Affinity labeling of the mu opioid receptor in bovine striatal membranes with [3H]-14 beta-(bromoacetamido)-7,8-dihydromorphine

[3H]-14 beta-(Bromoacetamido)-7,8-dihydromorphine ([3H]H2BAM) was synthesized and tested for its ability to selectively label mu opioid receptors in bovine striatal membranes. Incubating membranes with N-tosyl-L-phenylalanine chloromethyl ketone and dithiothreitol before the addition of [3H]H2BAM reduced nonspecific [3H]H2BAM binding so that [3H]H2BAM binding to opioid receptors was up to 70% of the total [3H]H2BAM binding and was dependent on [3H]H2BAM concentration, incubation time, and pH of the reaction. At pH 7.5, [3H]H2BAM bound selectively to the mu opioid receptor, but mainly noncovalently. After the initial binding of [3H]H2BAM to the receptor, membranes were washed and then incubated at 37 degrees C in 50 mM Tris-HCl, pH 8.5, for 3 h, a time that resulted in greater than 80% of the [3H]H2BAM associated with the receptor becoming covalently bound to the opioid receptor. The mu-selective peptide [D-Ala2,(Me)Phe4,Gly(ol)5]enkephalin inhibited [3H]H2BAM labeling of membranes, while delta- or kappa-selective compounds were ineffective. Both NaCl and the nonhydrolyzable guanine nucleotide analog guanylyl 5'-imidodiphosphate reduced the incorporation of [3H]H2BAM into membranes. When [3H]H2BAM-labeled striatal membranes were separated under reducing conditions on a sodium dodecyl sulfate-polyacrylamide gel, two proteins with molecular weights of 54,000 and 44,000 were specifically labeled. The 54-kDa protein was present in a greater amount than the 44-kDa protein. Both proteins bound to wheat germ agglutinin-Sepharose and concanavalin A-Sepharose, suggesting that both proteins contain multiple carbohydrate moieties. Despite the inclusion of protease inhibitors, the 44-kDa protein may be a proteolytic fragment of the 54-kDa protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacological study of 14 beta-(thioglycolamido)-7,8-dihydro-N(cyclopropylmethyl)-normor phinone (N-CPM-TAMO)

Opioid effects of 14 beta-(thioglycolamido)-7,8-dihydro-N(cyclopropylmethyl)- normorphinone (N-CPM-TAMO) were studied in the mouse tail-flick and acetic acid writhing assays. In the tail-flick test, N-CPM-TAMO failed to produce any antinociception after i.c.v. administration of up to 300 nmol. However, pretreatment of mice with N-CPM-TAMO produced a time- and dose-dependent antagonism of morphine-induced antinociception. The antagonism by N-CPM-TAMO lasted up to 48 hr, with a maximal effect at 24 hr after i.c.v. administration. Similarly, pretreatment of mice with N-CPM-TAMO at 24 hr also produced a dose-dependent antagonism of kappa-mediated antinociception, induced by U50,488 However, the antagonistic potency of N-CPM-TAMO against U50,488 was 100-fold less than against morphine. Pretreatment with N-CPM-TAMO had no effect on delta opioid receptor-mediated antinociception, as measured with [D-Pen2,D-Pen5]enkephalin. In the writhing assay, N-CPM-TAMO produced a time- and dose-dependent antinociception after i.c.v. administration, with a value of the dose producing 50% analgesia of 18.4 (10.6-31.9) nmol. The antinociceptive effect lasted up to 3 hr after administration. N-CPM-TAMO-induced antinociception was antagonized by coadministration of the kappa-selective antagonist, norbinaltorphimine. Pretreatment of mice with N-CPM-TAMO also produced a time- and dose-dependent antagonism of U50,488-induced antinociception, which lasted up to 72 hr, with a maximal effect at 24 hr after administration. These data indicate that N-CPM-TAMO is a mu-selective, long-term antagonist.(ABSTRACT TRUNCATED AT 250 WORDS)

5 beta-Methyl-14 beta-(p-nitrocinnamoylamino)-7,8-dihydromorphinone: a long-lasting mu-opioid receptor antagonist devoid of agonist properties

5 beta-Methyl-14 beta-(p-nitrocinnamoylamino)-7,8-dihydromorphinone (MET-CAMO) suppressed morphine-induced antinociception but had no effect on antinociception mediated by delta- or kappa-opioid receptors after a single i.c.v. 1-nmol injection from 8 to 72 h before testing. MET-CAMO had no agonist effects in the mouse tail-flick assay in doses up to 100 nmol. MET-CAMO is the first N-methylated morphine derivative which shows such long-lasting mu-selective opioid receptor antagonism with no agonistic properties.

