Transporters involved in glucose and water absorption in the Dysdercus peruvianus (Hemiptera: Pyrrhocoridae) anterior midgut.
ABSTRACT Little is known about insect intestinal sugar absorption, in spite of the recent findings, and even less has been published regarding water absorption. The aim of this study was to shed light on putative transporters of water and glucose in the insect midgut. Glucose and water absorptions by the anterior ventriculus of Dysdercus peruvianus midgut were determined by feeding the insects with a glucose and a non-absorbable dye solution, followed by periodical dissection of insects and analysis of ventricular contents. Glucose absorption decreases glucose/dye ratios and water absorption increases dye concentrations. Water and glucose transports are activated (water 50%, glucose 33%) by 50 mM K(2)SO(4) and are inhibited (water 46%, glucose 82%) by 0.2 mM phloretin, the inhibitor of the facilitative hexose transporter (GLUT) or are inhibited (water 45%, glucose 35%) by 0.1 mM phlorizin, the inhibitor of the Na(+)-glucose cotransporter (SGLT). The results also showed that the putative SGLT transports about two times more water relative to glucose than the putative GLUT. These results mean that D. peruvianus uses a GLUT-like transporter and an SGLT-like transporter (with K(+) instead of Na(+)) to absorb dietary glucose and water. A cDNA library from D. peruvianus midgut was screened and we found one sequence homologous to GLUT1, named DpGLUT, and another to a sodium/solute symporter, named DpSGLT. Semi-quantitative RT-PCR studies revealed that DpGLUT and DpSGLTs mRNA were expressed in the anterior midgut, where glucose and water are absorbed, but not in fat body, salivary gland and Malpighian tubules. This is the first report showing the involvement of putative GLUT and SGLT in both water and glucose midgut absorption in insects.
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ABSTRACT: Facilitative glucose transport is mediated by members of the glucose transporter (GLUT) protein family that belong to the large superfamily of twelve transmembrane segment transporters. We have cloned and sequenced a 2,168 base-pair cDNA from Drosophila melanogaster (termed Dmglut1: GenBank accession number AF064703) with strong homology to the mammalian Glut genes. The cDNA has an open reading frame encoding a protein of 480 amino acids which shows a similarity of 68% to the human GLUT1 protein. We have done a phylogenetic analysis of the cDNA and the deduced protein sequences and found a significant homology to a putative coding sequence (Ceglut1) in Caenorhabditis elegans. Here we report the results of analyses of functional sites and secondary structures of the proposed proteins and conclude that the Dmglut1 and Ceglut1 genes encode functional glucose transporters.Hereditas 02/1999; 130(2):95-103. · 0.96 Impact Factor
- Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology - COMP BIOCHEM PHYSIOL B BIOCHEM MOL BIOL. 01/1994; 109(1):1-62.
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ABSTRACT: Glycation is a nonenzymatic process in which proteins react with reducing sugar molecules and thereby impair the function and change the characteristics of the proteins. Glycation is involved in diabetes and aging where the accumulation of glycation products causes side effects. In this study, we statistically investigate the glycation of epsilon amino groups of lysines and also train a sequence-based predictor. The statistical analysis suggests that acidic amino acids, mainly glutamate, and lysine residues catalyze the glycation of nearby lysines. The catalytic acidic amino acids are found mainly C-terminally from the glycation site, whereas the basic lysine residues are found mainly N-terminally. The predictor was made by combining 60 artificial neural networks in a balloting procedure. The cross-validated Matthews correlation coefficient for the predictor is 0.58, which is quite impressive given the relatively small amount of experimental data available. The method is made available at www.cbs.dtu.dk/services/NetGlycate-1.0.Glycobiology 10/2006; 16(9):844-53. · 3.54 Impact Factor