An anti-CD19 antibody inhibits the interaction between P-glycoprotein (P-gp) and CD19, causes P-gp to translocate out of lipid rafts, and chemosensitizes a multidrug-resistant (MDR) lymphoma cell line.
We have previously demonstrated that an anti-CD19 monoclonal antibody (MAb; HD37) inhibits the function of the P-glycoprotein (P-gp) pump in a multidrug-resistant (MDR) B-lymphoma cell line, Namalwa/MDR1, and that this effect is not due to the recognition of a cross-reactive epitope on P-gp. In this study, we have used the same cell line to define the mechanisms responsible for the effect of HD37 on the P-gp pump. Using fluorescence resonance energy transfer (FRET), we show that CD19 and P-gp are constitutively associated in cells. In the absence of treatment with anti-CD19, 40% of P-gp molecules expressed by Namalwa/MDR1 cells reside in the low-density lipid (ie, cholesterol-rich) microdomains (lipid rafts). Following treatment of the cells with HD37 and disruption of the interactions between P-gp and CD19, P-gp translocated out of lipid rafts and CD19 translocated into lipid rafts. The effect of chemosensitization on Namalwa/MDR1 cells was specific for CD19; an anti-CD22 MAb had no such effect, although the cells express CD22. These results suggest that anti-CD19 might chemosensitize P-gp(+) cells by interfering with interactions between CD19 and P-gp, rapidly resulting in the translocation of P-gp into a compartment on the plasma membrane where it is no longer active.
Cancer Immunobiology Center, University of Texas Southwestern Medical Center at Dallas, 75390, USA.
Maria-Ana
MA
Ghetie
Radu
R
Marches
Stephanie
S
Kufert
Ellen S
ES
Vitetta
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology*; D018941:Antigens, CD19 / Q000276:immunology* / Q000378:metabolism*; D002051:Burkitt Lymphoma / Q000188:drug therapy / Q000378:metabolism*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects / Q000276:immunology; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D005677:G(M1) Ganglioside / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D021962:Membrane Microdomains / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D020112:Rhodamine 123 / Q000378:metabolism
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000911:Antibodies, Monoclonal; D018941:Antigens, CD19; D020112:Rhodamine 123; D005677:G(M1) Ganglioside