Two monoclonal antibody lines directed against Subunit IV of cytochrome oxidase: A study of opposite effects

Gai, Wen Zhi; Sun, Shu Man; Ding, You Zhan; Freedman, Jo A.; Chan, Samuel H.P.

doi:10.1016/0003-9861(88)90296-2

Cited by 8 publications

(8 citation statements)

References 26 publications

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“…It is possible that the molecular activity of CO is regulated jointly with the amount of CO, but we have found no evidence to favor this possibility, nor has evidence of molecular activity regulation come from biochemical studies. [It has, however, been hypothesized that the metabolic flux through CO may be regulated conformationally by ATP effects on the K,,, for cytochrome c (Huther and Kadenbach, 1986;Bisson et al, 1987;Gai et al, 1988).] Our densitometric results roughly indicated that CO activity and protein content were directly related, but we were not able to establish that optical density and CO activity or amount were necessarily linear in these experiments.…”

Section: Discussioncontrasting

confidence: 47%

Regulation of cytochrome oxidase protein levels by functional activity in the macaque monkey visual system

1990

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While much progress has been made in studies of brain energy metabolism, relatively little is known about the biochemical regulation of neural energy metabolic capacity. It is known that the activities of several energy-metabolic enzymes are coupled to the functional activity of nerve cells (Dietrich et al., 1981(Dietrich et al., , 1982Wong-Riley, 1989), but it is not known how neural functional activity signals changes in enzyme activity, or at what levels (transcriptional, translational, distributional, etc.) expression of enzyme activity is regulated. These questions are important if we are to understand how nerve cell activity and nerve cell energy metabolism are linked, and how defective energy metabolic regulation causes neurological and muscular disease (Morgan-Hughes, 1986). These questions are difficult to address in brain tissue by traditional biochemical methods, since the distribution of energy metabolic enzymes is nonhomogeneous at very local (even subcellular) levels in the brain (Dietrich et al., 1981(Dietrich et al., , 1982Wong-Riley, 1989).Received Aug. 21, 1989; revised Oct. 23, 1989; accepted Oct. 25, 1989. This work was supported by NIH grants NS18122 and EY05439 to M.W. We have begun investigating these questions using a mitochondrial respiratory complex, cytochrome oxidase (CO; ferrocytochrome c: oxygen oxidoreductase, EC 1.9.3.1; for review, see Kadenbach et al., 1987) as a representative energy metabolic enzyme. While CO is well known among neuroscientists as a marker for neural functional activity (Wong-Riley, 1989) it also serves as an excellent model for studying regulation of enzyme activity. CO is a key enzyme of the oxidative pathway, the major pathway ofbrain energy metabolism (Erecinska and Silver, 1989); the activity of CO is regulated by neural functional activity (Wong-Riley, 1989); histochemical (Wong-Riley, 1979) and immunohistochemical (Hevner and Wong-Riley, 1989a) methods have been developed for studying CO in brain tissue; and genomit and cDNA clones encoding most mammalian CO subunits have been obtained and sequenced (Anderson et al., 198 1,1982; Bibb et al., 198 1;Lomax et al., 1984;Parimoo et al., 1984;Bachman et al., 1987;Suske et al., 1987;Zeviani et al., 1987Zeviani et al., , 1988Rizzuto et al., 1988Rizzuto et al., , 1989 Schlerfet al., 1988;Goto et al., 1989;Taanman et al., 1989). Thus, the role of the enzyme is well known, regulation of its activity has been demonstrated, and tools are available for studying its regulation.We recently found (Hevner and Wong-Riley, 1989a) that local differences in CO activity (shown histochemically) seen in the normal mouse and monkey brain reflect similar local differences in CO protein concentration (shown immunohistochemically), indicating that the local activity of CO is normally determined mainly by enzyme protein levels, and not by modulation of the molecular activity of homogeneously distributed enzyme (see Fig. 1). This finding suggested that changes in CO activity induced by altered neural functional activity might like...

