Peptide hormones internalization

Y2. Yandle, T. G The natriuretic peptide hormones. Biochemistry of natriuretic peptides. J. Intern. Med. 235,561-576(1994). 

As would be expected of active protein secreting cells, glandular epithelial tissue, the cytokine secreting cells of the immune system and the blood vessel endothelium, have an extensive internal structure consisting of rough endoplasmic reticulum and numerous mitochondria. Peptide hormones, growth factors and cytokines like all proteins are synthesized by DNA transcription and mRNA translation. The primary transcript of the mRNA may code for an inactive prohormone which requires careful proteolysis to produce the active hormone, as for example in the case of insulin. Adrenocorticotropic hormone (ACTH) is particularly interesting in this respect because... 

It should be pointed out, however, that not all hormones dissociate from their receptor in the pH 5.5 environment of the endosome [24], Some hormone-receptor complexes require much lower pH values for dissociation to occur. Although not a peptide hormone, the iron-transport protein transferrin is a peculiar example of this phenomenon and should be pointed out. In this case, at the neutral pH of the extracellular fluid transferrin containing bound iron binds to its cell surface receptor and is internalized. In the low pH environment of the endosome, iron becomes dissociated from transferrin, but transferrin remains bound to its receptor. The transferrin receptor, with bound transferrin, is then recycled to the cell surface. With iron no longer bound to the transferrin, the transferrin readily dissociates from its receptor at the neutral pH of the extracellular fluid [25,26]. This mechanism provides for an efficient continual uptake of iron into cells. Unlike transferrin, however, in those instances where peptide hormones have been documented not to be dissociated from their receptor in the endosome compartment, the hormone and receptor are delivered to the lysosomes via fusion of the endosomes with lyso-somes, where both hormone and receptor are degraded [24,27]. The continuous degradation of the receptor with each round of RME eventually leads to a decrease in the number of receptors on the cell surface, a phenomenon called down-regulation. 

DOTATATE, the somatostatin (cyclic peptide hormone) analogue TATE coupled with the macrocyclic chelator DOTA, is currently being studied for use for internal peptide receptor radionuclide therapy (PRRT). Two radionuclides, carrier-free and Lu obtained from enriched 1. ii. were used for labelling the peptide. 

Menotropins are a natural product that is obtained from the urine of postmenopausal women and then biologically standardized (International units [lU]) for FSH and LH activities in an approximate ratio of 1 1. Menotropins are used in males with primary (hypothalamic) or secondary (pituitary) hypogonadism to stimulate spermatogenesis, providing they have been treated previously with human chorionic gonadotropin (hCG a peptide hormone of placental origin that has activity very similar to LH discussed below) to effect masculinization (increased testosterone... 

Receptor down-regulation, internalization of a receptor induced by an excess of a peptide hormone, leading to disappearance of the receptor. This results in a temporary stimulation, followed by inhibition of the target cells. 

C5H7NO3, Mr 129.12, mp. 162-163°C, [a]g -11.9 (HjO). An internal amide of glutamic acid. It occurs in fruits, grasses, and molasses it is the (V-terminal component of a series of peptide hormones such as go-nadoliberin, thyroliberin, neurotensin, and gastrin and also occurs in bombesin and caerulein. 

Hruby, Victor J. (p. 246), born in Valley City, N. Dakota USA in 1938, Ph.D. Cornell Univ. 1965, Prof, of Chem. Univ. of Arizona since 1977. He became interested in peptide hormones as a postdoctoral fellow with Nobel prize-winner Vincent du Vigneaud at Cornell University in the late 1960s just before he joined the University of Arizona faculty. In the 20 years since, he has become a world leader in this important research field (synthesis, isolation, conformations, dynamics, mechanisms of action, and structure-activity relationships of peptide hormones and neurotransmitters and their analogs). He is the editor of the International Journal of Peptide and Protein Research as successor to Choh Hao Li who died in 1988. 

Stress can be defined as the physiological reaction of an organism to external or internal stimuli in which the body initiates various defense mechanisms to maintain homeostasis (Ramsey 1982 Cruz et al. 2012). The stress response involves a complex network of mechanisms essential for survival, mediated by neurotransmitters, peptidic hormones, and endocrine hormones from the enteric nervous system (ENS). These molecules modulate the humoral and cellular components of the intestinal immune system (de Jonge 2013). 

Insulin is a polypeptide hormone that consists of two peptide chains bonded by two disulfide bonds. The two chains are designated A and B. The A chain consists of 21 amino acids with a third internal disulfide bond, and the chain contains the remaining 30 amino acids. All vertebrates produce insulin and the structure is similar in these species. For example, the insulin produced in humans and porcine species differs by only one amino acid, and humans and bovine insulin differ by three amino acids. Insulin plays a crucial role in several physiological processes. These include the regulation of sugar in the body, fatty acid synthesis, formation of triglycerides, and amino acid synthesis. 

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