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A mammalian lysosomal membrane protein confers multidrug resistance upon expression in Saccharomyces cerevisiae
1British Columbia Cancer Research Centre, Vancouver, British Columbia V5Z 1L3 Canada. dhouge@bccancer.bc.ca
Abstract:
Mouse transporter protein (MTP) is a highly conserved polytopic membrane protein present in mammalian lysosomes and endosomes. The role of MTP in regulating the in vivo subcellular distribution of numerous structurally distinct small molecules has been examined in this study by its expression in a drug-sensitive strain of the yeast Saccharomyces cerevisiae. Surprisingly, the expression of MTP in membranes of an intracellular compartment resulted in a cellular resistance or hypersensitivity to a range of drugs that included nucleoside and nucleobase analogs, antibiotics, anthracyclines, ionophores, and steroid hormones. The intracellular bioavailability of steroid hormones was altered by MTP, as determined using an in vivo glucocorticoid receptor-driven reporter assay in yeast, suggesting that the MTP-regulated drug sensitivity arose due to a change in the subcellular compartmentalization of steroid hormones and other drugs. MTP-regulated drug sensitivity in yeast was blocked to varying degrees by compounds that inhibit lysosomal function, interfere with intracellular cholesterol transport, or modulate the multidrug resistance phenotype of mammalian cells. These results indicate that MTP is involved in the subcellular compartmentalization of diverse hydrophobic small molecules and contributes to the inherent drug sensitivity or resistance of the mammalian cell.
Insights
Mouse transporter protein (MTP) regulates drug distribution within cells. Expressing MTP in yeast altered cellular drug sensitivity, revealing its role in managing small molecule compartmentalization and cellular drug responses.
Area of Science:
- Cell Biology
- Molecular Biology
- Pharmacology
Background:
- Mouse transporter protein (MTP) is a conserved membrane protein found in mammalian lysosomes and endosomes.
- Its precise function in regulating the distribution of small molecules within cells remains incompletely understood.
Purpose of the Study:
- To investigate the role of MTP in the in vivo subcellular distribution of various small molecules.
- To determine how MTP expression affects cellular drug sensitivity and resistance.
Main Methods:
- MTP was expressed in a drug-sensitive strain of Saccharomyces cerevisiae (yeast).
- Cellular resistance and hypersensitivity to a wide range of drugs were assessed.
- An in vivo glucocorticoid receptor-driven reporter assay in yeast was used to measure intracellular steroid hormone bioavailability.
- The effects of compounds inhibiting lysosomal function or cholesterol transport were evaluated.
Main Results:
- MTP expression in yeast membranes led to altered cellular sensitivity (resistance or hypersensitivity) to diverse drugs, including analogs, antibiotics, anthracyclines, ionophores, and steroid hormones.
- MTP altered the intracellular bioavailability of steroid hormones, indicating a change in subcellular compartmentalization.
- Compounds affecting lysosomal function, cholesterol transport, or multidrug resistance modulated MTP-regulated drug sensitivity.
Conclusions:
- MTP plays a significant role in the subcellular compartmentalization of various hydrophobic small molecules.
- MTP influences the inherent drug sensitivity or resistance of mammalian cells by altering small molecule distribution.