A New AHI-1-DNM2-BCR-ABL Complex Regulates Endocytosis Processes in Chronic Myeloid Leukemia
Bibliographic record
Abstract
Abstract Tyrosine kinase inhibitors (TKIs) have been introduced into clinical practice with remarkable effects on chronic phase CML. However, early relapses, acquired drug resistance, and persistence of leukemic stem cells remain problematic. Improved treatment approaches to target other key molecular elements active in CML stem/progenitor cells are needed. One candidate is AHI-1 (Abelson helper integration site-1), an oncogene that is highly deregulated in CML stem cells. It harbors two key domains, SH3 and WD40-repeat, which are known important mediators of protein-protein interactions. The AHI-1-mediated protein complex containing BCR-ABL and JAK2 has been shown to mediate transforming activity and TKI-response/resistance of CML stem/progenitor cells. We have recently identified Dynamin-2 (DNM2) as another AHI-1 interacting protein using the AHI-1 SH3 domain as protein ‘bait’ in immunoprecipitation/mass spectrometry. DNM2, a large GTPase, is mainly involved in the trafficking processes such as endocytosis, and is activated through tyrosine phosphorylation. Its role in the mediation of CML stem cell functions is unknown. We have now demonstrated that transcript levels of DNM2 are significantly increased in pre-treatment CD34+ stem/progenitor cells from CML patients who were classified retrospectively, after IM therapy, as IM-responders (n=11) and IM-nonresponders (n=15) as compared to CD34+ normal bone marrow cells (n=7, p=0.013 and 0.037). In addition, DNM2 is more highly expressed in CML stem cells (CD34+CD38-) and progenitor cells (CD34+CD38+) than more mature cells (CD34- , 2-fold). Co-immunopreciptation with mutant forms of AHI-1 and DNM2 (HA-AHI-1, HA-AHI-1 SH3Δ, Myc-DNM2 and Myc-DNM2 PRDΔ) in 293T cells indicated that the PRD domain of DNM2 is mainly responsible for the interaction between AHI-1 and DMN2. Co-localization analysis using confocal microscopy further demonstrated that the interaction between full-length AHI-1 and DNM2 occurs in a “punctate dot” pattern throughout the whole cytoplasm; in contrast, the co-localization signals were significantly disrupted in cells co-transfected with AHI-1 and DNM2 mutants. Interestingly, in AHI-1 SH3D mutant cells, AHI-1was located in the nucleus, suggesting that the SH3 domain of AHI-1 is required for AHI-1 cytoplasmic retention. Moreover, AHI-1 was observed to co-localize with EEA-1 (early endosome marker) and LAMP-1 (late endosome marker) in cells co-transfected with full-length AHI-1 and DNM2, but not in AHI-1 and DNM2 mutant cells. Increased transferrin signals were also demonstrated in AHI-1 and DNM2 co-transfected cells compared to their mutant cells, using transferrin uptake assays, suggesting that the interaction between DNM2 and AHI-1 indeed increases the kinetics and efficiency of endocytosis. These results were further confirmed in BCR-ABL-transduced and BCR-ABL/AHI-1 co-transduced hematopoietic cells that are relatively resistant to TKI-induced apoptosis. Particularly, the co-localization signals between DNM2 and AHI-1 were stronger in BCR-ABL/AHI-1 co-transduced cells, and the transferrin uptake was also more efficient as compared to BCR-ABL-transduced cells. On the other hand, transferrin uptake was reduced in CML cells with knockdown of DNM2 and these cells also demonstrated reduced proliferation and increased sensitivity to IM treatment compared to control cells. Importantly, we further identified a new protein interaction between DNM2 and BCR-ABL in both BCR-ABL and BCR-ABL/AHI-1 co-transduced cells and this interaction is enhanced in BCR-ABL/AHI-1 co-transduced cells using co-IP/Western analysis. To the best of our knowledge, this is the first study to implicate this new AHI-1-DNM2-BCR-ABL complex in the deregulation of endocytosis signaling in CML, which may play an unusual role in regulation of the cellular properties of primitive CML cells, including their response/resistance to TKI, by aberrantly disrupting critical endocytosis processes in CML. Disclosures No relevant conflicts of interest to declare.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".