title: Characterization of lipid droplets in steroidogenic MLTC-1 Leydig cells: Protein profiles and the morphological change induced by hormone stimulation.
abstract: Lipid droplets (LDs) are functional subcellular organelles involved in multiple intracellular processes. LDs are found in nearly all types of eukaryotic cells, but their properties are highly variable in different types of tissues. Steroidogenic cells synthesize steroid hormones de novo from the cholesterol deposited in cytosolic LDs. However, the roles of LD proteins in steroidogenesis under pituitary hormone stimulation have not been well elucidated. The protein profile of isolated LDs from the mouse Leydig tumor cell line MLTC-1 was distinct from that of hepatic cells or macrophages. By proteomic analysis of the components using mass spectrometry, two enzymes for steroidogenesis, 3β-hydroxysteroid dehydrogenase type 1 (3βHSD1) and 17 β-hydroxysteroid dehydrogenase type 11 (17βHSD11), were identified in two strong bands in the LD fractions. The LD fraction of MLTC-1 cells also included CYP11A1 and CYP17, suggesting that the LDs contain all the enzymes needed for testosterone synthesis. The steroidogenesis in Leydig cells is activated by luteinizing hormone through a PKA-dependent pathway. Stimulation of MLTC-1 cells with luteinizing hormone or 8-bromo-cAMP caused drastic changes in the morphology of the LDs in the MLTC-1 cells. Upon stimulation, large perinuclear LDs are turned into much smaller LDs and dispersed throughout the cytosol. These results raise the possibility that LDs are involved in a regulatory pathway of steroidogenesis, not just by serving as a storage depot for cholesterol esters, but also by providing enzymes and generating sites for enzymatic activity.
authors.affiliation: Division of Biological Chemistry, Department of Molecular Biology, Showa University School of Pharmacy, 1-5-8 Hatanodai, Shinagawa, Tokyo 142-8555, Japan. Electronic address: tyamag@pharm.showa-u.ac.jp.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Yamaguchi
authors.affiliation: Division of Biological Chemistry, Department of Molecular Biology, Showa University School of Pharmacy, 1-5-8 Hatanodai, Shinagawa, Tokyo 142-8555, Japan.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Fujikawa
authors.affiliation: Division of Biological Chemistry, Department of Molecular Biology, Showa University School of Pharmacy, 1-5-8 Hatanodai, Shinagawa, Tokyo 142-8555, Japan.
authors.forename: Satomi
authors.initials: S
authors.lastname: Nimura
authors.affiliation: Division of Biological Chemistry, Department of Molecular Biology, Showa University School of Pharmacy, 1-5-8 Hatanodai, Shinagawa, Tokyo 142-8555, Japan.
authors.forename: Yutaro
authors.initials: Y
authors.lastname: Tokuoka
authors.affiliation: Division of Biological Chemistry, Department of Molecular Biology, Showa University School of Pharmacy, 1-5-8 Hatanodai, Shinagawa, Tokyo 142-8555, Japan.
authors.forename: Sonoka
authors.initials: S
authors.lastname: Tsuda
authors.affiliation: Division of Biological Chemistry, Department of Molecular Biology, Showa University School of Pharmacy, 1-5-8 Hatanodai, Shinagawa, Tokyo 142-8555, Japan.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Aiuchi
authors.affiliation: Division of Biological Chemistry, Department of Molecular Biology, Showa University School of Pharmacy, 1-5-8 Hatanodai, Shinagawa, Tokyo 142-8555, Japan.
authors.forename: Rina
authors.initials: R
authors.lastname: Kato
authors.affiliation: Division of Biological Chemistry, Department of Molecular Biology, Showa University School of Pharmacy, 1-5-8 Hatanodai, Shinagawa, Tokyo 142-8555, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Obama
authors.affiliation: Division of Biological Chemistry, Department of Molecular Biology, Showa University School of Pharmacy, 1-5-8 Hatanodai, Shinagawa, Tokyo 142-8555, Japan. Electronic address: h-itabe@pharm.showa-u.ac.jp.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Itabe
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D003600:Cytosol / Q000201:enzymology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D007985:Leydig Cells / Q000166:cytology / Q000201:enzymology*; D007986:Luteinizing Hormone / Q000494:pharmacology*; D008297:Male; D051379:Mice; D013739:Testosterone / Q000096:biosynthesis*
chemical_list: D013739:Testosterone; D007986:Luteinizing Hormone
keywords: 17beta-HSD11; 3beta-HSD1; Lipid droplets; Lydig cells; MLTC-1; Steroidogenesis