Direct Binding of the β1 Adrenergic Receptor to the Cyclic AMP-Dependent Guanine Nucleotide Exchange Factor CNrasGEF Leads to Ras Activation

Pak, Youngshil; Pham, Nam; Rotin, Daniela

doi:10.1128/mcb.22.22.7942-7952.2002

Cited by 62 publications

(47 citation statements)

References 58 publications

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“…In keeping, we show that NE and E are able to elicit activation of p42/p44 and p38 MAPKs, acknowledged to have mandatory roles for cell growth, survival and invasive ability, in both primary and metastatic cell lines. This observation is in agreement with the findings of Pak et al, 23 also indicating the Ras-MAPKs pathway as a target of b-adrenoceptors. These data could be of striking interest in order to find new strategies for melanoma treatment.…”

Section: Discussionsupporting

confidence: 83%

β-adrenoceptors are upregulated in human melanoma and their activation releases pro-tumorigenic cytokines and metalloproteases in melanoma cell lines

Moretti

Massi

Farini

et al. 2013

Laboratory Investigation

108

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Recent studies sight b-adrenergic receptor (AR) antagonists as novel therapeutic agents for melanoma, as they may reduce disease progression. Here within, we evaluated the expression of b-ARs in a series of human cutaneous melanocytic lesions, and studied the effect of their endogenous agonists, norepinephrine (NE) and epinephrine (E), on primary and metastatic human melanoma cell lines. Using immunohistochemistry, we found that both b1-and b2-ARs are expressed in tissues from benign melanocytic naevi, atypical naevi and malignant melanomas and that expression was significantly higher in malignant tumours. Melanoma cell lines (human A375 primary melanoma cell line and human Hs29-4T metastatic melanoma cell lines) also expressed b1-and b2-ARs by measuring transcripts and proteins. NE or E increased metalloprotease-dependent motility, released interleukin-6 and 8 (IL-6, IL-8) and vascular endothelial growth factor (VEGF). These effects of catecholamines were inhibited by the unselective b-AR antagonist propranolol. The role of soluble factors elicited by catecholamines seemed pleiotropic as VEGF synergized with NE increased melanoma invasiveness through 3D barriers, while IL-6 participated in stromal fibroblast activation towards a myofibroblastic phenotype. Our results indicate that NE and E produce in vitro via b-ARs activation a number of biological responses that may exert a pro-tumorigenic effect in melanoma cell lines. The observation that b-ARs are upregulated in malignant melanoma tissues support the hypothesis that circulating catecholamines NE and E, by activating their receptors, favour melanoma progression in vivo. Melanoma represents the most aggressive type of skin cancer, with an increasing incidence found especially in young adults. A significant reduction in mortality has been not observed, despite a noteworthy improvement in early diagnosis achieved in recent years. 1 At present, no medical option can cure metastatic melanoma (MM) and the only effective treatment for the eradication of the disease is early-phase surgery. 2 Hence, increased knowledge of the biological pathways underlying the process of melanoma dissemination and metastasis is crucial in order to identify new therapeutic targets.Previous studies have shown that various human solid tumours, such as breast, colon, prostatic, ovary, nasopharyngeal and oral cancer, express b2-adrenoceptor (b2-AR), raising the possibility that such receptors may affect invasion and dissemination processes. [3][4][5][6][7][8] Moreover, some stress neurotransmitters, such as norepinephrine (NE) and epinephrine (E), have been demonstrated to contribute to the regulation of tumour cell invasion, at least in part through b-AR activation. 6,7,9 Interactions between tumour cells and soluble factors originated from the nervous system has recently been proposed to favour metastasis formation. 10 Improved survival rates have been demonstrated in mice with metastatic tumour by combined administration of b-AR antagonists. 11 In addition, recent evidence suggests a ...

