Stable reduction of STARD4 alters cholesterol regulation and lipid homeostasis

• Published in: Biochimica et biophysica acta. Molecular and cell biology of lipids 2020-04, Vol.1865 (4), p.158609-158609, Article 158609
• Main Authors: Iaea, David B., Spahr, Zachary R., Singh, Rajesh K., Chan, Robin B., Zhou, Bowen, Bareja, Rohan, Elemento, Olivier, Di Paolo, Gilbert, Zhang, Xiaoxue, Maxfield, Frederick R.
• Format: Article
• Language: English
• Subjects: Biological Transport; Cell Line, Tumor; Cell Membrane - metabolism; Cholesterol; Cholesterol - metabolism; Computational biology; Endocytosis; endosomes; Gene expression; genes; homeostasis; human diseases; Humans; knockout mutants; Lipid Metabolism; Lipidomics; Lipids; lysosomes; membrane fluidity; Membrane lipids; Membrane Transport Proteins - genetics; Membrane Transport Proteins - metabolism; osteosarcoma; phenotype; plasma membrane; RNA Interference; RNA, Small Interfering - genetics; small interfering RNA; transcription (genetics); transport proteins
• ISSN: 1388-1981; 1879-2618
• DOI: 10.1016/j.bbalip.2020.158609

STARD4, a member of the evolutionarily conserved START gene family, is a soluble sterol transport protein implicated in cholesterol sensing and maintenance of cellular homeostasis. STARD4 is widely expressed and has been shown to transfer sterol between liposomes as well as organelles in cells. However, STARD4 knockout mice lack an obvious phenotype, so the overall role of STARD4 is unclear. To model long term depletion of STARD4 in cells, we use short hairpin RNA technology to stably decrease STARD4 expression in human U2OS osteosarcoma cells (STARD4-KD). We show that STARD4-KD cells display increased total cholesterol, slower cholesterol trafficking between the plasma membrane and the endocytic recycling compartment, and increased plasma membrane fluidity. These effects can all be rescued by transient expression of a short hairpin RNA-resistant STARD4 construct. Some of the cholesterol increase was due to excess storage in late endosomes or lysosomes. To understand the effects of reduced STARD4, we carried out transcriptional and lipidomic profiling of control and STARD4-KD cells. Reduction of STARD4 activates compensatory mechanisms that alter membrane composition and lipid homeostasis. Based on these observations, we propose that STARD4 functions as a critical sterol transport protein involved in sterol sensing and maintaining lipid homeostasis. •Knockdown of STARD4, a sterol transporter, leads to large changes in the lipidome.•STARD4-KD cells also have large changes in their mRNA profile.•There is an increase in cellular cholesterol, including in late endosomes.•These results indicate that STARD4 plays important roles in lipid homeostasis.