| 1. |
- Choi, Young-Hun, et al.
(författare)
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Identification of a novel isoform of the cyclic-nucleotide phosphodiesterase PDE3A expressed in vascular smooth-muscle myocytes
- 2001
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Ingår i: Biochemical Journal. - 0264-6021. ; 353:Pt 1, s. 41-50
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Tidskriftsartikel (refereegranskat)abstract
- We have identified a new cyclic-nucleotide phosphodiesterase isoform, PDE3A, and cloned its cDNA from cultured aortic myocytes. The nucleotide sequence of its coding region is similar to that of the previously cloned myocardial isoform except for the absence of the initial 300-400 nt that are present in the latter, as confirmed by reverse-transcriptase-mediated PCR, 5' rapid amplification of cDNA ends and a ribonuclease protection assay. Expression in Spodoptera frugiperda (Sf9) cells yields a protein with catalytic activity and inhibitor sensitivity typical of the PDE3 family. The recombinant protein's molecular mass of approx. 131 kDa is compatible with translation from an ATG sequence corresponding to nt 436-438 of the myocardial PDE3A coding region. Antibodies against residues 424-460 (nt 1270-1380) and 1125-1141 (nt 3373-3423) of the myocardial isoform react with an approx. 118 kDa band in Western blots of homogenates of human aortic myocytes, whereas antibodies against residues 29-42 (nt 85-126) do not react with any bands in these homogenates. Our results suggest that a vascular smooth-muscle isoform ('PDE3A2') is a product of the same gene as the longer myocardial ('PDE3A1') and the shorter placental ('PDE3A3') isoforms and is generated pre-translationally in a manner that results in the absence of the 145 N-terminal amino acids of PDE3A1.
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| 2. |
- Härndahl, Linda, et al.
(författare)
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Beta-cell-targeted overexpression of phosphodiesterase 3B in mice causes impaired insulin secretion, glucose intolerance, and deranged islet morphology.
- 2004
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Ingår i: The Journal of biological chemistry. - 0021-9258 .- 1083-351X. ; 279:15, s. 15214-22
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Tidskriftsartikel (refereegranskat)abstract
- The second messenger cAMP mediates potentiation of glucose-stimulated insulin release. Use of inhibitors of cAMP-hydrolyzing phosphodiesterase (PDE) 3 and overexpression of PDE3B in vitro have demonstrated a regulatory role for this enzyme in insulin secretion. In this work, the physiological significance of PDE3B-mediated degradation of cAMP for the regulation of insulin secretion in vivo and glucose homeostasis was investigated in transgenic mice overexpressing PDE3B in pancreatic beta-cells. A 2-fold overexpression of PDE3B protein and activity blunted the insulin response to intravenous glucose, resulting in reduced glucose disposal. The effects were "dose"-dependent because mice overexpressing PDE3B 7-fold failed to increase insulin in response to glucose and hence exhibited pronounced glucose intolerance. Also, the insulin secretory response to intravenous glucagon-like peptide 1 was reduced in vivo. Similarly, islets stimulated in vitro exhibited reduced insulin secretory capacity in response to glucose and glucagon-like peptide 1. Perifusion experiments revealed that the reduction specifically affected the first phase of glucose-stimulated insulin secretion. Furthermore, morphological examinations demonstrated deranged islet cytoarchitecture. In conclusion, these results are consistent with an essential role for PDE3B in cAMP-mediated regulation of insulin release and glucose homeostasis.
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| 3. |
- Härndahl, Linda, et al.
(författare)
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Important role of phosphodiesterase 3B for the stimulatory action of cAMP on pancreatic beta -cell exocytosis and release of insulin.
- 2002
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 277:40, s. 37446-37455
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Tidskriftsartikel (refereegranskat)abstract
- Cyclic AMP potentiates glucose-stimulated insulin release and mediates the stimulatory effects of hormones such as glucagon-like peptide 1 (GLP-1) on pancreatic b-cells. By inhibition of cAMP-degrading phosphodiesterase (PDE) and, in particular, selective inhibition of PDE3 activity, stimulatory effects on insulin secretion have been observed. Molecular and functional information on b-cell PDE3 is, however, scarce. To provide such information, we have studied the specific effects of the PDE3B isoform by adenovirus-mediated overexpression. In rat islets and rat insulinoma cells, approximate 10-fold overexpression of PDE3B was accompanied by a 6-8-fold increase in membrane-associated PDE3B activity. The cAMP concentration was significantly lowered in transduced cells (INS-1(832/13), and insulin secretion in response to stimulation with high glucose (11.1 mM) was reduced by 40% (islets) and 50% (INS-1). Further, the ability of GLP-1 (100 nM) to augment glucose-stimulated insulin secretion was inhibited by approximately 30% (islets) and 70% (INS-1). Accordingly, when stimulating with cAMP, a substantial decrease (65%) in exocytotic capacity was demonstrated in patch-clamped single b-cells. In untransduced insulinoma cells, application of the PDE3-selective inhibitor OPC3911 (10 mM) was shown to increase glucose-stimulated insulin release as well as cAMP-enhanced exocytosis. The findings suggest a significant role of PDE3B as an important regulator of insulin secretory processes.
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