Characterization of the sensor domain of QseE histidine kinase from Escherichia coli.

In enterohemorrhagic Escherichia coli (EHEC), the QseEF two-component system causes attaching and effacing (AE) lesion on epithelial cells. QseE histidine kinase senses the host hormone epinephrine, sulfate, and phosphate; it also regulates QseF response regulator, which activates LEE gene that encodes AE lesion. In order to understand the recognition of ligand molecules and signal transfer mechanism in pathogenic bacteria, structural studies of the sensor domain of QseE of Escherichia coli should be conducted. In this study, we describe the overexpression, purification, and structural and biophysical properties of the sensor domain of QseE. The fusion protein had a 6×His tag at its N-terminus; this protein was overexpressed as inclusion bodies in E. coli BL21 (DE3). The protein was denatured in 7M guanidine hydrochloride and refolded by dialysis. The purification of the refolded protein was carried out using Ni-NTA affinity column and size-exclusion chromatography. Thereafter, the characteristics of the refolded protein were determined from NMR, CD, and MALS spectroscopies. In a pH range of 7.4-5.0, the folded protein existed in a monomeric form with a predominantly helical structure. (1)H-(15)N HSQC NMR spectra shows that approximately 93% backbone amide peaks are detected at pH 5.0, suggesting that the number of backbone signals is sufficient for NMR studies. These data might provide an opportunity for structural and functional studies of the sensor domain of QseE.

Mutations in the zebrafish unmask shared regulatory pathways controlling the development of catecholaminergic neurons.

The mechanism by which pluripotent progenitors give rise to distinct classes of mature neurons in vertebrates is not well understood. To address this issue we undertook a genetic screen for mutations which affect the commitment and differentiation of catecholaminergic (CA) [dopaminergic (DA), noradrenergic (NA), and adrenergic] neurons in the zebrafish, Danio rerio. The identified mutations constitute five complementation groups. motionless and foggy affect the number and differentiation state of hypothalamic DA, telencephalic DA, retinal DA, locus coeruleus (LC) NA, and sympathetic NA neurons. The too few mutation leads to a specific reduction in the number of hypothalamic DA neurons. no soul lacks arch-associated NA cells and has defects in pharyngeal arches, and soulless lacks both arch-associated and LC cell groups. Our analyses suggest that the genes defined by these mutations regulate different steps in the differentiation of multipotent CA progenitors. They further reveal an underlying universal mechanism for the control of CA cell fates, which involve combinatorial usage of regulatory genes.

Intra-abdominal sepsis and adrenergic receptor response.

This study measured the adrenergic receptor response of 13 patients with severe intra-abdominal sepsis, who required laparotomy and an open abdominal closure with Marlex mesh. The source of the sepsis was gram-negative organisms of intestinal origin. There were seven survivors and six nonsurvivors. When the patients were stratified into survivors and nonsurvivors, the Septic Severity Score, the APACHE II score, the Acute Physiological Score, and the Glasgow Coma Scale score results were not significantly different between groups. The alpha-2 and beta-1 adrenergic receptor responses were measured in the adipose tissue of the abdominal wall and the small bowel mesentery on day 1 of admission to the intensive care unit. The results demonstrated that the alpha-2 and beta-1 receptors of the nonsurvivors had a significantly decreased receptor response with desensitization and down regulation. The alpha-2 and beta-1 receptors of the survivors had an increased response with hypersensitization and up regulation. This study indicates that the adrenergic receptor pattern is distinctly different between survivors and nonsurvivors with severe abdominal gram-negative sepsis. The pattern differences occurred early (within 24 hours) when the patients had similar physiologic profiles. It is concluded that adrenergic receptor response may be a biologic indicator of the magnitude of the septic injury and a predictor of outcome.

Isolation and N-terminal amino acid sequence of an octopamine ligand binding protein.