Kappa opioid binding sites on the R1.1 murine lymphoma cell line: sensitivity to cations and guanine nucleotides

The present study describes the characterization of an opioid binding site on membranes prepared from the R1.1 cell line, a murine thymoma. Specific (-)[3H]bremazocine binding was saturable, stereoselective, and limited to a single high affinity binding site with a Kd value of 15.2 +/- 1.6 pM and a Bmax value of 54.8 +/- 6.0 fmol/mg of protein. The kappa-selective alkaloids and dynorphin peptides inhibited (-)[3H]bremazocine binding with Ki values of less than 1 nM, in contrast to mu- and delta-selective ligands. The high affinity of this site for alpha-neo-endorphin and U50,488 suggests that this kappa opioid binding site resembles the kappa 1b subtype. NaCl, as well as other mono- and divalent cations, inhibited (-)[3H]bremazocine binding. In the presence of NaCl, the nucleotides GTP, GDP, and the nonhydrolyzable analog guanylyl-5'-imidodiphosphate (Gpp(NH)p) also decreased (-)[3H]bremazocine binding, suggesting that this kappa opioid binding site is coupled to a G-protein. In summary, R1.1 cells possess a single high affinity kappa opioid receptor that shares many properties with brain kappa 1b opioid receptors.

kappa-Opioid binding sites on a murine lymphoma cell line

As a first step in determining whether any subset of lymphocytes expresses opioid receptors, membranes prepared from mouse lymphoma cell lines were screened for [3H]naloxone binding sites. Membranes from the R1.1 cell line specifically bound [3H]naloxone. The Hill coefficient for [3H]naloxone binding was 0.93 +/- 0.18, and nonlinear regression analysis indicated that a one-site model was the best fit of the [3H[naloxone saturation binding data. Low concentrations of kappa-selective opioids, but neither mu nor delta opioids, inhibited [3H]naloxone binding. Saturation binding studies with the kappa-selective compound [3H]U69,593 revealed a single binding site with a KD value of 0.204 +/- 0.039 nM and a Bmax value of 31.7 +/- 3.1 fmol/mg of membrane protein. The Hill coefficient for [3H]U69,593 binding was 1.03 +/- 0.11, indicative of a single site. Time courses for the association and dissociation of [3H]U69,593 binding at 25 degrees C exhibited properties consistent with a single class of binding sites. Low concentrations of kappa-selective opioids, including dynorphin peptides, inhibited [3H]U69,593 binding, while high concentrations of mu opioids were needed to inhibit binding, and the delta-selective ligands were ineffective at concentrations up to 10 microM. Stereoselectivity of the binding site was demonstrated by the finding that the Ki value for (-)-pentazocine in inhibiting [3H]U69,593 binding was 25 times less than for the (+)-isomer. Based on its high affinity for U69,593, alpha-neo-endorphin, and dynorphin B, the kappa opioid binding site on R1.1 cell membranes belongs to the kappa 1b subtype. As observed with brain kappa opioid binding sites, sodium inhibited [3H]U69,593 binding to R1.1 cell membranes in a concentration-dependent manner. These data demonstrate that the murine lymphoma cell line R1.1 expresses kappa opioid binding sites that are very similar to brain kappa opioid binding sites.

Protein kinase C activation increases the rate and magnitude of agonist-induced delta-opioid receptor down-regulation in NG108-15 cells

Protein kinase C (PKC) activation was examined for its role in delta-opioid receptor down-regulation in the neuroblastoma X glioma hybrid cell line NG108-15. Incubation of NG108-15 cells for 2 hr at 37 degrees with up to 1 microM 4 beta-phorbol 12 beta-myristate 13 alpha-acetate (PMA), a phorbol ester that activates PKC, had no effect on opioid binding to membranes prepared from these cells. However, as little as 3 nM PMA incubated with an opioid agonist and NG108-15 cells potentiated the decrease and the rate of decrease of opioid binding, compared with agonist alone. Scatchard analysis of [3H][D-Ala2,D-Leu5]enkephalin (DADLE) binding revealed that NG108-15 cells incubated for 3 hr with 1 nM DADLE and 30 nM PMA displayed a > 50% reduction in the number of [3H]DADLE binding sites with no affinity change at the remaining sites, compared with cells treated with DADLE alone. The antagonist naloxone blocked both DADLE-induced and PMA-enhanced DADLE-induced down-regulation. The agonists morphine and cyclazocine, which alone were unable to induce delta receptor down-regulation, did so in the presence of PMA. The PKC inhibitor staurosporine and down-regulation of PKC by chronic PMA treatment blocked PMA potentiation of DADLE-induced down-regulation, but not "normal" DADLE-induced down-regulation. The enhancement of down-regulation by PMA was unaffected by either metabolic inhibitor or incubations at 20 degrees, conditions that blocked down-regulation by DADLE alone. NG108-15 cells incubated with [3H]DADLE and PMA retained more [3H]DADLE than cells incubated with [3H]DADLE alone, suggesting that PMA enhanced receptor internalization instead of merely inhibiting membrane binding. The diacylglycerol 1-oleoyl-2-acetyl-glycerol and bradykinin substituted for PMA but not carbachol, indicating that PKC activated physiologically may play a role in delta receptor down-regulation.

