title: Mg(2+) differentially regulates two modes of mitochondrial Ca(2+) uptake in isolated cardiac mitochondria: implications for mitochondrial Ca(2+) sequestration.
abstract: The manner in which mitochondria take up and store Ca(2+) remains highly debated. Recent experimental and computational evidence has suggested the presence of at least two modes of Ca(2+) uptake and a complex Ca(2+) sequestration mechanism in mitochondria. But how Mg(2+) regulates these different modes of Ca(2+) uptake as well as mitochondrial Ca(2+) sequestration is not known. In this study, we investigated two different ways by which mitochondria take up and sequester Ca(2+) by using two different protocols. Isolated guinea pig cardiac mitochondria were exposed to varying concentrations of CaCl2 in the presence or absence of MgCl2. In the first protocol, A, CaCl2 was added to the respiration buffer containing isolated mitochondria, whereas in the second protocol, B, mitochondria were added to the respiration buffer with CaCl2 already present. Protocol A resulted first in a fast transitory uptake followed by a slow gradual uptake. In contrast, protocol B only revealed a slow and gradual Ca(2+) uptake, which was approximately 40 % of the slow uptake rate observed in protocol A. These two types of Ca(2+) uptake modes were differentially modulated by extra-matrix Mg(2+). That is, Mg(2+) markedly inhibited the slow mode of Ca(2+) uptake in both protocols in a concentration-dependent manner, but not the fast mode of uptake exhibited in protocol A. Mg(2+) also inhibited Na(+)-dependent Ca(2+) extrusion. The general Ca(2+) binding properties of the mitochondrial Ca(2+) sequestration system were reaffirmed and shown to be independent of the mode of Ca(2+) uptake, i.e. through the fast or slow mode of uptake. In addition, extra-matrix Mg(2+) hindered Ca(2+) sequestration. Our results indicate that mitochondria exhibit different modes of Ca(2+) uptake depending on the nature of exposure to extra-matrix Ca(2+), which are differentially sensitive to Mg(2+). The implications of these findings in cardiomyocytes are discussed.
authors.affiliation: Department of Anesthesiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI, 53226, USA.
authors.forename: Christoph A
authors.initials: CA
authors.lastname: Blomeyer
authors.affiliation: Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, 48109, USA.|Biotechnology and Bioengineering Center, Medical College of Wisconsin, Milwaukee, WI, 53226, USA.|Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, 53226, USA.
authors.forename: Jason N
authors.initials: JN
authors.lastname: Bazil
authors.affiliation: Department of Anesthesiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI, 53226, USA.|Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, 53226, USA.|Department of Biomedical Engineering, Marquette University, Milwaukee, WI, 53233, USA.|Research Service, Zablocki Veterans Affairs Medical Center, Milwaukee, WI, 53295, USA.
authors.forename: David F
authors.initials: DF
authors.lastname: Stowe
authors.affiliation: Biotechnology and Bioengineering Center, Medical College of Wisconsin, Milwaukee, WI, 53226, USA.|Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, 53226, USA.|Department of Biomedical Engineering, Marquette University, Milwaukee, WI, 53233, USA.
authors.forename: Ranjan K
authors.initials: RK
authors.lastname: Dash
authors.affiliation: Department of Anesthesiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI, 53226, USA. aksc@mcw.edu.
authors.forename: Amadou K S
authors.initials: AK
authors.lastname: Camara
mesh_terms: D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism* / Q000493:pharmacokinetics; D006168:Guinea Pigs; D007700:Kinetics; D008274:Magnesium / Q000502:physiology*; D008929:Mitochondria, Heart / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000378:metabolism
chemical_list: D008274:Magnesium; D002118:Calcium
keywords: Calcium efflux; Calcium sequestration; Calcium uptake; Cardiac; Mitochondria
references.citation: Biochim Biophys Acta. 2010 Jun-Jul;1797(6-7):595-606
references.pmid: 20385096
references.citation: Am J Cardiol. 1989 Apr 18;63(14):4G-21G
references.pmid: 2650515
references.citation: Biophys J. 2010 Aug 9;99(4):997-1006
references.pmid: 20712982
references.citation: Am J Physiol Heart Circ Physiol. 2001 Jan;280(1):H280-93
references.pmid: 11123243
references.citation: Cell Calcium. 2012 Jul;52(1):28-35
references.pmid: 22502861
references.citation: Am Heart J. 1996 Sep;132(3):664-71
references.pmid: 8800040
references.citation: J Biol Chem. 1986 Nov 15;261(32):15166-71
references.pmid: 2429966
references.citation: Biochim Biophys Acta. 1964 Nov 29;88:645-7
references.pmid: 14252671
references.citation: PLoS One. 2011;6(6):e21324
references.pmid: 21731705
references.citation: Nature. 2011 Jun 19;476(7360):336-40
references.pmid: 21685888
