Hemodynamic molecular imaging of tumor-associated enzyme activity in the living brain

Molecular imaging could have great utility for detecting, classifying, and guiding treatment of brain disorders, but existing probes offer limited capability for assessing relevant physiological parameters. Here, we describe a potent approach for noninvasive mapping of cancer-associated enzyme activity using a molecular sensor that acts on the vasculature, providing a diagnostic readout via local changes in hemodynamic image contrast. The sensor is targeted at the fibroblast activation protein (FAP), an extracellular dipeptidase and clinically relevant biomarker of brain tumor biology. Optimal FAP sensor variants were identified by screening a series of prototypes for responsiveness in a cell-based bioassay. The best variant was then applied for quantitative neuroimaging of FAP activity in rats, where it reveals nanomolar-scale FAP expression by xenografted cells. The activated probe also induces robust hemodynamic contrast in nonhuman primate brain. This work thus demonstrates a potentially translatable strategy for ultrasensitive functional imaging of molecular targets in neuromedicine.

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Hemodynamic molecular imaging of tumor-associated enzyme activity in the living brain.

10.1101/2021.05.11.443603 ◽

2021 ◽

Author(s):

MITUL M DESAI ◽

Jitendra Sharma ◽

Adrian L Slusarczyk ◽

Ashley Chapin ◽

Agata Wisniowska ◽

...

Keyword(s):

Enzyme Activity ◽

Molecular Imaging ◽

Tumor Biology ◽

Brain Disorders ◽

Primate Brain ◽

Molecular Sensor ◽

Great Utility ◽

Noninvasive Mapping ◽

A Cell ◽

Quantitative Neuroimaging

Molecular imaging could have great utility for detecting, classifying, and guiding treatment of brain disorders, but existing probes offer limited capability for assessing relevant physiological parameters. Here we describe a potent approach for noninvasive mapping of cancer-associated enzyme activity using a molecular sensor that acts on the vasculature, providing a diagnostic readout via local changes in hemodynamic image contrast. The sensor is targeted at the fibroblast activation protein (FAP), an extracellular dipeptidase and clinically relevant biomarker of brain tumor biology. Optimal FAP sensor variants were identified by screening a series of prototypes for responsiveness in a cell-based bioassay. The best variant was then applied for quantitative neuroimaging of FAP activity in rats, where it reveals nanomolar-scale FAP expression by xenografted tumor cells. The activated probe also induces robust hemodynamic contrast in nonhuman primate brain. This work thus demonstrates a translatable strategy for ultrasensitive functional imaging of molecular targets in neuromedicine.

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Rat lung carbonic anhydrase: activity, localization, and isozymes

Journal of Applied Physiology ◽

10.1152/jappl.1986.60.2.638 ◽

1986 ◽

Vol 60 (2) ◽

pp. 638-645 ◽

Cited By ~ 28

Author(s):

R. P. Henry ◽

S. J. Dodgson ◽

R. E. Forster ◽

B. T. Storey

Keyword(s):

Enzyme Activity ◽

Carbonic Anhydrase ◽

Carbonic Anhydrase Activity ◽

Hydration Reaction ◽

Rat Lung ◽

Cell Debris ◽

Blood Contamination ◽

Total Enzyme Activity ◽

Erythrocyte Lysis ◽

A Cell

sCarbonic anhydrase activity in rat lungs perfused free of blood was localized by homogenization of the tissue followed by differential centrifugation. Four fractions were obtained from the homogenate, a cell debris pellet with a mitochondrial pellet and a microsomal pellet with a clear cytosol supernatant. The last named fraction contained 67% of the total enzyme activity; the cell debris contained 18%, and the mitochondrial and microsomal contained 8 and 7%, respectively. Of the 33% of enzyme activity associated with the pellet fraction, 25% could be experimentally defined as membrane associated by its solubilization with 0.3 M tris-(hydroxymethyl) aminoethane sulfate buffer. The remainder was defined as membrane bound. Purification of the soluble carbonic anhydrase from the lung yielded two isozymes with electrophoretic and inhibitor sensitivities apparently identical with the blood isozymes. Hemoglobin analysis showed that the lung isozymes could not have included more than 0.03% enzyme from blood contamination. The carbonic anhydrase activity present in the whole rat lung would give an average acceleration of the CO2 hydration reaction under physiological conditions over the uncatalyzed rate of 122, sufficient to maintain equilibration between CO2 and plasma HCO3- during blood transit of the lung. If the membrane-associated activity is mostly on the plasma membrane of the endothelial cells and available to the capillary blood, it would be sufficient to give this acceleration. We suggest that the possible source of this membrane-associated activity might be adsorption from the blood of carbonic anhydrase liberated by erythrocyte lysis.

