PP2A mediates apoptosis or autophagic cell death in multiple myeloma cell lines

Mechanism of DAPK1 for Regulating Cancer Stem Cells in Thyroid Cancer

Death-associated protein kinase 1 (DAPK1) is a calcium/calmodulin (Ca2+/CaM)-dependent serine/threonine (Ser/Thr) protein kinase and is characteristically downregulated in metastatic cancer. Several studies showed that DAPK1 is involved in both the early and late stages of cancer. DAPK1 downregulation is elaborately controlled by epigenetic, transcriptional, posttranscriptional, and posttranslational processes. DAPK1 is known to regulate not only cancer cells but also stromal cells. Recent studies showed that DAPK1 was involved not only in tumor suppression but also in epithelial-mesenchymal transition (EMT) and cancer stem cell (CSC) formation in colon and thyroid cancers. CSCs are major factors in determining cancer aggressiveness in cancer metastasis and treatment prognosis by influencing EMT. However, the molecular mechanism involved in the regulation of cancer cells by DAPK1 remains unclear. In particular, little is known about the existence of CSCs and how they are regulated in papillary thyroid carcinoma (PTC) among thyroid cancers. In this review, we describe the molecular mechanism of CSC regulation by DAPK1 in PTC progression.

Autophagy-related mechanisms for treatment of multiple myeloma

Multiple myeloma (MM) is a type of hematological cancer that occurs when B cells become malignant. Various drugs such as proteasome inhibitors, immunomodulators, and compounds that cause DNA damage can be used in the treatment of MM. Autophagy, a type 2 cell death mechanism, plays a crucial role in determining the fate of B cells, either promoting their survival or inducing cell death. Therefore, autophagy can either facilitate the progression or hinder the treatment of MM disease. In this review, autophagy mechanisms that may be effective in MM cells were covered and evaluated within the contexts of unfolded protein response (UPR), bone marrow microenvironment (BMME), drug resistance, hypoxia, DNA repair and transcriptional regulation, and apoptosis. The genes that are effective in each mechanism and research efforts on this subject were discussed in detail. Signaling pathways targeted by new drugs to benefit from autophagy in MM disease were covered. The efficacy of drugs that regulate autophagy in MM was examined, and clinical trials on this subject were included. Consequently, among the autophagy mechanisms that are effective in MM, the most suitable ones to be used in the treatment were expressed. The importance of 3D models and microfluidic systems for the discovery of new drugs for autophagy and personalized treatment was emphasized. Ultimately, this review aims to provide a comprehensive overview of MM disease, encompassing autophagy mechanisms, drugs, clinical studies, and further studies.

Novel Cellular Functions of ATR for Therapeutic Targeting: Embryogenesis to Tumorigenesis

The DNA damage response (DDR) is recognized as having an important role in cancer growth and treatment. ATR (ataxia telangiectasia mutated and Rad3-related) kinase, a major regulator of DDR, has shown significant therapeutic potential in cancer treatment. ATR inhibitors have shown anti-tumor effectiveness, not just as monotherapies but also in enhancing the effects of standard chemotherapy, radiation, and immunotherapy. The biological basis of ATR is examined in this review, as well as its functional significance in the development and therapy of cancer, and the justification for inhibiting this target as a therapeutic approach, including an assessment of the progress and status of previous decades' development of effective and selective ATR inhibitors. The current applications of these inhibitors in preclinical and clinical investigations as single medicines or in combination with chemotherapy, radiation, and immunotherapy are also fully reviewed. This review concludes with some insights into the many concerns highlighted or identified with ATR inhibitors in both the preclinical and clinical contexts, as well as potential remedies proposed.

