Disease relevance of ENOX2

• In this report, we describe a series of eight amino acid replacements in tNOX which, when expressed in Escherichia coli, were analyzed for enzymatic activity, drug response and period length [1].
• Non-steroidal anti-inflammatory drugs (NSAIDS), piroxicam, aspirin, ibuprofen, naproxen and celecoxib all specifically inhibited tNOX activity of HeLa (human cervical carcinoma) and BT-20 (human mammary carcinoma) cells (IC(50) in the nanomolar range) without effect on ECTO-NOX activities of non-cancer MCF-10A mammary epithelial cells [2].
• An in vitro coculture model of prostate cancer cells (LNCaP) with human osteoblasts (hFOB) was utilized to define the efficacy of the tNOX inhibitors EGCg, capsaicin, Capsibiol-T and phenoxodiol against bone metastasis of prostate cancer alone and in combination with Taxol and cisplatin [3].

High impact information on ENOX2

• Molecular cloning and characterization of a tumor-associated, growth-related, and time-keeping hydroquinone (NADH) oxidase (tNOX) of the HeLa cell surface [4].
• The activities are inhibited completely by capsaicin, which represents a defining characteristic of tNOX activity [4].
• To determine if ECTO-NOX proteins might represent the ultradian time keepers (pacemakers) of the biological clock, COS cells were transfected with cDNAs encoding tNOX proteins having a period length of 22 min or with C575A or C558A cysteine to alanine replacements having period lengths of 36 or 42 min [5].
• Surprisingly, the tNOX-associated muscle GAPDH also was proteinase K resistant [6].
• Although the precise origin of BTS-induced ROS is not known, a clear correlation between their cytotoxic effect and ability to inhibit a tumour-associated NADH oxidase (tNOX) activity of the plasma membrane has been described [7].

Biological context of ENOX2

• Accordingly vector-forced over expression of tNOX in MCF-10A mammary epithelia or COS cells that lack tNOX or in COS cells that underexpress tNOX enhanced the susceptibility of growth and apoptosis to both EGCg and capsaicin [8].
• The recombinant tNOX with the modified drug binding site retained activity but the activity was no longer drug-responsive [1].
• In phase 2, this pool method was applied to all urine specimens from children received in the virology laboratory of the Centro Hospitalar Cova da Beira for diagnosis of HCMV infection, between January 2002 and March 2003 [9].
• The grape extracts interacted, often synergistically, with decaffeinated green tea extracts both in the inhibition of tNOX activity and in the inhibition of cancer cell growth [10].
• However, when tNOX is inhibited and plasma membrane electron transport is diminished, both reduced coenzyme Q(10) (ubiquinol) and NADH would be expected to accumulate [11].

Anatomical context of ENOX2

• Binding of NOX protein to the plasma membrane via amino acid side chain modification or by attachment of fatty acids also is unlikely based on use of specific fatty acid antisera to protein bound fatty acids and as a result of binding to the cancer cell surface of a truncated form of recombinant tNOX [12].
• Growth of LNCaP cells in monoculture and coculture with osteoblasts and response to tNOX inhibitors [3].

Associations of ENOX2 with chemical compounds

• Capsaicin and the principal green tea catechin, (-)-epigallocatechin-3-gallate (EGCg), target tNOX, a tumor (cancer)-specific surface hydroquinone (NADH) oxidase with protein disulfide-thiol interchange activity (ECTO-NOX protein) [8].
• The findings confirm the correctness of the drug and adenine nucleotide binding motifs within the tNOX protein and imply a potential critical role of cysteine residues in determining the period length [1].
• A tumor-associated NOX (tNOX) is unregulated, refractory to hormones and growth factors and responds to quinone-site inhibitors [13].
• When tNOX is active, coenzyme Q(10) (ubiquinone) of the plasma membrane is oxidized and NADH is oxidized at the cytosolic surface of the plasma membrane [11].
• Various oxidizing conditions known to render other antioxidants such as thiols, ascorbate and vitamin E ineffective did not reduce the effectiveness of EGCg in inhibiting either the tNOX activity or the growth of HeLa cells [14].

Physical interactions of ENOX2

• The tNOX protein from the HeLa cell surface copurified with authentic glyceraldehyde-3-phosphate dehydrogenase (muscle form) (GAPDH) [6].

Analytical, diagnostic and therapeutic context of ENOX2

• Functional motifs identified by site-directed mutagenesis within the C-terminal portion of the tNOX protein corresponding to the processed plasma membrane-associated form include quinone (capsaicin), copper and adenine nucleotide binding domains, and two cysteines essential for catalytic activity [4].
• Screening used Western blots with purified 34-kDa tNOX from HeLa cells and the sera of cancer patients [15].

References