scholarly journals Dual functions of a small regulatory subunit in the mitochondrial calcium uniporter complex

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Ming-Feng Tsai ◽  
Charles B Phillips ◽  
Matthew Ranaghan ◽  
Chen-Wei Tsai ◽  
Yujiao Wu ◽  
...  
Keyword(s):  
Regulatory Subunit ◽  
Mitochondrial Calcium ◽  
Transmembrane Helices ◽  
Mitochondrial Calcium Uniporter ◽  
Activating Function ◽  
Mitochondrial Inner Membrane ◽  
Calcium Uniporter ◽  
Regulatory Purpose ◽  
Inner Membrane Protein ◽  
Dual Functions

Mitochondrial Ca2+ uptake, a process crucial for bioenergetics and Ca2+ signaling, is catalyzed by the mitochondrial calcium uniporter. The uniporter is a multi-subunit Ca2+-activated Ca2+ channel, with the Ca2+ pore formed by the MCU protein and Ca2+-dependent activation mediated by MICU subunits. Recently, a mitochondrial inner membrane protein EMRE was identified as a uniporter subunit absolutely required for Ca2+ permeation. However, the molecular mechanism and regulatory purpose of EMRE remain largely unexplored. Here, we determine the transmembrane orientation of EMRE, and show that its known MCU-activating function is mediated by the interaction of transmembrane helices from both proteins. We also reveal a second function of EMRE: to maintain tight MICU regulation of the MCU pore, a role that requires EMRE to bind MICU1 using its conserved C-terminal polyaspartate tail. This dual functionality of EMRE ensures that all transport-competent uniporters are tightly regulated, responding appropriately to a dynamic intracellular Ca2+ landscape.

scholarly journals Correction: Dual functions of a small regulatory subunit in the mitochondrial calcium uniporter complex

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Ming-Feng Tsai ◽  
Charles B Phillips ◽  
Matthew Ranaghan ◽  
Chen-Wei Tsai ◽  
Yujiao Wu ◽  
...  
Keyword(s):  
Regulatory Subunit ◽  
Mitochondrial Calcium ◽  
Mitochondrial Calcium Uniporter ◽  
Calcium Uniporter ◽  
Dual Functions

scholarly journals Functional reconstitution of the mitochondrial Ca2+/H+ antiporter Letm1

2013 ◽  
Vol 143 (1) ◽  
pp. 67-73 ◽  
Author(s):  
Ming-Feng Tsai ◽  
Dawei Jiang ◽  
Linlin Zhao ◽  
David Clapham ◽  
Christopher Miller
Keyword(s):  
Transport Mechanism ◽  
Turnover Rate ◽  
Leucine Zipper ◽  
Transmembrane Protein ◽  
Ruthenium Red ◽  
Mitochondrial Calcium Uniporter ◽  
Mitochondrial Inner Membrane ◽  
Calcium Uniporter ◽  
Ef Hand ◽  
Inner Membrane Protein

The leucine zipper, EF hand–containing transmembrane protein 1 (Letm1) gene encodes a mitochondrial inner membrane protein, whose depletion severely perturbs mitochondrial Ca2+ and K+ homeostasis. Here we expressed, purified, and reconstituted human Letm1 protein in liposomes. Using Ca2+ fluorophore and 45Ca2+-based assays, we demonstrate directly that Letm1 is a Ca2+ transporter, with apparent affinities of cations in the sequence of Ca2+ ≈ Mn2+ > Gd3+ ≈ La3+ > Sr2+ >> Ba2+, Mg2+, K+, Na+. Kinetic analysis yields a Letm1 turnover rate of 2 Ca2+/s and a Km of ∼25 µM. Further experiments show that Letm1 mediates electroneutral 1 Ca2+/2 H+ antiport. Letm1 is insensitive to ruthenium red, an inhibitor of the mitochondrial calcium uniporter, and CGP-37157, an inhibitor of the mitochondrial Na+/Ca2+ exchanger. Functional properties of Letm1 described here are remarkably similar to those of the H+-dependent Ca2+ transport mechanism identified in intact mitochondria.

scholarly journals The Mitochondrial Ca2+Uniporter Complex (MCUC) ofTrypanosoma bruceiIs a Hetero-oligomer That Contains Novel Subunits Essential for Ca2+Uptake

mBio ◽  
2018 ◽  
Vol 9 (5) ◽  
Author(s):  
Guozhong Huang ◽  
Roberto Docampo
Keyword(s):  
Trypanosoma Brucei ◽  
Mitochondrial Calcium ◽  
Transmembrane Helices ◽  
Yeast Two Hybrid ◽  
Content Type ◽  
Mitochondrial Calcium Uniporter ◽  
Calcium Uniporter ◽  
Essential Components ◽  
Split Ubiquitin ◽  
Two Hybrid

