Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P01189 (beta-endorphin)
 21,003 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Secretory granules (SGs) from rat intermediate lobes (IL) were isolated in a highly purified form by differential centrifugation, followed by sucrose density gradient centrifugation. The purified IL-SGs were lysed by freezing and thawing. The granule lysate was then centrifuged to generate membrane and soluble fractions. Proopiocortin -converting enzyme (PCE) activity was assayed by incubation of [3H]arginine- or [3H] phenylalanine-labeled toad proopiocortin with the total granule lysate, the membrane, or the soluble fraction at pH 5.0. The processed products were identified by immunoprecipitation with ACTH and beta-endorphin antisera, followed by acid-urea-gel electrophoresis. The PCE activity in rat IL-SG lysate cleaved proopiocortin to 21,000 mol wt ACTH, 21,000 mol wt ACTH/lipotropin (LPH), 13,000 mol wt ACTH, beta LPH, beta-endorphin-like peptides, and alpha MSH-like peptides, similar to those synthesized by the toad intermediate lobe in situ. Treatment of the PCE cleavage products with carboxypeptidase B resulted in the liberation of free arginine. This observation together with the nature of the products formed suggest that the PCE activity cleaved at pairs of basic residues of proopiocortin , yielding one or more products that terminated with an arginine or an arginine-lysine. PCE activity was found in membrane and soluble granule fractions, and both activities were inhibited by leupeptin, p-chloromercuribenzoate, dithiodipyridine, and pepstatin A, but not by chloroquine or N-alpha-p-tosyl-L-lysine-chloromethylketone HCl. Diisopropyl fluorophosphate and other thiol protease reagents (p-chloromercuriphenyl sulfonic acid, iodoacetic acid, and HgCl2) had a small inhibitory effect. The products formed by PCE activities in the membrane and soluble fractions were similar to those cleaved by the total granule lysate. The membrane fraction primarily cleaved proopiocortin between ACTH and beta LPH to form 21,000 (21 K) mol wt ACTH and beta-LPH, similar to the first processing step in the IL in situ. The soluble fraction, however, showed a greater tendency to cleave proopiocortin between the 16 K N-terminal glycopeptide and ACTH, to yield twice as much 21 K ACTH/LPH product as the membrane fraction. The membrane-associated PCE activity was found to be easily solubilized by extraction with high salt (1 M NaCl), suggesting that it is not an integral granule membrane protein.
 ...
PMID:In vitro processing of proopiocortin by membrane-associated and soluble converting enzyme activities from rat intermediate lobe secretory granules. 632 33

This study was designed to examine the role of opioids in cell survival, with an emphasis on the mechanism of opioid growth factor (OGF, [Met(5)]-enkephalin)-dependent growth inhibition. Using three human cancer cell lines: MIA PaCa-2 pancreatic adenocarcinoma, HT-29 colon adenocarcinoma, and CAL-27 squamous cell carcinoma of the head and neck, and OGF and the opioid antagonist naltrexone (NTX) at a dosage (10(-6)M) selected because it is known to repress or increase, respectively, cell replication, the effects on apoptosis (TUNEL, Annexin V) and necrosis (trypan blue) were investigated on days 2, 5, and 7 of exposure. In addition, the influence of a variety of other natural and synthetic opioids on apoptosis and necrosis was examined at a dosage of 10(-6)M. OGF, NTX, naloxone, [D-Pen(2,5)]-enkephalin, [Leu(5)]-enkephalin, dynorphin A1-8, beta-endorphin, endomorphin-1 and -2, and methadone at concentrations of 10(-6)M did not alter cell viability of any cancer cell line. Exposure of cultures to [D-Ala(2),MePhe(4),Glycol(5)]-enkephalin (DAMGO), morphine, or etorphine at 10(-6)M significantly increased the number of adherent cells positively stained for TUNEL and Annexin V, as well as the number of necrotic cells in the supernatant, from control levels at all time points studied. The effects of DAMGO, morphine, and etorphine on apoptosis/necrosis were not fully blocked by concomitant administration of naloxone. Despite the increase in cell death in some opioid-treated groups, the number of apoptotic and necrotic adherent cells, and the number of necrotic cells in the supernatant, was no more than 1-2% of the total cell population. These results indicate that the inhibitory (OGF) or stimulatory (NTX) action on cell growth in tissue culture is not due to alterations in apoptotic or necrotic pathways. Moreover, although some opioids increased cell death, and dose-effect relationships need to be established, this activity was not of great magnitude and supports the previously reported lack of growth inhibition of many of these compounds.
 ...
PMID:Opioids and the apoptotic pathway in human cancer cells. 1274 39

This study was designed to examine the role of opioids on cell migration, chemotaxis, invasion, and adhesion, with an emphasis on whether the opioid growth factor (OGF, [Met(5)]-enkephalin) or the opioid antagonist naltrexone (NTX) impacts any or all of these processes. Drug concentrations of OGF and NTX known to depress or stimulate, respectively, cell proliferation and growth were analyzed. Three different human cancers (pancreatic, colon, and squamous cell carcinoma of the head and neck), represented by seven different cancer cell lines (PANC-1, MIA PaCa-2, BxPC-3, CAL-27, SCC-1, HCT-116, and HT-29), were evaluated. In addition, the influence of a variety of other natural and synthetic opioids on cell motility, invasion, and adhesion was assessed. Positive and negative controls were included for comparison. OGF and NTX at concentrations of 10(-4) to 10(-6)M, and dynorphin A1-8, beta-endorphin, endomorphin-1, endomorphin-2, leucine enkephalin, [D-Pen(2,5)]-enkephalin (DPDPE), [D-Ala(2), MePhe(4), Glycol(5)]-enkephalin (DAMGO), morphine, and U69,593 at concentrations of 10(-6)M, did not alter cell migration, chemotaxis, or invasion of any cancer cell line. OGF and NTX at a concentration of 10(-6)M, and incubation for 24 or 72h, did not change adhesion of these cancer cells to collagen I, collagen IV, fibronectin, laminin, or vitronectin. Moreover, all other opioids tested at 10(-6)M concentrations and for 24h had no effect on adhesion. These results indicate that the inhibitory or stimulatory actions of OGF and NTX, respectively, on cell replication and growth are independent of cell migration, chemotaxis, invasion, and adhesive properties. Moreover, a variety of other exogenous and endogenous opioids, many specific for the micro, delta, or kappa opioid receptors, also did not alter these biological processes, consonant with previous observations of a lack of effects of these compounds and their receptors on the biology of cancer cells.
 ...
PMID:Opioids and migration, chemotaxis, invasion, and adhesion of human cancer cells. 1791 Aug 95