Total Matrix Ca2+ Modulates Ca2+ Efflux via the Ca2+/H+ Exchanger in Cardiac Mitochondria
Mitochondrial Ca2+ handling is accomplished by balancing Ca2+ uptake, primarily via the Ru360-sensitive mitochondrial calcium uniporter (MCU), Ca2+ buffering in the matrix and Ca2+ efflux mainly via Ca2+ ion exchangers, such as the Na+/Ca2+ exchanger (NCLX) and the Ca2+/H+ exchanger (CHE). The mecha...
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| Format: | Article |
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Frontiers Media S.A.
2020-09-01
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| Series: | Frontiers in Physiology |
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| Online Access: | https://www.frontiersin.org/article/10.3389/fphys.2020.510600/full |
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| author | Gayathri K. Natarajan Lyall Glait Jyotsna Mishra David F. Stowe David F. Stowe David F. Stowe David F. Stowe David F. Stowe Amadou K. S. Camara Amadou K. S. Camara Amadou K. S. Camara Amadou K. S. Camara Wai-Meng Kwok Wai-Meng Kwok Wai-Meng Kwok Wai-Meng Kwok |
| author_facet | Gayathri K. Natarajan Lyall Glait Jyotsna Mishra David F. Stowe David F. Stowe David F. Stowe David F. Stowe David F. Stowe Amadou K. S. Camara Amadou K. S. Camara Amadou K. S. Camara Amadou K. S. Camara Wai-Meng Kwok Wai-Meng Kwok Wai-Meng Kwok Wai-Meng Kwok |
| author_sort | Gayathri K. Natarajan |
| collection | DOAJ |
| description | Mitochondrial Ca2+ handling is accomplished by balancing Ca2+ uptake, primarily via the Ru360-sensitive mitochondrial calcium uniporter (MCU), Ca2+ buffering in the matrix and Ca2+ efflux mainly via Ca2+ ion exchangers, such as the Na+/Ca2+ exchanger (NCLX) and the Ca2+/H+ exchanger (CHE). The mechanism of CHE in cardiac mitochondria is not well-understood and its contribution to matrix Ca2+ regulation is thought to be negligible, despite higher expression of the putative CHE protein, LETM1, compared to hepatic mitochondria. In this study, Ca2+ efflux via the CHE was investigated in isolated rat cardiac mitochondria and permeabilized H9c2 cells. Mitochondria were exposed to (a) increasing matrix Ca2+ load via repetitive application of a finite CaCl2 bolus to the external medium and (b) change in the pH gradient across the inner mitochondrial membrane (IMM). Ca2+ efflux at different matrix Ca2+ loads was revealed by inhibiting Ca2+ uptake or reuptake with Ru360 after increasing number of CaCl2 boluses. In Na+-free experimental buffer and with Ca2+ uptake inhibited, the rate of Ca2+ efflux and steady-state free matrix Ca2+ [mCa2+]ss increased as the number of administered CaCl2 boluses increased. ADP and cyclosporine A (CsA), which are known to increase Ca2+ buffering while maintaining a constant [mCa2+]ss, decreased the rate of Ca2+ efflux via the CHE, with a significantly greater decrease in the presence of ADP. ADP also increased Ca2+ buffering rate and decreased [mCa2+]ss. A change in the pH of the external medium to a more acidic value from 7.15 to 6.8∼6.9 caused a twofold increase in the Ca2+ efflux rate, while an alkaline change in pH from 7.15 to 7.4∼7.5 did not change the Ca2+ efflux rate. In addition, CHE activation was associated with membrane depolarization. Targeted transient knockdown of LETM1 in permeabilized H9c2 cells modulated Ca2+ efflux. The results indicate that Ca2+ efflux via the CHE in cardiac mitochondria is modulated by acidic buffer pH and by total matrix Ca2+. A mechanism is proposed whereby activation of CHE is sensitive to changes in both the matrix Ca2+ buffering system and the matrix free Ca2+ concentration. |
| first_indexed | 2024-12-21T08:48:08Z |
| format | Article |
| id | doaj.art-1b879d862eda49ef893cc49c12fcdda3 |
| institution | Directory Open Access Journal |
| issn | 1664-042X |
| language | English |
| last_indexed | 2024-12-21T08:48:08Z |
| publishDate | 2020-09-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Physiology |
| spelling | doaj.art-1b879d862eda49ef893cc49c12fcdda32022-12-21T19:09:45ZengFrontiers Media S.A.Frontiers in Physiology1664-042X2020-09-011110.3389/fphys.2020.510600510600Total Matrix Ca2+ Modulates Ca2+ Efflux via the Ca2+/H+ Exchanger in Cardiac MitochondriaGayathri K. Natarajan0Lyall Glait1Jyotsna Mishra2David F. Stowe3David F. Stowe4David F. Stowe5David F. Stowe6David F. Stowe7Amadou K. S. Camara8Amadou K. S. Camara9Amadou K. S. Camara10Amadou K. S. Camara11Wai-Meng Kwok12Wai-Meng Kwok13Wai-Meng Kwok14Wai-Meng Kwok15Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, United StatesDepartment of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, United StatesDepartment of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, United StatesDepartment