Quantum-based modeling implies that bidentate Arg89-substrate binding enhances serine/threonine protein phosphatase-2A(PPP2R5D/PPP2R1A/PPP2CA)-mediated dephosphorylation

PP2A-serine/threonine protein phosphatases function as heterotrimeric holoenzymes, composed of a common scaffold (A-subunit encoded by PPP2R1A/PPP2R1B), a common catalytic (C-subunit encoded by PPP2CA/PPP2CB), and one of many variable regulatory (B) subunits. The site of phosphoprotein phosphatase (PPP) hydrolysis features a bimetal system (M₁/M₂), an associated bridge hydroxide [W¹(OH^-)], and a highly-conserved core sequence. In the presumptive common mechanism, the phosphoprotein's seryl/threonyl phosphate coordinates the M₁/M₂ system, W¹(OH^-) attacks the central P atom, rupturing the antipodal bond, and simultaneously, a histidine/aspartate tandem protonates the exiting seryl/threonyl alkoxide. Based on studies of PPP5C, a conserved arginine proximal to M₁ is also expected to bind the substrate's phosphate group in a bidentate fashion. However, in PP2A isozymes, the role of the arginine (Arg⁸⁹) in hydrolysis is not clear because two independent structures for PP2A(PPP2R5C) and PP2A(PPP2R5D) show that Arg⁸⁹ engages in a weak salt bridge at the B:C interface. These observations raise the question of whether hydrolysis proceeds with or without direct involvement of Arg⁸⁹. The interaction of Arg⁸⁹ with B:Glu¹⁹⁸ in PP2A(PPP2R5D) is significant because the pathogenic E198K variant of B56δ is associated with irregular protein phosphorylation levels and consequent developmental disorders (Jordan's Syndrome; OMIM #616355). In this study, we perform quantum-based hybrid [ONIOM(UB3LYP/6-31G(d):UPM7)] calculations on 39-residue models of the PP2A(PPP2R5D)/pSer (phosphoserine) system to estimate activation barriers for hydrolysis in the presence of bidentate Arg⁸⁹-substrate binding and when Arg⁸⁹ is otherwise engaged in the salt-bridge interaction. Our solvation-corrected results yield ΔH^‡ ≈ ΔE^‡ = +15.5 kcal/mol for the former case, versus +18.8 kcal/mol for the latter, indicating that bidentate Arg⁸⁹-substrate binding is critical for optimal catalytic function of the enzyme. We speculate that PP2A(PPP2R5D) activity is suppressed by B:Glu¹⁹⁸ sequestration of C:Arg⁸⁹ under native conditions, whereas the PP2A(PPP2R5D)-holoenzyme containing the E198K variant has a positively-charged lysine in this position that alters normal function.

Targeting Death-Associated Protein Kinases for Treatment of Human Diseases: Recent Advances and Future Directions

The death-associated protein kinase (DAPK) family is a member of the calcium/calmodulin-regulated serine/threonine protein kinase family, and studies have shown that its role, as its name suggests, is mainly to regulate cell death. The DAPK family comprises five members, including DAPK1, DAPK2, DAPK3, DRAK1 and DRAK2, which show high homology in the common N-terminal kinase domain but differ in the extra-catalytic domain. Notably, previous research has suggested that the DAPK family plays an essential role in both the development and regulation of human diseases. However, only a few small-molecule inhibitors have been reported. In this Perspective, we mainly discuss the structure, biological function, and role of DAPKs in diseases and the currently discovered small-molecule inhibitors, providing valuable information for the development of the DAPK field.

Analysis of Huntington's Disease Modifiers Using the Hyperbolic Mapping of the Protein Interaction Network

Huntington's disease (HD) is caused by the production of a mutant huntingtin (HTT) with an abnormally long poly-glutamine (polyQ) tract, forming aggregates and inclusions in neurons. Previous work by us and others has shown that an increase or decrease in polyQ-triggered aggregates can be passive simply due to the interaction of proteins with the aggregates. To search for proteins with active (functional) effects, which might be more effective in finding therapies and mechanisms of HD, we selected among the proteins that interact with HTT a total of 49 pairs of proteins that, while being paralogous to each other (and thus expected to have similar passive interaction with HTT), are located in different regions of the protein interaction network (suggesting participation in different pathways or complexes). Three of these 49 pairs contained members with opposite effects on HD, according to the literature. The negative members of the three pairs, MID1, IKBKG, and IKBKB, interact with PPP2CA and TUBB, which are known negative factors in HD, as well as with HSP90AA1 and RPS3. The positive members of the three pairs interact with HSPA9. Our results provide potential HD modifiers of functional relevance and reveal the dynamic aspect of paralog evolution within the interaction network.

