Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:4.6.1.1 (adenylate cyclase)
19,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A lysophospholipid series, such as lysophosphatidic acid, lysophosphatidylserine, and lysophosphatidylcholine (LPC), is a bioactive lipid mediator with diverse physiological and pathological functions. LPC has been reported to induce insulin secretion from pancreatic beta-cells, however, the precise mechanism has remained elusive to date. Here we show that an orphan G-protein-coupled receptor GPR119 plays a pivotal role in this event. LPC potently enhances insulin secretion in response to high concentrations of glucose in the perfused rat pancreas via stimulation of adenylate cyclase, and dose-dependently induces intracellular cAMP accumulation and insulin secretion in a mouse pancreatic beta-cell line, NIT-1 cells. The Gs-protein-coupled receptor for LPC was identified as GPR119, which is predominantly expressed in the pancreas. GPR119-specific siRNA significantly blocked LPC-induced insulin secretion from NIT-1 cells. Our findings suggest that GPR119, which is a novel endogenous receptor for LPC, is involved in insulin secretion from beta-cells, and is a potential target for anti-diabetic drug development.
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PMID:Lysophosphatidylcholine enhances glucose-dependent insulin secretion via an orphan G-protein-coupled receptor. 1560 32

The fission yeast Schizosaccharomyces pombe primarily detects glucose via a cAMP-signalling pathway. Components of this pathway include the Git3 G-protein-coupled receptor and a heterotrimeric G-protein, from which the Gpa2 Galpha subunit activates adenylate cyclase (Git2/Cyr1). Three additional proteins, Git1, Git7 and Git10 are required to generate a cAMP response even in a strain expressing an activated form of Gpa2, which is capable of bypassing the loss of the GPCR and Gbetagamma dimer. Therefore, Git1, Git7 and Git10 either act in a G-protein-independent manner or are required to stabilize or assemble a functional signalling complex. Although prior data suggested that the Cgs2 cAMP phosphodiesterase (PDE) does not regulate the cAMP response, we now have evidence that along with adenylate cyclase regulation, PDE activation is important for limiting the response to glucose. Finally, regulation of protein kinase A activation appears to involve both traditional post-translational regulation of the function of the components of the cAMP pathway and glucose-dependent transcriptional regulation of some of these cAMP pathway genes.
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PMID:Glucose sensing via the protein kinase A pathway in Schizosaccharomyces pombe. 1566 20

The VPAC(2) receptor, as all members of the G-protein-coupled receptor (GPCR)-B family, has two highly conserved motifs in the third intracellular (IC(3)) loop: a lysine and a leucine located at the amino-terminus and two basic residues separated by a leucine and an alanine at the carboxyl-terminus. This study evaluates the involvement of those conserved amino acid sequences in VPAC(2) signal transduction and regulation. The residues were mutated into alanine and mutants were expressed in Chinese hamster ovary (CHO) cells stably transfected with Galpha16 and aequorin. Mutation of L310 reduced efficacy of vasoactive intestinal polypeptide (VIP) to stimulate adenylate cyclase activity through Galphas coupling by 75%, without affecting VIP capability to stimulate an increase in [Ca(2+)](i) through Galpha16 coupling. Mutation of R325 and, to a lesser extend, K328 reduced VIP efficacy to stimulate [Ca(2+)](i) increase and VIP potency to stimulate adenylate cyclase. The combination of mutations of both amino- and carboxyl-terminus located conserved motifs of the IC(3) loop generates an inactive receptor with respect to [Ca(2+)](i) increase and adenylate cyclase activation, but also with respect to receptor phosphorylation and internalization that were indeed directly correlated with the potency of inactivation of the receptors. The amino-terminus of the VPAC(2) receptor IC(3) loop is thus involved in adenylate cyclase activation and the carboxyl-terminus of the IC(3) loop participates in both Galphas and Galpha16 coupling. The mutations studied also reduced both receptor phosphorylation and internalization in a manner that appeared directly linked to the alteration of Galphas and Galpha16 coupling.
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PMID:Effect of inactivating mutations on phosphorylation and internalization of the human VPAC2 receptor. 1582 Nov 6

The heterodimeric peptide hormone relaxin in most cells appears to signal through a G-protein-coupled receptor, LGR7. Whereas in artificial cell systems, made by transfection of receptor-expressing gene constructs into cells normally not presenting the receptor, classic activation of adenylate cyclase appears to be mediated by Gs, in cells naturally expressing the receptor, this type of coupling appears to be very weak. Instead, there is good evidence of other intermediate steps involving cytoplasmic components and tyrosine kinase activity. Part of the complexity of relaxin signaling is also manifest in the variable time course of cAMP production evident in the THP-1 cell line, which appears to depend on passage number and, hence, presumably on differentiation status. It is therefore important to distinguish between immediate early effects, short to mid-term responses, and long-term responses likely the consequences of specific gene upregulation.
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PMID:Relaxin signaling from natural receptors. 1595 18