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Section: Discussionsupporting

confidence: 83%

β-adrenoceptors are upregulated in human melanoma and their activation releases pro-tumorigenic cytokines and metalloproteases in melanoma cell lines

Moretti

Massi

Farini

et al. 2013

Laboratory Investigation

108

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“…The intracellular domains of several GPCRs have been shown to bind to proteins that might function as alternative GPCR signal transducers, among which include GEFs for small G proteins, nonreceptor tyrosine kinases, and several proteins that function as adaptors or scaffolds. A specific peptide motif in the C terminus of the ␤ 1 -adrenergic receptor binds directly to the postsynaptic density protein of 95 kDa/ disc-large/zona occludens-1 (PDZ) domain of the cAMP-regulated Ras GEF (cyclic nucleotide-Ras GEF), allowing the receptor to stimulate guanine nucleotide exchange on the small G protein Ras (Pak et al, 2002). Another PDZ domaincontaining protein, the Na ϩ /H ϩ exchanger regulatory factor/ ezrin binding protein 50, binds to the C terminus of ␤ 2 -adrenergic and parathyroid hormone/parathyroid hormonerelated protein receptors and confers the ability to regulate Na ϩ /H ϩ exchanger 3 activity (Hall et al, 1998;Mahon et al, 2002).…”

Section: Gpcr Coupling To Non-g Protein Effectorsmentioning

confidence: 99%

The Origins of Diversity and Specificity in G Protein-Coupled Receptor Signaling

Maudsley¹,

Martin²,

Luttrell³

2005

J Pharmacol Exp Ther

173

172

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The modulation of transmembrane signaling by G protein-coupled receptors (GPCRs) constitutes the single most important therapeutic target in medicine. Drugs acting on GPCRs have traditionally been classified as agonists, partial agonists, or antagonists based on a two-state model of receptor function embodied in the ternary complex model. Over the past decade, however, many lines of investigation have shown that GPCR signaling exhibits greater diversity and "texture" than previously appreciated. Signal diversity arises from numerous factors, among which are the ability of receptors to adopt multiple "active" states with different effector-coupling profiles; the formation of receptor dimers that exhibit unique pharmacology, signaling, and trafficking; the dissociation of receptor "activation" from desensitization and internalization; and the discovery that non-G protein effectors mediate some aspects of GPCR signaling. At the same time, clustering of GPCRs with their downstream effectors in membrane microdomains and interactions between receptors and a plethora of multidomain scaffolding proteins and accessory/chaperone molecules confer signal preorganization, efficiency, and specificity. In this context, the concept of agonist-selective trafficking of receptor signaling, which recognizes that a bound ligand may select between a menu of active receptor conformations and induce only a subset of the possible response profile, presents the opportunity to develop drugs that change the quality as well as the quantity of efficacy. As a more comprehensive understanding of the complexity of GPCR signaling is developed, the rational design of ligands possessing increased specific efficacy and attenuated side effects may become the standard mode of drug development.The heptahelical G protein-coupled receptors (GPCRs) constitute the most diverse form of transmembrane signaling protein. An estimated 1% of the mammalian genome encodes GPCRs, and about 450 of the approximately 950 predicted human GPCRs are expected to be receptors for endogenous ligands (Takeda et al., 2002). GPCRs detect an extraordinarily diverse set of stimuli in the external environment, from photons of light and ions to small molecule neurotransmitters, peptides, glycoproteins, and phospholipids. In addition, nearly 40% of all current therapeutics target GPCRs (Brink et al., 2004).The mechanism by which GPCRs transduce extracellular messages into intracellular cellular responses was initially envisioned as a simple linear model in which agonist binding promotes transition of the receptor from an "off" to an "on" state capable of engaging heterotrimeric guanine nucleotidebinding (G) proteins, whose dissociated G␣ and G␤␥ subunits

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“…We and others have previously identified a guanine nucleotide exchange factor, called CNrasGEF (also known as PDZ-GEF1, nRapGEF, RA-GEF, and RAPGEF2) (20 -23). Our previous work showed that when expressed heterologously in HEK293T cells, CNras-GEF can activate Ras in response to elevation of cAMP levels (independent of protein kinase A), achieved by treatment with 8-Br-cAMP or forskolin plus IBMX (20) or by agonist (isoproterenol) stimulation of co-expressed b1 adrenergic receptor, a G protein-coupled receptor that activates G␣ s and leads to elevation of intracellular cAMP levels (24). CNrasGEF can also activate Rap1, independent of cAMP (20 -23).…”

mentioning

confidence: 99%

The Guanine Nucleotide Exchange Factor CNrasGEF Regulates Melanogenesis and Cell Survival in Melanoma Cells