Downregulation of NCL attenuates tumor formation and growth in HeLa cells by targeting the PI3K/AKT pathway

BACKGROUND

Nucleolin (NCL, C23) is a multifunctional phosphoprotein that plays a vital role in modulating the survival, proliferationand apoptosis of cancer cells. However, the effects of NCL on cervical cancer and the underlying mechanisms behind this are poorly understood.

METHODS

Lentiviral transfection technology was used to construct NCL knockdown cell lines. MTT, colony formation assays, and tumorigenic assays in vivo were performed to observe cell proliferation. HOECHST 33342 staining, flow cytometry, and caspase activity assay were used to test cell apoptosis. RNA-Seq, Western blotting, and RT-PCR were conducted to investigate the specific molecular mechanism.

RESULTS

NCL knockdown inhibited cell proliferation and promoted apoptosis both in vivo and in vitro. Mechanistic studies revealed that NCL knockdown inhibited the PI3K/AKT pathway by upregulating FGF, ITGA, TNXB, VEGF, Caspase 3, and Bax, as well as by downregulating AKT, GNB4, CDK6, IL6R, LAMA, PDGFD, PPP2RSA and BCL-2. In addition, the expression levels of apoptosis-related genes after using a PI3K inhibitor LY294002 were consistent with shRNA studies, while treatment with a 740Y-P agonist showed the opposite effect.

CONCLUSIONS

Our findings indicate that downregulation of NCL may be a novel treatment strategy forcervical cancer.

Diane-35 and Metformin Induce Autophagy and Apoptosis in Polycystic Ovary Syndrome Women with Early-Stage Endometrial Carcinoma

Objective: Women with polycystic ovary syndrome (PCOS) are at increased risk ofendometrial carcinoma (EC). Previous studies indicated that the combined therapy of Diane-35 and metformin significantly suppresses disease progression in PCOS patients with early EC; however, the mechanisms remain unclear. Methods: An established murine model of PCOS with early EC, clinical specimens, and human EC cells was used in this study. The levels of protein and mRNA were measured with Western blotting and RT-PCR, respectively. Cell proliferation was determined with MTT, colony formation, and flow cytometry. Proteins were analyzed with immunofluorescence and immunohistochemistry. Results: Diane-35 and metformin significantly inhibited proliferative activity and promoted apoptosis in EC cells. Additionally, cell autophagy was induced by the combined therapy. Quantitive PCR revealed that Diane-35 and metformin decreased androgen receptor (AR) expression but elevated GLUT4 expression. AR was found to repress GLUT4 expression by binding to the promoter of GLUT4. Moreover, the combined treatment mediated the onset of cellular autophagy by regulating the mTORC pathway via the suppression of IGF-1 and inhibited the development of EC by the activation of the PI3K/mTORC pathway. Conclusion: The results and previous clinical evidence support the use of Diane-35 and metformin combination therapy for patients with PCOS and early EC.

Vorinostat in autophagic cell death: A critical insight into autophagy-mediated, -associated and -dependent cell death for cancer prevention

Histone deacetylases (HDACs) inhibit the acetylation of crucial autophagy genes, thereby deregulating autophagy and autophagic cell death (ACD) and facilitating cancer cell survival. Vorinostat, a broad-spectrum pan-HDAC inhibitor, inhibits the deacetylation of key autophagic markers and thus interferes with ACD. Vorinostat-regulated ACD can have an autophagy-mediated, -associated or -dependent mechanism depending on the involvement of apoptosis. Molecular insights revealed that hyperactivation of the PIK3C3/VPS34-BECN1 complex increases lysosomal disparity and enhances mitophagy. These changes are followed by reduced mitochondrial biogenesis and by secondary signals that enable superactivated, nonselective or bulk autophagy, leading to ACD. Although the evidence is limited, this review focuses on molecular insights into vorinostat-regulated ACD and describes critical concepts for clinical translation.