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Control and localization of the phosphatases in conidia of Neurospora crassa

Canadian Journal of Microbiology ◽

10.1139/m89-139 ◽

1989 ◽

Vol 35 (9) ◽

pp. 830-835 ◽

Cited By ~ 3

Author(s):

E. Nahas

Keyword(s):

Alkaline Phosphatase ◽

Enzyme Activity ◽

Neurospora Crassa ◽

Culture Medium ◽

Alkaline Phosphatases ◽

Cell Compartments ◽

Surface Active Agents ◽

Cell Enzyme ◽

A Cell ◽

Surface Active

Repressible acid, repressible alkaline, and constitutive alkaline phosphatases were studied with respect to their control and localization in conidia of Neurospora crassa. In contrast to constitutive alkaline phosphatase, the production and secretion of repressible phosphatases is regulated by phosphate level and pH of the culture medium. Phosphatase activity increased with conidial germination and was detectable partially in the growth medium after 5 h incubation. These enzymes were found to be located in different cell compartments. Part of the whole cell enzyme activity involved a soluble exoconidial fraction, and another part, a cell-bound enzyme that remained after successive washes. The cell-bound enzyme was sensitive to treatment with dilute acid and was thought to be located in the mural space. A third part of the enzyme activity was judged to be intracellular, as shown by treatments with surface-active agents and heat, which disrupted the conidia or destroyed the conidial permeability barriers. On the basis of these criteria, the constitutive alkaline phosphatase was considered to be more cryptic than the repressible phosphatases. The alkaline phosphatases were also active during heat treatment, suggesting they may be involved in the mechanism of secretion.Key words: Neurospora crassa, repressible acid phosphatase, repressible alkaline phosphatase, constitutive alkaline phosphatase, conidia.

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Molecular imaging of regional brain tumor biology

Journal of Cellular Biochemistry ◽

10.1002/jcb.10406 ◽

2002 ◽

Vol 87 (S39) ◽

pp. 25-35 ◽

Cited By ~ 12

Author(s):

A.M. Spence ◽

M. Muzi ◽

K.A. Krohn

Keyword(s):

Brain Tumor ◽

Molecular Imaging ◽

Tumor Biology ◽

Regional Brain

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Fungal α-arabinofuranosidases of glycosyl hydrolase families 51 and 54 show a dual arabinofuranosyl- and galactofuranosyl-hydrolyzing activity

Biological Chemistry ◽

10.1515/hsz-2012-0134 ◽

2012 ◽

Vol 393 (8) ◽

pp. 767-775 ◽

Cited By ~ 9

Author(s):

Boris Tefsen ◽

Ellen L. Lagendijk ◽

Joohae Park ◽

Michiel Akeroyd ◽

Doreen Schachtschabel ◽

...

Keyword(s):

Cell Wall ◽

Enzyme Activity ◽

Molecular Modeling ◽

Aspergillus Niger ◽

Glycosyl Hydrolase ◽

Hydrolase Activity ◽

Gene Encoding ◽

A Cell ◽

Or Gene

Abstract Aspergillus niger possesses a galactofuranosidase activity, however, the corresponding enzyme or gene encoding this enzyme has never been identified. As evidence is mounting that enzymes exist with affinity for both arabinofuranose and galactofuranose, we investigated the possibility that α-l-arabinofuranosidases, encoded by the abfA and abfB genes, are responsible for the galactofuranosidase activity of A. niger. Characterization of the recombinant AbfA and AbfB proteins revealed that both enzymes do not only hydrolyze p-nitrophenyl-α-l-arabinofuranoside (pNp-α-Araf) but are also capable of hydrolyzing p-nitrophenyl-β-d-galactofuranoside (pNp-β-Galf). Molecular modeling of the AbfB protein with pNp-β-Galf confirmed the possibility for AbfB to interact with this substrate, similarly as with pNp-α-Araf. We also show that galactomannan, a cell wall compound of A. niger, containing β-linked terminal and internal galactofuranosyl moieties, can be degraded by an enzyme activity that is present in the supernatant of inulin-grown A. niger. Interestingly, purified AbfA and AbfB did not show this hydrolyzing activity toward A. nigergalactomannan. In summary, our studies demonstrate that AbfA and AbfB, α-l-arabinofuranosidases from different families, both contain a galactofuranose (Galf)-hydrolyzing activity. In addition, our data support the presence of a Galf-hydrolase activity expressed by A. niger that is capable of degrading fungal galactomannan.

