Suppression of the protein tyrosine phosphatase LAR reduces apolipoprotein B secretion by McA-RH7777 rat hepatoma cells.
Apolipoprotein B (apo B) secretion is reduced by insulin in rat hepatocytes. To evaluate possible mechanisms by which insulin action leads to inhibition of apo B secretion, we evaluated the effect of suppression of the protein-tyrosine phosphatase LAR on apo B secretion by McA-RH7777 (McA) rat hepatoma cells. A reduction in cellular LAR levels was accomplished by stable transfection of McA cells with LAR antisense cDNA. Previous studies indicate that LAR-antisense transfectants demonstrate increased insulin receptor signaling. In current studies, reduced LAR expression results in a 60% to 70% reduction in apo B secretion compared with null vector control. The reduction in apo B secretion correlated with a significant decrease in cellular apo B mRNA levels. Results suggests there is a relationship of protein tyrosine phosphorylation with regulation of apo B mRNA abundance in McA cells.
Phung
T L
TL
Department of Pathology and Laboratory Medicine, University of Rochester School of Medicine and DentistryJ, 601 Elmwood Avenue, Rochester, New York, 14642, USA.
Mooney
R A
RA
Kulas
D T
DT
Sparks
C E
CE
Sparks
J D
JD
D000818:Animals; D001055:Apolipoproteins B / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D016373:DNA, Antisense / Q000494:pharmacology; D018076:DNA, Complementary; D007328:Insulin / Q000378:metabolism; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D054630:Receptor-Like Protein Tyrosine Phosphatases, Class 4; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors*; D015398:Signal Transduction; D014407:Tumor Cells, Cultured
D001055:Apolipoproteins B; D016373:DNA, Antisense; D018076:DNA, Complementary; D007328:Insulin; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D017027:Protein Tyrosine Phosphatases; C516845:Ptpra protein, rat; D054630:Receptor-Like Protein Tyrosine Phosphatases, Class 4