A-kinase anchoring proteins (AKAPs) define an expanding group of scaffold proteins that display a signature binding site for the RI/RII subunit of protein kinase A. AKAPs are multivalent and a subset of these scaffold proteins also display the ability to associate with the prototypic member of G-protein-coupled receptors, the beta(2)-adrenergic receptor. Both AKAP79 (also known as AKAP5) and AKAP250 (also known as gravin or AKAP12) have been shown to associate with the beta(2)-adrenergic receptor, but each directs downstream signaling events in decidedly different manners. The primary structures, common and unique protein motifs are of interest. Both proteins display largely natively unfolded primary sequences that provide a necklace on which short, structured regions of sequence are found. Membrane association appears to involve both interactions with the lipid bilayer via docking to a G-protein-coupled receptor as well as interactions of short positively charged domains with the inner leaflet of the cell membrane. Gravin, unlike AKAP79, displays a canonical site at its N-terminus that is subject to N-myristoylation. AKAP79 appears to function in switching signaling pathways of the receptor from adenylylcyclase to activation of the mitogen-activated protein kinase cascade. Gravin, in contrast, is essential for the resensitization and recycling of the receptors following agonist-induced activation, desensitization, and internalization. Each AKAP provides a template that enables space-time continuum features to G-protein-coupled signaling pathways as well as a paradigm for explaining apparent compartmentalization of cell signaling.
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PMID:G-Protein-coupled receptor-associated A-kinase anchoring proteins: AKAP79 and AKAP250 (gravin). 1644 64

GPR48, also known as leucine-rich repeat (LRR)-containing G-protein-coupled receptor 4 (LGR4), is a member of the G-protein-coupled receptor (GPCR) family of proteins. However, its biological functions remain unclear, since neither its ligand nor signal transduction pathway have been identified, and it is usually difficult to solve the function of such orphan receptors. The aim of this study was to generate a constitutively active form of human GPR48, that would form a ligand-independent active conformation and may function in a similar manner to activated GPR48 following ligand binding. We introduced four independent mutations into transmembrane domains V and VI of a human GPR48 cDNA. The wild-type and mutant GPR48s were expressed in HEK293 cells by transient transfection of appropriate expression plasmids. Since ligand-activated receptors for gonadotropins, which are structurally similar to GPR48, stimulate adenylate cyclase and increase cellular cyclic AMP, we investigated, whether the GPR48-transfected cells showed altered cyclic AMP levels. The cellular cyclic AMP level in HEK293 cells was increased following transfection of wild-type GPR48 in a dose-dependent manner. Moreover, transfection of a GPR48-T7551 mutant, in which threonine-755 was replaced with isoleucine, dramatically increased the cyclic AMP level. Stable transformants derived from HCT116 cells that constitutively expressed the GPR48-T7551 mutant also showed high cyclic AMP levels. These results indicate that the GPR48-T7551 mutant is a constitutively active mutant. This mutant may be useful for studying the biological functions of GPR48 and GPR48-mediated signal transduction, even if the specific ligand remains unknown in the future.
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PMID:Generation of a constitutively active mutant of human GPR48/LGR4, a G-protein-coupled receptor. 1660 82

Pituitary adenylate cyclase-activating polypeptide (PACAP), a member of the secretin/glucagon/vasoactive intestinal peptide family expressed throughout the nervous system, binds to the PACAP-specific G-protein-coupled receptor family members to promote both neuronal differentiation and survival. Although the PACAP receptor is known to activate its effector protein, adenylate cyclase (AC), and thus enhance cAMP generation, the molecular mechanism utilized by the receptor to activate AC is lacking. Here, we show that PACAP induces neurite outgrowth in PC12 cells by induction of translocation of the PACAP type 1 receptor (PAC1R) into caveolin-enriched Triton X-100-insoluble microdomains, leading to stronger PAC1R-AC interaction and elevated cAMP production. Moreover, we demonstrate that translocation of PAC1R is blocked by various treatments that selectively disrupt caveolae. As a result, intracellular cAMP level is decreased and consequently the PACAP-induced neurite outgrowth retarded. In contrast, addition of exogenous ganglioside GM1 to the cells shows the opposite effects. These results therefore identify the PACAP-induced translocation of its G-protein-coupled receptor into caveolae, where both AC and the regulating G-proteins reside, as the key molecular event in activating AC and inducing cAMP-mediated differentiation of PC12 cells.
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PMID:Pituitary adenylate cyclase-activating polypeptide induces translocation of its G-protein-coupled receptor into caveolin-enriched membrane microdomains, leading to enhanced cyclic AMP generation and neurite outgrowth in PC12 cells. 1768 Sep 96

