The development of the nervous system is a temporally and spatially coordinated process that relies on the proper regulation of the genes involved. Neurotrophins and their receptors are directly responsible for the survival and differentiation of sensory and sympathetic neurons; however, it is not fully understood how genes encoding Trk neurotrophin receptors are regulated. Here, we show that rat Bex3 protein specifically regulates TrkA expression by acting at thetrkAgene promoter level. Bex3 dimerization and shuttling to the nucleus regulate the transcription of thetrkApromoter under basal conditions and also enhance nerve growth factor (NGF)-mediatedtrkApromoter activation. Moreover, qChIP assays indicate that Bex3 associates with thetrkApromoter within a 150 bp sequence, immediately upstream from the transcription start site, which is sufficient to mediate the effects of Bex3. Consequently, the downregulation of Bex3 using shRNA increases neuronal apoptosis in NGF-dependent sensory neurons deprived of NGF and compromises PC12 cell differentiation in response to NGF. Our results support an important role for Bex3 in the regulation of TrkA expression and in NGF-mediated functions through modulation of thetrkApromoter.

Ubiquitylation of receptor tyrosine kinases (RTKs) regulates both the levels and functions of these receptors. The neurotrophin receptor TrkB (also known as NTRK2), a RTK, is ubiquitylated upon activation by brain-derived neurotrophic factor (BDNF) binding. Although TrkB ubiquitylation has been demonstrated, there is a lack of knowledge regarding the precise repertoire of proteins that regulates TrkB ubiquitylation. Here, we provide mechanistic evidence indicating that ubiquitin carboxyl-terminal hydrolase 8 (USP8) modulates BDNF- and TrkB-dependent neuronal differentiation. USP8 binds to the C-terminus of TrkB using its microtubule-interacting domain (MIT). Immunopurified USP8 deubiquitylates TrkB in vitro, whereas knockdown of USP8 results in enhanced ubiquitylation of TrkB upon BDNF treatment in neurons. As a consequence of USP8 depletion, TrkB levels and its activation are reduced. Moreover, USP8 protein regulates the differentiation and correct BDNF-dependent dendritic formation of hippocampal neurons in vitro and in vivo. We conclude that USP8 positively regulates the levels and activation of TrkB, modulating BDNF-dependent neuronal differentiation. This article has an associated First Person interview with the first author of the paper.

Ubiquitination of the TrkA neurotrophin receptor in response to NGF is critical in the regulation of TrkA activation and its functions. TrkA is ubiquitinated among other E3 ubiquitin ligases by Nedd4-2. To understand mechanistically how TrkA ubiquitination is regulated, we performed a siRNA screening to identify deubiquitinating enzymes and found that USP36 acts as an important regulator of TrkA activation kinetics and ubiquitination. However, USP36 action on TrkA was indirect since it does not deubiquitinate TrkA. Instead, USP36 binds to Nedd4-2 and regulates the association of TrkA and Nedd4-2. In addition, depletion of USP36 increases TrkA-Nedd4-2 complex formation whereas USP36 expression disrupts the complex resulting in an enhancement or impairment of Nedd4-2-dependent TrkA ubiquitination, respectively. Moreover, USP36 depletion leads to enhanced total and surface TrkA expression that results in increased NGF-mediated TrkA activation and signalling that augments PC12 cell differentiation. USP36 actions extend beyond TrkA since the presence of USP36 interferes with Nedd4-2-dependent Kv7.2/3 channel regulation. Our results demonstrate that USP36 binds to and regulates the actions of Nedd4-2 over different substrates affecting their expression and functions.

This multicenter study sponsored by the GETH-TC investigates the incidence and predictors of early (first 100 days) and late cardiac events (CEs; ECEs and LCEs, respectively) after allo-HCT in patients with acute myeloid leukemia (AML) treated with anthracyclines, focusing on exploring the impact of PTCY on cardiac complications and the impact of CEs on OS and NRM. A total of 1020 patients with AML were included. PTCY was given to 450 (44.1%) adults. Overall, 94 (9.2) patients experienced CEs, with arrythmias, pericardial complications, and heart failure the most prevalent. ECEs occurred in 49 (4.8%) patients within a median of 13 days after allo-HCT, whereas LCEs were diagnosed in 45 (4.4%) patients within a median of 3.6 years after transplant. Using PTCY increased the risk for ECEs in multivariate analysis (hazard ratio [HR], 2.86; P = .007) but did not significantly affect the risk for LCEs (HR, 1.06; P = .892). The impact of variables on outcomes revealed was investigated using multivariate regression analyses and revealed that the diagnosis of CEs decreased the likelihood of OS (HR, 1.66; P = .005) and increased the likelihood of NRM (HR, 2.88; P < .001). Furthermore, despite using PTCY increased ECEs risk, its administration was beneficial for OS (HR, 0.71; P = .026). In conclusion, although the incidence of CEs was relatively low, it significantly affected mortality. Standard doses of PTCY increased ECE risk but were associated with improved OS. Therefore, protocols for preventing cardiac complications among these patients are needed.

Background: Post-transplant cyclophosphamide (PTCy) is a standard graft-versus-host disease (GVHD) prophylaxis in allogeneic hematopoietic cell transplantation (allo-HCT). While effective, concerns remain about cyclophosphamide-related cardiotoxicity, especially in patients with pre-existing cardiac morbidity, a population often underrepresented in clinical trials. Objectives: To assess the incidence and outcomes of early (ECE, ≤100 days) and late (LCE, >100 days) cardiac events in acute myeloid leukemia (AML) patients with and without baseline cardiac morbidity undergoing allo-HCT with PTCy. Study Design: Retrospective multicenter study by the Grupo Español de Trasplante Hematopoyético y Terapia Celular (GETH-TC) including 461 AML patients (62 with cardiac morbidity) transplanted between 2012 and 2022. Cardiac morbidity was defined by documented cardiac disease or left ventricular ejection fraction < 45%. Cumulative incidence, overall survival (OS), and non-relapse mortality (NRM) were analyzed using competing risks models and adjusted with propensity score matching (PSM) and inverse probability weighting (IPW). Results: Cardiac events occurred in 13.2% of patients: 11% vs. 7% ECE (p = 0.93) and 8% vs. 5.3% LCE (p = 0.85) in those with vs. without cardiac morbidity. Most ECEs were arrhythmias or heart failure. Adjusted analyses confirmed no significant differences in CE incidence, OS, or NRM between groups. Two-year OS was 69% vs. 70% (p = 0.50); NRM was 18% vs. 17% (p = 0.20). ECE was associated with higher mortality in both groups. Conclusions: PTCy is feasible in AML patients with pre-existing cardiac morbidity when combined with comprehensive cardiovascular evaluation and cardio-oncology follow-up, supporting its safe use in broader patient populations with appropriate cardiologic support.