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Fld1p, a functional homologue of human seipin, regulates the size of lipid droplets in yeast.

Fei W, Shui G, Gaeta B, Du X, Kuerschner L, Li P, Brown AJ, Wenk MR, Parton RG, Yang H - J. Cell Biol. (2008)

Bottom Line: Cells lacking FLD1 contain strikingly enlarged (supersized) LDs, and LDs from fld1Delta cells demonstrate significantly enhanced fusion activities both in vivo and in vitro.Interestingly, the expression of human seipin, whose mutant forms are associated with Berardinelli-Seip congenital lipodystrophy and motoneuron disorders, rescues LD-associated defects in fld1Delta cells.These results suggest that an evolutionally conserved function of seipin in phospholipid metabolism and LD formation may be functionally important in human adipogenesis.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, National University of Singapore, Singapore 117597, Republic of Singapore.

ABSTRACT
Lipid droplets (LDs) are emerging cellular organelles that are of crucial importance in cell biology and human diseases. In this study, we present our screen of approximately 4,700 Saccharomyces cerevisiae mutants for abnormalities in the number and morphology of LDs; we identify 17 fld (few LDs) and 116 mld (many LDs) mutants. One of the fld mutants (fld1) is caused by the deletion of YLR404W, a previously uncharacterized open reading frame. Cells lacking FLD1 contain strikingly enlarged (supersized) LDs, and LDs from fld1Delta cells demonstrate significantly enhanced fusion activities both in vivo and in vitro. Interestingly, the expression of human seipin, whose mutant forms are associated with Berardinelli-Seip congenital lipodystrophy and motoneuron disorders, rescues LD-associated defects in fld1Delta cells. Lipid profiling reveals alterations in acyl chain compositions of major phospholipids in fld1Delta cells. These results suggest that an evolutionally conserved function of seipin in phospholipid metabolism and LD formation may be functionally important in human adipogenesis.

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Mass spectrometry analysis of glycerophospholipids. (A and B) Wild-type and fld1Δ cells were grown to stationary phase in SC media. Total lipids were extracted and analyzed by high performance liquid chromatography/mass spectrometry. The results for phosphatidylinositol (PI) and phosphatidylserine (PS) are shown in A and B, respectively. Data for phosphatidylethanolamine and phosphatidylcholine are shown in Fig. S3 (available at http://www.jcb.org/cgi/content/full/jcb.200711136/DC1). Data are represented as normalized intensities based on a formula described in Materials and methods. (C) Fatty acyl (FA) profiles of polar lipids. The y axis represents the normalized values of each fatty acyl to the sum of intensities of all fatty acyls. n = 4; values are means ± SD (error bars).
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fig5: Mass spectrometry analysis of glycerophospholipids. (A and B) Wild-type and fld1Δ cells were grown to stationary phase in SC media. Total lipids were extracted and analyzed by high performance liquid chromatography/mass spectrometry. The results for phosphatidylinositol (PI) and phosphatidylserine (PS) are shown in A and B, respectively. Data for phosphatidylethanolamine and phosphatidylcholine are shown in Fig. S3 (available at http://www.jcb.org/cgi/content/full/jcb.200711136/DC1). Data are represented as normalized intensities based on a formula described in Materials and methods. (C) Fatty acyl (FA) profiles of polar lipids. The y axis represents the normalized values of each fatty acyl to the sum of intensities of all fatty acyls. n = 4; values are means ± SD (error bars).

Mentions: Congenital generalized lipodystrophy (CGL; or BSCL) is an autosomal recessive disorder that is characterized by the almost complete absence of adipose tissue and severe insulin resistance (Agarwal and Garg, 2004). Genome-wide linkage analysis identified two loci for CGL: CGL type 1 (CGL1) is caused by mutations in the AGPAT2 (1-acylglycerol-3-phosphate-O-acyl transferase 2) gene, and CGL2 is caused by mutations in BSCL2, which encodes seipin (Magre et al., 2001; Agarwal et al., 2002). AGPAT2 catalyzes the formation of phosphatidic acid (PA), but knocking down AGPAT2 led to elevated levels of several phospholipid species, including PA, and to a delay in the activation of key transcription factors for adipogenesis such as C/EBPβ and PPARγ (Gale et al., 2006). Therefore, AGPAT2 controls adipogenesis through modulation of the synthesis of phospholipids. In contrast, little is known about the role of seipin in adipogenesis and lipodystrophy. Because mutations in AGPAT2 and BSCL2 cause similar clinical manifestations, we wondered whether aberrant phospholipid metabolism may underlie the cellular defects for both conditions. Lipid species from wild-type and fld1Δ whole cell extracts were analyzed by electrospray ionization tandem mass spectrometry. The level of PA increased slightly in fld1Δ cells (unpublished data). Interestingly, there is a shift from long-chain (18:1) to medium/short-chain (16:0, 14:0, and 12:0) fatty acid incorporation into all major phospholipids as a result of the deletion of FLD1 (Fig. 5 and Fig. S3, available at http://www.jcb.org/cgi/content/full/jcb.200711136/DC1).