The physiological function of dopamine is mediated through its G-protein-coupled receptor family. In Drosophila, four dopamine receptors have been molecularly characterized so far. However, due largely to the absence of a suitable preparation, the role of Drosophila dopamine receptors in modulating central synaptic transmission has not been examined. The present study investigated mechanisms by which dopamine modulates excitatory cholinergic synaptic transmission in Drosophila using primary neuronal cultures. Whole-cell recordings demonstrated that cholinergic excitatory postsynaptic currents (EPSCs) were down-regulated by focally applied dopamine (10-500 microm). The vertebrate D1 specific agonists SKF38393 and 6-chloro-APB (10 microm) mimicked dopamine-mediated suppression of cholinergic synaptic transmission with higher potency. In contrast, the D2 agonists quinpirole and bromocriptine did not alter cholinergic EPSCs, demonstrating that dopamine-mediated suppression of cholinergic synaptic transmission is specifically through activation of Drosophila D1-like receptors. Biophysical analysis of miniature EPSCs indicated that cholinergic suppression by activation of D1-like receptors is presynaptic in origin. Dopamine modulation of cholinergic transmission is not mediated through the cAMP/protein kinase A signaling pathway as cholinergic suppression by dopamine occurred in the presence of the protein kinase A inhibitor H-89. In addition, an adenylate cyclase activator, forskolin, led to an increase, not a decrease, of cholinergic EPSC frequency. Finally, we showed that activation of D1-like receptors decreased the frequency of action potentials in cultured Drosophila neurons by inhibiting excitatory cholinergic transmission. All our data demonstrated that activation of D1-like receptors in Drosophila neurons negatively modulates excitatory cholinergic synaptic transmission and thus inhibits neuronal excitability.
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PMID:Suppression of excitatory cholinergic synaptic transmission by Drosophila dopamine D1-like receptors. 1798 26

In the yeast Saccharomyces cerevisiae, glucose signals activate the production of cellular cAMP. This signaling pathway is called the cAMP-protein kinase A (PKA) pathway, which plays a major role in the regulation of cell growth, metabolism, and stress resistance. Extensive studies have been carried out to clarify the mechanism of this pathway, and many factors involved in the pathway have been identified such as small G proteins, the GDP-GTP exchange factor, adenylate cyclase, and PKA. Also, additional elements involved in this pathway have been evaluated in the last decade. A heterotrimeric G protein alpha subunit was identified as a mammalian Galpha homologue, and a G-protein-coupled receptor (GPCR), which initiates the signaling pathway in response to glucose addition, was identified. GPCR-Galpha was shown to function in a signaling pathway that acts parallel to small G proteins. These signaling pathways regulate cell growth and differentiation in response to nutrients.
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PMID:Glucose-stimulated cAMP-protein kinase A pathway in yeast Saccharomyces cerevisiae. 1802 94

Sphingosine-1-phosphate (Sph-1-P) is an essential bioactive sphingolipid metabolite that has currently become the focus of intense interest. Sph-1-P is generated by the enzyme sphingosine kinase (SphK) in response to diverse stimuli, including growth factors, cytokines, and G-protein-coupled receptor (GPCR) agonists. Its precursor, sphingosine (Sph), is produced from the precursor ceramide (Cer) via a ceramidase (CDase) that is released from membrane sphingomyelin (SPM) by sphingomyelinases (SMase). Accumulating evidence indicates that Sph-1-P is the key regulatory lipid involved in the metabolism of sphingolipids and is involved in the control of numerous aspects of cell physiology, including mitogenesis, differentiation, migration, and apoptosis. These actions of Sph-1-P are mediated by a family of high-affinity S1P receptors, named S1P1-5, which are coupled differentially via G(i), G(q), G(12/13), and Rho to multiple effector systems, including adenylate cyclase, phospholipases C (PLC) and D (PLD), extracellular-signal-regulated kinase, c-Jun N-terminal kinase, p38 mitogen-activated protein kinase, and nonreceptor tyrosine kinases. In this Review, we accumulate available evidence implying that sphingolipid signaling may represent a novel neuroprotective target to counteract the pathophysiology of acute brain and spinal cord injury in regard to apoptotic cell death mechanisms, mitochondrial dysfunction, lipid hydrolysis, and oxidative damage mechanisms. Furthermore, we discuss how Sph-1-P agonist approaches might be expected to increase the resistance of the central nervous system to injury by promoting neurotrophic activity, neurogenesis, and angiogenesis. On the other hand, antagonists of certain Sph-1-P-related activity might possess proregenerative effects via promotion of neurite growth and inhibition of astrogliotic scarring.
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PMID:Multifaceted roles of sphingosine-1-phosphate: how does this bioactive sphingolipid fit with acute neurological injury? 1805 48


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