Neuroblastoma × Glioma Hybrid Cells Synthesize Enkephalin‐Like Opioid Peptides

Abstract

Partially purified extracts from neuroblastoma X glioma hybrid cells 108CC15 inhibit, like opioids, the prostaglandin E1-evoked formation of cyclic AMP in a dose-dependent manner in the same hybrid cells. The inhibition is prevented by the opioid antagonist naloxone. In addition, the same extract competes with [3H]naloxone and [3H]Leu-enkephalin for binding to opioid receptors of hybrid cell membranes and to a specific antiserum, respectively. The opioid activity in the extracts is destroyed by carboxypeptidase A and leucine aminopeptidase, but not by trypsin. Further purification of the extracts by HPLC, TLC, or high-voltage paper electrophoresis reveals in each case two active fractions which behave like Met- and Leu-enkephalin. The Met-enkephalin-like, but not the Leu-enkephalin-like, fraction is inactivated by treatment with BrCN. Dimethylaminonaphtylsulfonyl (dansyl) derivatives of Met- and Leu-enkephalin correspond to [3H]dansyl derivatives of Met-like substances from hybrid cells. Three to four times as much Met-enkephalin-like as Leu-enkephalin-like material is present in the extract. The overall concentration of opioid peptides in the hybrid cells varies between 0.03 and 1.0 pmol Leu-enkephalin equivalents per mg protein. The amount of opioids in the hybrid cells is strongly dependent on the cell density. The findings suggest that neuroblastoma X glioma hybrid cells contain opioid peptides that are very similar, if not identical, to Met- and Leu-enkephalin. Opioid activity can also be detected in other neuronal cell lines and even in glioma cells.

Antagonists with negative intrinsic activity at delta opioid receptors coupled to GTP-binding proteins.

“…The question remained as to whether these findings could be explained in terms of true ability of some antagonists to reduce the probability of spontaneous interactions between unoccupied receptors and transduction protein, or whether they simply indicated that native membranes were contaminated by an endogenous agonist. Indeed, opioid peptides are synthesized in small amounts by the NG108-15 cell line (25). Fig.…”

Presence of Somatostatin, Enkephalins, and Substance P‐Like Peptides in Cultured Neurons from Embryonic Chick Cerebral Hemispheres

“…The presence of IR-enkephalins has also been demonstrated at concentrations which can be estimated to be of the same order of magnitude as that found in neuroblastoma x glioma hybrid cells (Glaser et al, 1982). Identity of enkephalins was confirmed by HPLC.…”

“…IR-enkephalins have been demonstrated by immunocytochemical methods in dissociated rat spinal cord cultures (Neale et al, 1978), in explant cultures of rat spinal cord (Haynes and Zakarian, 1979), in aggregating cultures from fetal rat brain (Knodel and Richelson, 1980), in dissociated rat brain cell cultures (Weyhenmeyer et al, 1980), and in mouse neuroblastoma (Knodel and Richelson, 1980). Biochemical identification of enkephalins has been performed in neuroblastoma x glioma hybrid cells (Glaser et al, 1982). The presence of IR-somatostatin has been shown in rat hypothalamic cell cultures (Gamse et al, 1980;Peterfreund and Vale, 1982) and in cultures of rat cortical cells (Delfs et al, 1980;Peterfreund and Vale, 1982).…”