Regulation of fat specific protein 27 by isoproterenol and TNF-α to control lipolysis in murine adipocytes

Srijana Ranjit; Emilie Boutet; Pallavi Gandhi; Matthieu Prot; Yoshikazu Tamori; Anil Chawla; Andrew S. Greenberg; Vishwajeet Puri; Michael P. Czech

doi:10.1194/jlr.M008771

Regulation of fat specific protein 27 by isoproterenol and TNF-α to control lipolysis in murine adipocytes[S]

^*Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605
^†Division of Diabetes, Metabolism and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
^§Friedman School of Nutrition Science and Policy, Tufts University School of Medicine, Boston, MA 02111
^**Department of Medicine, Section of Endocrinology, Diabetes and Nutrition, Boston University School of Medicine, Boston, MA 02118

2To whom correspondence should be addressed. e-mail: Michael.Czech{at}umassmed.edu

Abstract

The lipid droplet-associated fat specific protein 27 (FSP27) suppresses lipolysis and thereby enhances triglyceride accumulation in adipocytes. We and others have recently found FSP27 to be a remarkably short-lived protein (half-life, 15 min) due to its rapid ubiquitination and proteasomal degradation. Thus, we tested the hypothesis that lipolytic agents such as tumor necrosis factor-α (TNF-α) and isoproterenol modulate FSP27 levels to regulate FFA release. Consistent with this concept, we showed that the lipolytic actions of TNF-α, interleukin-1β (IL-1β), and IFN-γ are accompanied by marked decreases in FSP27 expression and lipid droplet size in mouse adipocytes. Similar depletion of FSP27 using short interfering RNA (siRNA) mimicked the lipolysis-enhancing effect of TNF-α, while maintaining stable FSP27 levels using expression of hemagglutinin epitope-tagged FSP27 blocked TNF-α-mediated lipolysis. In contrast, we show the robust lipolytic action of isoproterenol is paradoxically associated with increases in FSP27 levels and a delayed degradation rate corresponding to decreased ubiquitination. This catecholamine-mediated increase in FSP27 abundance, probably a feedback mechanism for restraining excessive lipolysis by catecholamines, is mimicked by forskolin or 8-bromo-cAMP treatment and is prevented by the protein kinase A (PKA) inhibitor KT5720 or by PKA depletion using siRNA. Taken together, these data identify the regulation of FSP27 as an important intermediate in the mechanism of lipolysis in adipocytes in response to TNF-α and isoproterenol.

Footnotes

↵1 S. Ranjit and E. Boutet contributed equally to this work.
Abbreviations:

A.U.

arbitrary unit

ATGL

adipose triacylglycerol lipase

C/EBPα

CCAAT/enhancer binding protein α

CIDEC

cell death-inducing DNA fragmentation factor like effector-α C

DAPI

4',6-diamidino-2-phenylindole

FSP27

fat specific protein 27

GFP

green fluorescent protein

HA

hemagglutinin

HSL

hormone-sensitive lipase

IBMX

isobutylmethylxanthine

IL

interleukin

OXPAT/MLDP

oxidative tissues-enriched PAT protein/myocardial lipid droplet protein

PAT

perilipin-adipophilin-TIP47

PKA

protein kinase A

PLIN

perilipin

PPARγ

peroxisome proliferator-activated receptor γ

SVF

stromal–vascular fraction

TAG

triacylglycerol

TIP47

tail interacting protein 47

TNF-α

tumor necrosis factor-α
This work was supported by National Institutes of Health Grants DK-30898 and DK-60837 (to M. P. Czech), American Diabetes Association Grant: 7-08-RA-57, USDA, Agricultural Research Service under Contract no. 58-1950-7-707 and NIH Grant DK0822574 (to A. S. Greenberg). Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the National Institutes of Health or other funding agencies.
↵[S] The online version of this article (available at http://www.jlr.org) contains supplementary data in the form of two figures.