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Alternative splicing of the guanylyl cyclase-A receptor modulates atrial natriuretic peptide signaling.

ABSTRACT: Atrial (ANP) and B-type natriuretic peptides (BNP) modulate blood pressure and volume through the stimulation of cyclic GMP production by their guanylyl cyclase-A (GC-A) receptor. A novel isoform of GC-A has been identified that is the result of differential splicing of exon 4. The deletion of a 51-bp sequence is predicted to delete 17 amino acids (Lys314-Gln330) in the membrane-distal part of the extracellular domain. Reverse transcription-PCR analyses demonstrated low messenger RNA expression levels of spliced GC-A in all tissues. Homology modeling suggested that the alterations in the protein structure could interfere with ANP binding or signaling. Indeed, functional studies in transfected HEK 293 cells demonstrated that binding of ANP and ANP-induced cyclic GMP formation by GC-ADelta(Lys314-Gln330) were totally abolished. Furthermore, cotransfection studies showed that this GC-A variant forms heterodimers with the wild type receptor and inhibits ligand-inducible cGMP generation. Finally, treatment of mice with angiotensin II (300 ng/kg/min during 7 days) resulted in enhanced pulmonary mRNA expression of spliced GC-A, which was concomitant to diminished GC-A/cGMP responses to ANP. We conclude that alternative splicing can regulate endogenous ANP/GC-A signaling. Angiotensin II-induced alternative splicing of GC-A may represent a novel mechanism for reducing the sensitivity to ANP.

SUBMITTER: Hartmann M

PROVIDER: S-EPMC2661397 | biostudies-literature | 2008 Oct

REPOSITORIES: biostudies-literature

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Alternative splicing of the guanylyl cyclase-A receptor modulates atrial natriuretic peptide signaling.

Hartmann Michael M Skryabin Boris V BV Müller Thomas T Gazinski Alexandra A Schröter Juliane J Gassner Birgit B Nikolaev Viacheslav O VO Bünemann Moritz M Kuhn Michaela M

The Journal of biological chemistry 20080818 42

Atrial (ANP) and B-type natriuretic peptides (BNP) modulate blood pressure and volume through the stimulation of cyclic GMP production by their guanylyl cyclase-A (GC-A) receptor. A novel isoform of GC-A has been identified that is the result of differential splicing of exon 4. The deletion of a 51-bp sequence is predicted to delete 17 amino acids (Lys314-Gln330) in the membrane-distal part of the extracellular domain. Reverse transcription-PCR analyses demonstrated low messenger RNA expression ...[more]

PMID: 18713751

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Project description:Atrial natriuretic peptide (ANP), via its guanylyl cyclase A (GC-A) receptor and intracellular guanosine 3',5'-cyclic monophosphate production, is critically involved in the regulation of blood pressure. In patients with chronic heart failure, the plasma levels of ANP are increased, but the cardiovascular actions are severely blunted, indicating a receptor or postreceptor defect. Studies on metabolically labelled GC-A-overexpressing cells have indicated that GC-A is extensively phosphorylated, and that ANP-induced homologous desensitization of GC-A correlates with receptor dephosphorylation, a mechanism which might contribute to a loss of function in vivo. In this study, tandem MS analysis of the GC-A receptor, expressed in the human embryonic kidney cell line HEK293, revealed unambiguously that the intracellular domain of the receptor is phosphorylated at multiple residues: Ser487, Ser497, Thr500, Ser502, Ser506, Ser510 and Thr513. MS quantification based on multiple reaction monitoring demonstrated that ANP-provoked desensitization was accompanied by a complex pattern of receptor phosphorylation and dephosphorylation. The population of completely phosphorylated GC-A was diminished. However, intriguingly, the phosphorylation of GC-A at Ser487 was selectively enhanced after exposure to ANP. The functional relevance of this observation was analysed by site-directed mutagenesis. The substitution of Ser487 by glutamate (which mimics phosphorylation) blunted the activation of the GC-A receptor by ANP, but prevented further desensitization. Our data corroborate previous studies suggesting that the responsiveness of GC-A to ANP is regulated by phosphorylation. However, in addition to the dephosphorylation of the previously postulated sites (Ser497, Thr500, Ser502, Ser506, Ser510), homologous desensitization seems to involve the phosphorylation of GC-A at Ser487, a newly identified site of phosphorylation. The identification and further characterization of the specific mechanisms involved in the downregulation of GC-A responsiveness to ANP may have important pathophysiological implications.

Project description:BACKGROUND:The cardiac hormones atrial (ANP) and B-type natriuretic peptides (BNP) moderate arterial blood pressure and improve energy metabolism as well as insulin sensitivity via their shared cGMP-producing guanylyl cyclase-A (GC-A) receptor. Obesity is associated with impaired NP/GC-A/cGMP signaling, which possibly contributes to the development of type 2 diabetes and its cardiometabolic complications. In vitro, synthetic ANP, via GC-A, stimulates glucose-dependent insulin release from cultured pancreatic islets and ?-cell proliferation. However, the relevance for systemic glucose homeostasis in vivo is not known. To dissect whether the endogenous cardiac hormones modulate the secretory function and/or proliferation of ?-cells under (patho)physiological conditions in vivo, here we generated a novel genetic mouse model with selective disruption of the GC-A receptor in ?-cells. METHODS:Mice with a floxed GC-A gene were bred to Rip-CreTG mice, thereby deleting GC-A selectively in ?-cells (? GC-A KO). Weight gain, glucose tolerance, insulin sensitivity, and glucose-stimulated insulin secretion were monitored in normal diet (ND)- and high-fat diet (HFD)-fed mice. ?-cell size and number were measured by immunofluorescence-based islet morphometry. RESULTS:In vitro, the insulinotropic and proliferative actions of ANP were abolished in islets isolated from ? GC-A KO mice. Concordantly, in vivo, infusion of BNP mildly enhanced baseline plasma insulin levels and glucose-induced insulin secretion in control mice. This effect of exogenous BNP was abolished in ? GC-A KO mice, corroborating the efficient inactivation of the GC-A receptor in ?-cells. Despite this under physiological, ND conditions, fasted and fed insulin levels, glucose-induced insulin secretion, glucose tolerance and ?-cell morphology were similar in ? GC-A KO mice and control littermates. However, HFD-fed ? GC-A KO animals had accelerated glucose intolerance and diminished adaptative ?-cell proliferation. CONCLUSIONS:Our studies of ? GC-A KO mice demonstrate that the cardiac hormones ANP and BNP do not modulate ?-cell's growth and secretory functions under physiological, normal dietary conditions. However, endogenous NP/GC-A signaling improves the initial adaptative response of ?-cells to HFD-induced obesity. Impaired ?-cell NP/GC-A signaling in obese individuals might contribute to the development of type 2 diabetes.

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Alternative splicing of the guanylyl cyclase-A receptor modulates atrial natriuretic peptide signaling.

Publications

Alternative splicing of the guanylyl cyclase-A receptor modulates atrial natriuretic peptide signaling.

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