Cytochrome
            <i>c</i>
            binding to Apaf-1: The effects of dATP and ionic strength

Purring-Koch, Cherie; McLendon, George

doi:10.1073/pnas.220416197

Cited by 102 publications

(77 citation statements)

References 20 publications

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“…Therefore, the inhibitory effect of blockage of K þ efflux on apoptosome formation and its downstream events might be explained in terms of ionic strength rather than K þ specificity. This view is in agreement with the previous observation that the interaction of cytochrome c and Apaf-1 highly depends on ionic strength 27 and efficacy of some cations along with K þ to inhibit the cleavage of procaspase-9 and -3. 28 However, being the predominant ion in vivo, the efflux of K þ may handle the major regulatory role during apoptosis.…”

Section: Resultssupporting

confidence: 93%

“…19 Although there is controversy whether Apaf-1 interacts with cytochrome c or dATP first, 31,32 a reconstitution experiment with purified Apaf-1 and cytochrome c showed that the former protein bound the latter with high affinity (association constant ¼ B10 10 M -1 ). 27 The same study demonstrated that Na þ (B200 mM) decreased the association constant by an order of 1000. Due to the similarity between two cations, it can be speculated that K þ may similarly affect the formation of apoptosome.…”

Section: Discussionmentioning

confidence: 89%

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Intracellular K+ inhibits apoptosis by suppressing the Apaf-1 apoptosome formation and subsequent downstream pathways but not cytochrome c release

Karki

Seong

et al. 2007

Cell Death Differ

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Cellular ionic homeostasis, fundamentally K þ homeostasis, has been implicated as a critical regulator of apoptosis. The intracellular K þ efflux on apoptotic insult and suppression of apoptosis by high concentration of extracellular K þ or after inhibition of this efflux by K þ channel blockers have established the crucial role of K þ in turning on the apoptotic machinery. Several contrasting observations have reported the antiapoptotic effect of intracellular K þ concentration to be the result of inhibition of cytochrome c release from mitochondria, but the exact inhibitory mechanism remains obscure. However, here we show the blockage of K þ efflux during apoptosis did not affect cytochrome c release from the mitochondria, still completely inhibited the formation of the apoptosome comprising Apaf-1, cytochrome c, caspase-9 and other accessories. As a consequence of this event, procaspase-9, -3, -8 and other death-related proteins were not processed. Furthermore, physiological concentrations of K þ also inhibited the processing of procaspase-3 by purified caspase-8 or -9, the nucleosomal DNA fragmentation by purified DFF40/CAD and the nuclear fragmentation to varying extents. Altogether, these findings suggest that the efflux of K þ is prerequisite not only for the formation of the apoptosome but also for the downstream apoptotic signaltransduction pathways.

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Section: Resultssupporting

confidence: 93%

Section: Discussionmentioning

confidence: 89%

Intracellular K+ inhibits apoptosis by suppressing the Apaf-1 apoptosome formation and subsequent downstream pathways but not cytochrome c release

Karki

Seong

et al. 2007

Cell Death Differ

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“…Amplified viral stock (50 ml) was used to infect 500 ml of cells at a density of 2 ϫ 10 6 /ml. Cells were harvested 44 h postinfection, and a S100 lysate was prepared essentially as previously described (12,18). Briefly, cells were harvested and washed in cold phosphate-buffered saline and resuspended in 5 volumes of lysate buffer (20 mM Hepes-KOH, pH 8.0, 10 mM KCl, 1.5 mM MgCl 2 , 0.1 mM DTT, 0.1 M aprotinin, and 1 M ethanol).…”

Section: Methodsmentioning

confidence: 99%

“…Initial studies showed that cytochrome c binds to Apaf-1 in a 2:1 stoichiometry with high affinity (K a ϭ 10 (17,18). These findings imply that the ionic conditions in the cell may regulate cytochrome c binding to Apaf-1, thereby modulating apoptosome formation.…”

mentioning

confidence: 99%

Physiological Concentrations of K+ Inhibit Cytochrome c-dependent Formation of the Apoptosome

Cain

Langlais²,

Sun

et al. 2001

Journal of Biological Chemistry

175

137

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In many forms of apoptosis, cytochrome c released from mitochondria induces the oligomerization of Apaf-1 to form a caspase-activating apoptosome complex. Activation of lysates in vitro with dATP and cytochrome c results in the formation of an active caspaseprocessing ϳ700-kDa apoptosome complex, which predominates in apoptotic cells, and a relatively inactive ϳ1.4-MDa complex. We now demonstrate that assembly of the active complex is suppressed by normal intracellular concentrations of K ؉ . Using a defined apoptosome reconstitution system with recombinant Apaf-1 and cytochrome c, K ؉ also inhibits caspase activation by abrogating Apaf-1 oligomerization and apoptosome assembly. Once assembled, the apoptosome is relatively insensitive to the effects of ionic strength and processes/ activates effector caspases. The inhibitory effects of K ؉ on apoptosome formation are antagonized in a concentrationdependent manner by cytochrome c. These studies support the hypothesis that the normal intracellular concentrations of K ؉ act to safeguard the cell against inappropriate formation of the apoptosome complex, caused by the inadvertent release of small amounts of cytochrome c. Thus, the assembly and activation of the apoptosome complex in the cell requires the rapid and extensive release of cytochrome c to overcome the inhibitory effects of normal intracellular concentrations of K ؉

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“…These events, tightly regulated by several heat shock proteins ( Fig. 1), allow for the catalytic maturation of caspase 3 and other caspases, which eventually mediate the biochemical and morphological features of apoptosis (9)(10)(11)(12)(13).…”

mentioning

confidence: 99%

Cardiolipin drives cytochrome c proapoptotic and antiapoptotic actions

Ascenzi¹,

Polticelli²,

Marino³

et al. 2011

IUBMB Life

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SummaryCytochrome c (cytc) is pivotal in mitochondrial respiration and apoptosis. The heme-Fe-atom of native hexacoordinated horse heart cytc (hhcytc) displays a very low reactivity toward ligands and does not exhibit catalytic properties. However, on interaction with cardiolipin (CL), hhcytc changes its tertiary structure disrupting the heme-Fe-Met80 distal bond. The CLhhcytc complex displays a very low midpoint potential, out of the range required for its physiological role, binds CO and NO with high affinity, facilitates peroxynitrite isomerization to NO 3 2 , and displays peroxidase activity. As a whole, the CL-hhcytc complex could play either proapoptotic effects, catalyzing lipid peroxidation and the subsequent hhcytc release into the cytoplasm, or antiapoptotic actions, such as scavenging peroxynitrite (i.e., protecting the mitochondrion from reactive nitrogen and oxygen species), and binding of CO and NO (i.e., inhibiting lipid peroxidation and hhcytc traslocation). Here, the CL-driven allosteric modulation of hhcytc properties is reviewed, highlighting proapoptotic and antiapoptotic actions.

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Cytochrome c binding to Apaf-1: The effects of dATP and ionic strength

Cited by 102 publications

References 20 publications

Intracellular K+ inhibits apoptosis by suppressing the Apaf-1 apoptosome formation and subsequent downstream pathways but not cytochrome c release

Intracellular K+ inhibits apoptosis by suppressing the Apaf-1 apoptosome formation and subsequent downstream pathways but not cytochrome c release

Physiological Concentrations of K+ Inhibit Cytochrome c-dependent Formation of the Apoptosome

Cardiolipin drives cytochrome c proapoptotic and antiapoptotic actions

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