MICU1 Motifs Define Mitochondrial Calcium Uniporter Binding and Activity

Abstract

SUMMARY Resting mitochondrial matrix Ca2+ is maintained through a MICU1-established threshold inhibition of MCU activity. It is not known how MICU1 interacts with MCU to establish this Ca2+ threshold for mitochondrial Ca2+ uptake and MCU activity. Here, we show that MICU1 localizes to the mitochondrial matrix side of the inner mitochondrial membrane and MICU1/MCU binding is determined by a MICU1 N-terminal polybasic domain and two interacting coiled-coil domains of MCU. Further investigation reveals MICU1 forms homo-oligomers, and this oligomerization is independent of the polybasic region. However the polybasic region confers MICU1 oligomeric binding to MCU and controls mitochondrial Ca2+ current (IMCU). Moreover, MICU1 EF-hands regulate MCU channel activity but do not determine MCU binding. Loss of MICU1 promotes MCU activation leading to oxidative burden and a halt to cell migration. These studies establish a molecular mechanism for MICU1 control of MCU-mediated mitochondrial Ca2+ accumulation, and dysregulation of this mechanism likely enhances vascular dysfunction.

The EF-Hand Ca2+ Binding Protein MICU Choreographs Mitochondrial Ca2+ Dynamics in Arabidopsis

“…Moreover, the fluorescence distribution of MICU:GFP in Arabidopsis mitochondria (Figure 3) sheds light on the controversy of IMS versus matrix localization of MICU (Perocchi et al, 2010;Csordás et al, 2013;Hoffman et al, 2013;Patron et al, 2014;Pendin et al, 2014). Our data add weight to the hypothesis that the C terminus of MICU is localized in the IMS and that MICU is not a matrix protein.…”

“…The recent identification of several protein families making up the mitochondrial Ca 2+ uniporter complex (MCUC) in mammals, including the pore-forming MCU (MCU and MCUb;Baughman et al, 2011;De Stefani et al, 2011;Raffaello et al, 2013), and the regulatory, associated MICUs (MICU1, 2, and 3; Perocchi et al, 2010;Plovanich et al, 2013), EMRE (Sancak et al, 2013), and MCUR1/CCDC90A (although potentially not directly; Mallilankaraman et al, 2012b;Paupe et al, 2015), has spurred intense research across the biomedical disciplines Mallilankaraman et al, 2012a;Csordás et al, 2013;Hoffman et al, 2013;Marchi et al, 2013;Pan et al, 2013;Raffaello et al, 2013;Kovács-Bogdán et al, 2014;Logan et al, 2014;Patron et al, 2014;Wang et al, 2014). While some genes of the complex components appear not to be present in plants (e.g., MCUb and EMRE), others have multiple homologs (six for the functional poreforming subunit MCU in Arabidopsis [Stael et al, 2012] and maize [Zea mays; Meng et al, 2015] and two for MCUR1/CCDC90A in Arabidopsis), suggesting potential functional modification and/or differentiation.…”

TRPM2 Channels Protect against Cardiac Ischemia-Reperfusion Injury

“…7). Surprisingly, at equivalent membrane potential, I MCU was still lower in mitoplasts prepared from KO myocytes, suggesting the perturbation of MCU complex (30,33,(41)(42)(43)(44)(45)(46). Impaired mitochondrial function in KO myocytes was manifested as lower ATP levels and O 2 consumption in both KO myocytes and intact KO hearts (Figs.…”

“…2ϩ Uniporter (MCU) Current (I MCU )-Mitoplast patch clamp recordings were conducted at 30°C as previously described (32,33). I MCU was recorded using a computer controlled Axon200B patch clamp amplifier with a Digidata 1320A acquisition board (pClamp 10.0 software; Axon Instruments).…”

Mitochondrial Ca 2+ transport in the endothelium: regulation by ions, redox signalling and mechanical forces

“…The mitochondrial Ca 2þ uptake system is a heterogeneous protein complex with the molecular identity mixed and matched with the mitochondrial Ca 2þ uniporter (MCU) as the core component [14,15]. The MCU is regulated by an array of proteins including mitochondrial Ca 2þ uptake 1 (MICU1), 2 (MICU2), 3 (MICU3), essential MCU regulator (EMRE), MCU regulating protein 1 (MCUR1) and MCU dominant negative beta subunit (MCUb) (see §2 for a complete description) [16][17][18][19][20][21][22][23][24]. Besides protein regulation (positive by MCUR1 and EMRE [19,23] and negative by MICU1 [22]), recent studies from our group and others demonstrated a regulation of mitochondrial Ca 2þ uptake by ions and redox signalling.…”