Seipin performs dissectible functions in promoting lipid droplet biogenesis and regulating droplet morphology.
Bottom Line: Furthermore, we find that the normal rate of droplet initiation depends on 14 amino acids at the amino terminus of seipin, deletion of which results in fewer, larger droplets that are consistent with a delay in initiation but are otherwise normal in morphology.Importantly, other functions of seipin, namely vectorial budding and resistance to inositol, are retained in this mutant.We conclude that seipin has dissectible roles in both promoting early LD initiation and in regulating LD morphology, supporting its importance in LD biogenesis.
Affiliation: Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75235-9041.Show MeSH
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Mentions: We further analyzed the supersized droplet phenotype of fld1∆Nterm from oleate-grown cells by electron microscopy (Figure 3, D–F; sample images are in Figure 4A), finding fewer droplets in fld1∆Nterm with an increased number of supersized droplets, consistent with the phenotype from fluorescence microscopy. Additionally, we detected a concomitant decrease in the prevalence of LD clusters (defined as at least five droplets adjacent to one another) compared with fld1∆ cells. This was consistent with a decrease in LD–ER tangles later observed by fluorescence microscopy in minimal medium (Figure 5, C and E). The N-terminal deletion therefore appears to display an extreme supersized phenotype but is otherwise normal in droplet morphology, without the droplet clustering or size heterogeneity of the knockout strain.
Affiliation: Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75235-9041.