Immunofluorescence of arginine deprived cells infected with adenovirus type 12

Susammenfassung KB-Zellen, die mit Adenovirus 12 infiziert waren und entweder in argininfreiem Medium oder in Medium, das 125 g/mll-Canavanin enthielt, gehalten wurden, entwickelten kein nukleares Antigen, das durch indirekte Immunofluoreszens ermittelt werden konnte.

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We thank Mrs.Rebecca Castleberry for her excellent technical assistance.     

Induction of interferon by levamisole and concanavalin A in HA/ICR and NZB/W mouse spleen cells

Summary Levamisole alone and in combination with concanavalin A (Con A) induced interferon in splenic cultures of NZB/W and HA/ICR mice. Levamisole did not potentiate interferon induction by Con A. HA/ICR mice consistently produced greater amounts of interferon than NZB/W.     

Differential regulation of the alpha 2-adrenergic receptor by Na+ and guanine nucleotides

Many hormones interact with receptors which stimulate the enzyme adenylate cyclase. Less well characterized ar those receptors which mediate an inhibition of adenylate cyclase activity. However, guanine nucleotides are clearly important in the regulation of both stimulatory and inhibitory receptors. Monovalent cations, notably Na+, regulate many inhibitory receptor systems but apparently not stimulatory receptors. We investigate here the effects of Na+ and guanine nucleotides on the adenylate cyclase-coupled inhibitory alpha 2-adrenergic receptor of the rabbit platelet. Computer modelling of adrenaline competition curves with 3H-dihydroergocryptine (3H-DHE) indicates that adrenaline induces two distinct affinity states of the alpha 2 receptor--one of higher (alpha 2H) and the other of lower (alpha 2L) affinity. Guanyl-5'-yl-imidodiphosphate (Gpp(NH)p) seems to reduce adrenaline affinity to converting the high-affinity state into the low-affinity form of the receptor. In contrast, Na+ reduces adrenaline affinity at both the high- and low-affinity states of the alpha 2 receptor while preserving receptor heterogeneity. Thus, guanine nucleotides and Na+ differ in the manner by which each reduces agonist affinity for the alpha 2-adrenergic receptor.     

The genomic clone G-21 which resembles a beta-adrenergic receptor sequence encodes the 5-HT1A receptor

The recent cloning of the complementary DNAs and/or genes for several receptors linked to guanine nucleotide regulatory proteins including the adrenergic receptors (alpha 1, alpha 2A, alpha 2B, beta 1, beta 2), several subtypes of the muscarinic cholinergic receptors, and the visual 'receptor' rhodopsin has revealed considerable similarity in the primary structure of these proteins. In addition, all of these proteins contain seven putative transmembrane alpha-helices. We have previously described a genomic clone, G-21, isolated by cross-hybridization at reduced stringency with a full length beta 2-adrenergic receptor probe. This clone contains an intronless gene which, because of its striking sequence resemblance to the adrenergic receptors, is presumed to encode a G-protein-coupled receptor. Previous attempts to identify this putative receptor by expression studies have failed. We now report that the protein product of the genomic clone, G21, transiently expressed in monkey kidney cells has all the typical ligand-binding characteristics of the 5-hydroxytryptamine (5-HT1A) receptor.     

Properties of bovine interferons

Summary This study was done in an attempt to elucidate some of the properties of bovine IFNs. Maximum levels of both fibroblast and leukocyte IFNs occurred prior to 24 h whereas maximum levels of immune IFN were not reached until after 72 h. The latter species of IFN was unstable at either pH 2 or 56°C whereas both the fibroblast and leukocyte IFNs were more stable under these conditions. Studies of cross-species protection between fibroblast and leukocyte IFNs indicate that the former was more protective for other species than the latter.Supported in part by National Institutes of Health Biomedical Research Support Grant RR05773-08.     

Pure beta-adrenergic receptor: the single polypeptide confers catecholamine responsiveness to adenylate cyclase

The beta-adrenergic receptor binding subunits from frog erythrocytes, hamster lung and guinea pig lung have been purified to apparent homogeneity and in all cases reside on a single polypeptide. Insertion of the pure receptors into phospholipid vesicles and subsequent fusion of these vesicles with a receptor-deficient cell conveys beta-adrenergic responsiveness to the adenylate cyclase system of the acceptor cell. Such responsiveness is linearly dependent on the amount of receptor used in the fusion experiments and is independent of the receptor source. Moreover, this responsiveness displays appropriate beta-adrenergic specificity. These results indicate that the beta-adrenergic receptor polypeptide contains both the ligand binding site and the site responsible for mediating stimulation of adenylate cyclase activity, presumably via interaction with the guanine nucleotide regulatory protein.     

Isoprenylation in regulation of signal transduction by G-protein-coupled receptor kinases.

Rhodopsin kinase and beta-adrenergic receptor kinase (beta ARK) are related members of a serine/threonine kinase family that specifically initiate deactivation of G-protein-coupled receptors. After stimulus-mediated receptor activation, these cytoplasmic kinases translocate to the plasma membrane. Here we show that the molecular basis for this event involves a class of unsaturated lipids called isoprenoids. Covalent modification in vivo of rhodopsin kinase by a 15-C (farnesyl) isoprenoid enables the kinase to anchor to photon-activated rhodopsin. Mutations that alter or eliminate the isoprenoid, fully disable light-specific Rhodopsin kinase translocation. Other receptor kinases (such as beta ARK), which lack an intrinsic lipid, are activated on exposure to brain beta gamma subunits of the signal-transducing G proteins, the gamma subunit of which bears a 20-C (geranylgeranyl) isoprenoid. Using chimaeric beta ARKs that undergo isoprenylation in vitro, we demonstrate that membrane association and activation of these kinases can occur in the absence of beta gamma. These results indicate that rhodopsin kinase (by means of an integral isoprenoid) and beta ARK (through its association with beta gamma) both rely on the function of isoprenyl moieties for their translocation and activity, illustrating distinct, though related, modes of biological regulation of receptor function.     

Overview of the Alliance for Cellular Signaling

The Alliance for Cellular Signaling is a large-scale collaboration designed to answer global questions about signalling networks. Pathways will be studied intensively in two cells--B lymphocytes (the cells of the immune system) and cardiac myocytes--to facilitate quantitative modelling. One goal is to catalyse complementary research in individual laboratories; to facilitate this, all alliance data are freely available for use by the entire research community.     

Properties of bovine interferons

This study was done in an attempt to elucidate some of the properties of bovine IFNs. Maximum levels of both fibroblast and leukocyte IFNs occurred prior to 24 h whereas maximum levels of immune IFN were not reached until after 72 h. The latter species of IFN was unstable at either pH 2 or 56 degrees C whereas both the fibroblast and leukocyte IFNs were more stable under these conditions. Studies of cross-species protection between fibroblast and leukocyte IFNs indicate that the former was more protective for other species than the latter.