Perilipins Are Associated with Cholesteryl Ester Droplets in Steroidogenic Adrenal Cortical and Leydig Cells (*)
- Diane A. Servetnick(1),
- Dawn L. Brasaemle(1),
- Jasmine Gruia-Gray(2),
- Alan R. Kimmel(2),
- J. Wolff(3) and
- Constantine Londos(1)(§)
- From the (1)Laboratory of Cellular and Developmental Biology, Membrane Regulation Section,
- (2)Molecular Mechanisms of Development Section and
- (3)Laboratory of Biochemical Pharmacology, Endocrine Biochemistry Section, NIDDK, National Institutes of Health, Bethesda, Maryland 20892
- § To whom correspondence should be addressed: Bldg. 6, Rm. B1-32, National Institutes of Health, Bethesda, MD 20892-2715. Tel.: 301-496-6991; Fax: 301-496-5239; E-mail: clondos{at}helix.nih.gov.
Abstract
Steroidogenic cells store cholesteryl esters, precursors for steroid hormone synthesis, in intracellular lipid droplets. Cholesteryl ester hydrolysis is activated by protein kinase A and catalyzed by cholesteryl esterase. The esterase is similar, if not identical, to hormone-sensitive lipase in adipocytes where an analogous lipolytic mechanism occurs. Perilipins, proteins located exclusively at lipid droplet surfaces in adipocytes, are polyphosphorylated by protein kinase A in response to lipolytic stimuli, suggesting a role for these proteins in mediating lipid metabolism. The present study reveals that perilipins are associated with cholesteryl ester droplets in two steroidogenic cell lines: Y-1 adrenal cortical cells and MA-10 Leydig cells. The relative abundance of perilipin mRNAs and protein is much less in steroidogenic cells than in adipocytes. Like adipocytes, steroidogenic cells express perilipin A; additionally, the latter cells contain relatively abundant amounts of perilipin C, a protein that is not detectable in adipocytes by Western analysis. The data suggest a strong link between perilipins and lipid hydrolysis that is mediated by the hormone-sensitive lipase/cholesteryl esterase class of enzymes.
Footnotes
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↵* The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵1 The abbreviations used are:
- PAGE
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polyacrylamide gel electrophoresis
- ACTH
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adrenocorticotropic hormone
- PKA
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cAMP-dependent protein kinase
- kb
-
kilobase.
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↵2 With minor exceptions, as noted in the present paper, the perilipin proteins found in murine adipocytes are nearly identical to those in rat adipocytes (T. Takeda, C. M. Rondinone, J. L. Theodorakis, T. Barber, E. J. Blanchette-Mackie, R. H. Pointer, A. R. Kimmel, A. S. Greenberg, and C. Londos, submitted for publication).
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↵3 T. Barber, E. J. Blanchette-Mackie, J. Wolff, and C. Londos, unpublished data.
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↵4 Antisera raised against perilipin that was purified from rat fat cakes have strong reactivity against a recombinant peptide containing the COOH-terminal 97 amino acids of perilipin A. These antisera have weak reactivity against recombinant peptides containing the NH2-terminal sequence, amino acids 17-121 (D. L. Brasaemle and C. Londos, unpublished data).
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↵5 Rat and murine perilipin A cDNAs share 93% identity at the amino acid level. Five different
400-base pair polymerase chain reaction-derived fragments, corresponding to the entire murine perilipin A coding region, hybridize
with the 3.0-kb mRNA (J. Gruia-Gray, unpublished data).
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↵6 Blanchette-Mackie, E. J., Dwyer, N. K., Barber, T., Coxey, R. A., Takeda, T., Rondinone, C. M., Theodorakis, J. L., Greenberg, A. S., and Londos, C., J. Lipid Res. (1995) 36, in press.
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↵7 A. S. Greenberg, personal communication.
