the IL2 receptor alpha-subunit (Tac) to secretory granules.