An octopamine receptor photoaffinity probe was used to label membranes from the light organs of Photinus pyralis, a tissue highly enriched in octopamine receptors. Labeling was concentrated in a glycoprotein of 75 +/- 2 kDa with lesser labeling of a 79 +/- 2 kDa component. Labeling could be displaced by prior incubation with octopamine, mianserin, cyproheptadine, phentolamine or propranolol, with a relative potency that correlated with the ability of these same agents to modulate light organ octopamine-sensitive adenylate cyclase. The 75 kDa binding protein was isolated and its N-terminal amino acid sequence was determined.

[Evaluation of the density of acetylcholinesterase-positive and intrinsic adrenergic innervation of the uterus in rats]. / Evaluation de la densité de l'innervation acétylcholinestérase-positive et adrénergique intrinsèque de l'utérus chez le rat.

According to the Karnovsky and Roots modified by E1 Badawi and Schenk's technique for the acetylcholinesterase-positive innervation and according to the Lindvall and Björklund modified by de la Torre and Surgeon's method for the adrenergic one, we have demonstrated the nervous fibers in the different tissues of the cervix, the corpus and the cornu of the she-rat in pro-oestrus. A statistic evaluation of the density of these nervous networks has been established for the different regions. The study of the histograms demonstrates the predominance of acetylcholinesterase-positive innervation versus the adrenergic one. The evolution of the nervous densities is similar for each tissue in the corpus and the cornu, these of the myometrium are the highest. In the cervix, the acetylcholinesterase-positive fibers dominate over the mucosal and submucosal ones, on the other hand, the adrenergic ones are richest in the muscle. Our morphometric studies confirm statistically the optic observations of the others authors.

Structural analysis of purified beta-adrenergic receptors.

We have characterized the structure of purified beta-adrenergic receptors by a combination of photoaffinity labeling, high performance liquid chromatography (HPLC)-tryptic mapping, CNBr fragmentation, target size analysis, and electron microscopy of purified receptor molecules. Guinea pig lung beta-adrenergic receptors purified by affinity chromatography, ion exchange chromatography, and HPLC size exclusion chromatography or photoaffinity labeled with [125]-iodocyanopindolol diazirine displayed mobilities on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) that corresponded to Mr = 68,000. Purified, radioiodinated guinea pig lung beta-receptors were subjected to complete trypsin digestion and subsequent reverse-phase HPLC analysis, which revealed nine peptides. Active site labeling and tryptic digestion of partially purified hamster lung beta-receptors produced one peptide, whereas CNBr digestion of the same material produced two labeled fragments, yielding information about the location of the active site within the primary sequence. Purified guinea pig lung receptors were examined with transmission electron microscopy. Electron micrographs revealed slightly asymmetric, rod-shaped structures with an average length of 13 nm and width of 3.4 nm. Many receptors were arranged as apparent dimeric structures. These findings confirm data obtained from target size analysis of guinea pig lung beta-receptors in situ which suggest that receptors may exist as oligomeric arrays in the native membrane. Taken together, these data provide information about putative functional domains of the beta-adrenergic receptor and its quaternary structure.

Ciba-Geigy award for outstanding research. Regulation of adrenergic receptor function by phosphorylation.

The various subtypes of adrenergic receptors represent distinct structural entities which are coupled in different ways to two major transmembrane signalling systems, the adenylate cyclase and phosphatidyl-inositol pathways. Recent evidence suggests that the functional linkage of both beta and alpha 1-adrenergic receptors to their respective effector systems is regulated by covalent modification of the receptors by phosphorylation-dephosphorylation reactions. Receptor phosphorylation appears to lead to desensitization of the biological response to receptor stimulation. Several kinases including protein kinase A, protein kinase C and a cAMP independent kinase appear to participate in these reactions.

The human heart beta-adrenergic receptors. I. Heterogeneity of the binding sites: presence of 50% beta 1- and 50% beta 2-adrenergic receptors.

