1
|
Yao Q, Mascarenhas dos Santos AC, Zhang H, Mañas A, Hussaini A, Kim U, Xu C, Basheer S, Tasaki S, Xiang J. Unconventional Source of Neurotoxic Protein Aggregation from Organelle Off-Target Bax∆2 in Alzheimer's Disease. Biomolecules 2023; 13:970. [PMID: 37371550 PMCID: PMC10296721 DOI: 10.3390/biom13060970] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 05/30/2023] [Accepted: 06/06/2023] [Indexed: 06/29/2023] Open
Abstract
Protein aggregates are a hallmark of Alzheimer's disease (AD). Extensive studies have focused on β-amyloid plaques and Tau tangles. Here, we illustrate a novel source of protein aggregates in AD neurons from organelle off-target proteins. Bax is a mitochondrial pore-forming pro-death protein. What happens to Bax if it fails to target mitochondria? We previously showed that a mitochondrial target-deficient alternatively spliced variant, Bax∆2, formed large cytosolic protein aggregates and triggered caspase 8-mediated cell death. Bax∆2 protein levels were low in most normal organs and the proteins were quickly degraded in cancer. Here, we found that 85% of AD patients had Bax∆2 required alternative splicing. Increased Bax∆2 proteins were mostly accumulated in neurons of AD-susceptible brain regions. Intracellularly, Bax∆2 aggregates distributed independently of Tau tangles. Interestingly, Bax∆2 aggregates triggered the formation of stress granules (SGs), a large protein-RNA complex involved in AD pathogenesis. Although the functional domains required for aggregation and cell death are the same as in cancer cells, Bax∆2 relied on SGs, not caspase 8, for neuronal cell death. These results imply that the aggregation of organelle off-target proteins, such as Bax∆2, broadens the scope of traditional AD pathogenic proteins that contribute to the neuronal stress responses and AD pathogenesis.
Collapse
Affiliation(s)
- Qi Yao
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA (C.X.)
| | | | - Huaiyuan Zhang
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA (C.X.)
| | - Adriana Mañas
- Department of Laboratory Medicine, Lund University, 22381 Lund, Sweden
| | - Ammarah Hussaini
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA (C.X.)
| | - Ujin Kim
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA (C.X.)
| | - Congtai Xu
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA (C.X.)
| | - Sana Basheer
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA (C.X.)
| | - Shinya Tasaki
- Rush Alzheimer’s Disease Center, Rush University Medical Center, Chicago, IL 60612, USA
| | - Jialing Xiang
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA (C.X.)
| |
Collapse
|
2
|
Yao Q, Zhang H, Standish C, Grube J, Mañas A, Xiang J. Expression profile of the proapoptotic protein Bax in the human brain. Histochem Cell Biol 2023; 159:209-220. [PMID: 35951115 DOI: 10.1007/s00418-022-02146-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/27/2022] [Indexed: 11/27/2022]
Abstract
Bax is a well-known universal proapoptotic protein. Bax protein is detected in almost all human organs, and its expression levels can be correlated with disease progression and therapeutic efficacy in certain settings. Interestingly, increasing evidence has shown that mature neuronal cell death is often not typical apoptosis. Most results on the expression of Bax proteins (predominantly Baxα) in the human brain come from disease-oriented studies, and the data on Bax protein expression in the normal brain are limited and lack consistency due to many variable factors. Here, we analyzed Bax RNA and protein expression data from multiple databases and performed immunostaining of over 80 samples from 25 healthy subjects across 7 different brain regions. We found that Bax protein expression was heterogeneous across brain regions and individual subjects. Both neurons and glial cells, such as astrocytes, could be Bax positive, but Bax positivity appeared to be highly selective, even within the same cell type in the same region. Furthermore, Bax proteins could be localized in the cytosol (evenly spread or concentrated to one region), nucleus or nucleolus depending on the cell type. Such variation and distribution in Bax expression suggest that Bax may function differently in the human brain than in other organs.
Collapse
Affiliation(s)
- Qi Yao
- Department of Biology, Lewis College of Science and Letters, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL, 60616, USA
| | - Huaiyuan Zhang
- Department of Biology, Lewis College of Science and Letters, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL, 60616, USA
| | - Collin Standish
- Department of Biology, Lewis College of Science and Letters, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL, 60616, USA
| | - Joshua Grube
- Department of Biology, Lewis College of Science and Letters, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL, 60616, USA
| | - Adriana Mañas
- Department of Biology, Lewis College of Science and Letters, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL, 60616, USA
| | - Jialing Xiang
- Department of Biology, Lewis College of Science and Letters, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL, 60616, USA.
