Limits...
Increase in cellular triacylglycerol content and emergence of large ER-associated lipid droplets in the absence of CDP-DG synthase function.

He Y, Yam C, Pomraning K, Chin JS, Yew JY, Freitag M, Oliferenko S - Mol. Biol. Cell (2014)

Bottom Line: Understanding what determines the cellular amount of neutral lipids and their packaging into lipid droplets is of fundamental and applied interest.Using two species of fission yeast, we show that cycling cells deficient in the function of the ER-resident CDP-DG synthase Cds1 exhibit markedly increased triacylglycerol content and assemble large lipid droplets closely associated with the ER membranes.Our results suggest that interfering with the CDP-DG route of phosphatidic acid utilization rewires cellular metabolism to adopt a triacylglycerol-rich lifestyle reliant on the Kennedy pathway.

View Article: PubMed Central - PubMed

Affiliation: Temasek Life Sciences Laboratory, 117604 Singapore Department of Biological Sciences, National University of Singapore, 117543 Singapore.

Show MeSH
ER-associated lipid droplets in cds1-9 S. pombe cells grow by expansion. (A) A time-lapse sequence showing emergence and expansion of the Tgl4-GFP–marked lipid droplet in cds1-9 mutant cell (indicated by yellow arrowhead) at the restrictive temperature of 36°C. Also shown are the corresponding phase-contrast images. (B) A time-lapse sequence of GFP-ADEL– expressing cds1-9 mutant cell documents emergence of the ER-associated LD at the restrictive temperature of 36°C. Insets, magnified views of an indicated area. (A, B) Cells grown in rich yeast extract–based medium. Time is in hours and minutes. Scale bar, 5 μm; inset, 2 μm.
© Copyright Policy - creative-commons
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4263451&req=5

Figure 8: ER-associated lipid droplets in cds1-9 S. pombe cells grow by expansion. (A) A time-lapse sequence showing emergence and expansion of the Tgl4-GFP–marked lipid droplet in cds1-9 mutant cell (indicated by yellow arrowhead) at the restrictive temperature of 36°C. Also shown are the corresponding phase-contrast images. (B) A time-lapse sequence of GFP-ADEL– expressing cds1-9 mutant cell documents emergence of the ER-associated LD at the restrictive temperature of 36°C. Insets, magnified views of an indicated area. (A, B) Cells grown in rich yeast extract–based medium. Time is in hours and minutes. Scale bar, 5 μm; inset, 2 μm.

Mentions: It was previously proposed that deficiency in the Cds1 function in budding yeast could lead to LD fusion and emergence of supersized LDs caused by a rise in intracellular PA levels (Fei et al., 2011). Strong enrichment of TG synthases at abnormal lipid droplets in cds1-9 cells, together with the fact that they were closely associated with the ER, raised a possibility that these structures arose as a result of progressive enlargement rather than fusion of the preexisting, normally sized LDs. To evaluate this possibility, we performed time-lapse imaging of cds1-9 cells expressing the LD marker Tgl4-GFP or the artificial luminal ER marker GFP-ADEL (Zhang et al., 2010). Cells were shifted to the restrictive temperature of 36°C, and imaging started 2 h after the shift. We observed emergence of highly refractile bodies that recruited Tgl4-GFP and expanded over time (Figure 8A; n = 3 cells). Imaging using GFP-ADEL showed initial clustering of the ER membranes, followed by their outward expansion and eventual formation of large, “bubble”-like structures (Figure 8B; n = 14 cells). Thus abnormally large LDs in cells lacking the ER-localized CDP-DG synthase activity form through continuous growth rather than fusion between the preexisting LDs.


Increase in cellular triacylglycerol content and emergence of large ER-associated lipid droplets in the absence of CDP-DG synthase function.

He Y, Yam C, Pomraning K, Chin JS, Yew JY, Freitag M, Oliferenko S - Mol. Biol. Cell (2014)

ER-associated lipid droplets in cds1-9 S. pombe cells grow by expansion. (A) A time-lapse sequence showing emergence and expansion of the Tgl4-GFP–marked lipid droplet in cds1-9 mutant cell (indicated by yellow arrowhead) at the restrictive temperature of 36°C. Also shown are the corresponding phase-contrast images. (B) A time-lapse sequence of GFP-ADEL– expressing cds1-9 mutant cell documents emergence of the ER-associated LD at the restrictive temperature of 36°C. Insets, magnified views of an indicated area. (A, B) Cells grown in rich yeast extract–based medium. Time is in hours and minutes. Scale bar, 5 μm; inset, 2 μm.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4263451&req=5

Figure 8: ER-associated lipid droplets in cds1-9 S. pombe cells grow by expansion. (A) A time-lapse sequence showing emergence and expansion of the Tgl4-GFP–marked lipid droplet in cds1-9 mutant cell (indicated by yellow arrowhead) at the restrictive temperature of 36°C. Also shown are the corresponding phase-contrast images. (B) A time-lapse sequence of GFP-ADEL– expressing cds1-9 mutant cell documents emergence of the ER-associated LD at the restrictive temperature of 36°C. Insets, magnified views of an indicated area. (A, B) Cells grown in rich yeast extract–based medium. Time is in hours and minutes. Scale bar, 5 μm; inset, 2 μm.
Mentions: It was previously proposed that deficiency in the Cds1 function in budding yeast could lead to LD fusion and emergence of supersized LDs caused by a rise in intracellular PA levels (Fei et al., 2011). Strong enrichment of TG synthases at abnormal lipid droplets in cds1-9 cells, together with the fact that they were closely associated with the ER, raised a possibility that these structures arose as a result of progressive enlargement rather than fusion of the preexisting, normally sized LDs. To evaluate this possibility, we performed time-lapse imaging of cds1-9 cells expressing the LD marker Tgl4-GFP or the artificial luminal ER marker GFP-ADEL (Zhang et al., 2010). Cells were shifted to the restrictive temperature of 36°C, and imaging started 2 h after the shift. We observed emergence of highly refractile bodies that recruited Tgl4-GFP and expanded over time (Figure 8A; n = 3 cells). Imaging using GFP-ADEL showed initial clustering of the ER membranes, followed by their outward expansion and eventual formation of large, “bubble”-like structures (Figure 8B; n = 14 cells). Thus abnormally large LDs in cells lacking the ER-localized CDP-DG synthase activity form through continuous growth rather than fusion between the preexisting LDs.

Bottom Line: Understanding what determines the cellular amount of neutral lipids and their packaging into lipid droplets is of fundamental and applied interest.Using two species of fission yeast, we show that cycling cells deficient in the function of the ER-resident CDP-DG synthase Cds1 exhibit markedly increased triacylglycerol content and assemble large lipid droplets closely associated with the ER membranes.Our results suggest that interfering with the CDP-DG route of phosphatidic acid utilization rewires cellular metabolism to adopt a triacylglycerol-rich lifestyle reliant on the Kennedy pathway.

View Article: PubMed Central - PubMed

Affiliation: Temasek Life Sciences Laboratory, 117604 Singapore Department of Biological Sciences, National University of Singapore, 117543 Singapore.

Show MeSH