Cellular Protein Phosphatase 2A Regulates Cell Survival Mechanisms in Influenza A Virus Infection

Influenza A viruses (IAVs) are respiratory pathogens that are able to hijack multiple cellular mechanisms to drive their replication. Consequently, several viral and cellular proteins undergo posttranslational modifications such as dynamic phosphorylation/dephosphorylation. In eukaryotic cells, dephosphorylation is mainly catalyzed by protein phosphatase 2A (PP2A). While the function of kinases in IAV infection is quite well studied, only little is known about the role of PP2A in IAV replication. Here, we show, by using knockdown and inhibition approaches of the catalytic subunit PP2Ac, that this phosphatase is important for efficient replication of several IAV subtypes. This could neither be attributed to alterations in the antiviral immune response nor to changes in transcription or translation of viral genes. Interestingly, decreased PP2Ac levels resulted in a significantly reduced cell viability after IAV infection. Comprehensive kinase activity profiling identified an enrichment of process networks related to apoptosis and indicated a synergistic action of hyper-activated PI3K/Akt, MAPK/JAK-STAT and NF-kB signaling pathways, collectively resulting in increased cell death. Taken together, while IAV seems to effectively tap leftover PP2A activity to ensure efficient viral replication, reduced PP2Ac levels fail to orchestrate cell survival mechanisms to protect infected cells from early cell death.

5,6-Epoxycholesterol Isomers Induce Oxiapoptophagy in Myeloma Cells

Simple Summary

As the second most frequent hematological malignancy, multiple myeloma remains incurable with recurrent patient relapse due to drug resistance. Therefore, the development of novel and potent therapies is urgently required. Herein, we demonstrated the anti-tumor activity of 5,6 α- and 5,6 β-epoxycholesterol isomers against human myeloma cells. Our results highlighted a striking anti-myeloma efficiency of these bioactive molecules and their added value in future potential treatments including combination therapy of multiple myeloma.

Abstract

Multiple myeloma (MM) is an incurable plasma cell malignancy with frequent patient relapse due to innate or acquired drug resistance. Cholesterol metabolism is reported to be altered in MM; therefore, we investigated the potential anti-myeloma activity of two cholesterol derivatives: the 5,6 α- and 5,6 β-epoxycholesterol (EC) isomers. To this end, viability assays were used, and isomers were shown to exhibit important anti-tumor activity in vitro in JJN3 and U266 human myeloma cell lines (HMCLs) and ex vivo in myeloma patients’ sorted CD138+ malignant cells. Moreover, we confirmed that 5,6 α-EC and 5,6 β-EC induced oxiapoptophagy through concomitant oxidative stress and caspase-3-mediated apoptosis and autophagy. Interestingly, in combination treatment a synergistic interaction was observed between 5,6 α-EC and 5,6 β-EC on myeloma cells. These data highlight a striking anti-tumor activity of 5,6 α-EC and 5,6 β-EC bioactive molecules against human myeloma cells, paving the way for their potential role in future therapeutic strategies in MM.

