The mitochondrial respiratory chain controls intracellular calcium signaling and NFAT activity essential for heart formation in Xenopus laevis.
The mitochondrial respiratory chain (MRC) plays crucial roles in cellular energy production. However, its function in early embryonic development remains largely unknown. To address this issue, GRIM-19, a newly identified MRC complex I subunit, was knocked down in Xenopus laevis embryos. A severe deficiency in heart formation was observed, and the deficiency could be rescued by reintroducing human GRIM-19 mRNA. The mechanism involved was further investigated. We found that the activity of NFAT, a transcription factor family that contributes to early organ development, was downregulated in GRIM-19 knockdown embryos. Furthermore, the expression of a constitutively active form of mouse NFATc4 in these embryos rescued the heart developmental defects. NFAT activity is controlled by a calcium-dependent protein phosphatase, calcineurin, which suggests that calcium signaling may be disrupted by GRIM-19 knockdown. Indeed, both the calcium response and calcium-induced NFAT activity were impaired in the GRIM-19 or NDUFS3 (another complex I subunit) knockdown cell lines. We also showed that NFAT can rescue expression of Nkx2.5, which is one of the key genes for early heart development. Our data demonstrated the essential role of MRC in heart formation and revealed the signal transduction and gene expression cascade involved in this process.
Chen
Yong
Y
Signal Transduction Laboratory, Institute of Molecular and Cell Biology, National University of Singapore, Singapore, Republic of Singapore.
Yuen
Wai Hong
WH
Fu
Jianlin
J
Huang
Guochang
G
Melendez
Alirio J
AJ
Ibrahim
Farazeela Bte Mohod
FB
Lu
Hao
H
Cao
Xinmin
X
D000595:Amino Acid Sequence; D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D001943:Breast Neoplasms / Q000473:pathology; D019703:Calcineurin / Q000378:metabolism; D002118:Calcium / Q000032:analysis; D020013:Calcium Signaling; D045744:Cell Line, Tumor; D018076:DNA, Complementary; D004579:Electron Transport; D004625:Embryo, Nonmammalian; D005260:Female; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter; D006367:HeLa Cells; D006321:Heart / Q000196:embryology*; D006801:Humans; D017403:In Situ Hybridization; D019169:Jurkat Cells; D008156:Luciferases / Q000378:metabolism; D008928:Mitochondria / Q000502:physiology*; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000648:ultrastructure; D009206:Myocardium / Q000648:ultrastructure; D009247:NADH, NADPH Oxidoreductases / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D050778:NFATC Transcription Factors / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic; D014162:Transfection; D014982:Xenopus laevis / Q000196:embryology*
D051017:Apoptosis Regulatory Proteins; D018076:DNA, Complementary; D050778:NFATC Transcription Factors; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D008156:Luciferases; D009247:NADH, NADPH Oxidoreductases; C439057:NDUFA13 protein, human; D019703:Calcineurin; D002118:Calcium