Entrainment in solution of an oscillating NADH oxidase activity from the bovine milk fat globule membrane with a temperature-compensated period length suggestive of an ultradian time-keeping (clock) function

Metabolic Reprogramming is a Hallmark of Metabolism Itself

The reprogramming of metabolism has been identified as one of the hallmarks of cancer. It is becoming more and more frequent to connect other diseases with metabolic reprogramming. This article aims to argue that metabolic reprogramming is not driven by disease but instead is the main hallmark of metabolism, based on its dynamic behavior that allows it to continuously adapt to changes in the internal and external conditions.

ENOX2 target for the anticancer isoflavone ME-143

ME-143 (NV-143), a synthetic isoflavone under clinical evaluation for efficacy in the management of ovarian and other forms of human cancer, blocked the activity of a cancer-specific and growth-related cell surface ECTO-NOX protein with both oxidative (hydroquinone) and protein disulfide-thiol interchange activity designated ENOX2 (tNOX) and inhibited the growth of cultured cancer cells with EC₅₀s in the range of 20–50 nM. Purified recombinant ENOX2 also bound ME-143 with a K_d of 43 (40–50) nM. Both the oxidative and protein disulfide-thiol interchange activities of ENOX proteins that alternate to generate a complex set of oscillations with a period length of 22 min compared to 24 min for the constitutive counterpart ENOX1 (CNOX) that characterizes ENOX proteins responded to ME-143. Oxidation of NADH or reduced coenzyme Q₁₀ was rapidly blocked. In contrast, the protein disulfide-thiol interchange activity measured from the cleavage of dithiodipyridine (EC₅₀ of ca. 50 nM) was inhibited progressively over an interval of 60 min that spanned three cycles of activity. Inhibition of the latter paralleled the inhibition of cell enlargement and the consequent inability of inhibited cells to initiate traverse of the cell cycle. Activities of constitutive ENOX1 (CNOX) forms of either cancer or noncancer cells were unaffected by ME-143 over the range of concentrations inhibiting ENOX2. Taken together, the findings show that ME-143 binds to ENOX2 with an affinity 4 to 10 times greater than that reported previously for the related anticancer isoflavone, phenoxodiol.

Response to lithium of a cell surface ECTO-NOX protein with time-keeping characteristics

Lithium has been used widely both as a clinical agent to treat manic depressive disorders and as a substance targeted to the regulation of the circadian cycle. In this study, we show that lithium at physiological concentrations of less than 1microM uniquely induces an ECTO-NOX activity previously inactive from plant (soybean), murine (3T3 cells) and human (HUVEC and HeLa cells) sources and resets the period of the constitutive CNOX. The average period length of the new oscillation set induced by the presence of lithium of 23.5min was slightly less than the period length in the absence of lithium (24min). The constitutive period was retained in the presence of lithium but the period length was increased on an average by 4% to about 25min. Targeting circadian rhythm abnormalities may be a particularly useful strategy in management of bipolar disorder and related illnesses since circadian cycles appear to be an inherent function conserved through evolution in all organisms and consistently implicated in the pathophysiology of bipolar disorder.

Structural changes revealed by Fourier transform infrared and circular dichroism spectroscopic analyses underlie tNOX periodic oscillations

A recurring pattern of spectral changes indicative of periodic changes in the proportion of beta-structure and a-helix of a recombinant ECTO-NOX fusion protein of tNOX, with a cellulose binding domain peptide, was demonstrated by Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopic analyses. The pattern of structural changes correlated with oscillatory patterns of enzymatic activities exhibited by the protein previously interpreted as indicative of a clock function. The pattern consisted of a repeating pattern of oscillations with a period length of 21 min with five maxima (two separated by 5 min and 3 separated by 4 to 4.5 min) within each 21 min repeat. Oscillatory patterns were not obvious in comparable FTIR or CD spectra of albumin, ribonuclease or concanavalin A. The period length was constant at 5, 15, 25, 35 and 45 degrees C (temperature compensated) and oscillations occurred independently of substrate presence. Spectra obtained in deuterium oxide yielded a longer period length of 26 min both for oscillations in enzymatic activity and absorbance ratios determined by FTIR. Taken together the findings suggest that the regular patterns of oscillations exhibited by the ECTO-NOX proteins are accompanied by recurrent global changes in the conformation of the protein backbone that directly modulate enzymatic activity.

