title: On the formation of lipid droplets in human adipocytes: the organization of the perilipin-vimentin cortex.
abstract: We report on the heterogeneity and diversity of lipid droplets (LDs) in early stages of adipogenesis by elucidating the cell and molecular biology of amphiphilic and cytoskeletal proteins regulating and stabilizing the generation of LDs in human adipose cells. A plethora of distinct and differently sized LDs was detected by a brief application of adipocyte differentiation medium and additional short treatment with oleic acid. Using these cells and highly specific antibodies for LD-binding proteins of the perilipin (PLIN) family, we could distinguish between endogenously derived LDs (endogenous LDs) positive for perilipin from exogenously induced LDs (exogenous LDs) positive for adipophilin, TIP47 and S3-12. Having optimized these stimulation conditions, we used early adipogenic differentiation stages to investigate small-sized LDs and concentrated on LD-protein associations with the intermediate-sized filament (IF) vimentin. This IF protein was described earlier to surround lipid globules, showing spherical, cage-like structures. Consequently - by biochemical methods, by immunofluorescence microscopy and by electron- and immunoelectron microscopy - various stages of emerging lipid globules were revealed with perilipin as linking protein between LDs and vimentin. For this LD-PLIN-Vimentin connection, a model is now proposed, suggesting an interaction of proteins via opposed charged amino acid domains respectively. In addition, multiple sheaths of smooth endoplasmic reticulum cisternae surrounding concentrically nascent LDs are shown. Based on our comprehensive localization studies we present and discuss a novel pathway for the LD formation.
authors.affiliation: Helmholtz Group for Cell Biology, German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Hans
authors.initials: H
authors.lastname: Heid
authors.affiliation: Helmholtz Group for Cell Biology, German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Rickelt
authors.affiliation: Helmholtz Group for Cell Biology, German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Zimbelmann
authors.affiliation: Helmholtz Group for Cell Biology, German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Winter
authors.affiliation: Helmholtz Group for Cell Biology, German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Heiderose
authors.initials: H
authors.lastname: Schumacher
authors.affiliation: Helmholtz Group for Cell Biology, German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Yvette
authors.initials: Y
authors.lastname: Dörflinger
authors.affiliation: Progen Biotechnik, Heidelberg, Germany.
authors.forename: Caecilia
authors.initials: C
authors.lastname: Kuhn
authors.affiliation: Helmholtz Group for Cell Biology, German Cancer Research Center (DKFZ), Heidelberg, Germany ; Progen Biotechnik, Heidelberg, Germany.
authors.forename: Werner W
authors.initials: WW
authors.lastname: Franke
mesh_terms: D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D050156:Adipogenesis / Q000235:genetics; D000906:Antibodies / Q000737:chemistry; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation; D002460:Cell Line; D003470:Culture Media / Q000737:chemistry; D015870:Gene Expression; D006801:Humans; D007382:Intermediate Filaments / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D050356:Lipid Metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D019301:Oleic Acid / Q000494:pharmacology; D000070780:Perilipin-2; D000070796:Perilipin-3; D000071229:Perilipin-4; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism*; D014746:Vimentin / Q000235:genetics / Q000378:metabolism*
chemical_list: D000906:Antibodies; D002352:Carrier Proteins; D003470:Culture Media; D008565:Membrane Proteins; C000602982:PLIN2 protein, human; C038196:PLIN3 protein, human; C560544:PLIN4 protein, human; D000070780:Perilipin-2; D000070796:Perilipin-3; D000071229:Perilipin-4; D010750:Phosphoproteins; D033921:Vesicular Transport Proteins; D014746:Vimentin; D019301:Oleic Acid