title: Protein kinases reduce mitochondrial Ca2+ uptake through an action on the outer mitochondrial membrane.
abstract: Cytosolic Ca(2+) signal induces mitochondrial Ca(2+) uptake that has far-reaching effect on several cellular functions. We have previously shown in H295R cells that the transfer of cytosolic Ca(2+) signal into mitochondria is attenuated by the simultaneous activation of p38 MAPK and novel-type PKC isoforms (Szanda et al. (2008) [1], Koncz et al. (2009) [2]). In the present study we show that (i) kinase-mediated inhibition of mitochondrial Ca(2+) uptake persists after clamping or dissipation of the mitochondrial membrane potential; (ii) kinase activation increases the [Ca(2+)] required for half-maximal Ca(2+) uptake rate in permeabilized cells; (iii) inhibition of the Ca(2+) uptake by the kinases is dependent on an intact mitochondrial outer membrane; (iv) when p38 MAPK and novel-type PKC isoforms are activated, the outer mitochondrial membrane may limit Ca(2+) diffusion even in the low micromolar [Ca(2+)] range. These findings confirm the concept that the outer mitochondrial membrane impedes mitochondrial Ca(2+) uptake by reducing the availability of Ca(2+) at the transport sites (i.e. the inner mitochondrial membrane), and suggest that Ca(2+) transport through the outer membrane is controlled by the activity of p38 MAPK and novel-type PKC isoforms.
authors.affiliation: Department of Physiology, Semmelweis University, Budapest, Hungary.
authors.forename: Gergö
authors.initials: G
authors.lastname: Szanda
authors.forename: Eszter
authors.initials: E
authors.lastname: Halász
authors.forename: András
authors.initials: A
authors.lastname: Spät
mesh_terms: D000818:Animals; D002118:Calcium / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D002460:Cell Line; D015536:Down-Regulation / Q000502:physiology*; D004789:Enzyme Activation / Q000502:physiology; D006801:Humans; D007527:Isoenzymes / Q000502:physiology; D020935:MAP Kinase Signaling System / Q000502:physiology; D053078:Membrane Potential, Mitochondrial / Q000502:physiology; D008928:Mitochondria / Q000201:enzymology* / Q000378:metabolism; D051336:Mitochondrial Membranes / Q000201:enzymology* / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism / Q000502:physiology*
chemical_list: D007527:Isoenzymes; D011493:Protein Kinase C; D048051:p38 Mitogen-Activated Protein Kinases; D002118:Calcium