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The Gene Expression and Enzyme Activity of Plant 3-Deoxy-D-Manno-2-Octulosonic Acid-8-Phosphate Synthase Are Preferentially Associated with Cell Division in a Cell Cycle-Dependent Manner

PLANT PHYSIOLOGY ◽

10.1104/pp.103.026872 ◽

2003 ◽

Vol 133 (1) ◽

pp. 348-360 ◽

Cited By ~ 20

Author(s):

Frédéric Delmas ◽

Johann Petit ◽

Jérôme Joubès ◽

Martial Séveno ◽

Thomas Paccalet ◽

...

Keyword(s):

Gene Expression ◽

Cell Cycle ◽

Enzyme Activity ◽

Cell Division ◽

Dependent Manner ◽

A Cell ◽

Cycle Dependent ◽

Phosphate Synthase

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Xanthine dehydrogenase is transported to the Drosophila eye.

Genetics ◽

10.1093/genetics/123.3.503 ◽

1989 ◽

Vol 123 (3) ◽

pp. 503-509 ◽

Cited By ~ 1

Author(s):

A G Reaume ◽

S H Clark ◽

A Chovnick

Keyword(s):

Enzyme Activity ◽

Drosophila Melanogaster ◽

Xanthine Dehydrogenase ◽

Leader Sequence ◽

Intermediary Metabolism ◽

Peroxisomal Protein ◽

Eye Color ◽

Peroxisomal Targeting ◽

A Cell ◽

Color Phenotype

Abstract The rosy (ry) locus in Drosophila melanogaster codes for the enzyme xanthine dehydrogenase. Mutants that have no enzyme activity are characterized by a brownish eye color phenotype reflecting a deficiency in the red eye pigment. This report demonstrates that enzyme which is synthesized in some tissue other than the eye is transported and sequestered at the eye. Previous studies find that no leader sequence is associated with this molecule but a peroxisomal targeting sequence has been noted, and the enzyme has been localized to peroxisomes. This represents a rare example of an enzyme involved in intermediary metabolism being transported from one tissue to another and may also be the first example of a peroxisomal protein being secreted from a cell.

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Bestimmung der Strahlenwirkung auf die Thymidinkinaseaktivität innerhalb eines Zellzyklus synchroner Chlorella / Determination of Irradiation Effects on the Thymidine Kinase Activities Within a Cell-Cycle of Synchronously Growing Chlorella

Zeitschrift für Naturforschung B ◽

10.1515/znb-1971-0217 ◽

1971 ◽

Vol 26 (2) ◽

pp. 141-143 ◽

Cited By ~ 6

Author(s):

E. Cabela ◽

H. Altmann

Keyword(s):

Cell Cycle ◽

Enzyme Activity ◽

Thymidine Kinase ◽

Irradiation Effects ◽

Γ Irradiation ◽

A Cell

Ingestigations on the thymidine kinase activities within a cell-cycle of synchronously growing Chlorella cells showed a marked increase of the enzyme-activity towards the end of the DNA-reduplication.Immediately after γ-irradiation with doses of 15 krad and 35 krad, no significant changes in activity could be found; three hours after irradiation a remarkable decrease of the enzyme-activity was observed.

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Synthesis of denitrification enzymes in activated sludge: modelling with structured biomass

Water Science & Technology ◽

10.2166/wst.1994.0258 ◽

1994 ◽

Vol 30 (6) ◽

pp. 113-122 ◽

Cited By ~ 7

Author(s):

D. Wild ◽

R. von Schulthess ◽

W. Gujer

Keyword(s):

Enzyme Activity ◽

Activated Sludge ◽

Selection Process ◽

Waste Water Treatment ◽

Enzyme Synthesis ◽

Plant Design ◽

Unknown Parameters ◽

Ecological Selection ◽

Water Treatment Process ◽

A Cell

Three mechanisms are responsible for microbiological elimination processes in activated sludge: the survival of qualified organisms in the ecological selection process, the expression of specific enzymes and the absence of inhibitors limiting enzyme activity. A mathematical model with structured biomass has been formulated to improve the description of data from denitrification experiments. The model includes synthesis and decay of denitrification enzymes and is able to predict nitrate, nitrite and N2O concentrations. Kinetic parameters have been estimated and used to simulate the effect of cell saturation with enzymes in a waste water treatment process. Low dissolved oxygen concentrations in the anoxic reactor reduce the denitrification efficiency equally by inhibiting enzyme activity and enzyme synthesis: at 0.5 gm−3 O2 enzyme decay causes a cell saturation of below 40 %. Enzyme synthesis can take place in the sludge blanket of a secondary sedimentation tank and improve denitrification efficiency. The benefit of modelling with structured biomass is shown. The comprehension of experimental observations has been improved, and plant design and operation can be optimized. However, the multitude of unknown parameters still may restrict the validity of complex models.

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