Chabbott H, Cabot MC. Phorbol diesters inhibit enzymatic hydrolysis of diacylglycerols in vitro.
Proc Natl Acad Sci U S A 1986;
83:3126-30. [PMID:
3458169 PMCID:
PMC323465 DOI:
10.1073/pnas.83.10.3126]
[Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The effect of phorbol 12-myristate 13-acetate (PMA) on diacylglycerol lipase activity was examined in rat serum, tissue, and cellular preparations by using di[14C]oleoylglycerol, [3H]palmitoylacetylglycerol, and membrane-resident phospholipase C-generated diacylglycerols as substrates. These experiments were conducted to address whether phorbol esters can mimic diacylglycerols in interacting with enzymes other than protein kinase C. Serum hydrolysis of palmitoylacetylglycerol, assayed by the formation of [3H]palmitic acid, was inhibited by PMA, 4-O-methyl-PMA, or phorbol 12,13-dibutyrate (in order of decreasing potency). The hydrolysis of palmitoylacetylglycerol was inhibited more than 40% by the addition of PMA at a 1:1 molar ratio with substrate. The inhibition resembled the competitive type, with a Ki of approximately 2.7 microM. PMA in the 10-60 microM range also inhibited hydrolysis of palmitoylacetylglycerol by lipases from rat brain microsomes and by homogenates of C3H/10T1/2 mouse fibroblasts. PMA was likewise inhibitory when assayed in an intramembrane enzyme-substrate milieu in which diacylglycerols were generated, in situ, by treatment of [3H]palmitate-labeled cell homogenates with phospholipase C. Collectively, these data demonstrate that PMA, which is now thought to act by mimicry of diacylglycerols, can inhibit the action of diacylglycerol lipase. It is possible that such a mechanism is linked to the multiplicity of responses elicited by phorbol diesters and that other agents may function by means of enzyme interactions (post-phospholipase C) to influence the levels of the cellular diacylglycerol mediators.
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