Tyrosine phosphorylation of HSC70 and its interaction with RFC mediates methotrexate resistance in murine L1210 leukemia cells. 2015

Tuoen Liu, and Ratan Singh, and Zechary Rios, and Alok Bhushan, and Mengxiong Li, and Peter P Sheridan, and Shawn E Bearden, and James C K Lai, and Senyo Agbenowu, and Shousong Cao, and Christopher K Daniels
Department of Internal Medicine, Division of Oncology, Washington University School of Medicine, St. Louis, MO, United States.

We previously identified and characterized a 66-68 kDa membrane-associated, tyrosine phosphorylated protein in murine leukemia L1210 cells as HSC70 which is a methotrexate (MTX)-binding protein. In order to further characterize the functional role of HSC70 in regulating MTX resistance in L1210 cells, we first showed that HSC70 colocalizes and interacts with reduced folate carrier (RFC) in L1210 cells by confocal laser scanning microscopy and Duolink in situ proximity ligation assay. The tyrosine phosphorylation status of HSC70 found in the membrane fraction was different from the parental L1210/0 and cisplatin (CDDP)-MTX cross resistant L1210/DDP cells. In MTX-binding assays, HSC70 from L1210/DDP cells showed less affinity for MTX-agarose beads than that of L1210/0 cells. In addition, genistein (a tyrosine phosphorylation inhibitor) significantly enhanced the resistance of L1210/0 cells to MTX. Moreover, site-directed mutation studies indicated the importance of tyrosine phosphorylation of HSC70 in regulating its binding to MTX. These findings suggest that tyrosine phosphorylation of HSC70 regulates the transportation of MTX into the cells via the HSC70-RFC system and contributes to MTX resistance in L1210 cells.

UI MeSH Term Description Entries
D007939 Leukemia L1210 An experimental LYMPHOCYTIC LEUKEMIA of mice. Leukemia L 1210,L 1210, Leukemia,L1210, Leukemia
D008727 Methotrexate An antineoplastic antimetabolite with immunosuppressant properties. It is an inhibitor of TETRAHYDROFOLATE DEHYDROGENASE and prevents the formation of tetrahydrofolate, necessary for synthesis of thymidylate, an essential component of DNA. Amethopterin,Methotrexate Hydrate,Methotrexate Sodium,Methotrexate, (D)-Isomer,Methotrexate, (DL)-Isomer,Methotrexate, Dicesium Salt,Methotrexate, Disodium Salt,Methotrexate, Sodium Salt,Mexate,Dicesium Salt Methotrexate,Hydrate, Methotrexate,Sodium, Methotrexate
D010766 Phosphorylation The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety. Phosphorylations
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D014443 Tyrosine A non-essential amino acid. In animals it is synthesized from PHENYLALANINE. It is also the precursor of EPINEPHRINE; THYROID HORMONES; and melanin. L-Tyrosine,Tyrosine, L-isomer,para-Tyrosine,L Tyrosine,Tyrosine, L isomer,para Tyrosine
D050883 HSC70 Heat-Shock Proteins A constitutively expressed subfamily of the HSP70 heat-shock proteins. They preferentially bind and release hydrophobic peptides by an ATP-dependent process and are involved in post-translational PROTEIN TRANSLOCATION. Heat-Shock Cognate 70 Protein,Hsc70 Protein,70 kDa Heat-Shock Cognate Protein,Clathrin Uncoating Protein,HSC73 Protein,70 kDa Heat Shock Cognate Protein,HSC70 Heat Shock Proteins,Heat Shock Cognate 70 Protein,Heat-Shock Proteins, HSC70,Uncoating Protein, Clathrin
D051379 Mice The common name for the genus Mus. Mice, House,Mus,Mus musculus,Mice, Laboratory,Mouse,Mouse, House,Mouse, Laboratory,Mouse, Swiss,Mus domesticus,Mus musculus domesticus,Swiss Mice,House Mice,House Mouse,Laboratory Mice,Laboratory Mouse,Mice, Swiss,Swiss Mouse,domesticus, Mus musculus
D058978 Reduced Folate Carrier Protein A ubiquitously expressed folic acid transporter that functions via an antiporter mechanism which is coupled to the transport of organic phosphates. Folate Transporter 1,Reduced Folate Carrier,SLC19a1 Protein,SLC19a1 Transporter,Solute Carrier Family 19, Member 1,Carrier, Reduced Folate,Folate Carrier, Reduced,Protein, SLC19a1,Transporter 1, Folate,Transporter, SLC19a1
D018613 Microscopy, Confocal A light microscopic technique in which only a small spot is illuminated and observed at a time. An image is constructed through point-by-point scanning of the field in this manner. Light sources may be conventional or laser, and fluorescence or transmitted observations are possible. Confocal Microscopy,Confocal Microscopy, Scanning Laser,Laser Microscopy,Laser Scanning Confocal Microscopy,Laser Scanning Microscopy,Microscopy, Confocal, Laser Scanning,Confocal Laser Scanning Microscopy,Confocal Microscopies,Laser Microscopies,Laser Scanning Microscopies,Microscopies, Confocal,Microscopies, Laser,Microscopies, Laser Scanning,Microscopy, Laser,Microscopy, Laser Scanning,Scanning Microscopies, Laser,Scanning Microscopy, Laser
D019008 Drug Resistance, Neoplasm Resistance or diminished response of a neoplasm to an antineoplastic agent in humans, animals, or cell or tissue cultures. Antibiotic Resistance, Neoplasm,Antineoplastic Drug Resistance,Drug Resistance, Antineoplastic,Antineoplastic Agent Resistance,Neoplasm Drug Resistance,Resistance, Antineoplastic Agent,Resistance, Antineoplastic Drug

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