Multidrug resistance P-glycoprotein monoclonal antibody JSB-1 crossreacts with pyruvate carboxylaseVV Rao, DC Anthony and D Piwnica-Worms Laboratory of Molecular Radiopharmacology, Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA. Multidrug resistance (MDR) is associated with overexpression of a 170 KD plasma membrane P-glycoprotein (P-gp), a putative energy-dependent efflux transporter that reduces intracellular accumulation of chemotherapeutic agents. For detection of P-gp expression in normal and malignant tissues, an MDR1-specific monoclonal antibody (MAb) JSB-1 has been used extensively. In this report we show that MAb JSB-1 crossreacts with a protein of M(r) approximately 130,000 present in rat liver mitochondrial inner membrane/matrix fractions. Peptide mapping and microsequencing identify this protein as pyruvate carboxylase (PC), an abundant mitochondrial enzyme. MAb JSB-1 also crossreacts with purified PC from bovine liver. Under immunoblotting conditions, this crossreactivity is partially abolished by pre-incubation of MAb JSB-1 with a 1000-fold molar excess of MAb C494 epitope-specific peptide (PNTLEGN), indicating that the epitope of MAb JSB-1 may either overlap with or be in close proximity to that of MAb C494. Immunohistochemical cross-reactivity was also demonstrated in cryosections of human skeletal muscle, a tissue known not to express P-gp. MAb JSB-1 strongly immunostained Type 1 fibers, the subtype known to contain abundant mitochondria. Use of MAb JSB-1 for detection of MDR1 P-gp expression should be approached with caution.
Volume 43,
Issue 12,
pp. 1187-1192,
12/01/1995
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P. S. Rao, R. Govindarajan, K. B. Mallya, W. West, and U. S. Rao Characterization of a New Antibody Raised against the NH2 Terminus of P-Glycoprotein Clin. Cancer Res., August 15, 2005; 11(16): 5833 - 5839. [Abstract] [Full Text] [PDF] |
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J. S. Wunder, S. B. Bull, V. Aneliunas, P. D. Lee, A. M. Davis, C. P. Beauchamp, E. U. Conrad, R. J. Grimer, J. H. Healey, M. J. Rock, et al. MDR1 Gene Expression and Outcome in Osteosarcoma: A Prospective, Multicenter Study J. Clin. Oncol., July 14, 2000; 18(14): 2685 - 2694. [Abstract] [Full Text] [PDF] |
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S. Barg, E. Renstrom, P.-O. Berggren, A. Bertorello, K. Bokvist, M. Braun, L. Eliasson, W. E. Holmes, M. Kohler, P. Rorsman, et al. The stimulatory action of tolbutamide on Ca2+-dependent exocytosis in pancreatic beta cells is mediated by a 65-kDa mdr-like P-glycoprotein PNAS, May 11, 1999; 96(10): 5539 - 5544. [Abstract] [Full Text] [PDF] |
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