Amsen

Pham

Pak

et al. 2006

Journal of Biological Chemistry

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cAMP-dependent Ras activation has been demonstrated in numerous cell types, particularly of neuronal (including melanoma cells) and endocrine origin, but the Ras activator involved has not been identified. In B16 melanoma cells, cAMP activates the Ras/Erk pathway, leading initially to stimulation but subsequently to long term (>24-h) inhibition of melanogenesis (dendrite extension and melanin production). Here we identify CNrasGEF as the Ras guanine nucleotide exchange factor (GEF) involved. We demonstrate that CNrasGEF is expressed endogenously in B16 melanoma cells and that cAMP-mediated activation of Ras and Erk1/2 in these cells can be augmented by CNrasGEF overexpression and reduced by its knockdown by RNA interference. Moreover, we show that CNras-GEF participates in the regulation of melanogenesis. Knockdown of CNrasGEF leads to increased dendrite extension and melanin production observed ϳ50 h after forskolin/isobutylmethylxanthine treatment, suggesting that CNrasGEF inhibits melanogenesis in the long term. Independently, we find that overexpression of CNras-GEF leads to apoptosis, whereas its knockdown by RNAi enhances cell proliferation, independent of cAMP. Collectively, these results suggest that CNrasGEF regulates melanogenesis but that it also has a distinct role in regulating cell proliferation/apoptosis. cAMP exhibits differential mitogenic effects in different cell types (1). In several endocrine, neuronal, or Schwann cells and in some 3T3 cells, cAMP promotes cell proliferation, often by activating Ras. For example, in thyroid cells, cAMP-stimulated mitogenesis following thyroid stimulating hormone binding to its receptor is mediated via Ras activation, independent of protein kinase A (2). Moreover, cAMP-dependent activation of Erk in NIH-3T3 cells was recently demonstrated to be carried out independently of Rap1-Epac and instead was proposed to be mediated via Ras activation (3). The cAMP-dependent Ras activator involved in these cases has not been identified. Recently, a pathway for cAMPdependent Ras/Erk activation (independent of protein kinase A or Rap1) has been proposed in melanoma cells (4).Melanocytes are specialized epidermal cells of neurocrest origin that synthesize melanin and are responsible for skin pigmentation and protection from UV radiation (5, 6). Melanoma cells are transformed melanocytes that give rise to a very aggressive skin cancer, melanoma. B16 mouse melanoma cells, particularly B16-F10, have been characterized extensively with regard to their tumorigenic and metastatic potential (e.g. Refs. 7-9) and the signaling pathways responsible for melanin production (5). Melanin synthesis takes place in intracellular organelles called melanosomes. Upon stimulation by UV radiation, several factors are released, including ␣-melanocyte-stimulating hormone (10), a strong melanogenic factor that acts by binding to the melanocortin receptor, MC1R. MC1R is a G protein-coupled receptor coupled to G␣ s , causing elevation of intracellular cAMP upon ligand binding. cAMP is a critical com...

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Direct Binding of the β1 Adrenergic Receptor to the Cyclic AMP-Dependent Guanine Nucleotide Exchange Factor CNrasGEF Leads to Ras Activation

Cited by 62 publications

References 58 publications

β-adrenoceptors are upregulated in human melanoma and their activation releases pro-tumorigenic cytokines and metalloproteases in melanoma cell lines

β-adrenoceptors are upregulated in human melanoma and their activation releases pro-tumorigenic cytokines and metalloproteases in melanoma cell lines

The Origins of Diversity and Specificity in G Protein-Coupled Receptor Signaling

The Guanine Nucleotide Exchange Factor CNrasGEF Regulates Melanogenesis and Cell Survival in Melanoma Cells

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