Divalent cations directly affect the conductance of excised patches of rod photoreceptor membrane

Phototransduction in rod cells is likely to involve an intracellular messenger system that links the absorption of light by rhodopsin to a change in membrane conductance. The direct effect of guanosine 3',5'-monophosphate (cGMP) on excised patches of rod outer segment membrane strongly supports a role for cGMP as an intracellular messenger in phototransduction. It is reported here that magnesium and calcium directly affect the conductance of excised patches of rod membrane in the absence of cGMP and that magnesium, applied to intact rod cells, blocks a component of the cellular light response. The divalent cation-suppressed conductance in excised patches showed outward rectification and cation-selective permeability resembling those of the light-suppressed conductance measured from the intact rod cell. The divalent cation-suppressed conductance was partly blocked by a concentration of the pharmacological agent L-cis-diltiazem that blocked all of the cGMP-activated conductance. Divalent cations may act, together with cGMP, as an intracellular messenger system that mediates the light response of the rod photoreceptor cell.     

The protein kinase domain of the ANP receptor is required for signaling

A plasma membrane form of guanylate cyclase is a cell surface receptor for atrial natriuretic peptide (ANP). In response to ANP binding, the receptor-enzyme produces increased amounts of the second messenger, guanosine 3',5'-monophosphate. Maximal activation of the cyclase requires the presence of adenosine 5'-triphosphate (ATP) or nonhydrolyzable ATP analogs. The intracellular region of the receptor contains at least two domains with homology to other proteins, one possessing sequence similarity to protein kinase catalytic domains, the other to regions of unknown function in a cytoplasmic form of guanylate cyclase and in adenylate cyclase. It is now shown that the protein kinase-like domain functions as a regulatory element and that the second domain possesses catalytic activity. When the kinase-like domain was removed by deletion mutagenesis, the resulting ANP receptor retained guanylate cyclase activity, but this activity was independent of ANP and its stimulation by ATP was markedly reduced. A model for signal transduction is suggested in which binding of ANP to the extracellular domain of its receptor initiates a conformational change in the protein kinase-like domain, resulting in derepression of guanylate cyclase activity.     

Enzyme release from polymorphonuclear leukocyte lysosomes: regulation by autonomic drugs and cyclic nucleotides

Osmotic release of beta-glucuronidase from polymorphonuclear leukocyte lysosomes is inhibited by catecholamines and adenosine 3',5'-monophosphate, and accelerated by cholinergic agents and guanosine 3',5'-monophosphate. These actions are specific for the sympathetic and parasympathetic neurotransmitters and for the two cyclic nucleotides, as phenylephrine, tyramine, choline, adenosine 5'-monophosphate and guanosine 5'-monophosphate do not inodify lysosomal enzyme release.     

Adenosine 3',5'-monophosphate: electrophysiological evidence for a role in synaptic transmission

Synaptic potentials and changes in resting membrane potentials of superior cervical ganglia of the rabbit were measured in the presence of adenosine 3',5'-monophosphate and agents that affect its metabolism. Adenosine 3',5'-monophosphate and its mono- and dibutyryl derivatives caused a hyperpolarization of the postganglionic neurons. Theophylline potentiated the slow inhibitory postsynaptic potential that follows synaptic transmission, as well as the hyperpolarization of postganglionic neurons caused by exogenous dopamine. Conversely, prostaglandin E(1) inhibited both the slow inhibitory postsynaptic potential and the dopamine-induced hyperpolarization. We hypothesize that the slow inhibitory postsynaptic potential as well as the dopamine-induced hyperpolarization result from increased amounts of adenosine 3'5'-monophosphate in the postganglionic neurons. The dibutyryl derivative of guanosine 3'5'-monophosphate caused a depolarization of the postganglionic neurons, which is consistent with the possibility that guanosine 3'5'-monophosphate mediates synaptic transmission at muscarinic cholinergic synapses.     

Adenosine 3',5'-monophosphate-dependent protein kinase of cultured mammalian cells

Protein kinase was partially purified from Chang's liver cells, 3T6 mouse embryo fibroblasts, and HeLa cells. The rate of histone phosphorylation catalyzed by the kinase from each of these cell lines was stimulated two- to three-fold by 1 x 10(-6) molar adenosine 3',5'-monophosphate. The same concentration of guanosine 3',5'-monophosphate failed to stimulate these kinases.     

Signaling of rat Frizzled-2 through phosphodiesterase and cyclic GMP

The Frizzled-2 receptor (Rfz2) from rat binds Wnt proteins and can signal by activating calcium release from intracellular stores. We show that wild-type Rfz2 and a chimeric receptor consisting of the extracellular and transmembrane portions of the beta2-adrenergic receptor with cytoplasmic domains of Rfz2 also signaled through modulation of cyclic guanosine 3',5'-monophosphate (cGMP). Activation of either receptor led to a decline in the intracellular concentration of cGMP, a process that was inhibited in cells treated with pertussis toxin, reduced by suppression of the expression of the heterotrimeric GTP-binding protein (G protein) transducin, and suppressed through inhibition of cGMP-specific phosphodiesterase (PDE) activity. Moreover, PDE inhibitors blocked Rfz2-induced calcium transients in zebrafish embryos. Thus, Frizzled-2 appears to couple to PDEs and calcium transients through G proteins.     