Multiple Myeloma Inhibitory Activity of Plant Natural Products

A literature search on plant natural products with antimyeloma activity until the end of 2020 resulted in 92 compounds with effects on at least one human myeloma cell line. Compounds were divided in different compound classes and both their structure-activity-relationships as well as eventual correlations with the pathways described for Multiple Myeloma were discussed. Each of the major compound classes in this review (alkaloids, phenolics, terpenes) revealed interesting candidates, such as dioncophyllines, a group of naphtylisoquinoline alkaloids, which showed pronounced and selective induction of apoptosis when substituted in position 7 of the isoquinoline moiety. Interestingly, out of the phenolic compound class, two of the most noteworthy constituents belong to the relatively small subclass of xanthones, rendering this group a good starting point for possible further drug development. The class of terpenoids also provides noteworthy constituents, such as the highly oxygenated diterpenoid oridonin, which exhibited antiproliferative effects equal to those of bortezomib on RPMI8226 cells. Moreover, triterpenoids containing a lactone ring and/or quinone-like substructures, e.g., bruceantin, whitaferin A, withanolide F, celastrol, and pristimerin, displayed remarkable activity, with the latter two compounds acting as inhibitors of both NF-κB and proteasome chymotrypsin-like activity.

Chlorpromazine, an antipsychotic agent, induces G2/M phase arrest and apoptosis via regulation of the PI3K/AKT/mTOR-mediated autophagy pathways in human oral cancer

Chlorpromazine (CPZ), an FDA-approved phenothiazine derivative used to treat schizophrenia and other psychiatric disorders, has been demonstrated to have potential anti-tumor effects. However, the potential effects of CPZ on human oral cancer cells and the underlying molecular mechanisms remain unknown. In this study, treatment of human oral cancer cells with CPZ inhibited their proliferation and induced G2/M phase arrest. Treatment with CPZ induced apoptosis through the extrinsic death receptor and the intrinsic mitochondrial pathways. In addition, the induction of autophagy was observed by the formation of autophagosomes, the expression of autophagy-related proteins and activation of the PI3K/Akt/mTOR/p70S6K pathway. The CPZ-induced cell death was reversed by the pan-caspase inhibitor Z-VAD-FMK, by the autophagy inhibitor 3-MA and by the knockdown of LC3B using a shRNA (shLC3B), suggesting that autophagy promoted CPZ-induced apoptosis. Finally, CPZ significantly suppressed tumor growth in both a zebrafish oral cancer xenotransplantation model and in a murine model of 4-nitroquinoline-1-oxide (4NQO)-induced oral cancer. Overall, this evidence demonstrated that CPZ is a novel promising strategy for the treatment of oral cancer.

A disorder-related variant (E420K) of a PP2A-regulatory subunit (PPP2R5D) causes constitutively active AKT-mTOR signaling and uncoordinated cell growth

Functional genomic approaches have facilitated the discovery of rare genetic disorders and improved efforts to decipher their underlying etiology. PPP2R5D-related disorder is an early childhood onset condition characterized by intellectual disability, hypotonia, autism-spectrum disorder, macrocephaly, and dysmorphic features. The disorder is caused by de novo single nucleotide changes in PPP2R5D, which generate heterozygous dominant missense variants. PPP2R5D is known to encode a B'-type (B'56δ) regulatory subunit of a PP2A-serine/threonine phosphatase. To help elucidate the molecular mechanisms altered in PPP2R5D-related disorder, we used a CRISPR-single-base editor to generate HEK-293 cells in which a single transition (c.1258G>A) was introduced into one allele, precisely recapitulating a clinically relevant E420K variant. Unbiased quantitative proteomic and phosphoproteomic analyses of endogenously expressed proteins revealed heterozygous-dominant changes in kinase/phosphatase signaling. These data combined with orthogonal validation studies revealed a previously unrecognized interaction of PPP2R5D with AKT in human cells, leading to constitutively active AKT-mTOR signaling, increased cell size, and uncoordinated cellular growth in E420K-variant cells. Rapamycin reduced cell size and dose-dependently reduced RPS6 phosphorylation in E420K-variant cells, suggesting that inhibition of mTOR1 can suppress both the observed RPS6 hyperphosphorylation and increased cell size. Together, our findings provide a deeper understanding of PPP2R5D and insight into how the E420K-variant alters signaling networks influenced by PPP2R5D. Our comprehensive approach, which combines precise genome editing, isobaric tandem mass tag labeling of peptides generated from endogenously expressed proteins, and concurrent liquid chromatography-mass spectrometry (LC-MS³), also provides a roadmap that can be used to rapidly explore the etiologies of additional genetic disorders.

