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Activation of human and non-human colonic beta(beta)3-adrenoceptors causes smooth muscle relaxation. beta3-Adrenoceptor agonists protect against experimental indomethacin-induced jejunal ulceration. The mechanism of protection may involve spasmolytic/vasodilatory agonist activity. The precise localization of beta3-adrenoceptors in the human gut is not known.To localize the beta3-adrenoceptor within the human gastrointestinal tract using the immunohistochemical technique.Human beta3-adrenoceptors were immuno-localized in paraffin sections of human oesophagus (OS), stomach (ST), duodenum (DU), ileum (IL), sigmoid colon (SC), rectum (R) and gall-bladder (GB) using the rabbit polyclonal antibody anti-P12. Staining was graded , ++, + and 0. Immunostaining of SC was also done with pre-incubation of anti-P12 with P12 peptide. Western blotting of anti-P12 on human and murine IL and SC isolated membrane proteins was performed.All epithelia, vascular endothelial cells and ganglia scored 0. Smooth muscle of the vasculature, muscularis propria, muscularis mucosae and mucosa was graded, respectively, as follows; OS ( , , ,-), ST (++, , ++, ++), DU (++, , , +), IL (++, ++, ++, +), SC ( , ++, ++, ++), R (++, ++, +, +), GB ( , , -, 0). Pre-incubation of anti-P12 with P12 peptide almost abolished SC smooth muscle positivity. Western blot analysis using anti-P12 on human, but not murine, IL and SC membrane proteins revealed a single 5 5 kDa band, a size consistent with the predicted size of a partially glycosylated form of the human beta3-adrenoceptor.This immunohistochemical study has localized the beta3-adrenoceptor to vascular and nonvascular smooth muscle in the human gastrointestinal tract. These findings support a role for the beta3-adrenoceptor in the control of blood flow and motility in the human gastrointestinal tract.

As the beta 3-adrenergic receptor (beta3AR) is resistant to short term agonist-promoted desensitization and sequestration, chimeric beta3/beta2 receptors were generated to identify the molecular determinants responsible for these regulatory processes in the beta2AR. By exchanging single or multiple intracellular domains of the beta3AR for the corresponding regions of the beta2AR, we show that specific domains can be identified as additive determinants for desensitization, while sequestration is more dependent on global structural conformation. The carboxyl-terminal tail, the third and the second intracellular loops of the beta2AR provided additive contributions to the desensitization observed upon short term agonist stimulation. The second intracellular loop plays a role which is as important as that of third cytoplasmic loop and carboxyl-terminal tail which had previously been identified as the major determinants of agonist-promoted desensitization. Additive contributions of the cytoplasmic domains of the beta2AR were also observed for agonist-promoted sequestration. The substitution of the first and second intracellular loops and the carboxyl tail were associated with a beta2-like sequestration phenotype. However, in contrast to what is observed for desensitization the co-substitution of the third cytoplasmic loop with any of the other domains completely suppressed sequestration. These results suggest that sequestration depends not only on appropriate interactions of multiple molecular determinants within the cytoplasmic region of the beta2AR but also on conformational determinants that may influence their orientation.

We summarize here a number of properties that have been described for G protein coupled membrane receptors. These concern structure-function relationship, regulation of expression and activity and linkage with pathology. The existence of subfamilies and subtypes is discussed in terms of evolution and selectivity. A comparison is made between binding sites for small ligands such as monoamines and larger ligands such as peptides and glycohormones. Cross-talk of G protein coupled receptors with receptor tyrosine kinase pathways is also discussed. Finally, the role of mutations in modulating receptor activity is evaluated with respect to human disease.

A full-length clone encoding a beta-adrenergic receptor was isolated from a bovine brown adipose tissue cDNA library. By comparative sequence analysis, and pharmacological characterization of a Chinese hamster ovary cell line expressing the full-length cDNA, it was shown that the product of the cloned gene is the bovine equivalent of the atypical beta 3-adrenergic receptor previously described in human, mouse, and rat [Strosberg, A. D. (1993) Prot. Sci. 2, 1198-1209]. The cloned receptor exhibits a pharmacological profile very similar to those from other species. In particular, the receptor has high affinity for BRL 37344 [(RR,SS)-(+/-)-4-(2'-[2-hydroxy-2-(3- chlorophenyl)ethylamino]propyl)phenoxyacetate sodium salt sesquihydrate], and low affinity for the iodinated ligand(-)-[3-125I]-iodocyanopindolol. The bovine beta 3-adrenergic receptor has high affinity for beta 1-adrenergic receptor and beta 2-adrenergic receptor antagonists including ICI 201651 [(R)-4-(2-hydroxy-3-phenoxypropylaminoethoxy)-N-(2- methoxyethyl)phenoxy acetic acid], carazolol, and CGP 12177A [(+/-)-4-(3-t-butylamino-2- hydroxypropoxy)benzimidazol-2-one]. In contrast to the murine beta 3-adrenergic receptor, both bupranolol and (-)-propranolol were partial agonists of the bovine receptor. The isolation of the bovine beta 3-adrenergic receptor, and information obtained from detailed pharmacological profiling may allow for the development of selective compounds for producing beef cattle with a low-body-mass index, and also aid the ongoing search for more selective agonists for the human receptor.