Effects of beta-endorphin on mu and delta opioid receptor-coupled G-protein activity: low-Km GTPase studies

Human beta-endorphin 1-31 (beta-END) stimulated low-Km GTPase activity in a concentration-dependent and saturable manner in membranes prepared from the delta opioid receptor-containing hybrid cell line NG108-15 and from the mu opioid receptor-enriched human neuroblastoma cell line SK-N-SH. Naloxone and the delta-selective antagonist, ICI 174,864, blocked the stimulation of the GTPase activity produced by beta-END in NG108-15 cell membranes, whereas only naloxone inhibited the beta-END-induced stimulation in SK-N-SH cell membranes, suggesting that beta-END was acting through both mu and delta opioid receptors. Treatment of the cells with Bordetella pertussis toxin before the preparation of membranes blocked the stimulation of low-Km GTPase by beta-END in both cell lines. Activation of NG108-15 and SK-N-SH low-Km GTPase by beta-END was sodium-dependent, and lithium and potassium were poor promoters of this activation. These results demonstrate that beta-END stimulates the interaction of both mu and delta opioid receptors with B. pertussis toxin-sensitive G-proteins in SK-N-SH and NG108-15 cell membranes, respectively.

Antinociceptive properties of two alkylating derivatives of morphinone: 14 beta-(thioglycolamido)-7,8-dihydromorphinone (TAMO) and 14 beta-(bromoacetamido)-7,8-dihydromorphinone (H2BAMO)

This study investigated the antinociceptive properties of two alkylating derivatives of morphinone, 14 beta-(thioglycolamido)-7,8- dihydromorphinone (TAMO) and 14 beta-(bromoacetamido)-7,8-dihydromorphinone (H2BAMO) in the mouse tail-flick assay. Intracerebroventricular administration of either TAMO or H2BAMO produced short-term antinociception. Both TAMO and H2BAMO were 11.6-fold more potent than an i.c.v. administration of morphine. These effects were antagonized by the mu-selective antagonist, beta-funaltrexamine, but not by the delta-selective antagonist, N,N-diallyl-Tyr-Aib-Aib-Phe-Leu-OH. TAMO pretreatment from 8 to 48 hr produced a time-related, dose-dependent antagonism of morphine-induced antinociception without showing any agonistic effect. Pretreatment with TAMO for 24 hr antagonized antinociception produced by both H2BAMO and morphine, as well as TAMO itself, but not that of the delta-selective agonist [D-Pen2,D-Pen5]enkephalin (DPDPE) or U50,488, a kappa-selective agonist. In order to distinguish this antagonistic effect from cross-tolerance between TAMO and morphine, two mu agonists, [D-Ala2,N(Me)Phe4,Gly-ol]enkephalin (DAMGO) and H2BAMO, were chosen for comparison. A single i.c.v. pretreatment of DAMGO or H2BAMO, at a dose that had equivalent analgesic effects as TAMO, attenuated morphine-induced antinociception, reaching a maximal effect at the time of the disappearance of agonistic effects of DAMGO and H2BAMO and lasting up to 24 hr. Additionally, a 16-hr pretreatment with TAMO, but not DAMGO or H2BAMO, reduced the development of physical dependence to morphine at 24 hr after morphine pellet implantation. Therefore, this study demonstrated that both TAMO and H2BAMO act as mu opioid agonists to produce short-term antinociception.(ABSTRACT TRUNCATED AT 250 WORDS)

Beta-endorphin stimulates rat T lymphocyte proliferation

beta-Endorphin 1-31 and several structurally related peptides were tested for their ability to alter mitogen-induced T cell proliferation. Rat beta-endorphin 1-31 and human beta-endorphin 1-27 increased phytohemagglutinin (PHA)-induced [3H]thymidine incorporation into rat lymph node cells. However, when PHA-induced proliferation was suppressed by the inclusion of prostaglandin E1 (PGE1), human beta-endorphin 1-31 and a number of structurally similar peptides, including some peptides that did not alter mitogen-induced proliferation, significantly reduced the PGE1 inhibition of PHA-stimulated T cell proliferation. Although the N-terminus of beta-endorphin was necessary for potency, inclusion of the opioid antagonist naloxone together with beta-endorphin 1-31 did not alter the blockage of PGE1 inhibition of PHA-induced proliferation caused by beta-endorphin. The inhibition of mitogen-stimulated proliferation by either cholera toxin or forskolin, two additional compounds that like PGE1 also elevate cyclic AMP levels, was not blocked by beta-endorphin. Verapamil suppression of proliferation was not modified by beta-endorphin, indicating that the beta-endorphin stimulatory effect was probably not due to Ca2+ influx through verapamil-sensitive Ca2+ channels. These data suggest that beta-endorphin, acting through a nonopioid beta-endorphin receptor, may modulate immunocompetence by stimulating T cell proliferation and by counteracting the inhibitory effects of PGE1.

Purification, cloning, and tissue distribution of a 23-kDa rat protein isolated by morphine affinity chromatography

A 23-kDa (p23k) rat brain protein was stereospecifically eluted from a 14 beta-bromoacetamidomorphine affinity column, purified to apparent homogeneity by reverse phase HPLC, and partially sequenced. Three degenerate oligodeoxynucleotide probes were synthesized based on this partial amino acid sequence. A rat brain cDNA library was screened using these probes, and a full-length cDNA was isolated. The deduced protein, 187 amino acids long, is rich in glutamic and aspartic acid residues, endowing p23k with a net negative charge at neutral pH. The protein lacks a signal sequence as well as any transmembrane domains. Based on predictions of secondary structure, p23k is a globular protein composed of 30% alpha-helices and 18% beta-pleated sheets. Northern blot analysis revealed p23k transcripts in rat brain, liver, and the mouse x rat neuroblastoma-glioma NG108-14 cell line. Although not an opioid receptor itself, this protein may be associated with such a receptor or be related to a protein that has been shown to be cross-linked to the opioid peptide beta-endorphin.