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Section: Discussioncontrasting

confidence: 47%

Regulation of cytochrome oxidase protein levels by functional activity in the macaque monkey visual system

1990

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“…These data suggest that CO activity is regulated entirely by control of CO protein levels. Other studies, however, have found evidence that the molecular activity of CO may be regulated by isozyme switching or by conformational effects of ATP binding (Huther and Kadenbach, 1986;Bisson et al, 1987;Gai et al, 1988;Ewart et al, 1991).…”

Section: Co Protein Regulationmentioning

confidence: 99%

Mitochondrial and nuclear gene expression for cytochrome oxidase subunits are disproportionately regulated by functional activity in neurons

1993

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Mitochondrial respiratory complexes such as cytochrome oxidase (CO) contain both mitochondrialand nuclear-encoded subunits. To determine whether mitochondrial and nuclear gene expression are regulated proportionately in neurons, we analyzed CO subunit mRNA and mitochondrial DNA (mtDNA) levels by in situ hybridization and grain counting in the visual system of normal and monocular TTX-treated monkeys.We compared the regulation of these molecules with the regulation of CO activity and CO protein, analyzed by histochemistry and immunohistochemistry, respectively.In normal animals, CO activity was in general related more closely to mtDNA and CO subunit I (COI) (mitochondrial-encoded) mRNA levels than to COIV or COVIII (nuclear-encoded) mRNA levels. For example, puffs (also known as blobs) of high CO activity in striate cortex were enriched in mtDNA and COI mRNA, but not COIV or COVIII mRNA. In 3-7 d TTX-treated animals, proportionate decreases in CO activity and CO protein were observed in specific visual centers; these changes were accompanied by disproportionate decreases in COI, COIV, and COVIII mRNA levels. After 7 d of TTX, COI mRNA fell by 49 + 3% (mean f SEM) in LGN neurons, while COIV and COVIII mRNAs fell by only 18 + 3% and 29 + 3%, respectively.In comparison, CO activity decreased by 23 f 2%, and mtDNA by 26 f 4%. Qualitative obsenrations in striate cortex also indicated that COI mRNA changed more than COIV mRNA, COVIII mRNA, mtDNA, or CO activity. Our results suggest that the local distribution of CO within neurons, and acute regulatory changes in CO activity occurring over periods of days are controlled mainly by regulation of the mitochondrial genes that encode the catalytic subunits of the enzyme.

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“…As pointed out by Gai et al [11], the differential action of antibodies on the two kinetic phases of cytochrome c oxidation supports the idea of separate binding sites or at least separate reaction types for cytochrome c in the high-and low-affinity regions, as outlined in the model of Brooks and Nicholls [23]. Anti-subunit V apparemly binds to subunit V at the N (matrix) face of the enzyme [12,13] and in so doing it reduces the off constant for cytochrome c bound at the high affinity site.…”

Section: Discussionmentioning

confidence: 79%

“…Such a long range effect could be communicated directly from subunit V to subunit II as cross-linking experiments show the two subunits to be within 11 .~ of each other [25]. A very similar explanation can be advanced to account for the kinetic action of the two types of monoclonal antibodies prepared against subunit IV [11]. Monoclonal QA4 inhibits the enzyme by increasing the Km seen in the high-affinity region.…”

Section: Discussionmentioning

confidence: 95%

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Modulation of cytochrome oxidase kinetics by indirect antibody action

Nicholls

Cooper

1989

FEBS Letters

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Polyclonal antibodies raised against isolated subunit V from beef heart cytochrome oxidase or against the intact enzyme increase its apparent affinity for the substrate cytochrome c at the high-affinity site while diminishing the turnover at that site. At the low-affinity site the major action of both types of antibody is to reduce the apparent affinity for cytochrome c. At high ionic strengths the kinetic effect of anti-subunit V is very small although it still binds to the enzyme. The results are interpreted in terms of a model for the enzyme in which antibodies can modulate cytochrome oxidase kinetics by affecting the binding of cytochrome c, even if the antibody-binding site is on a subunit not directly involved in substrate binding.

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Two monoclonal antibody lines directed against Subunit IV of cytochrome oxidase: A study of opposite effects

Cited by 8 publications

References 26 publications

Regulation of cytochrome oxidase protein levels by functional activity in the macaque monkey visual system

Regulation of cytochrome oxidase protein levels by functional activity in the macaque monkey visual system

Mitochondrial and nuclear gene expression for cytochrome oxidase subunits are disproportionately regulated by functional activity in neurons

Modulation of cytochrome oxidase kinetics by indirect antibody action

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