On the structure of endogenous ouabain

Kawamura, Akira; Guo, Jinsong; Itagaki, Yasuhiro; Bell, Charles D.; Wang, Yi; Haupert, Garner T.; Magil, Sheila G.; Gallagher, Rex T.; Berova, Nina; Nakanishi, Koji

doi:10.1073/pnas.96.12.6654

Cited by 172 publications

(59 citation statements)

References 30 publications

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“…Endogenous ouabain is, like other steroid hormones, synthesized and released from the adrenals (21). It is also locally produced in other tissues, such as the hypothalamus (16,18). Its physiological role has not been clarified (37).…”

Section: Discussionmentioning

confidence: 99%

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Ouabain, a steroid hormone that signals with slow calcium oscillations

Aizman

Uhlén

Lal

et al. 2001

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

273

230

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The plant-derived steroid, digoxin, a specific inhibitor of Na,KATPase, has been used for centuries in the treatment of heart disease. Recent studies demonstrate the presence of a digoxin analog, ouabain, in mammalian tissue, but its biological role has not been elucidated. Here, we show in renal epithelial cells that ouabain, in doses causing only partial Na,K-ATPase inhibition, acts as a biological inducer of regular, low-frequency intracellular calcium (

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Section: Discussionmentioning

confidence: 99%

“…Ouabain derivatives have been used for centuries in the treatment of heart disease. Recent studies demonstrate the presence of endogenous ouabain in mammalian tissues (16)(17)(18). The physiological role of the ouabain͞Na,K-ATPase complex has, despite extensive research, remained controversial.…”

mentioning

confidence: 99%

Ouabain, a steroid hormone that signals with slow calcium oscillations

Aizman

Uhlén

Lal

et al. 2001

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

273

230

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“…It is the target molecule for cardiac glycosides, such as ouabain, which inhibit the enzyme activity by binding from the extracellular side of the enzyme. Recently, the presence of endogenous ouabain has been demonstrated in mammalians (2)(3)(4), and it is suggested that it may play a role in the pathogenesis of hypertension (5). The interaction between ouabain and Na ϩ ,K ϩ -ATPase appears to be important for understanding the regulation of Na ϩ ,K ϩ -ATPase activity.…”

mentioning

confidence: 99%

High-affinity ouabain binding by a chimeric gastric H ⁺ ,K ⁺ -ATPase containing transmembrane hairpins M3-M4 and M5-M6 of the α ₁ -subunit of rat Na ⁺ ,K ⁺ -ATPase

Koenderink

Hermsen²,

Swarts³

et al. 2000

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

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Na ؉ ,K ؉ -ATPase and gastric H ؉ ,K ؉ -ATPase are two related enzymes that are responsible for active cation transport. Na ؉ ,K ؉ -ATPase activity is inhibited specifically by ouabain, whereas H ؉ ,K ؉ -ATPase is insensitive to this drug. Because it is not known which parts of the catalytic subunit of Na ؉ ,K ؉ -ATPase are responsible for ouabain binding, we prepared chimeras in which small parts of the ␣-subunit of H ؉ ,K ؉ -ATPase were replaced by their counterparts of the ␣1-subunit of rat Na ؉ ,K ؉ -ATPase. A chimeric enzyme in which transmembrane segments 5 and 6 of H ؉ ,K ؉ -ATPase were replaced by those of Na ؉ ,K ؉ -ATPase could form a phosphorylated intermediate, but hardly showed a K ؉ -stimulated dephosphorylation reaction. When transmembrane segments 3 and 4 of Na ؉ ,K ؉ -ATPase were also included in this chimeric ATPase, K ؉ -stimulated dephosphorylation became apparent. This suggests that there is a direct interaction between the hairpins M3-M4 and M5-M6. Remarkably, this chimeric enzyme, HN34͞56, had obtained a high-affinity ouabain-binding site, whereas the rat Na ؉ ,K ؉ -ATPase, from which the hairpins originate, has a low affinity for ouabain. The low affinity of the rat Na ؉ ,K ؉ -ATPase previously had been attributed to the presence of two charged amino acids in the extracellular domain between M1 and M2. In the HN34͞56 chimera, the M1͞M2 loop, however, originates from H ؉ ,K ؉ -ATPase, which has two polar uncharged amino acids on this position. Placement of two charged amino acids in the M1͞M2 loop of chimera HN34͞56 results in a decreased ouabain affinity. This indicates that although the M1͞M2 loop affects the ouabain affinity, binding occurs when the M3͞M4 and M5͞M6 hairpins of Na ؉ ,K ؉ -ATPase are present.

