scholarly journals Testosterone Signaling through Internalizable Surface Receptors in Androgen Receptor-free Macrophages

1999 ◽  
Vol 10 (10) ◽  
pp. 3113-3123 ◽  
Author(s):  
W. Peter M. Benten ◽  
Michèle Lieberherr ◽  
Olaf Stamm ◽  
Christian Wrehlke ◽  
Zhiyong Guo ◽  
...  
Keyword(s):  
Phospholipase C ◽  
Binding Sites ◽  
Plasma Membranes ◽  
Androgen Receptors ◽  
Surface Receptors ◽  
Toxin Binding ◽  
Agonist Stimulation ◽  
Intracellular Ca ◽  
Cytoskeletal Elements ◽  
G Protein Coupled

Testosterone acts on cells through intracellular transcription-regulating androgen receptors (ARs). Here, we show that mouse IC-21 macrophages lack the classical AR yet exhibit specific nongenomic responses to testosterone. These manifest themselves as testosterone-induced rapid increase in intracellular free [Ca2+], which is due to release of Ca2+from intracellular Ca2+stores. This Ca2+mobilization is also inducible by plasma membrane-impermeable testosterone-BSA. It is not affected by the AR blockers cyproterone and flutamide, whereas it is completely inhibited by the phospholipase C inhibitor U-73122 and pertussis toxin. Binding sites for testosterone are detectable on the surface of intact IC-21 cells, which become selectively internalized independent on caveolae and clathrin-coated vesicles upon agonist stimulation. Internalization is dependent on temperature, ATP, cytoskeletal elements, phospholipase C, and G-proteins. Collectively, our data provide evidence for the existence of G-protein-coupled, agonist-sequestrable receptors for testosterone in plasma membranes, which initiate a transcription-independent signaling pathway of testosterone.

scholarly journals The Retinoid and Non-Retinoid Ligands of the Rod Visual G Protein-Coupled Receptor

2019 ◽  
Vol 20 (24) ◽  
pp. 6218 ◽  
Author(s):  
Joseph T. Ortega ◽  
Beata Jastrzebska
Keyword(s):  
Drug Discovery ◽  
G Protein ◽  
Binding Sites ◽  
Binding Pocket ◽  
Biologically Active ◽  
Surface Receptors ◽  
Beneficial Effects ◽  
Light Sensing ◽  
Potential Binding ◽  
G Protein Coupled

G protein-coupled receptors (GPCRs) play a predominant role in the drug discovery effort. These cell surface receptors are activated by a variety of specific ligands that bind to the orthosteric binding pocket located in the extracellular part of the receptor. In addition, the potential binding sites located on the surface of the receptor enable their allosteric modulation with critical consequences for their function and pharmacology. For decades, drug discovery focused on targeting the GPCR orthosteric binding sites. However, finding that GPCRs can be modulated allosterically opened a new venue for developing novel pharmacological modulators with higher specificity. Alternatively, focus on discovering of non-retinoid small molecules beneficial in retinopathies associated with mutations in rhodopsin is currently a fast-growing pharmacological field. In this review, we summarize the accumulated knowledge on retinoid ligands and non-retinoid modulators of the light-sensing GPCR, rhodopsin and their potential in combating the specific vision-related pathologies. Also, recent findings reporting the potential of biologically active compounds derived from natural products as potent rod opsin modulators with beneficial effects against degenerative diseases related to this receptor are highlighted here.

scholarly journals Lectin-binding sites on the plasma membranes of rabbit spermatozoa: Changes in surface receptors during epididymal maturation and after ejaculation

1977 ◽  
Vol 74 (3) ◽  
pp. 950-962 ◽  
Author(s):  
GL Nicolson ◽  
N Usui ◽  
R Yanagimachi ◽  
H Yanagimachi ◽  
Smith JR
Keyword(s):  
Binding Sites ◽  
Plasma Membranes ◽  
Ricinus Communis ◽  
Lectin Binding ◽  
Similar Degree ◽  
Con A ◽  
Lectin Receptors ◽  
Surface Receptors ◽  
Epididymal Spermatozoa ◽  
Lectin Binding Sites