Beta-adrenergic receptors were characterized in a particulate fraction of human auricles obtained from patients operated upon for coronary insufficiency or valvular disease. [125I] Hydroxybenzylpindolol binding was evaluated in terms of kinetics; KD and Bmax values; and inhibition of binding in the presence of 10 microM GTP and of increasing concentrations of four nonselective agonists giving a Hill coefficient of 1 (isoproterenol, salbutamol, fenoterol, and epinephrine), of two nonselective antagonists giving a Hill coefficient of 1 (pindolol and propranolol), and of a series of selective drugs giving a Hill coefficient of 0.60-0.72 that included three beta 1-selective antagonists (practolol, metoprolol, and atenolol) and two beta 2- selective agonists (procaterol and zinterol). KD values for all drugs were compatible with the coexistence in membranes from human auricles of beta 1- and beta 2-adrenergic receptors, the relative proportions of receptors of each subclass being approximately the same.

Solubilization of active brain alpha 1-adrenoceptors by a zwitterionic detergent.

Solubilization of rat brain alpha 1-adrenoceptors was performed by treatment with 6 mM CHAPS (3-[(3-cholamidopropyl)dimethylammonio] - 1 - propanesulfonate). The alpha 1-adrenoceptor antagonist [3H]prazosin was shown to bind reversibly and specifically to the soluble extract obtained after centrifugation at 150,000 X g for 1 h. Separation of the soluble [3H]prazosin-bound complexes was performed by the polyethylene glycol precipitation technique followed by filtration. A Scatchard plot of the concentration-dependent binding curve showed only one class of binding sites, with a high affinity for [3H]prazosin. Affinity of the solubilized receptors for the ligand increased as the CHAPS concentration in the assay medium decreased; the number of binding sites remained unchanged (approximately equal to 70 fmol/mg protein). This corresponds to a 30% recovery of original membrane sites. The solubilized receptors presented the same characteristics of specificity and stereospecificity as membrane alpha 1-adrenoceptors. Moreover, 150 mM NaCl was found to modulate the affinity of epinephrine for the [3H]prazosin-bound soluble complex, as previously described for membrane preparations. Thus, CHAPS appears to be a suitable detergent for solubilizing rat brain alpha 1-adrenoceptors and preserving their functional activities.

Delipidation of a beta-adrenergic receptor preparation and reconstitution by specific lipids.

The role of lipids in the function of membrane receptors for hormones and neurotransmitters is still obscure. To gain information on this subject, a delipidated receptor preparation was developed. The beta-adrenergic receptor from turkey erythrocyte membranes was solubilized in deoxycholate and was freed extensively of phospholipids and of cholesterol by gel filtration. The delipidated preparation, after removal of the detergent, showed little, if any, ligand binding to the receptor as measured with the beta-adrenergic antagonist [125I] iodocyanopindolol. Readdition of soybean lipids restored specific radioligand binding. The lipid reconstituted receptor demonstrated agonist and antagonist binding affinities which were not very different from those of the native receptor. The receptor also retained its ability to function, as demonstrated by transfer to a foreign adenylate cyclase system. The delipidated receptor preparation lent itself conveniently to study the requirement for specific lipids in restoration of agonist and antagonist binding. Phosphatidylethanolamine restored maximal binding. Acidic phospholipids and sphingomyelin were inefficient in reconstitution of the receptor. The effect of cholesterol addition was also investigated. Binding was dramatically increased when a cholesterol ester was added in mixture with the acidic phospholipids, cardiolipin or phosphatidylinositol. Further studies unexpectedly revealed that reconstitution of the delipidated receptor is not exclusively dependent on the addition of a phospholipid; a mixture of 1-monooleylglycerol with cholesteryl hemisuccinate restored binding as efficiently as phosphatidylethanolamine. The presently described preparation should be useful in elucidating the part played by lipids in the action of the receptor in the adenylate cyclase system.

Preponderance of alpha 2- over beta 1-adrenergic receptor sites in human fat cells is not predictive of the lipolytic effect of physiological catecholamines.