Inside-out but not right side-out plasma membrane vesicles from soybean enlarge when treated with ATP + 2,4-D as determined by electron microscopy and light scattering: evidence for involvement of a plasma membrane AAA-ATPase

The concept that the location of an AAA-ATPase associated with the plant plasma membrane may be indicative of a functional relationship to growth or cell enlargement by analogy with roles in physical membrane displacements as proposed for AAA-ATPases associated with internal membranes was tested. A plant growth hormone-responsive and nucleoside triphosphate-dependent enlargement of inside-out vesicles of plasma membranes from soybeans was utilized in a completely cell-free system. The rate of enlargement was accelerated by the synthetic plant growth factor 2,4-dichlorophenoxyacetic acid (2,4-D) in a log dose-dependent manner and was increased approximately 2-fold with the addition of 1 microM 2,4-D plus 100 microM ATP compared to 100 microM ATP alone, 1 microM 2,4-D alone or no additions. The cell-free enlargement was inhibited by AAA-ATPase-specific antisera and by CoCl2, an inhibitor specific for AAA-ATPases. The responsible ATP site appears to be on the inside of the cell, since right side-out vesicles did not enlarge in response to either ATP, 2,4-D or the two in combination.

Prion proteins and ECTO-NOX proteins exhibit similar oscillating redox activities

Both recombinant full-length mouse prion protein expressed in Escherichia coli and native prion protein (PrPsc) from mouse brain exhibited NADH oxidase and protein disulfide-thiol interchange activities similar to those formerly thought to be properties exclusive to the growth-related, cell surface ECTO-NOX proteins. The two activities exhibited the complex 2+3 pattern of oscillations characteristic of ECTO-NOX proteins where the two activities alternate to generate a period length of 24 min. The oscillations were augmented by copper and diminished by addition of the copper chelator bathocuproene. That the activity might be attributable to a contaminating protein was ruled out by experiments where the purified recombinant prion-containing extracts were resolved by SDS-PAGE and the activity was restricted to a single band corresponding to the predicted Mr of the recombinant prion as verified by Western blot analyses.

Human amyloid peptides Abeta1-40 and Abeta1-42 exhibit NADH oxidase activity with copper-induced oscillations and a period length of 24 min

Human amyloid beta peptides Abeta1-40 and Abeta1-42 exhibit NADH oxidase activity with regular oscillations at intervals of ca 6 min. In the presence of copper, the oscillations in Abeta1-40 and Abeta1-42 become more pronounced and now assume a period length of 24 min. In the presence of copper, the oscillations are similar to those observed with NADH oxidase activities of cell surface ECTO-NOX proteins in general including a period length of 24 min. Solutions of copper sulphate in the presence of all the reagents except for the peptides did not exhibit the oscillatory behavior. NOX proteins have been reported previously to have properties of prions and to form amyloid rods of indeterminant length similar to those formed by the 39-43 residue amyloid beta proteins (Abeta). In this report, we demonstrate a second similarity between ECTO-NOX proteins and amyloid beta, that of an oscillating NADH oxidase activity with a period length of 24 min when assayed in the presence of copper.

Spectroscopic Analyses of Oscillations in ECTO-NOX-Catalyzed Oxidation of NADH

Spectroscopic strategies that substantiate periodic oscillations in low rates of NADH oxidation exhibited by ECTO-NOX proteins at the animal and plant cell surface are described. Both continuous display and discontinuous rate determinations exhibit the oscillations but continuous displays lack sufficient resolution to discern details. A procedure is documented where rates are determined by least squares analyses of traces recorded over 1 min at intervals of 1.5 min. These traces recapitulate the continuous displays but offer an opportunity to reliably estimate changes in reaction rates over short time intervals not afforded by the continuous traces. Results from previously used rate determination over 5 min intervals are included for comparison. Turbidity is identified as the major contributor to losses in resolution. Even highly purified NOX preparations tend to aggregate to form turbid suspensions. With turbid suspensions, double beam or dual wavelength instrumentation where the sample is placed immediately adjacent to the photomultiplier tube are required to reduce losses in resolution from turbidity. Also required are high levels of synchronous ECTO-NOX function. Blue or red (plants) light, small molecules (i.e., melatonin) and autosynchrony alone or in combination were used to synchronize the oscillations. Special problems posed by preparations containing more than one ECTO-NOX form and where the different ECTO-NOX forms do not cross entrain are discussed.

