Role of Sterols in the Functional Reconstitution of Water-Soluble Mitochondrial Porins from Different Organisms

Popp, Birgit; Schmid, Alex P.; Benz, Roland

doi:10.1021/bi00010a026

Cited by 54 publications

(46 citation statements)

References 56 publications

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“…Indeed, localization of eNOS to the caveolae is critical for proper regulation of eNOS activity, because numerous signaling molecules such as G protein-coupled receptors, growth factor receptors, the plasma membrane Ca 2ϩ pump, an inositol 1,4,5-trisphosphate-sensitive Ca 2ϩ channel, and protein kinases such as protein kinase B͞Akt are present in caveolae (33). The binding of porin to cholesterol (34,35) may also play an important role in porin trafficking in caveolae because caveolae are especially rich in cholesterol (36). Cholesterol inhibits eNOS activity and it is possible that competition for porin within the caveolae by cholesterol and eNOS may be the mechanism by which cholesterol regulates the activity of eNOS.…”

Section: Discussionmentioning

confidence: 99%

Functional interaction of endothelial nitric oxide synthase with a voltage-dependent anion channel

Sun

Liao

2002

Proc. Natl. Acad. Sci. U.S.A.

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Endothelium-derived nitric oxide (NO) is an important regulator of vascular function. NO is produced by endothelial NO synthase (eNOS) whose function is modulated, in part, by specific protein interactions. By coimmunoprecipitation experiments followed by MS analyses, we identified a human voltage-dependent anion͞ cation channel or porin as a binding partner of eNOS. The interaction between porin and eNOS was demonstrated by coimmunoprecipitation studies in nontransfected human endothelial cells and Cos-7 cells transiently transfected with eNOS and porin cDNAs. In vitro binding studies with glutathione S-transferase-porin indicated that porin binds directly to eNOS and that this interaction augmented eNOS activity. The calcium ionophore, A23187, and bradykinin, which are known to activate eNOS, markedly increased porin-eNOS interaction, suggesting a potential role of intracellular Ca 2؉ in mediating this interaction. Theses results indicate that the interaction between a voltage-dependent membrane channel and eNOS may be important for regulating eNOS activity.

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Section: Discussionmentioning

confidence: 99%

Functional interaction of endothelial nitric oxide synthase with a voltage-dependent anion channel

Sun

Liao

2002

Proc. Natl. Acad. Sci. U.S.A.

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“…Porin might be present in caveolae and caveolae-like domains simply because these are stations on the way to its final destination(s). Porin binds cholesterol (28,41,42), and caveolae are especially rich in cholesterol, playing an important role in its traffic (43). Thus an alternative working hypothesis may be that porin mRNA(s) are translated in the cytosol, and some molecules are transported to the caveolar region by means of caveolin-cholesterol complexes.…”

Section: Discussionmentioning

confidence: 99%

Porin Is Present in the Plasma Membrane Where It Is Concentrated in Caveolae and Caveolae-related Domains

Báthori¹,

Parolini²,

Tombola³

et al. 1999

Journal of Biological Chemistry

114

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Mitochondrial porin, or voltage-dependent anion channel, is a pore-forming protein first discovered in the outer mitochondrial membrane. Later investigations have provided indications for its presence also in other cellular membranes, including the plasma membrane, and in caveolae. This extra-mitochondrial localization is debated and no clear-cut conclusion has been reached up to now. In this work, we used biochemical and electrophysiological techniques to detect and characterize porin within isolated caveolae and caveolaelike domains (low density Triton-insoluble fractions). A new procedure was used to isolate porin from plasma membrane. The outer surface of cultured CEM cells was biotinylated by an impermeable reagent. Low density Triton-insoluble fractions were prepared from the labeled cells and used as starting material to purify a biotinylated protein with the same electrophoretic mobility and immunoreactivity of mitochondrial porin. In planar bilayers, the porin from these sources formed slightly anion-selective pores with properties indistinguishable from those of mitochondrial porin. This work thus provides a strong indication of the presence of porin in the plasma membrane, and specifically in caveolae and caveolae-like domains.

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“…Sterols have been found to be associated with VDAC isolated from Neurospora crassa and bovine heart mitochondria (38,39). It has been suggested recently that sterols are essential for the proper folding of VDAC (40).…”

Section: Discussionmentioning

confidence: 99%

Structure and Orientation of Two Voltage-dependent Anion-selective Channel Isoforms

Abrecht

Goormaghtigh²,

Ruysschaert³

et al. 2000

Journal of Biological Chemistry

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Two VDAC (voltage-dependent anion-selective channel) isoforms were purified from seed cotyledons of Phaseolus vulgaris by chromatofocusing chromatography. Attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy was used to study the structural properties of the two isoforms reconstituted in a mixture of asolectin and 5% stigmasterol. The IR spectra of the two VDAC isoforms were highly similar indicating 50 to 53% anti-parallel ␤-sheet. The orientation of the ␤-strands relative to the barrel axis was calculated from the experimentally obtained dichroic ratios of the amide I ␤-sheet component and the amide II band. Comparing the IR spectra of the reconstituted VDAC isoforms with the IR spectra of the bacterial porin OmpF, for which a high resolution structure is available, provided evidence for a general structural organization of the VDAC isoforms similar to that of bacterial porins. Hydrogen-deuterium exchange measurements indicated that the exchange of the amide protons occurs to a higher extent in the two VDAC isoforms than in the OmpF porin.Mitochondria are surrounded by two distinct membranes. The mitochondrial outer membrane is freely permeable for small hydrophilic solutes up to approximately 6 kDa. This property has been attributed to the presence of a pore forming protein, the voltage-dependent anion-selective channel (VDAC) 1 or mitochondrial porin (1). Biophysical properties of VDAC channels inserted in planar lipid bilayers have been studied in a large variety of organisms. VDAC channels switch from a high conducting fully open state (3.6 to 4.5 nS in 1 M KCl) at low voltages to several low-conducting substates upon application of voltages higher than Ϯ20 mV. VDAC is slightly anion selective in the fully open state but switches to cation selectivity in the low-conducting substates (2). In these substates, the flow of negatively charged metabolites such as succinate, citrate, phosphate (3), and adenine nucleotides (4, 5) through the channel is strongly reduced compared with the fully open state. Therefore, VDAC is thought to regulate the mitochondrial metabolism by regulating the flux of metabolites across the mitochondrial outer membrane.VDAC channels are involved in different cellular events like the induced release of cytochrome c, which constitutes an early step in apoptosis (6). VDAC is the binding site for cytoplasmic enzymes like glycerol kinase and hexokinase (7) and for the cytoskeleton (8). The different VDAC isoforms that exist in yeast, plants, and mammals could be involved in specific functions. Two human VDAC isoforms have different binding affinities for hexokinase (9). Plant VDAC isoforms have slightly different electrophysiological properties (10), and mitochondria isolated from yeast vdac minus mutants show differences in their outer membrane permeability to NADH depending on which of the three mouse VDAC isoforms was expressed (11). Therefore, it seems reasonable to assume that the multitude of functional properties that are attributed to VDAC could arise from ...

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Role of Sterols in the Functional Reconstitution of Water-Soluble Mitochondrial Porins from Different Organisms

Cited by 54 publications

References 56 publications

Functional interaction of endothelial nitric oxide synthase with a voltage-dependent anion channel

Functional interaction of endothelial nitric oxide synthase with a voltage-dependent anion channel

Porin Is Present in the Plasma Membrane Where It Is Concentrated in Caveolae and Caveolae-related Domains

Structure and Orientation of Two Voltage-dependent Anion-selective Channel Isoforms

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