Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.27.1 (RNase)
 16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In pancreatic beta-cells, the high Km glucose transporter GLUT2 catalyzes the first step in glucose-induced insulin secretion by glucose uptake. Expression of the transporter has been reported to be modulated by glucose either at the protein or mRNA levels. In this study we used the differentiated insulinoma cell line INS-1 which expresses high levels of GLUT2 and show that the expression of GLUT2 is regulated by glucose at the transcriptional level. By run-on transcription assays we showed that glucose induced GLUT2 gene transcription 3-4-fold in INS-1 cells which was paralleled by a 1.7-2.3-fold increase in cytoplasmic GLUT2 mRNA levels. To determine whether glucose regulatory sequences were present in the promoter region of GLUT2, we cloned and characterized a 1.4-kilobase region of mouse genomic DNA located 5' of the translation initiation site. By RNase protection assays and primer extension, we determined that multiple transcription initiation sites were present at positions -55, -64, and -115 from the first coding ATG and which were identified in liver, intestine, kidney, and beta-cells mRNAs. Plasmids were constructed with the mouse promoter region linked to the reporter gene chloramphenicol acetyltransferase (CAT), and transiently and stably transfected in the INS-1 cells. Glucose induced a concentration-dependent increase in CAT activity which reached a maximum of 3.6-fold at 20 mM glucose. Similar CAT constructs made of the human GLUT2 promoter region and the CAT gene displayed the same glucose-dependent increase in transcriptional activity when transfected into INS-1 cells. Comparison of the mouse and human promoter regions revealed sequence identity restricted to a few stretches of sequences which suggests that the glucose responsive element(s) may be conserved in these common sequences.
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PMID:Characterization of the murine high Km glucose transporter GLUT2 gene and its transcriptional regulation by glucose in a differentiated insulin-secreting cell line. 792 31

During pregnancy, marked hyperplasia of the pancreatic islet cells has been observed. This effect may be mediated by the pregnancy-associated peptide hormones, placental lactogen, PRL, and GH, which were previously shown to be mitogenic to beta-cells in vitro. To study whether the responsiveness of islet cells to these hormones is regulated on the receptor level, GH and PRL receptor gene expression was studied in pancreata from male rats and virgin, pregnant, and lactating female rats and in cultured islets and insulinoma cells (RIN-5AH) in response to various hormones. The mRNA levels were quantitated by ribonuclease protection assay, using probes specific for mRNA encoding, extracellular and intracellular domains of the GH receptor, and short and long forms of the PRL receptor, respectively. Specific transcripts for the GH receptor were present in pancreas, islets, and RIN-5AH cells. Furthermore, as previously observed in RIN-5AH cells, a predominant expression of the long form of PRL receptor vs. the short form was also found in pancreas and islet cells. Male and nonpregnant female pancreas did not differ significantly in their levels of GH and PRL receptor mRNAs. On day 14 of pregnancy, increases in both GH and PRL receptor mRNA levels were observed (1.7- and 2.4-fold, respectively), and a further increase occurred in late pregnancy (day 19), when GH and PRL receptor mRNA levels were 2.7- and 3.9-fold higher than those in the nonpregnant state. mRNA levels returned toward the basal level during lactation. In the cultured islets, PRL receptor mRNA levels were markedly increased by GH and PRL (3.5- and 6.5-fold, respectively) after exposure for 24 h, whereas estradiol and testosterone had modest stimulating effects (1.8- and 1.5-fold increases, respectively). Dexamethasone induced a 2.5-fold increase in GH receptor mRNA levels, and a weak stimulatory effect was also observed for progesterone. In RIN-5AH cells, the effect of dexamethasone on GH receptor mRNA was detectable after 2 h and maximal after 16 h. In contrast, the effects of GH and PRL on PRL receptor mRNA required 24-48 h of exposure. The effective doses were within the physiological ranges. In conclusion, these results show a differential hormonal regulation of GH and PRL receptor gene expression in the pancreatic islets, which may play a role in the adaptive beta-cell growth during pregnancy.
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PMID:Effects of sex and pregnancy hormones on growth hormone and prolactin receptor gene expression in insulin-producing cells. 836 59

The alpha 1E voltage-dependent calcium channel has not been clearly identified with a specific neuronal calcium current. To help identify the role of alpha 1E, we examined differential expression of alpha 1E splice variants in mouse brain and cultured cell lines and examined the gene structure of the region encoding the amino terminal. Three splice variants were analyzed by a ribonuclease protection assay, and a fourth variant reported previously in a fetal human alpha 1E sequence was also detected in mouse brain and a pituitary cell line. Whole brain, telencephalon, and olfactory bulb contained predominantly the splice variant corresponding to alpha 1E-1 although other known variants could be detected. Neuroendocrine cells in vitro (beta TC3 insulinoma cells and AtT-20 pituitary cell lines) expressed predominantly one alpha 1E isoform. The existence of a 5' exon accounting for the origin of variant 5' ends reported in different species was suggested by the sequence of the mouse alpha 1E gene in the region encoding the amino terminal.
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PMID:Isoform expression of the voltage-dependent calcium channel alpha 1E. 906 72

