The role of PKCalpha and RLIP76 in transport-mediated doxorubicin-resistance in lung cancer.
In deletion mutant analyses of potential phosphorylation sites in RLIP76, we identified T297 and S509 as targets for phosphorylation by PKCalpha. Phosphorylation at T297 increased doxorubicin (DOX)-transport activity approximately 2-fold for RLIP76 purified from recombinant source, or from three small (H69, H1417, H1618) and three non-small cell, one each derived from H226 (squamous), H358 (bronchio alveolar), and H1395 (adenocarcinoma) lung cancer cell lines. T297 phosphorylation conferred sensitivity to tryptic digestion at R293. The specific activity for DOX-transport by RLIP76 purified from non-small cell, which was primarily in the phosphorylated form, was approximately twice that in small cell lung cancer cell lines. These finding offer a novel explanation for the observed intrinsic differences in sensitivity to DOX between non-small cell and small cell lung cancer cell lines.
Singhal
Sharad S
SS
Department of Chemistry and Biochemistry, 502 Yates St., Science Hall #223, University of Texas at Arlington, Arlington, TX 76019-0065, USA. ssinghal@uta.edu
Yadav
Sushma
S
Singhal
Jyotsana
J
Drake
Kenneth
K
Awasthi
Yogesh C
YC
Awasthi
Sanjay
S
D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000502:physiology; D045744:Cell Line, Tumor; D004317:Doxorubicin / Q000378:metabolism / Q000627:therapeutic use*; D019008:Drug Resistance, Neoplasm; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D051571:Protein Kinase C-alpha
D018528:ATP-Binding Cassette Transporters; D020690:GTPase-Activating Proteins; C095637:RALBP1 protein, human; D004317:Doxorubicin; C496628:PRKCA protein, human; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha