Martell R L, Slapak C A, Levy S B
Center for Adaptation Genetics and Drug Resistance, Tufts University School of Medicine, Boston, MA 02111, USA.
Br J Cancer. 1997;75(2):161-8. doi: 10.1038/bjc.1997.27.
The relationship between mammalian facilitative glucose transport proteins (GLUT) and multidrug resistance was examined in two vincristine (VCR)-selected murine erythroleukaemia (MEL) PC4 cell lines. GLUT proteins, GLUT1 and GLUT3, were constitutively coexpressed in the parental cell line and also in the VCR-selected cell lines. Increased expression of the GLUT1 isoform was noted both in the PC-V40 (a non-P-glycoprotein, mrp-overexpressing subline) and in the more resistant PC-V160 (overexpressing mrp and mdr3) cell lines. Overexpression of GLUT3 was detected only in the PC-V160 subline. An increased rate of facilitative glucose transport (Vmax) and level of plasma membrane GLUT protein expression paralleled increased VCR resistance, active VCR efflux and decreased VCR steady-state accumulation in these cell lines. Glucose transport inhibitors (GTIs), cytochalasin B (CB) and phloretin blocked the active efflux and decreased steady-state accumulation of VCR in the PC-V40 subline. GTIs did not significantly affect VCR accumulation in the parental or PC-V160 cells. A comparison of protein sequences among GLUT1, GLUT3 and MRP revealed a putative cytochalasin B binding site in MRP, which displayed 44% sequence similarity/12% identity with that previously identified in GLUT1 and GLUT3; these regions also exhibited a similar hydropathy plot pattern. The findings suggested that CB bound to MRP and directly or indirectly lowered VCR efflux and/or CB bound to one or both GLUT proteins, which acted to lower the VCR efflux mediated by MRP. This is the first report of a non-neuronal murine cell line that expressed GLUT3.
在两种经长春新碱（VCR）筛选的小鼠红白血病（MEL）PC4细胞系中，研究了哺乳动物易化性葡萄糖转运蛋白（GLUT）与多药耐药性之间的关系。GLUT蛋白GLUT1和GLUT3在亲代细胞系以及VCR筛选的细胞系中均组成性共表达。在PC-V40（一种非P-糖蛋白、多药耐药相关蛋白过表达的亚系）和耐药性更强的PC-V160（多药耐药相关蛋白和多药耐药蛋白3过表达）细胞系中，均观察到GLUT1亚型的表达增加。仅在PC-V160亚系中检测到GLUT3过表达。在这些细胞系中，易化性葡萄糖转运速率（Vmax）的增加以及质膜GLUT蛋白表达水平的升高与VCR耐药性增加、VCR主动外排增加以及VCR稳态蓄积减少平行。葡萄糖转运抑制剂（GTIs）、细胞松弛素B（CB）和根皮素可阻断PC-V40亚系中VCR的主动外排并减少其稳态蓄积。GTIs对亲代细胞或PC-V160细胞中VCR的蓄积没有显著影响。GLUT1、GLUT3和多药耐药相关蛋白的蛋白质序列比较显示，多药耐药相关蛋白中有一个假定的细胞松弛素B结合位点，与先前在GLUT1和GLUT3中鉴定的位点具有44%的序列相似性/12%的一致性；这些区域还呈现出相似的亲水性图谱模式。研究结果表明，CB与多药耐药相关蛋白结合并直接或间接降低VCR外排，和/或CB与一种或两种GLUT蛋白结合，从而降低由多药耐药相关蛋白介导的VCR外排。这是关于表达GLUT3的非神经元小鼠细胞系的首次报道。