Modifications in rabbit sperm plasma membranes during epididymal passage and after ejaculation were investigated by used of three lectins: concanavalin A (Con A); Ricinus communis I (RCA(I)); and wheat germ agglutinin (WGA). During sperm passage from caput to cauda epididymis, agglutination by WGA drastically decreased, and agglutination by RCA(I) slightly decreased, although agglutination by Con A remained approximately unchanged. After ejaculation, spermatozoa were agglutinated to a similar degree or slightly less by Con A, WGA, and RCA(I), compared to cauda epididymal spermatozoa. Ultrastructural examination of sperm lectin-binding sites with ferritin- lectin conjugates revealed differences in the densities of lectin receptors in various sperm regions, and changes in the same regions during epididymal passage and after ejaculation. Ferritin-RCA(I) showed abrupt changes in lectin site densities between acrosomal and postacrosomal regions of sperm heads. The relative amounts of ferritin-RCA(I) bound to heads of caput epididymal or ejaculated spermatozoa. Tail regions were labeled by ferritin RCA(I) almost equally on caput and cauda epididymal spermatozoa, but the middle-piece region of ejaculated spermatozoa was slightly more densely labeled than the principal-piece region, and these two regions on ejaculated spermatozoa were labeled less than on caput and cuada epididymal spermatozoa. Ferritin-WGA densely labeled the acrosomal region of caput epididymal spermatozoa, although labeling of cauda epidiymal spermatozoa was relatively sparse except in the apical area of the acrosomal region. Ejaculated spermatozoa bound only a few molecules of ferritin-WGA, even at the highest conjugate concentrations used. Caput epididymal, but not cauda epididymal or ejaculated spermatozoa, bound ferritin-WGA in the tail regions. Dramatic differences in labeling densities during epididymal passage and after ejaculation were not found with ferritin-Con A.

Glucagon-mediated Ca2+signaling in BHK cells expressing cloned human glucagon receptors

1998 ◽  
Vol 274 (6) ◽  
pp. C1552-C1562 ◽  
Author(s):  
Lars H. Hansen ◽  
Jesper Gromada ◽  
Pierre Bouchelouche ◽  
Ted Whitmore ◽  
Laura Jelinek ◽  
...  
Keyword(s):  
Phospholipase C ◽  
Acetylcholine Receptors ◽  
Glucagon Receptor ◽  
Bhk Cells ◽  
Mediated Effects ◽  
Intracellular Ca ◽  
Glucagon Receptors ◽  
G Protein Coupled ◽  
Dose Dependent ◽  
Stimulation Of

From video imaging of fura 2-loaded baby hamster kidney (BHK) cells stably expressing the cloned human glucagon receptor, we found the Ca2+ response to glucagon to be specific, dose dependent, synchronous, sensitive to pertussis toxin, and independent of Ca2+ influx. Forskolin did not elicit a Ca2+response, but treatment with a protein kinase A inhibitor, the Rp diastereomer of 8-bromoadenosine-3′,5′-cyclic monophosphothioate, resulted in a reduced glucagon-mediated Ca2+ response as well as Ca2+ oscillations. The specific phospholipase C inhibitor U-73122 abolished the Ca2+ response to glucagon, and a modest twofold increase in inositol trisphosphate (IP3) production could be observed after stimulation with glucagon. In BHK cells coexpressing glucagon and muscarinic (M1) acetylcholine receptors, carbachol blocked the rise in intracellular free Ca2+ concentrations in response to glucagon, whereas glucagon did not affect the carbachol-induced increase in Ca2+. Furthermore, carbachol, but not glucagon, could block thapsigargin-activated increases in intracellular free Ca2+concentration. These results indicate that, in BHK cells, glucagon receptors can activate not only adenylate cyclase but also a second independent G protein-coupled pathway that leads to the stimulation of phospholipase C and the release of Ca2+ from IP3-sensitive intracellular Ca2+ stores. Finally, we provide evidence to suggest that cAMP potentiates the IP3-mediated effects on intracellular Ca2+ handling.

Survey of the Taxonomic and Tissue Distribution of Microsomal Binding Sites for the Non-Host Selective Fungal Phytotoxin, Fusicoccin

1993 ◽  
Vol 48 (7-8) ◽  
pp. 595-602 ◽  
Author(s):  
Christiane Meyer ◽  
Kerstin Waldkötter ◽  
Annegret Sprenger ◽  
Uwe G. Schlösset ◽  
Markus Luther ◽  
...  
Keyword(s):  
Tissue Distribution ◽  
Binding Sites ◽  
Plasma Membranes ◽  
Guard Cells ◽  
Land Plants ◽  
Mesophyll Cells ◽  
Specific Expression ◽  
Toxin Binding ◽  
Site Density ◽  
Number Of Binding Sites

