StarD7 Protein Deficiency Adversely Affects the Phosphatidylcholine Composition, Respiratory Activity, and Cristae Structure of Mitochondria.
Phosphatidylcholine (PC) is a major phospholipid of mitochondria, comprising 40-50% of both the outer and the inner membranes. However, PC must be imported from its production organelles because mitochondria lack the enzymes essential for PC biosynthesis. In a previous study, we found that StarD7 mediates the intracellular transfer of PC to mitochondria. Therefore, in this study, we analyzed the contribution of StarD7 to the maintenance of mitochondrial phospholipid content and function using siRNA-mediated knockdown and knock-out (KO) of the StarD7 gene in HEPA-1 cells. Real time analysis of respiratory activity demonstrated that the oxygen consumption rate and activity of mitochondrial complexes were impaired in StarD7-KD cells. To confirm these results, we established StarD7-KO HEPA-1 cells by double nicking using CRISPR/Cas9n. As expected, StarD7-KD and -KO cells showed a significant reduction in mitochondrial PC content. The ATP level and growth rate of KO cells were notably lower compared with wild-type cells when cultured in glucose-free galactose-containing medium to force cells to rely on mitochondrial ATP production. In KO cells, the level of the MTCO1 protein, a primary subunit of complex IV, was reduced without a concomitant decrease in its mRNA, but the level was restored when StarD7-I was overexpressed. StarD7-KO cells showed impaired formation of the mitochondrial supercomplexes and exhibited a disorganized cristae structure, with no changes in optic atrophy 1 protein. These findings indicate that StarD7 plays important roles in maintaining the proper composition of mitochondrial phospholipids as well as mitochondrial function and morphogenesis.
From the Department of Biochemistry, Dokkyo Medical University School of Medicine, 880 Kitakobayashi, Mibu, Tochigi, Japan and.
Yasuhiro
Y
Horibata
From the Department of Biochemistry, Dokkyo Medical University School of Medicine, 880 Kitakobayashi, Mibu, Tochigi, Japan and.
Hiromi
H
Ando
the Department of Human Genetics, David Geffen School of Medicine and.
Peixiang
P
Zhang
the Department of Human Genetics, David Geffen School of Medicine and.
Laurent
L
Vergnes
From the Department of Biochemistry, Dokkyo Medical University School of Medicine, 880 Kitakobayashi, Mibu, Tochigi, Japan and.
Chieko
C
Aoyama
From the Department of Biochemistry, Dokkyo Medical University School of Medicine, 880 Kitakobayashi, Mibu, Tochigi, Japan and.
Masahiko
M
Itoh
the Department of Human Genetics, David Geffen School of Medicine and.|the Molecular Biology Institute at UCLA, Los Angeles, California 90095.
Karen
K
Reue
From the Department of Biochemistry, Dokkyo Medical University School of Medicine, 880 Kitakobayashi, Mibu, Tochigi, Japan and h-sugi@dokkyomed.ac.jp.
Hiroyuki
H
Sugimoto
D000255:Adenosine Triphosphate / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D003576:Electron Transport Complex IV / Q000235:genetics / Q000378:metabolism; D055785:Gene Knockdown Techniques; D051379:Mice; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology*; D010713:Phosphatidylcholines / Q000235:genetics / Q000378:metabolism*
D002352:Carrier Proteins; D024101:Mitochondrial Proteins; D010713:Phosphatidylcholines; C000600335:STARD7 protein, mouse; D000255:Adenosine Triphosphate; D003576:Electron Transport Complex IV
lipid trafficking; mitochondria; mitochondrial respiratory chain complex; phosphatidylcholine; phospholipid
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