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Functional analysis of FSP27 protein regions for lipid droplet localization, caspase-dependent apoptosis, and

Kun Liu1, Shengli Zhou, Ji-Young Kim

  • 1Department of Biochemistry and Cancer Biology and Center for Diabetes and Endocrine Research, The University of Toledo College of Medicine, Toledo, Ohio 43614, USA.

American Journal of Physiology. Endocrinology and Metabolism
|October 22, 2009
PubMed

Insights

Fatty acid-binding protein 27 (FSP27) induces enlarged lipid droplets and apoptosis through its CIDE C domain. This domain is crucial for both functions and interaction with CIDEA, influencing FSP27 protein levels.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • FSP27 (CIDEC) is an adipocyte protein involved in energy metabolism and apoptosis.
  • FSP27 localizes to lipid droplets and promotes their enlargement.
  • The dual role of FSP27 in apoptosis and lipid metabolism requires further elucidation.

Purpose of the Study:

  • To investigate the relationship between FSP27's apoptotic function and its lipid droplet localization.
  • To identify the specific domains of FSP27 responsible for these functions.
  • To explore FSP27's interaction with other CIDE proteins, specifically CIDEA.

Main Methods:

  • Ectopic expression of FSP27 in various human cell lines (e.g., HeLa).
  • Lipid droplet analysis using oleic acid treatment and stable FSP27 expression.
  • Domain mapping using eGFP-FSP27 deletion constructs.
  • Caspase-9 and cytochrome c assays.
  • Protein interaction assays and Western blotting for CIDEA interaction.

Main Results:

  • Ectopic FSP27 expression induces enlarged lipid droplets in non-adipocyte cell lines, suggesting universal mechanisms.
  • Lipid droplet formation via oleic acid partially rescues FSP27-induced apoptosis.
  • The CIDE C domain (amino acids 174-192) is essential for both lipid droplet localization and apoptotic activity.
  • FSP27 does not inhibit ATGL lipase activity on lipid droplets.
  • The FSP27 CIDE C domain interacts with CIDEA, and CIDEA co-expression reduces FSP27 protein levels.

Conclusions:

  • The FSP27 CIDE C domain is a critical functional unit for both apoptosis induction and lipid droplet association.
  • FSP27's apoptotic mechanism involves caspase-9 and cytochrome c release, dependent on the CIDE C domain.
  • FSP27 interacts with CIDEA, and this interaction influences FSP27 protein stability.

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