Affinity labeling of mu opioid receptors by sulfhydryl alkylating derivatives of morphine and morphinone

After reduction of a disulfide bond at or near the mu opioid binding site in rat brain membranes, incubating membranes with 14 beta-bromoacetamido derivatives of either morphine, dihydromorphine, morphinone, or dihydromorphinone resulted in the irreversible inhibition of mu opioid binding to rat brain membranes. Without the addition of the disulfide bond-reducing reagent dithiothreitol, these affinity ligands bound reversibly to opioid binding sites. Binding to either delta or kappa opioid binding sites was not altered by alkylation of the membranes with the affinity ligands. The percentage of irreversible inhibition of mu opioid binding was dependent on the time and temperature of the incubation of membranes with the affinity ligands and on the concentrations of dithiothreitol and the affinity ligands. Incubating membranes with morphine afforded almost complete protection from alkylation of the mu opioid binding site. Naloxone and the l-isomer levorphanol also protected the site from alkylation, whereas the d-isomer dextrorphan and the kappa-selective opioid U50,488H did not protect the site. The mu-selective peptide [D-Ala2, (Me)Phe4,Gly(ol)5]enkephalin was the peptide that afforded the greatest protection. These studies have shown that, after the reduction of a disulfide bond at or near the mu opioid binding site, this sulfhydryl group can be specifically alkylated, resulting in the affinity labeling of the mu opioid binding site.

Guanine nucleotide regulation of [125I]beta-endorphin binding to NG108-15 and SK-N-SH cell membranes: specific cation requirements

Regulation of [125I]beta h-endorphin binding by guanine nucleotides was investigated in membrane preparations from two opioid receptor-containing cell lines: NG108-15, which contains only delta opioid receptors, and SK-N-SH, which contains predominantly mu opioid receptors. In contrast to the binding of the delta-selective agonist [3H][D-penicillamine2,D-penicillamine5]enkephalin to NG108-15 cell membranes, and of the mu-selective agonist [3H][D-Ala2,MePhe4,Gly-ol5]enkephalin to SK-N-SH cell membranes, [125I]beta h-endorphin binding to NG108-15 and SK-N-SH cell membranes was not altered by guanosine triphosphate (GTP) or guanylyl-5'-imidodiphosphate (Gpp(NH)p) in the absence of cations. However, in the presence of NaCl, [125I]beta h-endorphin binding to both cell lines was inhibited by GTP and Gpp(NH)p in a concentration-dependent manner. In SK-N-SH cell membranes, the ability of sodium to promote regulation of [125I]beta h-endorphin binding by GTP was mimicked by the monovalent cations lithium and potassium, but not by the divalent cations magnesium, calcium, or manganese. In NG108-15 cell membranes, only sodium was effective in promoting inhibition of [125I]beta h-endorphin binding by GTP. The effect of GTP or Gpp(NH)p in the presence of sodium was also observed with guanosine diphosphate, but not guanosine monophosphate or any of the non-guanine nucleotides tested. These results indicate that the presence of monovalent cations is required for regulation of [125I]beta h-endorphin binding by guanine nucleotides, and that the specificity of this cation requirement differs between the mu and delta receptor-containing cell lines.

Beta-endorphin suppresses rat plaque-forming cell response by a non-opioid mechanism

The opioid peptide beta h-endorphin 1-31 inhibited the plaque-forming cell (PFC) response to sheep red blood cells when rat splenocytes, immunized in vivo, were cultured in vitro with the peptide. The opioid antagonist naloxone failed to reverse the beta h-endorphin 1-31 suppression of the PFC response. Peptide fragments of beta h-endorphin 1-31, other opioid peptides, and alkaloids had no effect on the response. These data indicate that beta h-endorphin 1-31 suppresses antibody production or secretion by a specific, non-opioid receptor on the rat splenocytes.

14 beta-(Bromoacetamido)morphine irreversibly labels mu opioid receptors in rat brain membranes

The binding properties of 14 beta-(bromoacetamido)morphine (BAM) and the ability of BAM to irreversibly inhibit opioid binding to rat brain membranes were examined to characterize the affinity and selectivity of BAM as an irreversible affinity ligand for opioid receptors. BAM had the same receptor selectivity as morphine, with a 3-5-fold decrease in affinity for the different types of opioid receptors. When brain membranes were incubated with BAM, followed by extensive washing, opioid binding was restored to control levels. However, when membranes were incubated with dithiothreitol (DTT), followed by BAM, and subsequently washed, 90% of the 0.25 nM [3H] [D-Ala2,(Me)Phe4,Gly(ol)5]enkephalin (DAGO) binding was irreversibly inhibited as a result of the specific alkylation of a sulfhydryl group at the mu binding site. This inhibition was dependent on the concentrations of both DTT and BAM. The mu receptor specificity of BAM alkylation was demonstrated by the ability of BAM alkylated membranes to still bind the delta-selective peptide [3H] [D-penicillamine2,D-penicillamine5]enkephalin (DPDPE) and (-)-[3H]bremazocine in the presence of mu and delta blockers, selective for kappa binding sites. Under conditions where 90% of the 0.25 nM [3H]DAGO binding sites were blocked, 80% of the 0.8 nM [3H]naloxone binding and 50% of the 0.25 nM 125I-labeled beta h-endorphin binding were inhibited by BAM alkylation. Morphine and naloxone partially protected the binding site from alkylation with BAM, while ligands that did not bind to the mu site did not afford protection.2+hese studies have demonstrated that when a disulfide bond