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“…In addition to the cardiac glycosides of plant origin, the endogenous CTS were recently described as a new class of steroid hormones, endogenously produced in mammalian adrenal glands and central nervous system (3). Endogenous ouabain (EO) has been isolated as a stereoisomer of ouabain and identified as a constituent of human blood, bovine adrenal glands, and hypothalamus (3,4) and circulates in elevated concentrations in the blood of 50% of Caucasians with high blood pressure (5). Bovine adrenal cortical cells in tissue culture release EO in response to norepinephrine, corticotropin, and angiotensin II (6,7).…”

mentioning

confidence: 99%

Cardiotonic Steroids Stimulate Glycogen Synthesis in Human Skeletal Muscle Cells via a Src- and ERK1/2-dependent Mechanism

Kotova

Al-Khalili

Talia

et al. 2006

Journal of Biological Chemistry

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The cardiotonic steroid, ouabain, a specific inhibitor of Na ؉ ,K ؉ -ATPase, initiates protein-protein interactions that lead to an increase in growth and proliferation in different cell types. We explored the effects of ouabain on glucose metabolism in human skeletal muscle cells (HSMC) and clarified the mechanisms of ouabain signal transduction. In HSMC, ouabain increased glycogen synthesis in a concentration-dependent manner reaching the maximum at 100 nM. The effect of ouabain was additive to the effect of insulin and was independent of phosphatidylinositol 3-kinase inhibitor LY294002 but was abolished in the presence of a MEK1/2 inhibitor (PD98059) or a Src inhibitor (PP2). Ouabain increased Src-dependent tyrosine phosphorylation of ␣ 1 -and ␣ 2 -subunits of Na ؉ ,K ؉ -ATPase and promoted interaction of ␣ 1 -and ␣ 2 -subunits with Src, as assessed by co-immunoprecipitation with Src. Phosphorylation of ERK1/2 and GSK3␣/␤, as well as p90rsk activity, was increased in response to ouabain in HSMC, and these responses were prevented in the presence of PD98059 and PP2. Incubation of HSMC with 100 nM ouabain increased phosphorylation of the ␣-subunits of the Na-pump at a MAPK-specific Thr-Pro motif. Ouabain treatment decreased the surface abundance of ␣ 2 -subunit, whereas abundance of the ␣ 1 -subunit was unchanged. Marinobufagenin, an endogenous vertebrate bufadienolide cardiotonic steroid, increased glycogen synthesis in HSMC at 10 nM concentration, similarly to 100 nM ouabain. In conclusion, ouabain and marinobufagenin stimulate glycogen synthesis in skeletal muscle. This effect is mediated by activation of a Src-, ERK1/2-, p90rsk-, and GSK3-dependent signaling pathway.

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On the structure of endogenous ouabain

Cited by 172 publications

References 30 publications

Ouabain, a steroid hormone that signals with slow calcium oscillations

Ouabain, a steroid hormone that signals with slow calcium oscillations

High-affinity ouabain binding by a chimeric gastric H ⁺ ,K ⁺ -ATPase containing transmembrane hairpins M3-M4 and M5-M6 of the α ₁ -subunit of rat Na ⁺ ,K ⁺ -ATPase

Cardiotonic Steroids Stimulate Glycogen Synthesis in Human Skeletal Muscle Cells via a Src- and ERK1/2-dependent Mechanism

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On the structure of endogenous ouabain

Cited by 172 publications

References 30 publications

Ouabain, a steroid hormone that signals with slow calcium oscillations

Ouabain, a steroid hormone that signals with slow calcium oscillations

High-affinity ouabain binding by a chimeric gastric H + ,K + -ATPase containing transmembrane hairpins M3-M4 and M5-M6 of the α 1 -subunit of rat Na + ,K + -ATPase

Cardiotonic Steroids Stimulate Glycogen Synthesis in Human Skeletal Muscle Cells via a Src- and ERK1/2-dependent Mechanism

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High-affinity ouabain binding by a chimeric gastric H ⁺ ,K ⁺ -ATPase containing transmembrane hairpins M3-M4 and M5-M6 of the α ₁ -subunit of rat Na ⁺ ,K ⁺ -ATPase