Fld1p, a functional homologue of human seipin, regulates the size of lipid droplets in yeast.

Fei W, Shui G, Gaeta B, Du X, Kuerschner L, Li P, Brown AJ, Wenk MR, Parton RG, Yang H - J. Cell Biol. (2008)

Mass spectrometry analysis of glycerophospholipids. (A and B) Wild-type and fld1Δ cells were grown to stationary phase in SC media. Total lipids were extracted and analyzed by high performance liquid chromatography/mass spectrometry. The results for phosphatidylinositol (PI) and phosphatidylserine (PS) are shown in A and B, respectively. Data for phosphatidylethanolamine and phosphatidylcholine are shown in Fig. S3 (available at http://www.jcb.org/cgi/content/full/jcb.200711136/DC1). Data are represented as normalized intensities based on a formula described in Materials and methods. (C) Fatty acyl (FA) profiles of polar lipids. The y axis represents the normalized values of each fatty acyl to the sum of intensities of all fatty acyls. n = 4; values are means ± SD (error bars).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2234226&req=5

fig5: Mass spectrometry analysis of glycerophospholipids. (A and B) Wild-type and fld1Δ cells were grown to stationary phase in SC media. Total lipids were extracted and analyzed by high performance liquid chromatography/mass spectrometry. The results for phosphatidylinositol (PI) and phosphatidylserine (PS) are shown in A and B, respectively. Data for phosphatidylethanolamine and phosphatidylcholine are shown in Fig. S3 (available at http://www.jcb.org/cgi/content/full/jcb.200711136/DC1). Data are represented as normalized intensities based on a formula described in Materials and methods. (C) Fatty acyl (FA) profiles of polar lipids. The y axis represents the normalized values of each fatty acyl to the sum of intensities of all fatty acyls. n = 4; values are means ± SD (error bars).
Mentions: Congenital generalized lipodystrophy (CGL; or BSCL) is an autosomal recessive disorder that is characterized by the almost complete absence of adipose tissue and severe insulin resistance (Agarwal and Garg, 2004). Genome-wide linkage analysis identified two loci for CGL: CGL type 1 (CGL1) is caused by mutations in the AGPAT2 (1-acylglycerol-3-phosphate-O-acyl transferase 2) gene, and CGL2 is caused by mutations in BSCL2, which encodes seipin (Magre et al., 2001; Agarwal et al., 2002). AGPAT2 catalyzes the formation of phosphatidic acid (PA), but knocking down AGPAT2 led to elevated levels of several phospholipid species, including PA, and to a delay in the activation of key transcription factors for adipogenesis such as C/EBPβ and PPARγ (Gale et al., 2006). Therefore, AGPAT2 controls adipogenesis through modulation of the synthesis of phospholipids. In contrast, little is known about the role of seipin in adipogenesis and lipodystrophy. Because mutations in AGPAT2 and BSCL2 cause similar clinical manifestations, we wondered whether aberrant phospholipid metabolism may underlie the cellular defects for both conditions. Lipid species from wild-type and fld1Δ whole cell extracts were analyzed by electrospray ionization tandem mass spectrometry. The level of PA increased slightly in fld1Δ cells (unpublished data). Interestingly, there is a shift from long-chain (18:1) to medium/short-chain (16:0, 14:0, and 12:0) fatty acid incorporation into all major phospholipids as a result of the deletion of FLD1 (Fig. 5 and Fig. S3, available at http://www.jcb.org/cgi/content/full/jcb.200711136/DC1).

Bottom Line: Cells lacking FLD1 contain strikingly enlarged (supersized) LDs, and LDs from fld1Delta cells demonstrate significantly enhanced fusion activities both in vivo and in vitro.Interestingly, the expression of human seipin, whose mutant forms are associated with Berardinelli-Seip congenital lipodystrophy and motoneuron disorders, rescues LD-associated defects in fld1Delta cells.These results suggest that an evolutionally conserved function of seipin in phospholipid metabolism and LD formation may be functionally important in human adipogenesis.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, National University of Singapore, Singapore 117597, Republic of Singapore.

ABSTRACT
Lipid droplets (LDs) are emerging cellular organelles that are of crucial importance in cell biology and human diseases. In this study, we present our screen of approximately 4,700 Saccharomyces cerevisiae mutants for abnormalities in the number and morphology of LDs; we identify 17 fld (few LDs) and 116 mld (many LDs) mutants. One of the fld mutants (fld1) is caused by the deletion of YLR404W, a previously uncharacterized open reading frame. Cells lacking FLD1 contain strikingly enlarged (supersized) LDs, and LDs from fld1Delta cells demonstrate significantly enhanced fusion activities both in vivo and in vitro. Interestingly, the expression of human seipin, whose mutant forms are associated with Berardinelli-Seip congenital lipodystrophy and motoneuron disorders, rescues LD-associated defects in fld1Delta cells. Lipid profiling reveals alterations in acyl chain compositions of major phospholipids in fld1Delta cells. These results suggest that an evolutionally conserved function of seipin in phospholipid metabolism and LD formation may be functionally important in human adipogenesis.

Show MeSH
Related in: MedlinePlus