Inhibition of (+)[3H]SKF 10,047 binding to rat brain membranes by FAB fragments from a monoclonal antibody directed against the opioid receptor

Examination of the binding of (+)[3H]SKF 10,047 to rat brain membranes indicated that at a low concentration most of the binding was to the haloperidol-sensitive binding site. Titration curves exhibited a displacement potency order of haloperidol greater than (+)SKF 10,047 = 1,3-diorthotolyl-guanidine much much greater than (-)SKF 10,047 much greater than phencyclidine analogues. The effect of Fab fragments from a monoclonal antibody, OR-689.2.4, directed against the opioid receptor on the binding of (+)[3H]SKF 10,047 to rat brain membranes was examined. The specificity of this antibody for the opioid receptor has been determined by its ability to inhibit the binding of mu and delta opioid peptides to rat brain but not the binding of kappa opioid ligands or nonopioid ligands specific for other receptors. The Fab fragments blocked and displaced specifically bound (+)[3H]SKF 10,047 in a titratable manner. Increasing the incubation time of the membranes with the Fab fragments increased the percent inhibition obtained. The Fab fragments acted as noncompetitive inhibitors of (+)[3H]SKF 10,047 binding. A (+)SKF 10,047 binding site in rat brain appears to share a common structural domain with mu and delta opioid receptors.

Guanine nucleotide regulation of [125I]beta-endorphin binding to rat brain membranes: monovalent cation requirement

The binding of [125I]beta h-endorphin to rat brain membranes was investigated in the presence of GTP and guanylyl-5'-imidodiphosphate. In contrast to the binding of the mu-selective opioid agonist, [3H][D-Ala2,MePhe4,Glyol5]enkephalin, and the delta-selective opioid agonist, [3H][D-penicillamine2, D-penicillamine5]enkephalin, [125I]beta h-endorphin binding was not affected by GTP or guanylyl-5'-imidodiphosphate in a concentration-dependent manner in the absence of cations. However, in the presence of NaCl, the inclusion of either GTP or guanylyl-5'-imidodiphosphate resulted in a concentration-dependent inhibition of [125I]beta h-endorphin binding. This inhibition was significantly greater than the decrease in [125I]beta h-endorphin binding observed in the presence of sodium alone. Although GTP most potently inhibited [125I]beta h-endorphin binding in the presence of sodium, inhibition of [125I]beta h-endorphin binding by GTP was also observed in the presence of the monovalent cations lithium and potassium, but not the divalent cations magnesium, calcium, or manganese. The effect produced by GTP in the presence of NaCl was mimicked by GDP, but not by GMP or other nucleotides. Unlike [125I]beta h-endorphin, the binding of the putative sigma receptor agonist, (+)-[3H]SKF 10,047, was not significantly altered by GTP or guanylyl-5'-imidodiphosphate in the absence or presence of sodium.

Comparison of [125I]beta-endorphin binding to rat brain and NG108-15 cells using a monoclonal antibody directed against the opioid receptor

The properties of [125I]beta h-endorphin-binding sites from rat brain membranes and membranes from the NG108-15 cell line were compared using a monoclonal antibody directed against the opioid receptor and opioid peptides as probes. The binding of [125I]beta h-endorphin to both rat brain and NG108-15 membranes yielded linear Scatchard plots with Kd values of 1.2 nM and 1.5 nM, respectively, and Bmax values of 865 fmol/mg rat brain membrane protein and 1077 fmol/mg NG108-15 membrane protein. A monoclonal antibody, OR-689.2.4, capable of inhibiting mu and delta binding but not kappa binding to rat brain membranes, noncompetitively inhibited the binding of 1 nM [125I]beta h-endorphin to rat brain and NG108-15 membranes with an IC50 value of 405 nM for rat brain membranes and 543 nM for NG108-15 membranes. The monoclonal antibody also inhibited the binding of 3 nM [3H] [D-penicillamine2, D-penicillamine5] enkephalin to NG108-15 membranes with an IC50 value of 370 nM. In addition to blocking the binding of [125I]beta h-endorphin to brain membranes, the antibody also displaced [125I]beta h-endorphin from membranes. Site-specific opioid peptides had large variations in their IC50 values depending on whether they were inhibiting [125I]beta h-endorphin binding to rat brain or the NG108-15 membranes. When the peptides were tested with the monoclonal antibody for their combined ability to inhibit [125I]beta h-endorphin binding to both membrane preparations, the peptides and antibody blocked binding as though they were acting at allosterically coupled sites, not two totally independent sites. These studies suggest that mu-, delta-, and beta-endorphin-binding sites share some sequence homology with the 35,000-dalton protein that the antibody is directed against.

