An unexpected protein interaction promotes drug resistance in leukemia

Abstract

The overall survival of patients with acute myeloid leukemia (AML) is poor and identification of new disease-related therapeutic targets remains a major goal for this disease. Here we show that expression of MPP1, a PDZ-domain-containing protein, highly correlated with ABCC4 in AML, is associated with worse overall survival in AML. Murine hematopoietic progenitor cells overexpressing MPP1 acquired the ability to serially replate in methylcellulose culture, a property crucially dependent upon ABCC4. The highly conserved PDZ-binding motif of ABCC4 is required for ABCC4 and MPP1 to form a protein complex, which increased ABCC4 membrane localization and retention, to enhance drug resistance. Specific disruption of this protein complex, either genetically or chemically, removed ABCC4 from the plasma membrane, increased drug sensitivity, and abrogated MPP1-dependent hematopoietic progenitor cell replating in methylcellulose. High-throughput screening identified Antimycin A as a small molecule that disrupted the ABCC4–MPP1 protein complex and reversed drug resistance in AML cell lines and in primary patient AML cells. In all, targeting the ABCC4–MPP1 protein complex can lead to new therapies to improve treatment outcome of AML, a disease where the long-term prognosis is poor.

Structural basis for substrate recognition and chemical inhibition of oncogenic MAGE ubiquitin ligases

“…TR-FRET screen for identifying MAGE-A11 small molecule inhibitors was performed as follows. The primary one-concentration screening and subsequent 10 or 20-concentration dose-response tests were accomplished with an automated High Throughput Screening system (HighRes Biosolutions, Beverly, MA) 30 . In the primary screening, 15 µl/well FAM-PCF11_4 (267 nM) was first dispensed with a Multidrop Combi Reagent Dispenser (Thermo Fisher Scientific, Waltham, MA) to black 384-well low-volume assay plates.…”

A high-throughput screening identifies histone deacetylase inhibitors as therapeutic agents against medulloblastoma

“…Examples include pitavastatin, which has an IC 50 value of 84 nM. The general screening process and data analysis have been previously described [12–15].…”

MPP1-based mechanism of resting state raft organization in the plasma membrane. Is it a general or specialized mechanism in erythroid cells?

“…It is also interesting that MPP1 is highly www.fhc.viamedica.pl abundant in AML (acute myeloid leukemia) cells, and interacts with the ABC transporter, ABCC4. The studies by Pitre et al [52] showed that the expression of MPP1 highly correlated with ABCC4 expression in AML, and moreover, it was also associated with poor prognosis for AML patients. The authors carried out an assessment of all PDZ-binding domain proteins on the oligonucleotide microarray with samples from the diagnostic leukemic blasts of 130 pediatric AML patients.…”

“…Furthermore, MPP1 regulates ABCC4 plasma membrane location and affects stability of ABCC4. Further research of this group indicated that this protein interaction is readily disrupted by a small molecule, antimycin A [52].…”