Phosphatidylcholine stimulates the activity of UDP-Gal beta 1-4 galactosyltransferase in normal human kidney proximal tumour cells.
Effects of various lipid components of low density lipoproteins (LDL) and serine on the regulation of UDP-Gal-beta 1-4-galactosyltransferase (GalT-2) activity have been investigated in normal proximal tubular (PT) cells. Addition of exogenous serine (0.1-0.75 mM), cholesterol (0-200 micrograms/ml medium), linoleic acid and oleic acid (0.1-0.75 mM) for 4 hr at 37 degrees C did not suppress the activity of GalT-2 in PT cells. Similarly, incubation of cells with glucosylceramide and lactosylceramide (25-50 micrograms/ml medium) did not alter GalT-2 activity in cells as compared to control. In contrast, palmitic acid (0-0.75 mM), phosphatidylethanolamine and sphingomyelin (0-200 micrograms/ml) stimulated GalT-2 activity by 20-36% as compared to control. Incubation of PT cells with D-alpha-dipalmitoyl phosphatidylcholine (0-200 micrograms/ml medium) also stimulated the activity of GalT-2, maximum stimulation (200%) occurring with 25 micrograms phosphatidylcholine/ml medium. However, at a higher concentration (200 micrograms/ml), the stimulation of the activity of GalT-2 was in the order of 27% compared to control. Dioleylphosphatidylcholine did not alter GalT-2 activity in PT cells. Thus, it is concluded that (i) various lipid components, sphingosine and serine present in LDL are not involved in the LDL-mediated suppression of GalT-2 activity in normal PT cells, and (ii) stringent structural requirements in the phosphatidylcholine molecule are necessary to exert a time and concentration dependent stimulation of GalT-2 activity.
Chatterjee
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S
Department of Pediatrics, Johns Hopkins University, School of Medicine, Baltimore, Maryland 21205.
Ghosh
N
N
D002478:Cells, Cultured; D008078:Cholesterol, LDL / Q000494:pharmacology*; D005700:Galactosyltransferases / Q000378:metabolism*; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D007700:Kinetics; D019787:Linoleic Acid; D008041:Linoleic Acids / Q000494:pharmacology; D019301:Oleic Acid; D009829:Oleic Acids / Q000494:pharmacology; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000494:pharmacology; D010713:Phosphatidylcholines / Q000494:pharmacology*; D010714:Phosphatidylethanolamines / Q000494:pharmacology; D012694:Serine / Q000494:pharmacology*; D013109:Sphingomyelins / Q000494:pharmacology
D008078:Cholesterol, LDL; D008041:Linoleic Acids; D009829:Oleic Acids; D010169:Palmitic Acids; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D013109:Sphingomyelins; D019301:Oleic Acid; D019308:Palmitic Acid; D012694:Serine; D019787:Linoleic Acid; D005700:Galactosyltransferases; C023235:glucosylceramide beta-1-4-galactosyltransferase