Beta-endorphin modulation of mitogen-stimulated calcium uptake by rat thymocytes

Lymphocytes stimulated by mitogens or antigens exhibit an enhanced calcium uptake early in the proliferation or activation response. Modulation of this calcium uptake results in alterations of proliferation and immunocompetence. beta-endorphin and other opioids affect several parameters of lymphocyte competence. Limited data are available concerning the mechanism(s) of these effects. This study examines whether a possible opioid mechanism is the modification of the early calcium influx into stimulated lymphocytes. The time course of both concanavalin A (Con A) and phytohemagglutinin (PHA)-stimulated 45Ca2+ uptake into thymocytes was characterized to determine the optimal time for testing the effects of opioids. beta-Endorphin 1-31 significantly enhanced Con A-stimulated 45Ca2+ uptake into rat thymocytes. This peptide had no significant effect on PHA-stimulated 45Ca2+ uptake or on basal thymocyte 45Ca2+ flux. The beta h-endorphin stimulatory effect was titratable in the range of 0.1 nM to 10 microM. Naloxone did not reverse the enhancement. Met-enkephalinamide and other opioid agonists did not duplicate the stimulatory effect. Thus, the beta h-endorphin 1-31 enhancement of Con A-stimulated 45Ca2+ uptake by rat thymocytes does not operate via classical opioid receptor mechanisms. beta h-endorphin 1-31 appears to be acting on a subset of T cells that are responsive to Con A but not to PHA.

Inhibition of mu and delta but not kappa opioid binding to membranes by Fab fragments from a monoclonal antibody directed against the opioid receptor

Fab fragments from a monoclonal antibody, OR-689.2.4, directed against the opioid receptor, selectively inhibited opioid binding to rat and guinea pig neural membranes. In a titratable manner, the Fab fragments noncompetitively inhibited the binding of the mu selective peptide [D-Ala2,(Me)Phe4,Gly(OH)5][3H] enkephalin and the delta selective peptide [D-Pen2,D-Pen5] [3H]enkephalin (where Pen represents penicillamine) to neural membranes. In contrast, kappa opioid binding, as measured by the binding of [3H]bremazocine to rat neural membranes and guinea pig cerebellum in the presence of mu and delta blockers, was not significantly altered by the Fab fragments. In addition to blocking the binding of mu and delta ligands, the Fab fragments displaced bound opioids from the membranes. When mu sites were blocked with [D-Ala2,(Me)Phe4,Gly(OH)5]enkephalin, the Fab fragments suppressed the binding of [D-Pen2,D-Pen5][3H]enkephalin to the same degree as when the mu binding site was not blocked. The Fab fragments also inhibited binding to the mu site regardless of whether or not the delta site was blocked with [D-Pen2,D-Pen5]enkephalin. This monoclonal antibody is directed against a 35,000-dalton protein. Since the antibody is able to inhibit mu and delta binding but not kappa opioid binding, it appears that this 35,000-dalton protein is an integral component of mu and delta opioid receptors but not kappa receptors.

Preparation of Fab fragments from a mouse monoclonal IgM

A procedure is described for preparing and purifying Fab fragments from a mouse monoclonal IgM. The IgM was digested with trypsin in the presence of the reducing agent, cysteine. The resulting Fab fragments were alkylated with iodoacetamide and purified using a Sephacryl S-200 column. The Fab fragments had a molecular weight of 48 000 as determined by SDS polyacrylamide gel electrophoresis and molecular sieve chromatography. This procedure has been successfully used with five different mouse monoclonal IgM. The Fab fragments bound antigen with the same specificity as the whole IgM.

Free kappa light chains in multiple sclerosis spinal fluid

Based on prior reports of free light chains of immunoglobulin G (IgG) in the cerebrospinal fluid (CSF) of patients with multiple sclerosis (MS), we quantitated free kappa and lambda chains and whole IgG concentrations using sensitive and specific radioimmunoassays (RIAs). The RIA for free kappa chains had a sensitivity of 0.25 micrograms/ml and was capable of specifically measuring free kappa chains in whole CSF or serum even in the presence of a 4-log excess of whole IgG. By RIA, free kappa chains were detected in CSF samples from 33 (84%) of 39 MS patients but in only 1 (2.4%) of 42 controls. The control patients included 10 with noninfectious inflammatory diseases and 9 with central nervous system infections. The concentration of free kappa chains in the CSF of the MS patients was 1.40 +/- 1.21 micrograms/ml. Free kappa chains were concentrated in the CSF 71- to 120-fold relative to reference proteins. In contrast, increased levels of free lambda chains or of whole IgG were nonspecific; abnormalities were seen in controls with infections or inflammatory diseases as often as in MS patients. These studies suggest that the measurement of free kappa light chains may have important diagnostic usefulness, since the specificity of the finding for MS appears to be high.

