Mitochondria-associated membrane formation in hormone-stimulated Leydig cell steroidogenesis: role of ATAD3.
Leydig cell steroidogenesis is a multistep process that takes place in the mitochondria and endoplasmic reticulum (ER). The physical association between these 2 organelles could facilitate both steroidogenesis substrate availability and mitochondrial product passage to steroidogenic enzymes in the ER, thus regulating the rate of steroid formation. Confocal microscopy, using antisera against organelle-specific antigens, and electron microscopy studies demonstrated that there is an increase in the number of mitochondria-ER contact sites in response to hormone treatment in MA-10 mouse tumor Leydig cells. Electron tomography and 3-dimensional reconstruction allowed for the visualization of mitochondria-associated membranes (MAMs). MAMs were isolated and found to contain the 67-kDa long isoform of the adenosine triphosphatase (ATPase) family, AAA domain-containing protein 3 (ATAD3). The 67-kDa ATAD3 is anchored in the inner mitochondrial membrane and is enriched in outer-inner mitochondrial membrane contact sites. ATAD3-depleted MA-10 cells showed reduced production of steroids in response to human choriogonadotropin but not to 22R-hydroxycholesterol treatment, indicating a role of ATAD3 in the delivery of the substrate cholesterol into the mitochondria. The N terminus of ATAD3 contains 50 amino acids that have been proposed to insert into the outer mitochondrial membrane and associated organelles such as the ER. Deletion of the ATAD3 N terminus resulted in the reduction of hormone-stimulated progesterone biosynthesis, suggesting a role of ATAD3 in mitochondria-ER contact site formation. Taken together, these results demonstrate that the hormone-induced, ATAD3-mediated, MAM formation participates in the optimal transfer of cholesterol from the ER into mitochondria for steroidogenesis.
Research Institute of the McGill University Health Centre (L.I., J.F., S.L., M.B.R., V.P.); Departments of Medicine (L.I., J.F., S.L., M.B.R., V.P.), Pharmacology and Therapeutics (V.P.), and Biochemistry (V.P.); and Facility for Electron Microscopy Research (K.B., J.M.), Department of Anatomy and Cell Biology, McGill University, Montréal, Québec H3G 1A4, Canada.
Leeyah
L
Issop
Jinjiang
J
Fan
Sunghoon
S
Lee
Malena B
MB
Rone
Kaustuv
K
Basu
Jeannie
J
Mui
Vassilios
V
Papadopoulos
D000074183:ATPases Associated with Diverse Cellular Activities; D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D000302:Adrenal Cortex / Q000166:cytology*; D000818:Animals; D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism; D004721:Endoplasmic Reticulum; D005786:Gene Expression Regulation / Q000502:physiology*; D006801:Humans; D007985:Leydig Cells / Q000166:cytology* / Q000378:metabolism*; D008297:Male; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D051336:Mitochondrial Membranes / Q000502:physiology*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D051381:Rats; D014162:Transfection
C549686:ATAD3A protein, human; C582415:Atad3a protein, mouse; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D002784:Cholesterol; D000251:Adenosine Triphosphatases; C000595966:Atad3a protein, rat; D000074183:ATPases Associated with Diverse Cellular Activities