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

Although the AE1 chloride/bicarbonate exchanger of the red blood cell is among the most thoroughly investigated of membrane transport proteins, less is known about the related AE2 polypeptide of parietal cells. We have studied enzymatic deglycosylation of native AE2 polypeptide in gastric mucosal membranes from pig and rabbit. Deglycosylation of AE2 was maximal at low ionic strength. Deglycosylation of AE2 in membranes was preferentially inhibited by bicarbonate compared with other anions. This inhibition was maximal at alkaline pH and was not evident after detergent solubilization of AE2. Deglycosylation of AE2 increased its susceptibility to proteolytic degradation, but the presence of bicarbonate protected against this degradation. Bicarbonate failed to inhibit deglycosylation of the membrane glycoproteins AE1 and gastric H(+)-K(+)-adenosinetriphosphatase beta-subunit or deglycosylation of the soluble glycoproteins fetuin and ribonuclease B. These data suggest that bicarbonate induces a conformational change in AE2 that can protect the polypeptide from deglycosylation and proteolysis. Pig AE2 was purified in sodium dodecyl sulfate, and its monosaccharide composition was determined after blotting onto polyvinylidene fluoride membrane. AE2 was found to be devoid of sialic acid, with a composition suggestive of the presence of lactosamine-type chains.
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PMID:HCO3(-)-dependent conformational change in gastric parietal cell AE2, a glycoprotein naturally lacking sialic acid. 877 47

Recent studies have indicated the presence of Na+/H+ and Cl-/HCO-3 exchange activities in lung alveolar and tracheal tissues of various species. To date, the identity of the Na+/H+ (NHE) and Cl-/HCO-3 (AE) exchanger isoforms and their regional distribution in human airways are not known. Molecular species of the NHE and AE gene families and their relative abundance in the human airway regions were assessed utilizing RT-PCR and the RNase protection assay, respectively. Organ donor lung epithelia from various bronchial regions (small, medium, and large bronchi and trachea) were harvested for RNA extraction. Gene-specific primers for the human NHE and AE isoforms were utilized for RT-PCR. Our results demonstrated that NHE1, AE2, and brain AE3 isoforms were expressed in all regions of the human airways, whereas NHE2, NHE3, AE1, and cardiac AE3 were not detected. RNase protection studies for NHE1 and AE2, utilizing glyceraldehyde-3-phosphate dehydrogenase as an internal standard, demonstrated that there were regional differences in the NHE1 mRNA levels in human airways. In contrast, the levels of AE2 mRNA remained unchanged. Differential expression of these isoforms in the human airways may have functional significance related to the airway absorption and secretion of electrolytes.
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PMID:Expression of the Na+/H+ and Cl-/HCO-3 exchanger isoforms in proximal and distal human airways. 1036 22

Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene that encodes a small conductance cAMP-activated chloride ion channel. In the CF pancreatic duct, mutations in CFTR cause a reduction in bicarbonate secretion. This is thought to result from CFTR operating in parallel with a chloride-bicarbonate (Cl(-)/HCO(-)(3)) exchanger, located in the apical membrane of pancreatic duct cells. The molecular basis of this Cl(-)/HCO(-)(3) exchanger has not been identified. A combination of screening cDNA libraries, RNase protection, and 5' RACE analysis was used to identify Cl(-)/HCO(-)(3) exchangers in human fetal pancreas. An AE2 Cl(-)/HCO(-)(3) exchanger was shown to be expressed in human fetal pancreas from the midtrimester of gestation, at a time when CF-associated pathology commences. In addition, an AE1 Cl(-)/HCO(3) was identified in fetal pancreas but was absent from the adult pancreas and cultured ductal epithelial cells from fetal and adult pancreas.
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PMID:Chloride-bicarbonate exchangers in the human fetal pancreas. 1049 Dec 90

Molecular species of the Na(+)-H(+) exchanger (NHE) and anion exchanger (AE) gene families and their relative abundance in the human airway regions were assessed utilizing RT-PCR and the RNase protection assay, respectively. Organ donor lung epithelia from various bronchial regions (small, medium, and large bronchi and trachea) were harvested for RNA extraction. Gene-specific primers for the human NHE and AE isoforms were utilized for RT-PCR. Our results demonstrated that NHE1, AE2, and brain AE3 isoforms were expressed in all regions of the human airway, whereas NHE2, NHE3, AE1, and cardiac AE3 were not detected. RNase protection studies for NHE1 and AE2, utilizing glyceraldehyde-3-phosphate dehydrogenase as an internal standard, demonstrated that there were regional differences in the NHE1 mRNA levels in human airways. In contrast, the levels of AE2 mRNA remained unchanged. Differential regional expression of NHE1 isoform may be related to a higher acid load in the tracheal epithelial cells than in epithelia of distal airways. Fluctuations in PCO(2) during inspiration and expiration are probably larger in the tracheal lumen than in the lumen of distal airways with associated larger swings in intracellular pH with each respiratory cycle. Immunohistochemical staining for AE2 protein demonstrated localization to the epithelial cells of human bronchial mucosa.
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PMID:Detection of Cl--HCO3- and Na+-H+ exchangers in human airways epithelium. 1187 73