Downregulation of taurine uptake in multidrug resistant Ehrlich ascites tumor cells

TY - JOUR

T1 - Downregulation of taurine uptake in multidrug resistant Ehrlich ascites tumor cells

AU - Poulsen, K A

AU - Litman, Thomas

AU - Eriksen, J

AU - Mollerup, J

AU - Lambert, I H

PY - 2002/6

Y1 - 2002/6

N2 - In daunorubicin resistant Ehrlich ascites tumor cells (DNR), the initial taurine uptake was reduced by 56% as compared to the parental, drug sensitive Ehrlich cells. Kinetic experiments indicated that taurine uptake in Ehrlich cells occurs via both high- and low-affinity transporters. The maximal rate constant for the initial taurine uptake was reduced by 45% (high-affinity system) and 49% (low affinity system) in the resistant subline whereas the affinity of the transporters to taurine was unchanged. By immunoblotting we identified 3 TauT protein bands in the 50-70 kDa region. A visible reduction in the intensity of the band with the lowest molecular weight was observed in resistant cells. Quantitative RT-PCR indicated a significant reduction in the amount of taurine transporter mRNA in the resistant cells. Drug resistance in DNR Ehrlich cells is associated with overexpression of the mdr1 gene product P-glycoprotein (P-gp). Using 5 progressively DNR resistant Ehrlich cell sublines with different P-gp expression pattern no correlation between taurine uptake and P-gp expression was found. Taurine uptake in MDR1 transfected NIH/3T3 mouse fibroblasts was in contrast to the findings in Ehrlich cells increased compared to the parental fibroblasts. It is concluded that the reduced taurine uptake in resistant Ehrlich cells reflects a down regulation of the taurine transporter at the mRNA and protein level and it is most probably not related to P-gp overexpression.

AB - In daunorubicin resistant Ehrlich ascites tumor cells (DNR), the initial taurine uptake was reduced by 56% as compared to the parental, drug sensitive Ehrlich cells. Kinetic experiments indicated that taurine uptake in Ehrlich cells occurs via both high- and low-affinity transporters. The maximal rate constant for the initial taurine uptake was reduced by 45% (high-affinity system) and 49% (low affinity system) in the resistant subline whereas the affinity of the transporters to taurine was unchanged. By immunoblotting we identified 3 TauT protein bands in the 50-70 kDa region. A visible reduction in the intensity of the band with the lowest molecular weight was observed in resistant cells. Quantitative RT-PCR indicated a significant reduction in the amount of taurine transporter mRNA in the resistant cells. Drug resistance in DNR Ehrlich cells is associated with overexpression of the mdr1 gene product P-glycoprotein (P-gp). Using 5 progressively DNR resistant Ehrlich cell sublines with different P-gp expression pattern no correlation between taurine uptake and P-gp expression was found. Taurine uptake in MDR1 transfected NIH/3T3 mouse fibroblasts was in contrast to the findings in Ehrlich cells increased compared to the parental fibroblasts. It is concluded that the reduced taurine uptake in resistant Ehrlich cells reflects a down regulation of the taurine transporter at the mRNA and protein level and it is most probably not related to P-gp overexpression.

KW - 3T3 Cells

KW - Animals

KW - Antibiotics, Antineoplastic

KW - Carcinoma, Ehrlich Tumor

KW - Cell Line, Tumor

KW - Daunorubicin

KW - Down-Regulation

KW - Drug Resistance, Multiple

KW - Drug Resistance, Neoplasm

KW - Gene Expression Regulation

KW - Humans

KW - Membrane Glycoproteins

KW - Membrane Transport Proteins

KW - Mice

KW - Mice, Inbred DBA

KW - P-Glycoprotein

KW - Phosphorylation

KW - Taurine

KW - Transcription, Genetic

U2 - 10.1007/s007260200019

DO - 10.1007/s007260200019

M3 - Journal article

C2 - 12107761

SN - 0939-4451

VL - 22

SP - 333

EP - 350

JO - Amino Acids

JF - Amino Acids

IS - 4

ER -