Journal
JOURNAL OF NEUROCHEMISTRY
Volume 89, Issue 3, Pages 636-644Publisher
WILEY
DOI: 10.1046/j.1471-4159.2004.02374.x
Keywords
phosphate; phosphatidylinositol-3-kinase; phosphatidyl-myo-inositol 3,4,5-triphosphate; PTEN; sphingomyelinase
Categories
Funding
- NICHD NIH HHS [HD-09402] Funding Source: Medline
- NINDS NIH HHS [NS-36866] Funding Source: Medline
Ask authors/readers for more resources
There is ample evidence that both acid (ASMase) and neutral (NSMase) sphingomyelinases play a role in cell death so inhibitors of either enzyme could have significant value as protectors against neurodegeneration. We used a fluorogenic sphingomyelinase substrate, 6-hexadecanoylamino-4-methylumbelliferyl-phosphorylcholine, and a [C-14]choline-labeled sphingomyelin substrate to screen large numbers of phosphocompounds for inhibition of ASMase in extracts of human oligodendroglioma cells (HOG) and neonatal rat oligodendrocytes. Non-competitive inhibition was observed with inorganic phosphate and AMP, which was a more potent inhibitor of ASMase than cyclic AMP, ADP or ATP. However, other nucleotide phosphates, sugar phosphates, nucleotide sugars and glycerol phosphate did not inhibit ASMase. Our key finding was that phosphatidyl-myo-inositol 3,4,5-triphosphate [PtdIns (3,4,5)P-3] was a much more potent inhibitor of ASMase than lysophosphatidic acid or phosphatidyl-myo-inositol 4,5-diphosphate [PtdIns(4,5)P-2]. When PtdIns(3,4,5)P-3 was added to cultured cells we observed 50% inhibition of ASMase but no inhibition of other lysosomal hydrolases. After transfection of HOG cells with the tumor supressor phosphatase and tensin homolog protein (PTEN), which hydrolyses PtdIns(3,4,5)P-3 to PtdIns(4,5)P-2, we observed a two-fold increase in ASMase activity. Furthermore, the phosphatidylinositol-3-kinase inhibitor wortmannin (which reduces PtdIns(3,4,5)P-3 levels) also resulted in activation of ASMase. We propose that the small amount of ASMase activity associated with detergent-resistant cell membranes (Rafts) is regulated by PtdIns(3,4,5)P-3 and is most likely involved in receptor clustering and capping.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available