of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, United StatesDepartment of Physiology, Medical College of Wisconsin, Milwaukee, WI, United StatesCardiovascular Center, Medical College of Wisconsin, Milwaukee, WI, United StatesDepartment of Biomedical Engineering, Medical College of Wisconsin and Marquette University, Milwaukee, WI, United StatesResearch Service, Veteran Affairs Medical Center, Milwaukee, WI, United StatesDepartment of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, United StatesDepartment of Physiology, Medical College of Wisconsin, Milwaukee, WI, United StatesCardiovascular Center, Medical College of Wisconsin, Milwaukee, WI, United StatesCancer Center, Medical College of Wisconsin, Milwaukee, WI, United StatesDepartment of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, United StatesCardiovascular Center, Medical College of Wisconsin, Milwaukee, WI, United StatesCancer Center, Medical College of Wisconsin, Milwaukee, WI, United StatesDepartment of Pharmacology & Toxicology, Medical College of Wisconsin, Milwaukee, WI, United StatesMitochondrial Ca2+ handling is accomplished by balancing Ca2+ uptake, primarily via the Ru360-sensitive mitochondrial calcium uniporter (MCU), Ca2+ buffering in the matrix and Ca2+ efflux mainly via Ca2+ ion exchangers, such as the Na+/Ca2+ exchanger (NCLX) and the Ca2+/H+ exchanger (CHE). The mechanism of CHE in cardiac mitochondria is not well-understood and its contribution to matrix Ca2+ regulation is thought to be negligible, despite higher expression of the putative CHE protein, LETM1, compared to hepatic mitochondria. In this study, Ca2+ efflux via the CHE was investigated in isolated rat cardiac mitochondria and permeabilized H9c2 cells. Mitochondria were exposed to (a) increasing matrix Ca2+ load via repetitive application of a finite CaCl2 bolus to the external medium and (b) change in the pH gradient across the inner mitochondrial membrane (IMM). Ca2+ efflux at different matrix Ca2+ loads was revealed by inhibiting Ca2+ uptake or reuptake with Ru360 after increasing number of CaCl2 boluses. In Na+-free experimental buffer and with Ca2+ uptake inhibited, the rate of Ca2+ efflux and steady-state free matrix Ca2+ [mCa2+]ss increased as the number of administered CaCl2 boluses increased. ADP and cyclosporine A (CsA), which are known to increase Ca2+ buffering while maintaining a constant [mCa2+]ss, decreased the rate of Ca2+ efflux via the CHE, with a significantly greater decrease in the presence of ADP. ADP also increased Ca2+ buffering rate and decreased [mCa2+]ss. A change in the pH of the external medium to a more acidic value from 7.15 to 6.8∼6.9 caused a twofold increase in the Ca2+ efflux rate, while an alkaline change in pH from 7.15 to 7.4∼7.5 did not change the Ca2+ efflux rate. In addition, CHE activation was associated with membrane depolarization. Targeted transient knockdown of LETM1 in permeabilized H9c2 cells modulated Ca2+ efflux. The results indicate that Ca2+ efflux via the CHE in cardiac mitochondria is modulated by acidic buffer pH and by total matrix Ca2+. A mechanism is proposed whereby activation of CHE is sensitive to changes in both the matrix Ca2+ buffering system and the matrix free Ca2+ concentration.https://www.frontiersin.org/article/10.3389/fphys.2020.510600/fullCHECa2+/H+ exchangerLETM1calcium retention capacitytotal matrix Ca2+cardiac mitochondria |
| spellingShingle | Gayathri K. Natarajan Lyall Glait Jyotsna Mishra David F. Stowe David F. Stowe David F. Stowe David F. Stowe David F. Stowe Amadou K. S. Camara Amadou K. S. Camara Amadou K. S. Camara Amadou K. S. Camara Wai-Meng Kwok Wai-Meng Kwok Wai-Meng Kwok Wai-Meng Kwok Total Matrix Ca2+ Modulates Ca2+ Efflux via the Ca2+/H+ Exchanger in Cardiac Mitochondria Frontiers in Physiology CHE Ca2+/H+ exchanger LETM1 calcium retention capacity total matrix Ca2+ cardiac mitochondria |
| title | Total Matrix Ca2+ Modulates Ca2+ Efflux via the Ca2+/H+ Exchanger in Cardiac Mitochondria |
| title_full | Total Matrix Ca2+ Modulates Ca2+ Efflux via the Ca2+/H+ Exchanger in Cardiac Mitochondria |
| title_fullStr | Total Matrix Ca2+ Modulates Ca2+ Efflux via the Ca2+/H+ Exchanger in Cardiac Mitochondria |
| title_full_unstemmed | Total Matrix Ca2+ Modulates Ca2+ Efflux via the Ca2+/H+ Exchanger in Cardiac Mitochondria |
| title_short | Total Matrix Ca2+ Modulates Ca2+ Efflux via the Ca2+/H+ Exchanger in Cardiac Mitochondria |
| title_sort | total matrix ca2 modulates ca2 efflux via the ca2 h exchanger in cardiac mitochondria |
| topic | CHE Ca2+/H+ exchanger LETM1 calcium retention capacity total matrix Ca2+ cardiac mitochondria |
| url | https://www.frontiersin.org/article/10.3389/fphys.2020.510600/full |
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