Challenges and Therapeutic Opportunities of Autophagy in Cancer Therapy

Simple Summary

Autophagy is a physiological process characterized by the degradation of the cell components through lysosomes due to stimuli/stress. In this study, we review the challenges and therapeutic opportunities that autophagy presents in the treatment of cancer. We discussed the results of several studies that evaluated autophagy as a therapeutic strategy in cancer, both through the modulation of therapeutic resistance and the death of cancer cells. Moreover, we discussed the role of autophagy in the biology of cancer stem cells and the inhibition of this process as a strategy to overcome resistance and progression of cancer stem cells.

Abstract

Autophagy is a physiological cellular process that is crucial for development and can occurs in response to nutrient deprivation or metabolic disorders. Interestingly, autophagy plays a dual role in cancer cells—while in some situations, it has a cytoprotective effect that causes chemotherapy resistance, in others, it has a cytotoxic effect in which some compounds induce autophagy-mediated cell death. In this review, we summarize strategies aimed at autophagy for the treatment of cancer, including studies of drugs that can modulate autophagy-mediated resistance, and/or drugs that cause autophagy-mediated cancer cell death. In addition, the role of autophagy in the biology of cancer stem cells has also been discussed.

PP2A Regulates Phosphorylation-Dependent Isomerization of Cytoplasmic and Mitochondrial-Associated ATR by Pin1 in DNA Damage Responses

Ataxia telangiectasia and Rad3-related protein (ATR) is a serine/threonine-protein kinase of the PI3K family and is well known for its key role in regulating DNA damage responses in the nucleus. In addition to its nuclear functions, ATR also was found to be a substrate of the prolyl isomerase Pin1 in the cytoplasm where Pin1 isomerizes cis ATR at the Ser428-Pro429 motif, leading to formation of trans ATR. Cis ATR is an antiapoptotic protein at mitochondria upon UV damage. Here we report that Pin1’s activity on cis ATR requires the phosphorylation of the S428 residue of ATR and describe the molecular mechanism by which Pin1-mediated ATR isomerization in the cytoplasm is regulated. We identified protein phosphatase 2A (PP2A) as the phosphatase that dephosphorylates Ser428 following DNA damage. The dephosphorylation led to an increased level of the antiapoptotic cis ATR (ATR-H) in the cytoplasm and, thus, its accumulation at mitochondria via binding with tBid. Inhibition or depletion of PP2A promoted the isomerization by Pin1, resulting in a reduction of cis ATR with an increased level of trans ATR. We conclude that PP2A plays an important role in regulating ATR’s anti-apoptotic activity at mitochondria in response to DNA damage. Our results also imply a potential strategy in enhancing cancer therapies via selective moderation of cis ATR levels.

Quantitative phosphoproteomics to unravel the cellular response to chemical stressors with different modes of action

Damage to cellular macromolecules and organelles by chemical exposure evokes activation of various stress response pathways. To what extent different chemical stressors activate common and stressor-specific pathways is largely unknown. Here, we used quantitative phosphoproteomics to compare the signaling events induced by four stressors with different modes of action: the DNA damaging agent: cisplatin (CDDP), the topoisomerase II inhibitor: etoposide (ETO), the pro-oxidant: diethyl maleate (DEM) and the immunosuppressant: cyclosporine A (CsA) administered at an equitoxic dose to mouse embryonic stem cells. We observed major differences between the stressors in the number and identity of responsive phosphosites and the amplitude of phosphorylation. Kinase motif and pathway analyses indicated that the DNA damage response (DDR) activation by CDDP occurs predominantly through the replication-stress-related Atr kinase, whereas ETO triggers the DDR through Atr as well as the DNA double-strand-break-associated Atm kinase. CsA shares with ETO activation of CK2 kinase. Congruent with their known modes of action, CsA-mediated signaling is related to down-regulation of pathways that control hematopoietic differentiation and immunity, whereas oxidative stress is the most prominent initiator of DEM-modulated stress signaling. This study shows that even at equitoxic doses, different stressors induce distinctive and complex phosphorylation signaling cascades.

