The human multidrug resistance-associated protein (MRP) family currently has seven members. The ability of several of these membrane proteins to transport a wide range of anticancer drugs out of cells and their presence in many tumors make them prime suspects in unexplained cases of drug resistance, although proof that they contribute to clinical drug resistance is still lacking. Recent studies have begun to clarify the function of the MRP family members. MRPs are organic anion transporters; i.e., they transport anionic drugs, exemplified by methotrexate, and neutral drugs conjugated to acidic ligands, such as glutathione (GSH), glucuronate, or sulfate. However, MRP1, MRP2, and MRP3 can also cause resistance to neutral organic drugs that are not known to be conjugated to acidic ligands by transporting these drugs together with free GSH. MRP1 can even confer resistance to arsenite and MRP2 to cisplatin, again probably by transporting these compounds in complexes with GSH. MRP4 overexpression is associated with high-level resistance to the nucleoside analogues 9-(2-phosphonylmethoxyethyl) adenine and azidothymidine, both of which are used as anti-human immunodeficiency virus drugs. MRPs may, therefore, also have a role in resistance against nucleoside analogues used in cancer chemotherapy. Mice without Mrp1, a high-affinity leukotriene C(4) transporter, have an altered response to inflammatory stimuli but are otherwise healthy and fertile. MRP2 is the major transporter responsible for the secretion of bilirubin glucuronides into bile, and humans without MRP2 develop a mild liver disease known as the Dubin-Johnson syndrome. The physiologic functions of the other MRPs are not known. Whether long-term inhibition of MRPs in humans can be tolerated (assuming that suitable inhibitors will be found) remains to be determined.

/pdf/a-family-of-drug-transporters-the-multidrug-resistance-46t7632289.pdf

A Family of Drug Transporters: the Multidrug Resistance-Associated Proteins

The ATP-binding cassette (ABC) transporters are a family of large proteins in membranes and are able to transport a variety of compounds through membranes against steep concentration gradients at the cost of ATP hydrolysis. The available outline of the human genome contains 48 ABC genes; 16 of these have a known function and 14 are associated with a defined human disease. Major physiological functions of ABC transporters include the transport of lipids, bile salts, toxic compounds, and peptides for antigen presentation or other purposes. We review the functions of mammalian ABC transporters, emphasizing biochemical mechanisms and genetic defects. Our overview illustrates the importance of ABC transporters in human physiology, toxicology, pharmacology, and disease. We focus on three topics: (a) ABC transporters transporting drugs (xenotoxins) and drug conjugates. (b) Mammalian secretory epithelia using ABC transporters to excrete a large number of substances, sometimes against a steep concentration gradient. Several inborn errors in liver metabolism are due to mutations in one of the genes for these pumps; these are discussed. (c) A rapidly increasing number of ABC transporters are found to play a role in lipid transport. Defects in each of these transporters are involved in human inborn or acquired diseases.

/pdf/mammalian-abc-transporters-in-health-and-disease-4l5ns15q3r.pdf

Mammalian ABC Transporters in Health and Disease

Direct cellular responses to platinum-induced DNA damage

1. P-glycoprotein (P-gp/MDR1), one of the most clinically important transmembrane transporters in humans, is encoded by the ABCB1/MDR1 gene. Recent insights into the structural features of P-gp/MDR...

Structure, function and regulation of P-glycoprotein and its clinical relevance in drug disposition

Cisplatin, carboplatin, and oxaliplatin are three FDA-approved members of the platinum anticancer drug family. These compounds induce apoptosis in tumor cells by binding to nuclear DNA, forming a variety of structural adducts and triggering cellular responses, one of which is the inhibition of transcription. In this report we present (i) a detailed review of the structural investigations of various Pt–DNA adducts and the effects of these lesions on global DNA geometry; (ii) research detailing inhibition of cellular transcription by Pt–DNA adducts; and (iii) a mechanistic analysis of how DNA structural distortions induced by platinum damage may inhibit RNA synthesis in vivo. A thorough understanding of the molecular mechanism of action of platinum antitumor agents will aid in the development of new compounds in the family.