A monoclonal antibody capable of modulating opioid binding to rat neural membranes

A monoclonal antibody capable of inhibiting opioid binding to rat neural membranes has been produced. Spleen cells from a BALB/c mouse, immunized with a partially purified opioid receptor complex, were fused with P3-X63.Ag8.653.3 myeloma cells. The cell line OR-689.2.4 secreted an IgM that was capable of partially inhibiting opioid binding to rat neural membranes under equilibrium binding conditions, while not affecting the binding of nonopioid ligands. Control mouse immunoglobulins and heat-denatured OR-689.2.4 did not inhibit opioid binding to membranes. The purified immunoglobulin inhibited the binding of [3H]dihydromorphine in a titrable, saturable, and reversible manner, as well as the binding of the delta-ligand [3H][D-Ala2,D-Leu5]enkephalin, the kappa-ligand [3H] ethylketocyclazocine, and 3H-labeled antagonists. In addition to blocking the binding of opioids to membranes, the immunoglobulin could also displace bound [3H]dihydromorphine from neural membranes. The 125I-labeled immunoglobulin specifically bound to neural membranes with a Kd of 1.3 nM and a maximal number of binding sites of 41.8 fmol/0.25 mg of membrane protein. In a titrable manner, the immunoglobulin precipitated opioid binding sites from a solubilized preparation of neural membranes. When OR-689.2.4 conjugated to Sepharose was incubated with the partially purified opioid receptor complex, labeled with 125I, a 35,000-dalton protein was specifically bound by the immunoglobulin. This antibody provides a tool for probing the multiple opioid binding sites.

Multiple sclerosis: free light chains in cerebrospinal fluid

We found free light chains in the CSF of 18 MS patients, but not in any of 14 patients with other neurologic disease. CSF from all MS patients contained kappa and lambda chain dimers, less frequently contained light chain monomers, and never contained free gamma heavy chains. Light chains were not detected in matched serum samples. CSF from MS patients did not release free light chains from whole IgG in CSF of controls. The findings suggest that these free light chains originate in plasma cells, not from degradation of whole IgG.

Multiple sclerosis. Cerebrospinal fluid immune complexes that bind C1q

We used a sensitive C1q-binding assay to measure levels of soluble immune complexes in 182 samples of cerebrospinal fluid (CSF) from control patients and patients with multiple sclerosis (MS). Soluble immune complexes in CSF were detected in 16% of patients with progressive MS, 38% of patients with exacerbating-remitting MS, 55% of patients with infectious or inflammatory diseases, 3% of patients with noninflammatory neurologic disorders, and in 0% of control patients with back pain. No correlations were found between the results of the C1q-binding assay and abnormalities of other CSF parameters. These included an elevated level of myelin basic protein, pleocytosis, oligoclonal bands, or an increased IgG level. Because of the lack of correlation to laboratory indexes of disease activity and the nonspecificity of a positive test, the C1q-binding assay seems to have little clinical usefulness in the diagnosis or management of patients with MS.

A freezing method for cell fusions to distribute and reduce labor and permit more thorough early evaluation of hybridomas

A method is described whereby cell fusions can be bulk-frozen shortly after the hybridization step. Recoveries are shown to be comparable to those obtained for control hybridomas cultured without freezing. Advantages are discussed in terms of labor distribution and antibody assay and evaluation strategies. It is further shown that peritoneal feeder cell preparations can be conveniently frozen as a means of workload reduction.

14 beta-(2-bromoacetamido)morphine and 14 beta-(2-bromoacetamido)morphinone

14 beta-(2-Bromoacetamido)morphine (6) and 14 beta-(2-bromoacetamido)morphinone (9) were prepared preferably from the adduct of thebaine and 1-chloro-1-nitrosocyclohexane, which on reduction in methanol solution gave 14-aminocodeinone (2) and the corresponding ketal (3). When tested in a receptor-binding assay, the IC50 values of 6 and 9 were 15 and 10 nM, respectively. If the incubation time during the assay was increased from 15 to 30 min, irreversible binding of both ligands was observed.

Generating monoclonal antibodies to the opioid receptor

BALB/c mice were immunized with an opioid receptor complex over the period of 1 year. Spleen cells from the mouse, whose serum inhibited opiate binding to rat neural membranes to the greatest extent, were fused with P3-X63-Ag8. 653.3 myeloma cells. By radioimmunoassay (RIA), 32 cell lines have been detected that secrete an antibody to a component of the isolated receptor complex. Antibodies from 2 of the cell lines have an effect on opiate binding to rat neural membranes. One antibody, OR-689.2.4 is an IgM cryoglobulin. This antibody partially inhibited the binding of 3H-dihydromorphine (3H-DHM), 3H-naloxone, 3H-ethylketocyclazocine (3H-EKC), and 3H-D-Ala2, D-Leu5 enkephalin (3H-DADLE) to rat neural membranes. The other antibody, OR-465.3, inhibited the binding of 3H-DHM and 3H-naloxone to rat neural membranes by a maximum of 70%. This antibody also inhibited the binding of 3H-DADLE to neural membranes but, did not affect the binding of this peptide to membranes from the neuroblastoma-glioma hybrid cell line, NG108-15. Work is ongoing to generate monoclonal antibodies specific for each subclass of opioid receptor.