We have cloned a novel winged helix factor, WIN, from the rat insulinoma cell line, INS-1. Northern blot analysis demonstrated that WIN is highly expressed in a variety of insulinoma cell lines and rat embryonic pancreas and liver. In adults, WIN expression was detected in thymus, testis, lung, and several intestinal regions. We determined the DNA sequences bound in vitro by baculovirus-expressed WIN protein in a polymerase chain reaction-based selection procedure. WIN was found to bind with high affinity to the selected sequence 5'-AGATTGAGTA-3', which is similar to the recently identified HNF-6 binding sequence 5'-DHWATTGAYTWWD-3' (where W = A or T, Y = T or C, H is not G, and D is not C). We have isolated human WIN cDNAs by library screening and 5'-rapid amplification of cDNA ends. Sequence analysis indicates that the carboxyl terminus of human WIN has been previously isolated as a putative phosphorylation substrate, MPM2-reactive phosphoprotein 2 (MPP2); WIN may be regulated by phosphorylation. Alignment of the rat and human WIN cDNAs and their comparison with mouse genomic sequence revealed that the WIN DNA binding domain is encoded by four exons, two of which (exons 4 and 6) are alternatively spliced to generate at least three classes of mRNA transcripts. These transcripts were shown by RNase protection assay to be differentially expressed in different tissues. Alternative splicing within the winged helix DNA binding domain might result in modulation of DNA binding specificity.
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PMID:Molecular analysis of a novel winged helix protein, WIN. Expression pattern, DNA binding property, and alternative splicing within the DNA binding domain. 924 44

Protein tyrosine phosphatases (PTPs) play important roles in cell growth and differentiation of normal and tumor cells. In this study, we analyzed the PTP profile in two pancreatic islet tumor cell lines. Transcripts were isolated from alphaTC-1 (glucagon-secreting) and betaTC-1 (insulin-secreting) cell lines for templates. A pair of degenerative primers, based on the conserved regions of known PTPs, was used to amplify the transcripts by polymerase chain reaction. A total of 1,620 clones was examined by restriction enzyme analysis and cDNA sequencing. Twenty-one PTPs were identified, including nine cytosolic PTPs (TcPTP, P19PTP, PTP1B, PTPMEG, PTP1C, SYP, PTPH1, PTPL1, and PTPD1), nine transmembrane PTPs (PTPdelta, PTPgamma, PTPkappa, DEP-1, IA-2, LAR, PTPalpha, PTPNE3, and PTPepsilon), and three new PTPs--PTPmu-like PTPkappa-like, and IA-2beta. An RNase protection assay demonstrated that some of these PTPs were expressed predominantly in glucagonoma (i.e., PTPdelta and IA-2) and others in insulinoma (i.e., PTP1C, PTPkappa, and PTPNE3) cells. In this report, we present the first profile of PTPs in alpha and beta tumor cell lines.
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PMID:Profile and differential expression of protein tyrosine phosphatases in mouse pancreatic islet tumor cell lines. 959 14

Primer extension analysis and RNase protection assays revealed the identity of glucose 6-phosphatase gene transcripts in both the insulinoma cell line INS-1 and hepatic cells. In transient transfection assays of INS-1 cells, using constructs between the human glucose 6-phosphatase gene promoter and a luciferase reporter gene, the reporter gene activity was induced by dexamethasone and dibutyryl cAMP. Furthermore, the promoter was regulated by the glucose concentration in the medium. This effect was dependent on glucose metabolism. The data indicated that glucose 6-phosphatase gene transcription is regulated in a similar way in the insulinoma cell line and in liver.
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PMID:Glucose induces glucose 6-phosphatase hydrolytic subunit gene transcription in an insulinoma cell line (INS-1). 992 51

Voltage-dependent calcium (Ca2+) channels are involved in many specialized cellular functions and are controlled by a diversity of intracellular signals. Recently, members of the RGK family of small GTPases (Rem, Rem2, Rad, Gem/Kir) have been identified as novel contributors to the regulation of L-type calcium channel activity. In this study, microarray analysis of the mouse insulinoma MIN6 cell line revealed that the transcription of Rem2 gene is strongly induced by exposure to high glucose, which was confirmed by real-time reverse transcriptase-PCR and RNase protection analysis. Because elevation of intracellular Ca2+ in pancreatic beta-cells is essential for insulin secretion, we tested the hypothesis that Rem2 attenuates Ca2+ currents to regulate insulin secretion. Co-expression of Rem2 with CaV 1.2 or CaV1.3 L-type Ca + channels in a heterologous expression system completely inhibits de novo Ca2+ current expression. In addition, ectopic overexpression of Rem2 both inhibited L-type Ca2+ channel activity and prevented glucose-stimulated insulin secretion in pancreatic beta-cell lines. Co-immunoprecipitation studies demonstrate that Rem2 associates with a variety of CaVbeta subunits. Importantly, surface biotinylation studies demonstrate that the membrane distribution of Ca2+ channels was not reduced at a time when channel activity was potently inhibited by Rem2 expression, indicating that Rem2 modulates channel function without interfering with membrane trafficking. Taken together, these data suggest that inhibition of L-type Ca2+ channels by Rem2 signaling may represent a new and potentially important mechanism for regulating Ca2+-triggered exocytosis in hormone-secreting cells, including insulin secretion in pancreatic beta-cells.
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PMID:Regulation of L-type Ca2+ channel activity and insulin secretion by the Rem2 GTPase. 1572 82