Effects of plasma membrane Ca(2+)-ATPase overexpression upon D-glucose metabolism in insulin-producing BRIN-BD11 cells.
In order to investigate the possible link between PMCA (plasma-membrane Ca(2+)-ATPase) activity and D-glucose catabolism in insulin-producing cells, BRIN-BD11 cells were transfected with two isoforms of PMCA2. Transfection of insulin-producing BRIN-BD11 cells with PMCA2yb and PMCA2wb was documented by RT-PCR (reverse transcription-PCR), Western blot analysis, indirect immunofluorescence microscopy and (45)Ca(2+) uptake by microsomes. In the transfected cells, the overexpression of PMCA coincided with three major anomalies of D-glucose metabolism, namely a lower rate of D-[5-(3)H]glucose utilization prevailing at a low extracellular concentration of D-glucose (1.1 mM), a low ratio between D-[U-(14)C]oxidation and D-[5-(3)H]glucose utilization prevailing at a high extracellular glucose concentration (16.7 mM), and a high ratio between the net generation of (14)C-labelled acidic metabolites and amino acids and that of (3)H(2)O from D-[5-(3)H]glucose. These anomalies resulted in a decreased estimated rate of ATP generation (linked to the catabolism of the hexose) and a lowered ATP cell content, whether at low or high extracellular D-glucose concentrations. The net uptake of (45)Ca(2+) by intact cells was also decreased in the transfected cells, but to a greater extent than can apparently be attributed to the change in the ATP-generation rate. These findings document the relevance of PMCA activity to both D-glucose metabolism and Ca(2+) handling in insulin-producing cells, with emphasis on the key role of both cytosolic and mitochondrial Ca(2+) concentrations in the regulation of D-glucose catabolism. They also reveal that overexpression of PMCA leads, in insulin-producing cells, to an imbalance between ATP generation and consumption.
Kamagate
Adama
A
Laboratoire de Pharmacodynamie et de Thérapeutique, Université Libre de Bruxelles (ULB), 808 Route de Lennik, B-1070 Brussels, Belgium.
Sener
Abdullah
A
Courtois
Philippe
P
Malaisse
Willy J
WJ
Herchuelz
André
A
D000255:Adenosine Triphosphate / Q000096:biosynthesis*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D015870:Gene Expression; D005947:Glucose / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000201:enzymology*; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics; D008861:Microsomes / Q000201:enzymology; D053499:Plasma Membrane Calcium-Transporting ATPases / Q000096:biosynthesis* / Q000235:genetics; D051381:Rats
D007328:Insulin; D007527:Isoenzymes; D000255:Adenosine Triphosphate; D053499:Plasma Membrane Calcium-Transporting ATPases; D005947:Glucose; D002118:Calcium