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.
Morimoto
C
C
Second Department of Medical Biochemistry, Central Research Laboratory, School of Medicine, Ehime University, Shigenobu-cho, Onsen-gun, Ehime, 791-0295, Japan.
Tsujita
T
T
Sumida
M
M
Okuda
H
H
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