Sera from cancer patients contain two oscillating ECTO-NOX activities with different period lengths

ECTO-NOX protein's are cell surface-associated and growth-related hydroquinone oxidases with both protein disulfide-thiol interchange activity and the capacity to oxidize NAD(P)H. The activities of these ECTO-NOX proteins are not steady state but fluctuate to create a repeating pattern of oscillations. Two forms of ECTO-NOX activities have been distinguished. The constitutive ECTO-NOX (CNOX), is hormone responsive and refractory to quinone-site inhibitors. A tumor-associated NOX (tNOX) is unregulated, refractory to hormones and growth factors and responds to quinone-site inhibitors. CNOX proteins are widely distributed and exhibit oscillations in enzymatic activity with a period length of 24 min. tNOX proteins are cancer specific and exhibit oscillations with a period length of about 22 min. Our findings now demonstrate the presence of the novel oscillating tNOX activity in sera of patients with cancer whereas the constitutive NOX of non-cancer cells is present in sera of both cancer patients and healthy volunteers. We conclude that ECTO-NOX proteins in sera exhibit oscillatory characteristics similar to those of ECTO-NOX forms of the cell surface.

Decomposition Analyses Applied to a Complex Ultradian Biorhythm: The Oscillating NADH Oxidase Activity of Plasma Membranes Having a Potential Time-Keeping (Clock) Function

Seasonal decomposition analyses were applied to the statistical evaluation of an oscillating activity for a plasma membrane NADH oxidase activity with a temperature compensated period of 24 min. The decomposition fits were used to validate the cyclic oscillatory pattern. Three measured values, average percentage error (MAPE), a measure of the periodic oscillation, mean average deviation (MAD), a measure of the absolute average deviations from the fitted values, and mean standard deviation (MSD), the measure of standard deviation from the fitted values plus R-squared and the Henriksson-Merton p value were used to evaluate accuracy.Decomposition was carried out by fitting a trend line to the data, then detrending the data if necessary, by subtracting the trend component. The data, with or without detrending, were then smoothed by subtracting a centered moving average of length equal to the period length determined by Fourier analysis. Finally, the time series were decomposed into cyclic and error components. The findings not only validate the periodic nature of the major oscillations but suggest, as well, that the minor intervening fluctuations also recur within each period with a reproducible pattern of recurrence.

The plasma membrane-associated NADH oxidase of spinach leaves responds to blue light

The plasma membrane-associated NADH oxidase (NOX) of spinach leaf disks is characterized by oscillations in activity with a regular period length of ca. 24 min. Within a single population of plants exposed to light at the same time, NOX activities of all plants function synchronously. Exposure of plants transferred from darkness to blue light (495 nm, 2 min, 50 micromoles m-2 s-1) resulted in a complex response pattern but with a new maximum in the rate of NOX activity 36 (24+12) min after illumination and then with maxima in the rate of NOX activity every 24 min thereafter. Transient maxima in NOX activity were observed as well after 9.3 + /- 1.4 and 20.7 +/- 2.1 min. The blue light response differed from the response to red (650 nm, 10 min, 50 micromoles m-2 s-1) or white light where activity maxima were initiated 12 min after the light exposure followed by maxima every 24 min thereafter. Green or yellow light was ineffective. The light response was independent of the time in the 24-min NOX cycle when the light was given. The net effects of blue and red light were ultimately the same with a new maximum in the rate of NOX activity at 12+24=36 min (and every 24 min thereafter), but the mechanisms appear to be distinct.