Latency-Associated Degradation of the MRP1 Drug Transporter During Latent Human Cytomegalovirus Infection

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Science  12 Apr 2013:
Vol. 340, Issue 6129, pp. 199-202
DOI: 10.1126/science.1235047

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Human cytomegalovirus (HCMV) establishes latent infection in human progenitor dendritic cells, causing significant morbidity and mortality on reactivation, which may occur in transplantation patients who are immunosuppressed. Neither detection nor selective removal of rare latent HCMV-infected cells has been possible. Weekes et al. (p. 199) have found that the multidrug-resistant ABC transporter, multidrug resistance–associated protein-1 (MRP1) is down-regulated during latent HCMV infection. Consequently, cytotoxic MRP1-specific substrates are not exported from HCMV-infected cells and accumulate—leading to cell death, which could potentially provide a mechanism for eliminating infected cells prior to transplantation.


The reactivation of latent human cytomegalovirus (HCMV) infection after transplantation is associated with high morbidity and mortality. In vivo, myeloid cells and their progenitors are an important site of HCMV latency, whose establishment and/or maintenance require expression of the viral transcript UL138. Using stable isotope labeling by amino acids in cell culture–based mass spectrometry, we found a dramatic UL138-mediated loss of cell surface multidrug resistance–associated protein-1 (MRP1) and the reduction of substrate export by this transporter. Latency-associated loss of MRP1 and accumulation of the cytotoxic drug vincristine, an MRP1 substrate, depleted virus from naturally latent CD14+ and CD34+ progenitors, all of which are in vivo sites of latency. The UL138-mediated loss of MRP1 provides a marker for detecting latent HCMV infection and a therapeutic target for eliminating latently infected cells before transplantation.

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