Adrenergic control of human fat cell lipolysis is mediated by two kinds of receptor sites that are simultaneously stimulated by physiological amines. To establish a correlation between the binding characteristics of the receptor and biological functions, the ability of physiological amines to stimulate or inhibit isolated fat cell lipolysis in vitro was compared to the beta- and alpha 2-adrenoceptor properties of the same fat cell batch. The beta-selective antagonist (-)[3H]dihydroalprenolol ([3H]DHA) and the alpha 2-selective antagonists [3H]yohimbine ([3H]YOH) and [3H]rauwolscine ([3H]RAU) were used to identify and characterize the two receptor sites. Binding of each ligand was rapid, saturable, and specific. The results demonstrate 1) the weaker lipolytic effect of epinephrine compared with norepinephrine. This can be explained by the equipotency of the amines at the beta 1-sites and the higher affinity of epinephrine for alpha 2-adrenergic receptors. 2) The preponderance of alpha 2-adrenergic receptor sites labeled by [3H]YOH (Bmax, 586 +/- 95 fmol/mg protein; KD, 2.7 +/- 0.2 nM) or [3H]RAU (Bmax, 580 +/- 100 fmol/mg protein; KD, 3.7 +/- 0.1 nM). These two ligands can be successfully used to label alpha 2-adrenergic receptor sites. 3) The beta 1-adrenergic receptor population labeled by [3H]DHA(Bmax, 234 +/- 37 fmol/mg protein; KD, 1.8 +/- 0.4 nM), although a third as numerous as the alpha 2-adrenergic population, is responsible for the lipolytic effect of physiological amines and is weakly counteracted by simultaneous alpha 2-adrenergic receptor stimulation under our experimental conditions. It is concluded that, in human fat cells, the characterization of beta 1- and alpha 2-adrenergic receptors by saturation studies or kinetic analysis to determine affinity (KD) and maximal number of binding sites (Bmax) is not sufficient for an accurate characterization of the functional adrenergic receptors involved in the observed biological effect.

Alpha-adrenoceptors in the developing kidney.

The maturation of renal alpha-adrenoceptors was investigated in dogs. Alpha-adrenoceptors were characterized by radioligand binding using the alpha-1-adrenergic antagonist, [3H]-WB-4101. In renal plasma membranes obtained from the outer cortex of neonates, the binding of the ligand was rapid, reversible, of high affinity, saturable, and stereoselective. The competition studies with adrenergic agonists and antagonists were indicative of alpha-receptors. In puppies less than 1-w-old, the binding affinity of [3H]-WB-4101 (Kd = 0.638 +/- 0.17 nM) was greater than 3-5 week-old puppies (Kd 1.573 +/- 0.315 nm); (P less than 0.05), but receptor number was similar (63.75 +/- 19.1 versus 79.10 +/- 5.99 fmole/mg protein). No consistent specific binding could be demonstrated in plasma membranes obtained from inner cortex of medulla. In the adult dog, no consistent specific binding could be demonstrated for plasma membranes obtained from any region of the kidney. These studies indicate that during maturation there is a decrease in alpha-adrenoceptor density and affinity in membranes from the outer cortex of the kidney.

beta-Adrenergic receptor isolation and characterization with immobilized drugs and monoclonal antibodies.

Immobilized catecholamines have played an important role in the localization of alpha- and beta-adrenergic receptors to the plasma membrane of effector cells, and in elucidating mechanisms of beta receptor activation of cardiac muscle. An extension of immobilized drug and affinity chromatography procedures has been developed by utilizing receptor-specific monoclonal antibodies. Structurally different beta 1- and beta 2-adrenergic receptors have been purified with a single monoclonal antibody affinity column, where the antibody is specific for an epitope in the ligand-binding site of both beta 1 and beta 2 receptors. Specificity was increased by elution of receptors from the monoclonal antibody affinity columns with low concentrations of beta-receptor antagonists. These studies indicate that the turkey erythrocyte beta 1-adrenergic receptor is most likely a monomer with a molecular weight of 65,000-70,000. beta 2-Adrenergic receptors have a primary subunit of 55,000-58,000 daltons, with the intact receptor in membranes having a molecular weight of 109,000, which suggests that the beta 2-adrenergic receptor is most likely a dimer of either two identical subunits or a binding subunit and an unidentified second subunit.