P56lck is a protein tyrosine kinase of the Src family specifically expressed in T lymphocytes. Triggering of T cells with anti-CD3 or with phorbol 12-myristate 13-acetate (PMA) results in the appearance of slower migrating forms (shift) of p56lck. To investigate the phosphorylation sites on the shifted forms of p56lck and to assess the role of protein kinase C in this phosphorylation, Jurkat cells were treated with a selective inhibitor of this kinase (GF 109203X). This inhibitor completely reversed the shift induced by PMA but only partially reversed the one induced after triggering with anti-CD3. To analyze the shift further, p56lck was immunoprecipitated from in vivo labeled cells treated either with anti-CD3 or with PMA. Tryptic phosphopeptides were generated and analyzed by using a combination of thin layer chromatography, high reticulation polyacrylamide gel electrophoresis, reverse phase chromatography, and phosphopeptide sequencing. We identified serine 158 as a newly phosphorylated site after PMA treatment and tyrosine 192 and serine 194 in the major tryptic phosphopeptide obtained after anti-CD3 triggering. The three sites identified are located in the SH2 domain of p56lck; this suggests that their phosphorylation may regulate the interaction with other proteins or with other internal domains in p56lck.

The amino terminal (positions 0 to 20) amino acid sequences of 22 rabbit antibody light chains are reported and compared with 44 amino terminal sequences previously described in the literature. Rabbit k light chains demonstrate three different amino terminal chain lengths and considerable variability at the amino terminal end. In relating amino terminal sequence to b locus allotype, allotype-specific residues (amino acid residues unique to all light chains having a given allotype) were not identified, although certain residue alternatives were unique to some of the b5 and b9 light chains. There was no correlation of antibody specificity with amino terminal sequence. In the most striking example, identical amino terminal sequences were associated with two different carbohydrate specificities (type VIII pneumococcal polysaccharide and streptococcal group A carbohydrate) and an aminophenyltrimethylammonium specificity. An obligatory association of amino terminal sequence with complete variable region framework sequences was not observed. Thus, it is not always possible to predict the framework homology among a given pair of light chains by examination of their amino terminal sequences. The limited diversity seen among the variable regions of murine myelomas that have the same antigen-binding properties is not found in the light chains of specifically elicited rabbit antibodies.

The subunit structure and complete amino acid sequence of the lectin extracted from Lens culinaris (LcL) seeds was determined. In previous studies, the primary structure of the alpha-chain (Mr = 5,710) was shown to be homologous to the alpha-chain of the lectin from Pisum sativum, the Vicia cracca glucose-specific lectin, and a region in the middle of the concanavalin A sequence (residues 70-121). The complete amino acid sequence of the beta-chain (Mr = 17,572) has been determined from 11 tryptic peptides, 4 peptides derived by chemical cleavage of the beta-chain at its three tryptophan residues, 11 peptides obtained after digestion with Staphylococcus aureus protease, and 5 tryptic peptides from the succinylated polypeptide chain. The extensive homologies by alignment of the alpha- and beta-chains of the L. culinaris lectin with portions of concanavalin A situated between 1 to 45 and 70 to 237, suggest that the L. culinaris and Canavalia ensiformis lectins have evolved from each other. A comparison was made between the secondary structure of the C. ensiformis lectin and the probable secondary structure of the L. culinaris lectin as predicted by two different methods. The results indicate that the folding of these two polypeptides has been particularly well conserved during evolution. It is suggested that the L. culinaris lectin is synthesized as a single polypeptide chain and cleaved subsequently into two or possibly three fragments, two of which would be alpha and beta and the third a fragment homologous to portion 46 to 69 in concanavalin A. As in favin, the amino acids postulated to be involved in the formation of the hydrophobic cavity and the sugar and metal binding sites are highly conserved in L. culinaris lectin.

Allotype Ighb congenic C.B20 mice when immunized with dextran B1355S are unable to produce anti-alpha (1----3) dextran antibodies that express the VH-associated cross-reactive IdX idiotype. This intrastrain-specific idiotype is normally associated only with the anti-dextran response of Igha mice of which BALB/c is a prototype strain. In this study we have obtained monoclonal hybridoma antibodies specific for the alpha (1----3) glucosidic linkage of dextran from C.B20 mice that were presensitized with rabbit anti-IdX antibodies. These antibodies display the light chain isotype distribution, the H chain amino terminal sequence, share VH-associated IdX idiotypic determinants, and finally the similar fine specificity for dextrans observed for anti-alpha (1----3) dextran antibodies of BALB/c mice.

