Cloning and characterization of a second member of the mouse mdr gene family.

Abstract

The mammalian mdr gene family comprises a small number of closely related genes. Previously, we have shown that one member, mdrl, has the capacity to convey multidrug resistance to drug-sensitive recipient cells in a gene transfer protocol. However, the functional characteristics of other members of this gene family have not been examined. In this report, we characterize a second member of the mdr gene family which we designated mdr2. We determined the nucleotide sequence corresponding to the complete coding region of this mdr2 transcript. The predicted amino acid sequence of this protein (1,276 amino acids) showed that it is a membrane glycoprotein highly homologous to mdrl (85%), strongly suggesting that both genes originate from a common ancestor. Regions of divergence between mdrl and mdr2 proteins are concentrated in two discrete segments of the predicted polypeptides, each approximately 100 residues in length. The mdr2 protein appears to be formed by the duplication of a structural unit which encodes three putative transmembrane loops and a predicted nucleotide-binding fold and is highly homologous to bacterial transport proteins such as hlyB. This strong homology suggests that mdr2 also participates in an energy-dependent membrane transport process. However, the direct relationship, if any, of this new member of the mdr family to multidrug resistance remains to be established. Knowledge of the complete nucleotide sequence and predicted amino acid sequence of the mdr2 gene product will enable the preparation of gene-specific probes and antibodies necessary to study the functional role of this gene in multidrug resistance and normal physiological processes.The emergence and outgrowth of populations of drugresistant tumor cells constitute a major limitation to the chemotherapeutic treatment of human cancers. Drug-resistant cell populations often display cross resistance to compounds unrelated in structure and intracellular target to which they have not been previously exposed (36 acid sequence of the mdr protein encoded by this clone indicates that it is most likely a membrane glycoprotein with a minimum molecular weight of 140,000 containing six transmembrane loops and a cluster of N-linked glycosylation sites near the amino terminus. The protein appears to be formed by the duplication of a structural unit formed by three transmembrane loops and a predicted ATP-binding site (18). This structural unit is highly homologous to the proposed energy-coupling subunit of bacterial periplasmic transport complexes, in particular, the hlyB gene implicated in the extracellular transport of hemolysin (12,15,33). This structural arrangement and homology to bacterial proteins are also shared by the human mdrl (7) and hamster Pglycoprotein (5, 11) genes.We now report the cloning and characterization of a second transcriptionally active member of the mdr family that we named mdr2. The complete nucleotide sequence of the mdr2 cDNA was obtained from the combined analysis of two overlapping cDNA clones, lambda DR27 and lambda ...

Aureobasidin A, an antifungal cyclic depsipeptide antibiotic, is a substrate for both human MDR1 and MDR2/P‐glycoproteins

“…In this paper, we reported that MDR2/Pgp expressed in yeast cells retains an ability to interact with a variety of typical MDRl substrates. Nevertheless, overexpression of human MDR2/ Pgp or mouse mdr2/Pgp cannot confer multidrug resistance on drug-sensitive mammalian cells, which has been confirmed by several groups [4,5]. We have reported [7] that human MDRl/Pgp transports cortisol, aldosterone, and dexamethasone, but not progesterone, although progesterone directly binds MDRl/Pgp, inhibits azidopine photoaffinity labeling of MDRlIPgp, and increases the sensitivity of multidrug-resistant cells to vinblastine.…”

“…Pgps are encoded by a small gene family, which includes two members in humans, MDRl and MDR2, and three members in mice, mdrla, mdrlb, and mdr2. Overexpression of human MDRl, or mouse mdrla and mdrlb, in drug-sensitive cultured cells can confer multidrug resistance [l-3], while human MDR2 and mouse mdr2 cannot [4,5].…”

P-glycoprotein (encoded by multidrug resistance genes) is not required for interleukin-2 secretion in mice and humans

“…1 In mammals, a small family of closely related genes [2][3][4][5][6][7][8] encodes P-glycoprotein (P-gp) with two members of the family in humans (MDR1 and MDR3) and three members in rodents (mdr1a, mdr1b, and mdr2). MDR1, mdr1a, and mdr1b confer MDR, whereas the closely related MDR3 and mdr2 do not.…”

P‐glycoproteins encoded by mdr 1b in murine gravid uterus and multidrug resistant tumor cell lines are differentially glycosylated

“…130 and 140 kDa, respectively, when the oligosaccharides are processed to complex-type sugar [6,7]. The mature protein is also phosphorylated [8-111. In mouse, 3 genes comprising this multigene family have been identified [2-51 and have been designated mdrl [2], mdr2 [3] and mdr3 [4]. mdrl and mdr3, also known as mdrlb and mdrla [5], respectively, have been associated with the multidrug-resistance phenotype [2,5].…”