Autoantibodies and monoclonal antibodies in the purification and molecular characterization of neurotransmitter receptors.

The combination of immunological advances with membrane receptor research has promoted rapid progress in the molecular characterization of neurotransmitter receptor molecules. We have to date produced monoclonal antibodies to beta 1-, beta 2-, and alpha 1-adrenergic, D2-dopaminergic, and muscarinic receptors. In addition we have discovered that some allergic respiratory disease patients possess circulating autoantibodies to beta 2-adrenergic receptors. These antireceptor antibodies in conjunction with specific receptor affinity reagents have allowed us to isolate, purify, and begin to characterize alpha- and beta-adrenergic, dopaminergic, and muscarinic receptors. For example, immunoprecipitation of turkey erythrocyte beta 1 receptors with monoclonal antibodies yields a single polypeptide Mr 65--70 K. In contrast, purification of beta 2-adrenergic receptors using either autoantibodies or monoclonal antibodies yields a receptor species with a subunit of Mr 55--59 K. Autoantibodies to beta 2 receptors demonstrate a 50--100% homology among beta 2 receptors from humans to rats, whereas monoclonal antibody FV-104 recognizes a determinant in the ligand binding site of all beta 1 and beta 2 receptors tested to date. These data suggest that beta 1- and beta 2-adrenergic receptors may have evolved from a common ancestor, perhaps by gene duplication.

Characterization of alpha 1- and alpha 2-adrenergic receptors.

Within the short period of 5 years, the availability of a variety of specific radioligands has allowed the resolution of alpha 1- and alpha 2-adrenergic receptor populations in many different tissues and enabled researchers to begin investigations of the mechanisms of regulation and coupling of alpha 1 and alpha 2 receptors to their different cellular effector systems. Binding data have demonstrated that the pharmacological properties of each type of alpha receptor are, in general, similar across tissues and species, although there are some differences in the relative affinities of antagonist drugs. Further attempts to subclassify alpha 1 and alpha 2 receptors may be expected in the future. The historical development of the interpretation of [3H]clonidine binding is of interest in this regard. [3H]Clonidine was proposed to label the "agonist state" of the alpha receptor, and then to label alpha 2 receptors. It is now thought that it labels the agonist state of alpha 2 receptors. Might it actually label a subpopulation of alpha 2 receptors or just the agonist state of that subpopulation? Alpha-1 receptors by and large appear to occur in a single-affinity state with respect to both agonists and antagonists. By comparison, alpha 2 receptors may exist in multiple-affinity states reflecting the ability of the alpha 2 binding site protein to complex to additional membrane proteins which themselves are receptors for the physiological substrates GTP, Na+, Mg2+, and possibly Ca2+-calmodulin. Binding studies have also strongly indicated that alpha 2 receptors in most, if not all, tissues are probably coupled in an inhibitory manner to adenylate cyclase, as has been demonstrated in platelets, adipocytes, and NG 108-15 cells. Clearly the present status of alpha-receptor research has left many questions unresolved. We still have no idea what membrane effector system and associated second messenger is coupled to the alpha 1 receptor. The prevailing belief is that Ca2+ and the membrane Ca2+ channel fulfill these roles. However, others have suggested that phosphoinositide turnover represents the proximal receptor response, and indeed a membrane-bound phospholipase C may play an analogous role to adenylate cyclase for other adrenergic receptors (Putney et al., 1980). There is, however, some evidence that in some situations alpha 1 receptors may directly stimulate adenylate cyclase, and guanine nucleotide modulation of agonist affinities at alpha 1-receptor sites has been reported. The significance of these data and reported modulatory effects of Na+ at alpha 1 receptors (Glossmann and Presek, 1979; Glossmann et al., 1981) is still to be resolved.(ABSTRACT TRUNCATED AT 400 WORDS)

Biophysical characterization of the purified alpha 1-adrenergic receptor and identification of the hormone binding subunit.