Effect of forskolin on voltage-gated K+ channels is independent of adenylate cyclase activation

Forskolin is commonly used to stimulate adenylate cyclase in the study of modulation of ion channels and other proteins by adenosine 3',5'-monophosphate (cAMP)-dependent second messenger systems. In addition to its action on adenylate cyclase, forskolin directly alters the gating of a single class of voltage-dependent potassium channels from a clonal pheochromocytoma (PC12) cell line. This alteration occurred in isolated cell-free patches independent of soluble cytoplasmic enzymes. The effect of forskolin was distinct from those of other agents that raise intracellular cAMP levels. The 1,9-dideoxy derivative of forskolin, which is unable to activate the cyclase, was also effective in altering the potassium channel activity. This direct action of forskolin can lead to misinterpretation of results in experiments in which forskolin is assumed to selectively activate adenylate cyclase.     

Influence of gene action across different time scales on behavior

Genes can affect natural behavioral variation in different ways. Allelic variation causes alternative behavioral phenotypes, whereas changes in gene expression can influence the initiation of behavior at different ages. We show that the age-related transition by honey bees from hive work to foraging is associated with an increase in the expression of the foraging (for) gene, which encodes a guanosine 3',5'-monophosphate (cGMP)-dependent protein kinase (PKG). cGMP treatment elevated PKG activity and caused foraging behavior. Previous research showed that allelic differences in PKG expression result in two Drosophila foraging variants. The same gene can thus exert different types of influence on a behavior.     

Mitochondrial biogenesis in mammals: the role of endogenous nitric oxide

Nitric oxide was found to trigger mitochondrial biogenesis in cells as diverse as brown adipocytes and 3T3-L1, U937, and HeLa cells. This effect of nitric oxide was dependent on guanosine 3',5'-monophosphate (cGMP) and was mediated by the induction of peroxisome proliferator-activated receptor gamma coactivator 1alpha, a master regulator of mitochondrial biogenesis. Moreover, the mitochondrial biogenesis induced by exposure to cold was markedly reduced in brown adipose tissue of endothelial nitric oxide synthase null-mutant (eNOS-/-) mice, which had a reduced metabolic rate and accelerated weight gain as compared to wild-type mice. Thus, a nitric oxide-cGMP-dependent pathway controls mitochondrial biogenesis and body energy balance.     

Cysteine redox sensor in PKGIa enables oxidant-induced activation

Changes in the concentration of oxidants in cells can regulate biochemical signaling mechanisms that control cell function. We have found that guanosine 3',5'-monophosphate (cGMP)-dependent protein kinase (PKG) functions directly as a redox sensor. The Ialpha isoform, PKGIalpha, formed an interprotein disulfide linking its two subunits in cells exposed to exogenous hydrogen peroxide. This oxidation directly activated the kinase in vitro, and in rat cells and tissues. The affinity of the kinase for substrates it phosphorylates was enhanced by disulfide formation. This oxidation-induced activation represents an alternate mechanism for regulation along with the classical activation involving nitric oxide and cGMP. This mechanism underlies cGMP-independent vasorelaxation in response to oxidants in the cardiovascular system and provides a molecular explantion for how hydrogen peroxide can operate as an endothelium-derived hyperpolarizing factor.     

充血性心力衰竭患儿治疗前后血浆ANP与cGMP的变化及其临床意义

目的：研究充血性心衰患儿治疗前后血浆ANP与cGMP的变化及临床意义。方法：用同位素放射免疫测定法。结果：心衰患儿血浆ANP与cGMP水平显著增高且与心衰的严重程度是正相关，但与心衰病因无关。结论：在治疗前后测定血浆ANP或cGMP的浓度变化，对判断有无心衰（早期诊断）、心衰严重程度（即心衰时的心功能情况）及评价。心衰的治疗效果均有一定的临床意义。     

Involvement of adenosine 3',5'-monophosphate in the activation of tyrosine hydroxylase elicited by drugs

Immediately after the injection of reserpine (16 micromoles per kilogram, intraperitoneally), aminophylline (200 micromoles per kilogram, intraperitoneally), and carbamylcholine (8.2 micromoles per kilogram, intraperitoneally), the concentration of adenosine 3',5'-monophosphate in adrenal medulla of rats is increased severalfold. The three drugs also cause a delayed increase of medullary tyrosine hydroxylase activity. Our results are consistent with the view that an increase of medullary adenosine 3',5'-monophosphate concentration is involved in the drug-induced increase of tyrosine hydroxylase activity in adrenal medulla. Experiments with tyramine (130 micromoles per kilogram, intraperitoneally) suggest that the increase of tyrosine hydroxylase activity and of adenosine 3',5'-monophosphate concentrations is independent of an increase in adrenal catecholamine turnover rate.     

