Phosphorylation of the multidrug resistance associated glycoprotein

Wilfredo Mellado, Susan Band Horwitz

Research output: Contribution to journalArticle

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Abstract

Drug-resistant cell lines derived from the mouse macrophage-like cell line J774.2 express the multidrug resistant phenotype which includes the overexpression of a membrane glycoprotein (130-140 kilodaltons). Phosphorylation of this resistant-specific glycoprotein (P-glycoprotein) in intact cells and in cell-free membrane fractions has been studied. The phosphorylated glycoprotein can be immunoprecipitated by a rabbit polyclonal antibody specific for the glycoprotein. Phosphorylation studies done with partially purified membrane fractions derived from colchicine-resistant cells indicated that (a) phosphorylation of the glycoprotein in 1 mM MgCl2 was enhanced a minimum of 2-fold by 10 μM cAMP and (b) the purified catalytic subunit of the cAMP-dependent protein kinase (protein kinase A) phosphorylated partially purified glycoprotein that was not phosphorylated by [γ-32P]ATP alone, suggesting that autophosphorylation was not involved. These results indicate that the glycoprotein is a phosphoprotein and that at least one of the kinases responsible for its phosphorylation is a membrane-associated protein kinase A. The state of phosphorylation of the glycoprotein, which is a major component of the multidrug resistance phenotype, may be related to the role of the glycoprotein in maintaining drug resistance.

Original languageEnglish (US)
Pages (from-to)6900-6904
Number of pages5
JournalBiochemistry
Volume26
Issue number22
StatePublished - 1987

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Phosphorylation
Multiple Drug Resistance
Glycoproteins
Cyclic AMP-Dependent Protein Kinases
Cells
Membranes
Phenotype
Cell Line
Magnesium Chloride
Macrophages
Phosphoproteins
Membrane Glycoproteins
Colchicine
Drug Resistance
Pharmaceutical Preparations
Catalytic Domain
Membrane Proteins
Phosphotransferases
Adenosine Triphosphate
Cell Membrane

ASJC Scopus subject areas

  • Biochemistry

Cite this

Phosphorylation of the multidrug resistance associated glycoprotein. / Mellado, Wilfredo; Band Horwitz, Susan.

In: Biochemistry, Vol. 26, No. 22, 1987, p. 6900-6904.

Research output: Contribution to journalArticle

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