Cloning of cDNAs encoding multidrug-resistance (MDR) associated, P-glycoprotein related protein (mini-P-glycoprotein) overexpressed in murine MDR cells.

根据先前的报道，最初在多药耐药(MDR)小鼠细胞系中发现了一种约65 kDa的细胞蛋白，命名为mini-P-糖蛋白(PGP_&lt；mini&gt；)。在这些研究中，Pgp_&lt；mini&gt；被认为与P-糖蛋白(P-gp)具有相同的抗原表位和一些核苷酸序列，该蛋白的表达增加与MDR水平有关，尽管与P-gp相反，Pgp_&lt；mini&gt；既没有糖基化也没有磷酸化。在本研究中，我们还证明了一些人MDR细胞过度表达Pgp；mini&gt；以及P-gp。此外，我们从一个高度耐多药的小鼠细胞系构建了一个入lambdagt10的cDNA文库，并通过改进的差异杂交筛选，我们已经鉴定了编码Pgp_&lt；mini&gt；的cDNA克隆。亚克隆入质粒载体后，我们对它们进行测序。序列同源性搜索表明，该基因与P-gp，尤其是mdr1a的关系最为密切。为了阐明这一功能，目前正在进行克隆产生针对Pgp_1；mini&gt；的单抗的杂交瘤细胞，并将其导入药物敏感细胞中表达。

As reported previously, an approximately 65 kDa cellular protein, designated mini-P-glycoprotein (Pgp_<mini>), was originally identified in multidrug resistant (MDR) murine cell lines. In those studies, the Pgp_<mini> was suggested to share both an antigen epitope and some nucleotide sequences with P-glycoprotein (P-gp), and increased expression of this protein was found to be correlated with the level of MDR,although, in contrast to the P-gp, Pgp_<mini> was neither glycosylated nor phosphorylated. In the present study, we also demonstrated that some human MDR cells overexpress Pgp_<mini> as well as P-gp. Furthermore, we constructed a cDNA library from a highly MDR murine cell line into lambdagt10, and using a modified differential hybridization screening, we have identified cDNA clones which encode Pgp_<mini>. After the subcloning into plasmid vectors, we sequenced them. Sequence homology search of this gene shows it to be most closely related to P-gp, particularly mdrla. To clarify the function, works are currently underway to clone hybridomas producing monoclonal antibodies specific to Pgp_<mini> and to transfect with the cDNA into drug-sensitive cells to express it.