| |
Collapse
|
3
|
Sora V, Papaleo E. Structural Details of BH3 Motifs and BH3-Mediated Interactions: an Updated Perspective. Front Mol Biosci 2022; 9:864874. [PMID: 35685242 PMCID: PMC9171138 DOI: 10.3389/fmolb.2022.864874] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 04/13/2022] [Indexed: 11/18/2022] Open
Abstract
Apoptosis is a mechanism of programmed cell death crucial in organism development, maintenance of tissue homeostasis, and several pathogenic processes. The B cell lymphoma 2 (BCL2) protein family lies at the core of the apoptotic process, and the delicate balance between its pro- and anti-apoptotic members ultimately decides the cell fate. BCL2 proteins can bind with each other and several other biological partners through the BCL2 homology domain 3 (BH3), which has been also classified as a possible Short Linear Motif and whose distinctive features remain elusive even after decades of studies. Here, we aim to provide an updated overview of the structural features characterizing BH3s and BH3-mediated interactions (with a focus on human proteins), elaborating on the plasticity of BCL2 proteins and the motif properties. We also discussed the implication of these findings for the discovery of interactors of the BH3-binding groove of BCL2 proteins and the design of mimetics for therapeutic purposes.
Collapse
Affiliation(s)
- Valentina Sora
- Cancer Structural Biology, Danish Cancer Society Research Center, Copenhagen, Denmark
- Cancer Systems Biology, Section for Bioinformatics, Department of Health and Technology, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Elena Papaleo
- Cancer Structural Biology, Danish Cancer Society Research Center, Copenhagen, Denmark
- Cancer Systems Biology, Section for Bioinformatics, Department of Health and Technology, Technical University of Denmark, Kongens Lyngby, Denmark
- *Correspondence: Elena Papaleo, ,
| |
Collapse
|
4
|
A Structural Model for Bax∆2-Mediated Activation of Caspase 8-Dependent Apoptosis. Int J Mol Sci 2020; 21:ijms21155476. [PMID: 32751845 PMCID: PMC7432750 DOI: 10.3390/ijms21155476] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 07/26/2020] [Accepted: 07/29/2020] [Indexed: 01/28/2023] Open
Abstract
Bax∆2 is a pro-apoptotic anti-tumor protein in the Bax family. While most of the Bax family causes cell death by targeting mitochondria, Bax∆2 forms cytosolic aggregates and activates caspase 8-dependent cell death. We previously showed that the Bax∆2 helix α9 is critical for caspase 8 recruitment. However, the interaction between these two proteins at the structural level is unknown. In this in silico study, we performed molecular dynamics (MD) simulations and protein-protein docking on Bax∆2 variants. The results suggest that the Bax∆2 variants have different stable states. Mutating the Baxα mitochondria-targeting signal [L26P/L27P] appears to introduce a kink into helix α1. Protein-protein docking suggests that helices α9 of both wild-type Bax∆2 and Bax∆2 caspase 8 binding-deficient mutant [L164P] can fit in the same caspase 8 binding site, but the mutant is unable to fit as well as wild-type Bax∆2. Together, these data point to a structural basis for explaining Bax∆2 function in caspase 8-dependent cell death.
Collapse
|
5
|
Roles and mechanisms of alternative splicing in cancer - implications for care. Nat Rev Clin Oncol 2020; 17:457-474. [PMID: 32303702 DOI: 10.1038/s41571-020-0350-x] [Citation(s) in RCA: 393] [Impact Index Per Article: 98.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/03/2020] [Indexed: 12/14/2022]
Abstract
Removal of introns from messenger RNA precursors (pre-mRNA splicing) is an essential step for the expression of most eukaryotic genes. Alternative splicing enables the regulated generation of multiple mRNA and protein products from a single gene. Cancer cells have general as well as cancer type-specific and subtype-specific alterations in the splicing process that can have prognostic value and contribute to every hallmark of cancer progression, including cancer immune responses. These splicing alterations are often linked to the occurrence of cancer driver mutations in genes encoding either core components or regulators of the splicing machinery. Of therapeutic relevance, the transcriptomic landscape of cancer cells makes them particularly vulnerable to pharmacological inhibition of splicing. Small-molecule splicing modulators are currently in clinical trials and, in addition to splice site-switching antisense oligonucleotides, offer the promise of novel and personalized approaches to cancer treatment.
