Substrate-dependent lipolysis induced by isoproterenol.
The relationship between isoproterenol-induced lipolysis and the phosphorylation of perilipin and hormone-sensitive lipase (HSL) was examined using cell-free systems consisting of lipid droplets isolated from rat fat cells and HSL, and/or trioleoylglycerol emulsified with gum arabic and HSL. Isoproterenol was found to stimulate lipolysis in the cell-free system with the lipid droplets without an increase in the phosphorylation of either perilipin or HSL. On the other hand, no stimulation of lipolysis was found in the cell-free system containing lipid droplets despite increases in the phosphorylation of perilipin and HSL. In the cell-free system consisting of trioleoylglycerol emulsified with gum arabic and HSL, neither isoproterenol nor increases in the phosphorylation of perilipin and HSL accelerated lipolysis. These results suggest that isoproterenol-induced lipolysis may not be mediated through the phosphorylation of perilipin and HSL, and may rather be dependent on the substrate of HSL.
Second Department of Medical Biochemistry, Central Research Laboratory, School of Medicine, Ehime University, Shigenobu-cho, Onsen-gun, Ehime, 791-0295, Japan.
C
C
Morimoto
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T
Tsujita
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M
Sumida
H
H
Okuda
D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D002352:Carrier Proteins; D002474:Cell-Free System; D007545:Isoproterenol / Q000494:pharmacology*; D008066:Lipolysis / Q000187:drug effects*; D008297:Male; D000070778:Perilipin-1; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D051381:Rats; D002787:Sterol Esterase / Q000378:metabolism; D013379:Substrate Specificity
D000318:Adrenergic beta-Agonists; D002352:Carrier Proteins; D000070778:Perilipin-1; D010750:Phosphoproteins; D002787:Sterol Esterase; D007545:Isoproterenol