Cyclic guanosine and adenosine 3',5'-monophosphates in canine thyroid: localization by immunofluorescence

When guanosine 3',5'-monophosphate (cyclic GMP) and adenosine 3',5'-monophosphate (cyclic AMP) are localized in canine thyroid by a flurescence Immunocytochemical procedure, distinct staining patterns for each nucleotide are seen: Cyclic AMP is distributed throughout the follicular cell cytoplasm before and after administration of thyroid-stimulating hormone, while cyclic GMP is localized to the follicular cell mumbrane in the control state, and increased cytoplasmic fluorescence is visualized after acetylcholine. These data provide histological evidence that correlates with cyclic nucleotide tissue measurements, sugesting diverse roles of the two nucleotides in thyroid function.     

Insect salivary glands: stimulation of fluid secretion by 5-hydroxytryptamine and adenosine-3',5'-monophosphate

Low concentrations (10(-9)M) of 5-hydroxytryptamine increase the rate of fluid secretion by isolated salivary glands of adult Calliphora. 5-Hydroxytry ptamine is present in Calliphora brain. Adenosine-3',5'-monophosphate (cyclic AMP) also stimulates fluid secretion and may be involved in the mode of action of 5-hydroxytryptamine.     

Oligodendrocyte adhesion activates protein kinase C-mediated phosphorylation of myelin basic protein

When isolated adult oligodendrocytes adhere to a substratum myelinogenesis occurs. Investigation of the mechanism by which this happens indicated that the oligodendrocyte-substratum interaction activated protein kinase C-dependent phosphorylation of myelin basic protein and promoted the synthesis of myelin basic protein. In addition, when agents that activate protein kinase C (second messenger diacylglycerol or a tumor-promoting phorbol ester) were added to nonattached oligodendrocytes, they mimicked the influence of the substratum by inducing phosphorylation of myelin basic protein; and reagents that increase cellular adenosine 3', 5'-monophosphate (cyclic AMP) inhibited phosphorylation of myelin basic protein. Thus, at least in vitro, the interaction between oligodendrocytes and the substratum may mediate myelinogenic events, and phosphorylation of myelin basic protein may be an early requirement in the sequence of steps that ultimately results in myelin formation.     

Inhibition of cell growth in vitro by adenosine 3',5'-monophosphate

Adenosine 3',5'-monophosphate, at a concentration of 40 micrograms per milliliter, inhibits the growth of HeLa and strain L cells in culture. The inhibition becomes progressively greater during the incubation of the cells. Adenosine 5'-monophosphate and adenosine, metabolites of adenosine 3',5'-monophosphate, do not affect the growth of either cell culture. This suggests that 3',5'-monophosphate enters the cell without alteration. Dibutyryl-adenosine 3',5'-monophosphate, reported to have a greater activity than adenosine 3'5'-monophosphate on several tissues, inhibited the growth of the cells much less.     

Histone phosphorylation: stimulation by adenosine 3',5'-monophosphate

Adenosine cyclic 3',5'-monophosphate at a concentration of 10-(7)M causes a four-to sixfold increase in the rate of histone phosphorylation catalyzed by a liver enzyme preparation. This observation suggests a mechanism for the induction of RNA synthesis by those hormones that cause increases in the concentration of cyclic AMP.     

Cyclic guanosine monophosphate: elevation in degenerating photoreceptor cells of the C3H mouse retina

As a result of an early deficiency in cyclic nucleotide phosphodiesterase activity, guanosine 3',5'-monophosphate accumulates in retinal photoreceptor cells before they begin to degenerate. It is suggested that degeneration of the photoreceptor cells is related to an imbalance in their metabolism or function which is caused by the elevated levels of cyclic guanosine monophosphate.     

Divergent biological effects of adenosine and dibutyryl adenosine 3',5'-monophosphate on the isolated fat cell

Adenosine 3',5'-monophosphate stimulated production of carbon dioxide and lipid from glucose, whereas its dibutyryl derivative inhibited this conversion. Addition of the dibutyryl derivative to the isolated fat cell further stimulated lipolysis induced by adrenocorticotropic hormone, whereas addition of adenosine 3',5'-monophosphate inhibited this lipolysis. Hence, measured by these two parameters, the biologic properties of adenosine 3',5'-monophosphate and its dibutyryl derivative are distinctly different.     

Adenosine 3',5'-monophosphate-dependent protein kinase from brain

Adenosine 3',5'-monophosphate at a concentration of 5 x 10(-7) mole per liter causes a 400 percent increase in the rate of phosphorylation of histone catalyzed by a partially purified enzyme preparation from rabbit brain. The data provide the first direct evidence of a biochemical action of adenosine 3',5'-monophosphate in the brain.