The recent identification of the fusicoccin-binding protein (FCBP) in plasma membranes from monocotyledonous and dicotyledonous angiosperms has opened the basis for an elucidation of the toxin’s mechanism(s) of action and indicated a widespread occurrence of the FCBP in plants. Results of a detailed taxonomic survey of fusicoccin-binding sites are reported. Binding sites were not found in prokaryotes, animal tissues, fungi and algae including the most direct extant ancestors of the land plants (Coleochaete). From the Psilotales (Psilophytatae) to the monocotyledonous angiosperms, all taxa analyzed possessed high-affinity microsomal fusicoccin-binding sites. A heterogeneous picture emerged for the Bryophvta. Anthoceros crispulus (Anthocerotae), the only hornwort available to study, lacked fusicoccin binding. Within the Hepaticae as well as the Musci, species lacking and species exhibiting toxin binding were found. The binding site thus seems to have emerged very early in the evolution of the land plants. The tissue distribution of fusicoccin-binding sites was studied in Vicia faba L. shoots. All tissues analyzed showed fusicoccin binding, although not to the same extent. On a per-cell basis, guard cells were found to contain, compared to mesophyll cells, a nine-fold higher number of binding sites. Based on cell surface area, the site density is by a factor of 32 higher in guard cells than in mesophyll cells. Tissue specific expression of the binding sites is suggested by these findings.

Angiotensin II (All)-binding sites in nuclei from rat liver: partial characterization of the mechanism of All accumulation in nuclei

1994 ◽  
Vol 143 (3) ◽  
pp. 449-453 ◽  
Author(s):  
E Jiménez ◽  
G P Vinson ◽  
M Montiel
Keyword(s):  
Angiotensin Ii ◽  
Binding Sites ◽  
Plasma Membranes ◽  
Nuclear Accumulation ◽  
Receptor Subtype ◽  
Charge Heterogeneity ◽  
Nuclear Extracts ◽  
A Charge ◽  
Cytoskeletal Elements

Abstract Isoelectric focusing analysis showed a single angiotensin II (All)-receptor complex migrating to pI 6·8 in nuclear preparations, while in plasma membranes a charge heterogeneity of the All receptor subtype AT1 was observed. 125I-Labelled All binding sites were found in intact nuclei and were not detected in nuclear extracts. Neither disruption of cytoskeletal elements by colchicine nor prevention of endosome acidification by chloroquine had any effect on nuclear accumulation of AIL Nevertheless, the monovalent ionophore monensin inhibited nuclear accumulation of 125I-Labelled All. Our findings are consistent with the hypothesis that processing through the Golgi apparatus could be involved in the nuclear accumulation of AIL Journal of Endocrinology (1994) 143, 449–453

scholarly journals Solubilization of rat liver vasopressin receptors as a complex with a guanine-nucleotide-binding protein and phosphoinositide-specific phospholipase C

1989 ◽  
Vol 261 (1) ◽  
pp. 63-70 ◽  
Author(s):  
N Aiyar ◽  
C F Bennett ◽  
P Nambi ◽  
W Valinski ◽  
M Angioli ◽  
...  
Keyword(s):  
Phospholipase C ◽  
Rat Liver ◽  
Binding Sites ◽  
Plasma Membranes ◽  
Specific Binding ◽  
Binding Protein ◽  
Protein S ◽  
Binding Activity ◽  
Affinity Column ◽  
Vasopressin Receptors

Vasopressin V1 receptors were solubilized from rat liver plasma membranes with the detergent lysophosphatidylcholine. [[3H]Arginine]vasopressin (AVP) binding to the solubilized preparations was specific and saturable, with a dissociation constant of 0.6 nM. Cross-linking of [125I]vasopressin to the solubilized fraction, studied by SDS/polyacrylamide-gel-electrophoretic analysis, demonstrated the presence of a 65 kDa band which was specifically labelled with [125I]vasopressin. Specific binding of [3H]AVP to these solubilized receptors was decreased by guanine nucleotides, but not by adenosine 5′-[beta gamma-imido]triphosphate. Addition of vasopressin increased specific binding of 35S-labelled guanosine 5′-[gamma-thio]triphosphate (GTP[35S]) to the solubilized fractions, indicating co-solubilization of GTP-binding protein(s) [G-protein(s)] and vasopressin receptors. The solubilized fraction was insensitive to both cholera- and pertussistoxin treatment. Immunoblotting of the solubilized fraction with antibodies specific for a phosphoinositide-specific phospholipase C (PI-PLC I) demonstrated the presence of a 60 kDa protein. Anti-PI-PLC I antiserum immunoprecipitated solubilized vasopressin-binding sites from rat liver (V1), but not solubilized vasopressin-binding sites from hog kidney (V2). Similar results were obtained with an anti-PI-PLC I IgG affinity column. The solubilized (V1) receptors were enriched by ion-exchange and high-performance gel-filtration liquid chromatography. Vasopressin-binding activity was co-eluted with PI-PLC I and GTP[S]-binding activity on a DEAE-Sepharose column. The major vasopressin- and GTP[35S]-binding activities were co-eluted with PI-PLC I activity at approx. 240 kDa suggesting that vasopressin receptors from rat liver membranes can be solubilized as a complex of receptor-coupler-effector by using the detergent lysophosphatidycholine.

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