references.citation: J Biol Chem. 1995 Nov 17;270(46):27510-5
references.pmid: 7499209
references.citation: J Bioenerg Biomembr. 2013 Jun;45(3):189-202
references.pmid: 23225099
references.citation: J Gen Physiol. 2012 Jun;139(6):465-78
references.pmid: 22641641
references.citation: Mol Pharmacol. 2007 Dec;72(6):1466-75
references.pmid: 17848600
references.citation: EMBO Rep. 2014 Mar;15(3):299-307
references.pmid: 24503055
references.citation: Cell Calcium. 2005 Sep-Oct;38(3-4):311-7
references.pmid: 16087232
references.citation: Biophys J. 2011 Nov 2;101(9):2071-81
references.pmid: 22067144
references.citation: Biochim Biophys Acta. 2001 Apr 2;1504(2-3):248-61
references.pmid: 11245789
references.citation: Biochim Biophys Acta. 1998 Aug 10;1366(1-2):5-15
references.pmid: 9714709
references.citation: J Cell Biol. 1964 Oct;23:21-38
references.pmid: 14228516
references.citation: J Physiol. 2014 Mar 1;592(5):829-39
references.pmid: 24366263
references.citation: J Mol Cell Cardiol. 2013 Jun;59:205-13
references.pmid: 23538132
references.citation: Am J Physiol Heart Circ Physiol. 2001 Oct;281(4):H1508-23
references.pmid: 11557539
references.citation: Cardiol Rev. 2014 Jul-Aug;22(4):182-92
references.pmid: 24896250
references.citation: J Biol Chem. 2001 Jun 15;276(24):21482-8
references.pmid: 11297554
references.citation: Biochim Biophys Acta. 2014 Mar;1837(3):354-65
references.pmid: 24355434
references.citation: J Biol Chem. 2008 Feb 15;283(7):3827-38
references.pmid: 18077457
references.citation: Am J Physiol Heart Circ Physiol. 2001 Dec;281(6):H2398-409
references.pmid: 11709405
references.citation: Nat Cell Biol. 2013 Dec;15(12):1464-72
references.pmid: 24212091
references.citation: Biophys J. 1999 Jan;76(1 Pt 1):469-77
references.pmid: 9876159
references.citation: Cell Rep. 2015 Jul 7;12(1):15-22
references.pmid: 26119742
references.citation: J Mol Cell Cardiol. 2009 Jun;46(6):767-74
references.pmid: 19162034
references.citation: Free Radic Biol Med. 2013 Mar;56:193-203
references.pmid: 23010495
references.citation: J Mol Cell Cardiol. 2013 Feb;55:42-9
references.pmid: 22902320
references.citation: Biophys J. 2014 Sep 16;107(6):1289-301
references.pmid: 25229137
references.citation: J Mol Cell Cardiol. 2015 Jan;78:46-53
references.pmid: 25451167
references.citation: J Bioenerg Biomembr. 2013 Jun;45(3):177-88
references.pmid: 23180139
references.citation: J Biol Chem. 1985 Mar 25;260(6):3440-50
references.pmid: 3838314
references.citation: Nature. 2011 Jun 19;476(7360):341-5
references.pmid: 21685886
references.citation: J Physiol. 2014 May 1;592(9):1917-30
references.pmid: 24591571
references.citation: Pharmacol Res. 2011 Oct;64(4):381-92
references.pmid: 21741479
references.citation: Nat Commun. 2015 Jan 20;6:6081
references.pmid: 25603276
references.citation: J Bioenerg Biomembr. 2000 Feb;32(1):27-33
references.pmid: 11768759
references.citation: J Biol Chem. 1963 Oct;238:3482-9
references.pmid: 14085406
references.citation: Adv Exp Med Biol. 2013;961:65-78
references.pmid: 23224871
references.citation: Cell Metab. 2013 Jun 4;17(6):976-87
references.pmid: 23747253
references.citation: Am J Physiol Cell Physiol. 2006 Nov;291(5):C840-50
references.pmid: 16723510
references.citation: Physiology (Bethesda). 2008 Apr;23:84-94
references.pmid: 18400691
references.citation: J Mol Cell Cardiol. 2013 May;58:125-33
references.pmid: 23306007
references.citation: Cell. 2012 Oct 26;151(3):630-44
references.pmid: 23101630
references.citation: J Biol Chem. 2004 Feb 13;279(7):5867-76
references.pmid: 14625281
references.citation: Circ Res. 2013 Feb 1;112(3):424-31
references.pmid: 23243207
references.citation: Anal Biochem. 1976 May 7;72:248-54
references.pmid: 942051
references.citation: Proc Natl Acad Sci U S A. 1962 Nov 15;48:1928-35
references.pmid: 14015424
references.citation: J Biol Chem. 2003 May 23;278(21):19062-70
references.pmid: 12660243
references.citation: J Cell Biol. 1968 Oct;39(1):55-76
references.pmid: 4878171
references.citation: Biochim Biophys Acta. 2012 Mar;1817(3):453-65
references.pmid: 22155157
references.citation: J Biol Chem. 1962 Aug;237:2670-7
references.pmid: 13925019
references.citation: J Neurochem. 2007 Aug;102(4):1346-56
references.pmid: 17663756
references.citation: J Inorg Biochem. 2009 Jul;103(7):948-62
references.pmid: 19477528
references.citation: Am J Physiol Heart Circ Physiol. 2003 Apr;284(4):H1217-29
references.pmid: 12531735
references.citation: Mol Cell. 2014 Mar 6;53(5):726-37
references.pmid: 24560927
references.citation: Cell Rep. 2015 Jul 7;12(1):23-34
references.pmid: 26119731
references.citation: J Bioenerg Biomembr. 2013 Jun;45(3):203-18
references.pmid: 23456198
references.citation: J Biol Chem. 2004 Jun 11;279(24):25234-40
references.pmid: 15060069
references.citation: Cell Calcium. 2011 Sep;50(3):222-33
references.pmid: 21601280
references.citation: Nature. 2004 Jan 22;427(6972):360-4
references.pmid: 14737170