Affinity labeling and purification of the opiate receptor from rat brain

Affinity labeling of the opiate receptor has been performed on neural membranes from rat brain utilizing[125I]-14-bromoacetamidomorphine, an opiate agonist, and [125I]-14-chloracetylmorphine, an antagonist. With the use of SDS gel electrophoresis it could be shown that the agonist labeled three proteins with molecular weights of 43,000, 35,000 and 23,000, whereas the antagonist only labeled the 23,000 component. The preferential labeling of the 23,000 protein by the antagonist suggests that this component may be a primary recognition site for opiate antagonists. Calcium was stimulatory to the affinity labeling of all three proteins while sodium was inhibitory. With the use of affinity columns prepared by conjugating either ligand to omega-aminohexyl Sepharose, a receptor complex was obtained consisting all three proteins. Stereospecific opiate binding was demonstrable in the complex prepared from either column.

Sites and mechanisms for nicotine's action in the brain

A variety of pharmacologic, behavioral, and receptor-binding studies were performed in an effort to determine the mechanism and site of action of nicotine on the rat brain. When nicotine was given into the lateral or fourth ventricles or directly into the lateral vestibular nuclei of rats, it produced a characteristic prostration often accompanied by tonic seizures and body rotation along a longitudinal axis. Of a variety of brain areas studied, the prostration response could only be elicited from the lateral and, to a lesser extent, medial vestibular nuclei. The response could not be produced by a variety of cholinergic agonists or antagonized with nicotinic cholinergic antagonists, with the possible exception of mecamylamine. A good correlation was observed between the ability of nicotine analogues to antagonize the nicotine-induced prostration and their ability to compete with 3H-nicotine binding to rat brain membranes. 3H-nicotine binding had a high affinity, was stereoselective and concentrated in nerve endings and such brain regions as the thalamus, cerebrum, and hippocampus. When nicotine was administered intraventricularly to rats, it significantly elevated the threshold to an aversive shock. It was concluded that many of the central actions of nicotine could not be explained on the basis of traditional nicotinic cholinergic mechanisms.

Purification of the opiate receptor from rat brain

The opiate receptor was purified from a Triton-solubilized preparation of rat neural membranes by the use of affinity chromatography. The affinity gel was prepared by coupling 14-beta-bromoacetamidomorphine, a newly synthesized ligand, to omega-aminohexyl-Sepharose. After elution of the nonspecific proteins with 50 mM Tris (pH 7.5), the receptor proteins were eluted with 1 microM levorphanol or etorphine. NaDodSO4/polyacrylamide gel electrophoresis revealed three major proteins associated with the opiate receptor, having molecular weights of 43,000, 35,000, and 23,000. The purified receptor binds 10(-11) mol of dihydromorphine/per mg of protein, with a Kd of 3.8 X 10(-9) M. Other opiates, naloxone, and methionine-enkephalin, inhibit [3H]dihydromorphine binding in a manner similar to that observed with intact and solubilized neural membranes.

Adenosine 3',5'-monophosphate-dependent phosphorylation of a 6000 and a 22,000 dalton protein from cardiac sarcoplasmic reticulum

In canine cardiac sarcoplasmic reticulum, adenosine 3',5'-monophosphate (cyclic AMP)-dependent protein kinase specifically phosphorylates two proteins, as seen by sodium dodecyl sulfate-slab gel electrophoresis and autoradiography. One protein has a molecular weight ranging between 22,000 and 24,000 daltons and has previously been identified and named phospholamban (Tada, M., Kirchberger, M.A. and Katz, A.M. (1975) J. Biol. Chem. 250, 2640-2647). The other protein that the 32P label incorporates into has a molecular weight of approximately 6000. Like the 22,000 dalton protein, the 6000 dalton protein has characteristics of phosphoester bonding. The time-dependent course of phosphorylation shows that initially the 32P label is incorporated more rapidly into the 22,000 dalton protein than the 6000 dalton protein, with both proteins reaching a steady-state level of phosphorylation after 10 min of incubation. When both protein kinase and cyclic AMP are eliminated from the incubation medium, both the 22,000 and the 6000 dalton protein are still phosphorylated, but only to about a quarter of the activity found when cyclic AMP and protein kinases are included in the incubation mixture. The addition of phosphodiesterase completely eliminates the phosphorylation of both proteins. Treating the microsomes with trypsin prevents subsequent phosphorylation of either protein. Phosphorylating the microsomes first, then treating with trypsin, renders both the 22,000 and the 6000 dalton proteins resistant to even prolonged trypsin attack. Unphosphorylated, both proteins are solubilized by a very low concentration of deoxycholate. After phosphorylation the proteins cannot be solubilized by deoxycholate. Phosphorylation appears to alter greatly the physical properties of these proteins. Control experiments exclude the possibility that a lipid is being phosphorylated. After phosphorylation the phosphorylated 22,000 dalton protein is separated from the 6000 dalton protein by proteolipid extraction. After first treating the microsomes with methanol, the 22,000 dalton protein is then soluble in acidified chloroform/methanol, while the 6000 dalton protein remains insoluble. The finding that both proteins have much different biochemical properties when phosphorylated than when not, may be relevant in how they regulate calcium transport in the sarcoplasmic reticulum.