3,5‐Diiodothyronine binds to subunit Va of cytochrome‐c oxidase and abolishes the allosteric inhibition of respiration by ATP

Abstract

The short-term effects of thyroid hormones, which do not occur via gene expression, were postulated to be based on interaction of diiodothyronines with mitochondria. We demonstrate specific binding of labelled 3,5-diiodothyronine to subunit Va of cytochrome-c oxidase from bovine heart. 3,5-Diiodothyronine, and to a small extent triiodothyronine, but not thyroxine and thyronine, abolish the allosteric inhibition of ascorbate respiration of reconstituted cytochrome c oxidase by ATP [Arnold, S. & Kadenbach, B. (1997) Eur. J. Biochem. 249, 350Ϫ354]. This abolition of ATP-inhibition by 3,5-diiodothyronine is completely prevented by a monoclonal antibody to subunit Va. The results explain at the molecular level the short-term action of thyroid hormones on basal metabolic rate.Keywords : cytochrome-c oxidase; 3,5-diiodothyronine ; ATP/ADP ratio; subunit Va; short-term action of thyroid hormones.Thyroid hormones act in two different ways on the energy diiodothyronines are able rapidly to stimulate the mitochondrial oxidative capacity and respiration rate in human and rat (Horst metabolism of higher organisms. The long-term effects induce within days the expression of specific genes of energy metabo-et al., 1989; Lanni et al., 1992 Lanni et al., , 1993 Lanni et al., , 1994aO'Reilly and Murphy, 1992; Kvetny, 1992). Similar results have been obtained on lism via interaction of triiodothyronine with the thyroid hormone receptor (Weinberger et al., 1986;Sap et al., 1986), which forms isolated mitochondria from fish (Leary et al., 1996), indicating that such effects are not restricted to mammalian species. Morehomodimers or heterodimers allowing complex interactions with genes (Glass and Holloway, 1990; Marks et al., 1992; Cheng et over, diiodothyronines were found to stimulate directly cytochrome-c oxidase activity in rat liver homogenate (Lanni et al., al., 1994;Bogazzi et al., 1994). The short-term effects refer to stimulation, within minutes, of mitochondrial activities (for 1994b) and of the isolated enzyme (Goglia et al., 1994b). Recently the stimulatory effect of diiodothyronines on the energy review see Soboll et al., 1993; Wrutniak and Cabello, 1996). While the mechanism of stimulation of gene expression has been metabolism was shown in vivo (Lanni et al., 1996; Cimmino et al., 1996), and in a very recent report it was shown that the investigated extensively, the mechanism of short-term stimulation of respiration by thyroid hormones remained obscure. The effect of diiodothyronines on the resting metabolism was more rapid than that exerted by triiodothyronine, with 3,5-diiodothyoriginal observation that thyroid hormones uncouple oxidative phosphorylation in mitochondria (Martius and Hess, 1951; ronine seeming to show a clearer effect .However, in spite of the presence of specific binding sites for Lardy and Feldott, 1951) was later withdrawn (Tata et al., 1962; Kadenbach, 1966a, b). Nevertheless, specific binding sites for diiodothyronines in rat liver mitochondria (Lanni et at., 1994a ; Goglia et al., 1994a) t...

Hormetic responses of thyroid hormone calorigenesis in the liver: Association with oxidative stress

“…Data discussed in this article indicate that redox regulation of gene transcription by T 3 (i) represents an additional nongenomic mechanism to those reported for different cellular processes, such as stimulation of plasma membrane transport, modulation of enzyme activity and mitochondrial processes, or signal transduction pathways underlying cell surface G protein-coupled T 3 /T 4 membrane-binding site mitogen-activated protein kinases (16,19,21,(85)(86)(87) and (ii) is dependent upon the genomic pathway triggering energy metabolism with ROS production ( Fig. 1; 12).…”

“…In agreement, proteomic studies revealed that the largest fraction (50%) of proteins affected by thyroid state was involved in substrate and energy metabolism (20). Nongenomic signaling occurring via 3,5-diiodothyronine (3,5-T 2 ) and T 3 may also be operative, leading to allosteric activation of cytochrome c oxidase (21). The net result of the activation of both signaling pathways is the enhancement in the rate of O 2 consumption of target tissues such as liver (22), which may be contributed by secondary processes induced by T 3 such as (i) induction of uncoupling proteins (23); (ii) energy expenditure due to futile cycles coupled to increase in catabolic and anabolic pathways (24); (iii) loss of energy due to higher active cation transport (16,19); and (iv) O 2 equivalents used in the generation of mitochondrial ROS ( Fig.…”

Regulation of Cytochrome c Oxidase by Adenylic Nucleotides. Is Oxidative Phosphorylation Feedback Regulated by its End‐Products?

“…In contrast to the external effect, the matrix-oriented inhibition of ATP is extensively documented in the literature for eucaryotic COX including yeast (80). There is strong evidence that this effect is linked to the cooperative binding of ferrocytochrome c to the dimeric enzyme, which can be abolished by decreasing the ATP/ADP (22,49,51,80). In addition to the effect on enzyme turnover, adenylic nucleotides seem to modulate the proton pumping ef ciency of isolated mammalian COX in a tissue-speci c manner (16,27).…”

“…In fact, cooperativity of COX is almost completely lost after reconstitution of the enzyme in the presence of intraliposomal ATP and 3,5-diiodothyronin e (22). Moreover, monoclonal antibodies raised against subunit Va completely abolished the effect of diiodothyronine , which was later shown to speci cally bind to subunit Va (22). Secondly, the allosteric ATP-inhibition of Tween 20-solubilized COX is reversibly switched on by cAMP-dependent phosphorylation (in the presence of ATP, cAMP, and protein kinase A) and switched off by subsequent treatment with protein phosphatase (52).…”

“…However, enzyme turnover has been shown to be more sensitive to 1pH (per mV) than to 19, because of a simultaneous regulatory effect of matrix pH on the enzyme (17,18). Thus, the electron ux through the cytochrome oxidase also depends on different effectors: inorganic phosphate (19), nitric oxide (20), fatty acids (21), and thyroid hormones (22).…”