Targeting Autophagy for Cancer Treatment and Tumor Chemosensitization

Autophagy is a tightly regulated catabolic process that facilitates nutrient recycling from damaged organelles and other cellular components through lysosomal degradation. Deregulation of this process has been associated with the development of several pathophysiological processes, such as cancer and neurodegenerative diseases. In cancer, autophagy has opposing roles, being either cytoprotective or cytotoxic. Thus, deciphering the role of autophagy in each tumor context is crucial. Moreover, autophagy has been shown to contribute to chemoresistance in some patients. In this regard, autophagy modulation has recently emerged as a promising therapeutic strategy for the treatment and chemosensitization of tumors, and has already demonstrated positive clinical results in patients. In this review, the dual role of autophagy during carcinogenesis is discussed and current therapeutic strategies aimed at targeting autophagy for the treatment of cancer, both under preclinical and clinical development, are presented. The use of autophagy modulators in combination therapies, in order to overcome drug resistance during cancer treatment, is also discussed as well as the potential challenges and limitations for the use of these novel therapeutic strategies in the clinic.

TAF-Iβ deficiency inhibits proliferation and promotes apoptosis by rescuing PP2A and inhibiting the AKT/GSK-3β pathway in leukemic cells

Template-activating factor Iβ (TAF-Iβ) has been associated with numerous pathophysiological processes and has been reported as an oncogene responsible for the regulation of important signaling pathways in various types of solid tumor; however, few studies have investigated the role of TAF-Iβ in leukemia. The present study reported the upregulated expression of TAF-Iβ in 36 patients with acute leukemia and six leukemic cell lines. In addition, TAF-Iβ-knockdown (KD) cells were generated via RNA interference. TAF-Iβ KD not only inhibited the proliferation of leukemia cells but also induced apoptosis. Furthermore, it was revealed that the mechanism underlying these effects may be associated with the upregulation of protein phosphatase type 2A and inhibition of the protein kinase B/glycogen synthase kinase-3β signaling pathway. Collectively, the findings demonstrated that TAF-Iβ serves an important role in various types of leukemia and may be considered as a potential therapeutic target for the treatment of leukemia.

Death-Associated Protein Kinase 1 Phosphorylation in Neuronal Cell Death and Neurodegenerative Disease

Regulated neuronal cell death plays an essential role in biological processes in normal physiology, including the development of the nervous system. However, the deregulation of neuronal apoptosis by various factors leads to neurodegenerative diseases such as ischemic stroke and Alzheimer’s disease (AD). Death-associated protein kinase 1 (DAPK1) is a calcium/calmodulin (Ca²⁺/CaM)-dependent serine/threonine (Ser/Thr) protein kinase that activates death signaling and regulates apoptotic neuronal cell death. Although DAPK1 is tightly regulated under physiological conditions, DAPK1 deregulation in the brain contributes to the development of neurological disorders. In this review, we describe the molecular mechanisms of DAPK1 regulation in neurons under various stresses. We also discuss the role of DAPK1 signaling in the phosphorylation-dependent and phosphorylation-independent regulation of its downstream targets in neuronal cell death. Moreover, we focus on the major impact of DAPK1 deregulation on the progression of neurodegenerative diseases and the development of drugs targeting DAPK1 for the treatment of diseases. Therefore, this review summarizes the DAPK1 phosphorylation signaling pathways in various neurodegenerative diseases.