The alpha 1-adrenergic receptor has been solubilized in active form from rat hepatic membranes with the nonionic detergent, digitonin, and purified by affinity and gel filtration chromatography to homogeneity with a specific activity of 14,400 pmol/mg of protein. The affinity chromatographic steps of the purification procedure were achieved by the use of a newly synthesized analog (2-[4(2-succinoyl)piperazin-1-yl]-4-amino-6,7-dimethoxyquinazoline, CP-57,609) of the highly selective alpha 1-adrenergic antagonist, prazosin, immobilized via an amide linkage to agarose. The resulting purified receptor bound [3H]prazosin and a variety of adrenergic agents with the specificity, stereoselectivity, and affinities equivalent to those observed with membrane-bound and solubilized receptor preparations. The purified receptor.digitonin complex had a Stokes radius of 49 A and a sedimentation coefficient (s20w) of 7.1, as determined by AcA-34 gel filtration chromatography and sucrose gradient density centrifugation, respectively. Based on these hydrodynamic parameters, the calculated molecular weight of the receptor.digitonin complex was estimated at 147,000. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis following the final purification step revealed a single band of protein at 59,000 daltons from which [3H]prazosin binding activity could be recovered after renaturation of the receptor protein. These findings indicate that the protein purified from rat hepatic membranes is the hormone binding component of the alpha 1-adrenergic receptor and that the receptor molecule most likely contains more than one Mr = 59,000 subunit.

Affinity chromatography of human platelet alpha 2-adrenergic receptors.

Catecholamines, such as epinephrine, inhibit the enzyme adenylate cyclase (EC 4.6.1.1) via a specific receptor mechanism involving alpha(2)-adrenergic receptors. In order to facilitate purification of these inhibitory receptors we have prepared a highly effective biospecific affinity adsorbent. The immobilized ligand SKF 101253 is a 3-benzazepine with alpha(2)-adrenergic antagonist activity. SKF 101253 is coupled to Sepharose CL-4B by using a bifunctional reagent (1,4-butanediol diglycidyl ether) which also provides a hydrophilic spacer moiety between the ligand and the gel matrix. Membranes from human platelets, containing alpha(2)-adrenergic receptors, can be specifically labeled with [(3)H]yohimbine and can be solubilized with digitonin without loss of their alpha(2)-adrenergic binding characteristics. Chromatography of solubilized human platelet membrane preparations on the SKF 101253-Sepharose CL-4B affinity gel results in the adsorption of 70-80% of the initial [(3)H]yohimbine binding activity. Adsorption to the affinity gel is blocked by both alpha-adrenergic antagonists (phentolamine >/= yohimbine > prazosin) and by alpha-adrenergic agonists [p-aminoclonidine > (-)-epinephrine > (+)-epinephrine]. Similarly, elution of specific [(3)H]yohimbine binding activity from the affinity gel is effected with the aforementioned agonists and antagonists in the same order of potency. Other drugs that do not interact appreciably with alpha-adrenergic receptors, such as (-)-isoproterenol, (-)-alprenolol, atropine, and carbachol, are ineffective for both the blockade of adsorption and the elution of specific [(3)H]yohimbine binding activity from the affinity gel. In addition to the specificity of the interaction, chromatography of solubilized human platelet membrane preparations on the SKF 101253-Sepharose CL-4B affinity gel results in a 40-50% overall yield and an approximately 200-fold increase in the specific binding activity for [(3)H]yohimbine. The results indicate that the SKF 101253-Sepharose CL-4B affinity adsorbent should provide a powerful tool for the purification of the adenylate cyclase-inhibitory alpha(2)-adrenergic receptor of human platelets.