The role of cholesterol in the association of endoplasmic reticulum membranes with mitochondria

Journal Article · Fri Jan 06 04:00:00 EST 2012 · Biochemical and Biophysical Research Communications

DOI:https://doi.org/10.1016/J.BBRC.2011.12.022· OSTI ID:22207646

Fujimoto, Michiko ^[1]; Hayashi, Teruo ^[1]; Su, Tsung-Ping ^[2]

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1. Cellular Stress Signaling Unit, Integrative Neuroscience Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, MD 21224 (United States)
2. Cellular Pathobiology Section, Integrative Neuroscience Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, MD 21224 (United States)

Highlights: Black-Right-Pointing-Pointer The endoplasmic reticulum subdomain termed MAM associates with mitochondria. Black-Right-Pointing-Pointer The biophysical role of lipids in the MAM-mitochondria association is unknown. Black-Right-Pointing-Pointer The in vitro membrane association assay was used to examine the role of lipids. Black-Right-Pointing-Pointer Cholesterol was found to negatively regulate the association. -- Abstract: The unique endoplasmic reticulum (ER) subdomain termed the mitochondria-associated ER membrane (MAM) engages the physical connection between the ER and the mitochondrial outer membrane and plays a role in regulating IP{sub 3} receptor-mediated Ca{sup 2+} influx and the phospholipid transport between the two organelles. The MAM contains certain signaling and membrane-tethering proteins but also lipids including cholesterol. The biophysical role of lipids at the MAM, specifically in the physical interaction between the MAM of the ER and mitochondria, remains not totally clarified. Here we employed the in vitro membrane association assay to investigate the role of cholesterol in the association between MAMs and mitochondria. The purified MAMs and mitochondria were mixed in vitro in a test tube and then the physical association of the two subcellular organelles was quantified indirectly by measuring the presence of the MAM-specific protein sigma-1 receptors in the mitochondria fraction. Purified MAMs contained free cholesterol approximately 7 times higher than that in microsomes. We found that depletion of cholesterol in MAMs with methyl-{beta}-cyclodextrin (M{beta}C) significantly increases the association between MAMs and mitochondria, whereas M{beta}C saturated with cholesterol does not change the association. {sup 14}C-Serine pulse-labeling demonstrated that the treatment of living cells with M{beta}C decreases the level of de novo synthesized {sup 14}C-phosphatidylserine (PtSer) and concomitantly increases greatly the synthesis of {sup 14}C-phosphatidylethanolamine (PtEt). Apparently, cholesterol depletion increased the PtSer transport from MAMs to mitochondria. Our findings suggest that cholesterol is an important substrate in regulating the association between MAMs of the ER and mitochondria.

• OSTI ID: 22207646
• Journal Information: Biochemical and Biophysical Research Communications, Journal Name: Biochemical and Biophysical Research Communications Journal Issue: 1 Vol. 417; ISSN BBRCA9; ISSN 0006-291X
• Country of Publication: United States
• Language: English

Related Subjects

60 APPLIED LIFE SCIENCES
BIOSYNTHESIS
CALCIUM IONS
CARBON 14
CHOLESTEROL
ENDOPLASMIC RETICULUM
HAMSTERS
IN VITRO
LABELLING
LECITHINS
MICROSOMES
MITOCHONDRIA
OLIGOSACCHARIDES
OVARIES
RECEPTORS
SERINE
SUBSTRATES
THIN-LAYER CHROMATOGRAPHY