To be or not to be: PP2A as a dual player in CNS functions, its role in neurodegeneration, and its interaction with brain insulin signaling

Accumulating evidence has reached the consensus that the balance of phosphorylation state of signaling molecules is a pivotal point in the regulation of cell signaling. Therefore, characterizing elements (kinases-phosphatases) in the phosphorylation balance are at great importance. However, the role of phosphatase enzymes is less investigated than kinase enzymes. PP2A is a member of serine/threonine protein phosphatase that its imbalance has been reported in neurodegenerative diseases. Therefore, we reviewed the superfamily of phosphatases and more specifically PP2A, its regulation, and physiological functions participate in CNS. Thereafter, we discussed the latest findings about PP2A dysregulation in Alzheimer and Parkinson diseases and possible interplay between this phosphatase and insulin signaling pathways. Finally, activating/inhibitory modulators for PP2A activity as well as experimental methods for PP2A study have been reviewed.

Therapeutic Modulation of Autophagy in Leukaemia and Lymphoma

Haematopoiesis is a tightly orchestrated process where a pool of hematopoietic stem and progenitor cells (HSPCs) with high self-renewal potential can give rise to both lymphoid and myeloid lineages. The HSPCs pool is reduced with ageing resulting in few HSPC clones maintaining haematopoiesis thereby reducing blood cell diversity, a phenomenon called clonal haematopoiesis. Clonal expansion of HSPCs carrying specific genetic mutations leads to increased risk for haematological malignancies. Therefore, it comes as no surprise that hematopoietic tumours develop in higher frequency in elderly people. Unfortunately, elderly patients with leukaemia or lymphoma still have an unsatisfactory prognosis compared to younger ones highlighting the need to develop more efficient therapies for this group of patients. Growing evidence indicates that macroautophagy (hereafter referred to as autophagy) is essential for health and longevity. This review is focusing on the role of autophagy in normal haematopoiesis as well as in leukaemia and lymphoma development. Attenuated autophagy may support early hematopoietic neoplasia whereas activation of autophagy in later stages of tumour development and in response to a variety of therapies rather triggers a pro-tumoral response. Novel insights into the role of autophagy in haematopoiesis will be discussed in light of designing new autophagy modulating therapies in hematopoietic cancers.

Autophagy-dependent cell death – where, how and why a cell eats itself to death

Autophagy as a means of cell killing was first advanced by Clark's phenotypic description of ‘Type II autophagic cell death’ in 1990. However, this phenomenon later came into question, because the presence of autophagosomes in dying cells does not necessarily signify that autophagy is the cause of demise, but rather may reflect the efforts of the cell to prevent it. Resolution of this issue comes from a more careful definition of autophagy-dependent cell death (ADCD) as a regulated cell death that is shown experimentally to require different components of the autophagy machinery without involvement of alternative cell death pathways. Following these strict criteria, ADCD has been validated in both lower model organisms and mammalian cells, highlighting its importance for developmental and pathophysiological cell death. Recently, researchers have defined additional morphological criteria that characterize ADCD and begun to explore how the established, well-studied autophagy pathway is subverted from a survival to a death function. This Review explores validated models of ADCD and focuses on the current understanding of the mechanisms by which autophagy can kill a cell.

ARD1 contributes to IKKβ-mediated breast cancer tumorigenesis

The expression of IκB kinase β (IKKβ) promotes the growth of breast cancer cells. Meanwhile, IKKβ mediates the phosphorylation and subsequent degradation of arrest-defective protein 1 (ARD1). However, the relationship between IKKβ and ARD1 in the occurrence of breast cancer has not been reported. In this study, we found that IKKβ not only acts directly on mammalian target of rapamycin (mTOR) activity but also indirectly acts on mTOR activity through posttranscriptional modification of ARD1, thereby effectively promoting the growth of breast cancer cells. ARD1 prevents mTOR activity and breast cancer cell growth by stabilizing tuberous sclerosis complex 2 (TSC2) to induce autophagy. Moreover, acetylation of heat shock protein 70 (Hsp70) also contributes to ARD1-mediated autophagy. Therefore, upstream IKKβ can further promote the occurrence of breast cancer by mediating the function of ARD1.