Rabbit light chain 3315, prepared from a homogeneous antipneumococcal antibody, was subjected to hydrolysis by pepsin without prior reduction and alkylation of the intrachain disulfide bonds. Gel filtration of the hydrolysate on Sephadex G-10, G-15, and G-25 and ion exchange chromatography on SP-Sephadex yielded several disulfide bridge peptides. These were fully reduced and alkulated and sequenced by Edman degradation. The peptides were located in the light chain sequence determined in independent studies from our laboratory. The half-cystine residues in this KB rabbit chain are located at positions 23, 80, 88, 134, 171, 194, and 214. The extra disulfide bridge extends between residues 80 and 171, thus joining the variable and constant domains. This is consistent with x-ray diffraction crystallographic studies showing that the corresponding residues in human light chains are separated by a distance compatible with disulfide bond formation.

Four homogeneous antibodies to type VIII pneumococcal polysaccharide (S8) were isolated from the serum of a single rabbit (3322) by affinity chromatography on an S8 immunoadsoebent by utilizing gradient elution with cellobiose and NaCl. The binding properties of these antibodies were determined by a radioimmunoassay with 125I-bovine gamma-globulin-S8. Cellobiose (a disaccharide unit of S8) was the immunodominant group of each of the four antibodies, but each antibody bound to this disaccharide with different relative affinities. The amino acid sequences (positions 0-40) of three of the four antibody light chains were each different both in framework and first hypervariable region sequences. The fourth antibody light chain has a blocked amino terminus. These findings indicate that antibodies elicited by a relatively simple antigen and examined at one time during the course of immunization in a single rabbit may exhibit common specificities for an oligosaccharide determinant, yet have different binding affinities for that determinant as well as different primary structures in the complementarity (hypervariable) regions and framework regions.

After somatic cell fusion between splenocytes of immunized BALB/c mice and NS-1 myeloma cells, a clone was obtained that secreted an anti-nortriptyline antibody of the IgG1 kappa isotype. The association constant of this antibody for pharmacologically active tricyclic antidepressant drugs ranged from 0.6 X 10(7) to 3 X 10(7) M-1. From thermodynamic and binding studies as well as tridimensional structures of tested compounds, the epitope recognized by the monoclonal antibody appeared to include both a hydrophobic tricycle in which the two phenyl rings form an angle of 120 to 130 degrees, and a side chain in which the amino group is separated from the two lateral rings of the tricyclic structure by a distance of approximately 5.9 A and 7.5 A, respectively. This conformation seems to be the one interacting with muscarinic acetylcholine brain receptors.

The V region genes (VH and VL) used in the immune response of BALB/c mice to alprenolol, a synthetic beta-adrenergic ligand, were examined by Southern blot and nucleotide sequence analyses. Fourteen anti-alprenolol hybridomas utilize 10 different combinations of six Vk, one V lambda, eight VH, three JK, one J lambda, and three JH genes. In addition to the combinatorial association, somatic mutations and junctional variation of assembled genes further contribute to diversity of the anti-alprenolol response. Although differing both in length and structure, the five H-chain third complementarity-determining region analyzed contain several acidic residues. Neither V gene utilization, nor H-chain third complementarity-determining-region structure can be simply correlated with affinity of the antibodies for the ligand. The anti-alprenolol V genes were compared with the corresponding sequences of unrelated antibodies. Antibody 37A4 shares a VH gene with anti-(Glu60Ala30Tyr10)n random terpolymer and anti-nitrophenyl antibodies, and a Vk gene with two anti-oxazolone antibodies. Antibodies 14C3 and 17C1 use the same germ-line VH and Vk genes as do anti-anti-idiotypic antibodies of the (Glu60Ala30Tyr10) system. These data demonstrate the genetic diversity of the antibody response to alprenolol, and illustrate the extensive flexibility of the immune system.

A rabbit antiserum raised against anti-alprenolol mAb 14C3 detects common antigenic determinants (ADC3) in 10 out of 14 anti-alprenolol mAb that use different germ-line VH and/or Vk genes. The anti-14C3 antiserum binds only to H chains in immunoblots, therefore suggesting that at least part of the ADC3 determinants may be encoded by H chain V region genes. Analysis of VH gene family usage among the anti-alprenolol mAb reveals that the expression of ADC3 correlates with utilization of VH genes that belong to the J558 gene family, regardless of the JH, Vk, and Jk genes. To determine whether the ADC3 determinants are general V region markers or whether they are unique to anti-alprenolol antibodies, we have extended our analysis to a random panel of antibodies that also use VH genes of the J558 family. Among 23 mAb of various specificities, 14 react with the anti-14C3 antiserum in immunoblot and in ELISA, irrespective of antibody specificity. Adsorption of the antiserum on one of these positive antibodies results in a loss of reactivity toward both anti-alprenolol and unrelated antibodies. Therefore, several but not all antibodies that use a J558 VH gene also express the complete set of epitopes defining ADC3. These results strongly suggest that ADC3 are markers of a subset of J558 VH gene products. The anti-14C3 antiserum may thus constitute a "serologic probe" for identification of a VH gene subgroup from the J558 gene family.