Inhibition of transcription by platinum antitumor compounds

The Y box-binding protein (YB-1) binds to DNA sequences, present in the control regions of many genes, that contain an inverted CCAAT box. The binding activity of a nuclear factor, designated MDR-NF1, to an inverted CCAAT box in the promoter of the multidrug resistance 1 (MDR1) gene has previously been shown to be increased in nuclear extracts of cells exposed to UV radiation or various anticancer agents. The MDR-NF1 cDNA has now been cloned by screening a human colon library with an active fragment of the MDR1 promoter. The amino acid sequence encoded by the cloned cDNA was identical to that of YB-1. Northern blot analysis revealed that YB-1 mRNA was present in all human tissues examined. Rabbit antibodies were generated against synthetic peptides corresponding to YB-1, and indirect immunofluorescence microscopy with these antibodies showed that the concentration of YB-1 in all cisplatin-resistant cell lines examined was higher than that in the respective drug-sensitive parental cells. Transfection of human epidermoid cancer KB cells with a YB-1 antisense construct established two cell lines with reduced concentrations of YB-1. These transfectants showed increased sensitivity to cisplatin, mitomycin C, and UV radiation but not to vincristine, doxorubicin, camptothecin, or etoposide. Thus, YB-1 may protect cells from the cytotoxic effects of agents that induce cross-linking of DNA, suggesting a novel function of this ancestor DNA-binding protein.

https://cancerres.aacrjournals.org/content/canres/56/18/4224.full.pdf

Role of the Human Y Box-binding Protein YB-1 in Cellular Sensitivity to the DNA-damaging Agents Cisplatin, Mitomycin C, and Ultraviolet Light

This invention provides compositions for fair-skin containing the phosphorylated polysaccharides produced by lactic acid bacteria as an effective ingredient. The phosphorylated polysaccharides are expressed, for example, by the following formula and contained in the compositions for fair-skin at concentrations of 0.01-20 weight % and are used such as creams, emulsions and toilet lotions. The compositions for fair-skin exhibit fair-skin effect by inhibiting activities to melanoma proliferation and melanin formation.
    (wherein, Glc, Gal and Rha represent glucose, galactose and rhamnose residues, respectively. Numerals shown by other than subscript represent the respective binding sites and n represents the degree of polymerization of 1,000-5,000).

Compositions for fair-skin

A novel primer is provided which is useful in the reverse transcription polymerase chain reaction to amplify α S1 -casein gene and keratin gene contained in milk. A method is also provided for using the expression ratio of their genes to examine the pathological conditions of mammalian mastitis or determine the milk protein synthesis level in mammary gland cells. The method is quick and accurate and avoids the need for excising mammary gland tissue.

Method for determining mastitis using keratin and casein which are amplified by primers

The present invention relates to a method of synchronizing epithelial cells into G0 phase, more specifically, a method of synchronizing epithelial cells into G0 phase characterized by culturing the cells in a synthetic medium for 5 days or more, wherein said synthetic medium is a medium with the lowered concentration of bovine fetal serum 5% or less and said epithelial cells is bovine mammary gland cells. Further, the present invention relates to a method of culturing cells characterized by using G0 phase synchronized cells obtained by the present invention, and a method of screening a related to differentiation and/or maturation of said cells by using G0 phase synchronized cells. The present invention is useful for easily synchronizing epithelial cells into G0 phase and for screening a factor related to differentiation and/or maturation of epithelial cells.

Method of synchronizing epithelial cells into G0 phase

To synthesize nonreducing oligosaccharide derived from trehalose, enzymatic transgalactosylation was investigated using lactose and trehalose as substrates and a commercially available β-ga-lactosidase, which has a tendency to transfer the galactosyl residue to the C4 position of acceptor sugars, from Bacillus circulans. The galactosylation successfully resulted in the efficient production of O-β-D-galactopyranosyl-(1-4)-α, α-trehalose. This trisaccharide showed good stability against acidic treatment.

Morimasa Tanimoto

Papers

Role of the Human Y Box-binding Protein YB-1 in Cellular Sensitivity to the DNA-damaging Agents Cisplatin, Mitomycin C, and Ultraviolet Light

Compositions for fair-skin

Method for determining mastitis using keratin and casein which are amplified by primers

Method of synchronizing epithelial cells into G0 phase

Enzymatic Synthesis of Nonreducing Trisaccharide Containing Both Lactose and Trehalose as a Part of the Structure