ABSTRACTThe mitochondrial calcium uniporter complex (MCUC) is a highly selective channel that conducts calcium ions across the organelle inner membrane. We previously characterizedTrypanosoma brucei’s MCU (TbMCU) as an essential component of the MCUC required for parasite viability and infectivity. In this study, we characterize its paralogT. bruceiMCUb (TbMCUb) and report the identification of two novel components of the complex that we named TbMCUc and TbMCUd. These new MCUC proteins are unique and conserved only in trypanosomatids.In situtagging and immunofluorescence microscopy revealed that they colocalize with TbMCU and TbMCUb to the mitochondria ofT. brucei. Blue Native PAGE and immunodetection analyses indicated that the MCUC proteins exist in a large protein complex with a molecular weight of approximately 380 kDa. RNA interference (RNAi) or overexpression of the TbMCUc and TbMCUd genes significantly reduced or enhanced mitochondrial Ca2+uptake inT. brucei, respectively, without affecting the mitochondrial membrane potential, indicating that they are essential components of the MCUC of this parasite. The specific interactions of TbMCU with TbMCUb, TbMCUc, or TbMCUd were confirmed by coimmunoprecipitation and split-ubiquitin membrane-based yeast two-hybrid (MYTH) assays. Furthermore, combining mutagenesis analysis with MYTH assays revealed that transmembrane helices (TMHs) were determinant of the interactions between TbMCUC subunits. In summary, our study has identified two novel essential components of the MCUC ofT. bruceiand defined their direct physical interactions with the other subunits that result in a hetero-oligomeric MCUC.IMPORTANCETrypanosoma bruceicauses human African trypanosomiasis and nagana in animals. The finding of a mitochondrial calcium uniporter (MCU) conserved in this parasite was essential for the discovery of the gene encoding the pore subunit. Mitochondrial Ca2+transport mediated by the MUC complex is critical inTrypanosoma bruceifor shaping the dynamics of cytosolic Ca2+increases, for the bioenergetics of the cells, and for viability and infectivity. We found that one component of the complex (MCUb) does not act as a dominant negative effector of the channel as in vertebrate cells and that the TbMCUC possesses two unique subunits (MCUc and MCUd) present only in trypanosomatids and required for Ca2+transport. The study of the interactions between these four subunits (MCU, MCUb, MCUc, and MCUd) by a variety of techniques that include coimmunoprecipitation, split-ubiquitin membrane-based yeast two-hybrid assays, and site-directed mutagenesis suggests that they interact through their transmembrane helices to form hetero-oligomers.

scholarly journals Cardiovascular homeostasis dependence on MICU2, a regulatory subunit of the mitochondrial calcium uniporter

2017 ◽  
Vol 114 (43) ◽  
pp. E9096-E9104 ◽  
Author(s):  
Alexander G. Bick ◽  
Hiroko Wakimoto ◽  
Kimberli J. Kamer ◽  
Yasemin Sancak ◽  
Olga Goldberger ◽  
...  
Keyword(s):  
Angiotensin Ii ◽  
Aortic Rupture ◽  
Systolic Dysfunction ◽  
Regulatory Subunit ◽  
Aortic Tissue ◽  
Mitochondrial Calcium ◽  
Rna Seq ◽  
Wild Type ◽  
Mitochondrial Calcium Uniporter ◽  
Calcium Uniporter

Comparative analyses of transcriptional profiles from humans and mice with cardiovascular pathologies revealed consistently elevated expression of MICU2, a regulatory subunit of the mitochondrial calcium uniporter complex. To determine if MICU2 expression was cardioprotective, we produced and characterized Micu2−/− mice. Mutant mice had left atrial enlargement and Micu2−/− cardiomyocytes had delayed sarcomere relaxation and cytosolic calcium reuptake kinetics, indicating diastolic dysfunction. RNA sequencing (RNA-seq) of Micu2−/− ventricular tissues revealed markedly reduced transcripts encoding the apelin receptor (Micu2−/− vs. wild type, P = 7.8 × 10−40), which suppresses angiotensin II receptor signaling via allosteric transinhibition. We found that Micu2−/− and wild-type mice had comparable basal blood pressures and elevated responses to angiotensin II infusion, but that Micu2−/− mice exhibited systolic dysfunction and 30% lethality from abdominal aortic rupture. Aneurysms and rupture did not occur with norepinephrine-induced hypertension. Aortic tissue from Micu2−/− mice had increased expression of extracellular matrix remodeling genes, while single-cell RNA-seq analyses showed increased expression of genes related to reactive oxygen species, inflammation, and proliferation in fibroblast and smooth muscle cells. We concluded that Micu2−/− mice recapitulate features of diastolic heart disease and define previously unappreciated roles for Micu2 in regulating angiotensin II-mediated hypertensive responses that are critical in protecting the abdominal aorta from injury.

288-LB: Effects of the Hepatic Mitochondrial Calcium Uniporter on Hepatic Gluconeogenesis and Mitochondrial Metabolism in Awake Mice

Diabetes ◽  
2019 ◽  
Vol 68 (Supplement 1) ◽  
pp. 288-LB
Author(s):  
JI EUN LEE ◽  
LEIGH GOEDEKE ◽  
YE ZHANG ◽  
RACHEL J. PERRY ◽  
RUSSELL GOODMAN ◽  
...  
Keyword(s):  
Mitochondrial Metabolism ◽  
Mitochondrial Calcium ◽  
Hepatic Gluconeogenesis ◽  
Mitochondrial Calcium Uniporter ◽  
Calcium Uniporter
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