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Updated: Jun 19, 2026
A Screenable In Vivo Assay for Mitochondrial Modulators Using Transgenic Bioluminescent Caenorhabditis elegans
Published on: October 16, 2015
Genome-wide RNAi screen identifies Letm1 as a mitochondrial Ca2+/H+ antiporter
Dawei Jiang1, Linlin Zhao, David E Clapham
1Department of Cardiology, Howard Hughes Medical Institute, Children's Hospital Boston, Manton Center for Orphan Disease, and Department of Neurobiology, Harvard Medical School, Enders Building 1309, 320 Longwood Avenue, Boston, MA 02115, USA.
Abstract:
Mitochondria are integral components of cellular calcium (Ca2+) signaling. Calcium stimulates mitochondrial adenosine 5'-triphosphate production, but can also initiate apoptosis. In turn, cytoplasmic Ca2+ concentrations are regulated by mitochondria. Although several transporter and ion-channel mechanisms have been measured in mitochondria, the molecules that govern Ca2+ movement across the inner mitochondrial membrane are unknown. We searched for genes that regulate mitochondrial Ca2+ and H+ concentrations using a genome-wide Drosophila RNA interference (RNAi) screen. The mammalian homolog of one Drosophila gene identified in the screen, Letm1, was found to specifically mediate coupled Ca2+/H+ exchange. RNAi knockdown, overexpression, and liposome reconstitution of the purified Letm1 protein demonstrate that Letm1 is a mitochondrial Ca2+/H+ antiporter.
Insights
Mitochondria regulate cellular calcium (Ca2+) signaling. A genome-wide screen identified Letm1 as a mitochondrial Ca2+/H+ antiporter, crucial for calcium and proton transport across the inner mitochondrial membrane.
Area of Science:
- Cell Biology
- Mitochondrial Function
- Ion Transport
Background:
- Mitochondria play a critical role in cellular calcium (Ca2+) signaling, influencing both ATP production and apoptosis.
- Mitochondria also regulate cytoplasmic Ca2+ levels, but the specific mechanisms for Ca2+ transport across the inner mitochondrial membrane remain largely unknown.
Purpose of the Study:
- To identify the molecular players responsible for regulating Ca2+ and H+ concentrations within mitochondria.
- To elucidate the function of these molecules in mitochondrial Ca2+ transport.
Main Methods:
- A genome-wide Drosophila RNA interference (RNAi) screen was employed to identify genes affecting mitochondrial Ca2+ and H+ concentrations.
- The identified gene, Letm1, was further characterized using RNAi knockdown, overexpression studies, and liposome reconstitution assays.
Main Results:
- The screen identified Letm1 as a key regulator of mitochondrial Ca2+ and H+ concentrations.
- Functional studies confirmed that Letm1 mediates coupled Ca2+/H+ exchange, acting as a mitochondrial Ca2+/H+ antiporter.
- Letm1's role in transporting Ca2+ across the inner mitochondrial membrane was validated through various experimental approaches.
Conclusions:
- Letm1 is a novel mitochondrial Ca2+/H+ antiporter essential for regulating mitochondrial and cellular ion homeostasis.
- This discovery provides critical insight into the molecular mechanisms governing mitochondrial calcium transport and its implications in cellular signaling.
