Spatial integration of TIP47 and adipophilin in macrophage lipid bodies.
We studied the distribution of the PAT family proteins TIP47 and adipophilin in lipid bodies of THP-1 cell-derived macrophages using freeze-fracture immunolabeling and other techniques. Lipid bodies in macrophages comprise lipid droplets and extensive, previously scantily characterized sheet-like organelles, which we descriptively call "lipid sails." TIP47 and adipophilin are components of many, but not all, the lipid droplets. Both proteins are not confined to the surface of lipid droplets, as supposed, but are also inside lipid droplet cores. They are not codistributed stoichiometrically in lipid droplets. How TIP47 and adipophilin, which are polar proteins, enter the lipid droplets and are packaged among the hydrophobic neutral lipids of the core is unclear. However, in the lipid layers of the core, these proteins are directed sometimes inward and sometimes outward. Because TIP47 and adipophilin also localize to lipid sails, lipid sails are intimately involved in intracellular lipid metabolism.
Robenek
Horst
H
Institute for Arteriosclerosis Research, University of Münster, Domagkstrasse 3, 48149 Münster, Germany. robenek@uni-muenster.de
Lorkowski
Stefan
S
Schnoor
Michael
M
Troyer
David
D
D000818:Animals; D000918:Antibody Specificity; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000276:immunology / Q000378:metabolism*; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry; D008264:Macrophages / Q000166:cytology* / Q000378:metabolism*; D008565:Membrane Proteins; D015388:Organelles / Q000737:chemistry / Q000378:metabolism*; D010455:Peptides / Q000276:immunology / Q000378:metabolism*; D000070780:Perilipin-2; D000070796:Perilipin-3; D011257:Pregnancy Proteins / Q000276:immunology / Q000378:metabolism*; D021381:Protein Transport; D033921:Vesicular Transport Proteins
D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008055:Lipids; D008565:Membrane Proteins; C000602982:PLIN2 protein, human; C038196:PLIN3 protein, human; D010455:Peptides; D000070780:Perilipin-2; D000070796:Perilipin-3; D011257:Pregnancy Proteins; D033921:Vesicular Transport Proteins