Collapse
|
6
|
Immunohistochemical detection of the pro-apoptotic Bax∆2 protein in human tissues. Histochem Cell Biol 2020; 154:41-53. [PMID: 32200452 DOI: 10.1007/s00418-020-01874-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/13/2020] [Indexed: 12/11/2022]
Abstract
The pro-apoptotic Bax isoform Bax∆2 was originally discovered in cancer patients with a microsatellite guanine deletion (G8 to G7). This deletion leads to an early stop codon; however, when combined with the alternative splicing of exon 2, the reading frame is restored allowing production of a full-length protein (Bax∆2). Unlike the parental Baxα, Bax∆2 triggers apoptosis through a non-mitochondrial pathway and the expression in human tissues was unknown. Here, we analyzed over 1000 tissue microarray samples from 13 different organs using immunohistochemistry. Bax∆2-positive cells were detected in all examined organs at low rates (1-5%) and mainly scattered throughout the connective tissues. Surprisingly, over 70% of normal colon samples scored high for BaxΔ2-positive staining. Only 7% of malignant colon samples scored high, with most high-grade tumors being negative. A similar pattern was observed in most organs examined. We also showed that both Baxα and Bax∆2 can co-exist in the same cells. Genotyping showed that the majority of Bax∆2-positive normal tissues contain no G7 mutation, but an unexpected high rate of G9 was observed. Although the underlying mechanism remains to be explored, the inverse correlation of Bax∆2 expression with tissue malignancy suggests that it may have a clinical implication in cancer development and treatment.
Collapse
|
7
|
Wang Y, Zhang H, Jiao B, Nie J, Li X, Wang W, Wang H. The Roles of Alternative Splicing in Tumor-immune Cell Interactions. Anticancer Agents Med Chem 2020; 20:729-740. [PMID: 32560607 PMCID: PMC8388066 DOI: 10.2174/1568009620666200619123725] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 05/09/2020] [Accepted: 05/11/2020] [Indexed: 12/27/2022]
Abstract
Alternative splicing (AS) plays a significant role in the hallmarks of cancer and can provide neoantigens for immunotherapy. Here, we summarize recent advances in immune system associated tumor specific-antigens (TSAs) produced by AS. We further discuss the regulating mechanisms involved in AS-mediated innate and adaptive immune responses and the anti-tumoral and protumoral roles in different types of cancer. For example, ULBP1_RI, MLL5Δ21spe, NKp44-1Δ5, MHC-IΔ7, CD200SΔ1, 2, PVR α/β/γ/δ and IL-33 variants 1/2/3 act as regulators in solid tumors and IPAK4-L and, FOXP1ΔN100 exhibit functions in hematological cancers.
Collapse
Affiliation(s)
| | - Honglei Zhang
- Address correspondence to these authors at Kunming Institute of Zoology, Chinese Academy of Sciences; 32 Jiaochang E. Road, Kunming, Yunnan, China; Tel: +86-871-68191706; E-mail: ; and Department of Breast Cancer, Third Affiliated Hospital, Kunming Medical University, 519 Kunzhou Road, Kunming, Yunnan, China; Tel: +86-13608815577; E-mail:
| | - Baowei Jiao
- Address correspondence to these authors at Kunming Institute of Zoology, Chinese Academy of Sciences; 32 Jiaochang E. Road, Kunming, Yunnan, China; Tel: +86-871-68191706; E-mail: ; and Department of Breast Cancer, Third Affiliated Hospital, Kunming Medical University, 519 Kunzhou Road, Kunming, Yunnan, China; Tel: +86-13608815577; E-mail:
| | - Jianyun Nie
- Address correspondence to these authors at Kunming Institute of Zoology, Chinese Academy of Sciences; 32 Jiaochang E. Road, Kunming, Yunnan, China; Tel: +86-871-68191706; E-mail: ; and Department of Breast Cancer, Third Affiliated Hospital, Kunming Medical University, 519 Kunzhou Road, Kunming, Yunnan, China; Tel: +86-13608815577; E-mail:
| | | | | | | |
Collapse
|
8
|
de Jong MRW, Langendonk M, Reitsma B, Herbers P, Nijland M, Huls G, van den Berg A, Ammatuna E, Visser L, van Meerten T. WEE1 Inhibition Enhances Anti-Apoptotic Dependency as a Result of Premature Mitotic Entry and DNA Damage. Cancers (Basel) 2019; 11:cancers11111743. [PMID: 31703356 PMCID: PMC6895818 DOI: 10.3390/cancers11111743] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 11/01/2019] [Accepted: 11/04/2019] [Indexed: 02/06/2023] Open
Abstract
Genomically unstable cancers are dependent on specific cell cycle checkpoints to maintain viability and prevent apoptosis. The cell cycle checkpoint protein WEE1 is highly expressed in genomically unstable cancers, including diffuse large B-cell lymphoma (DLBCL). Although WEE1 inhibition effectively induces apoptosis in cancer cells, the effect of WEE1 inhibition on anti-apoptotic dependency is not well understood. We show that inhibition of WEE1 by AZD1775 induces DNA damage and pre-mitotic entry in DLBCL, thereby enhancing dependency on BCL-2 and/or MCL-1. Combining AZD1775 with anti-apoptotic inhibitors such as venetoclax (BCL-2i) or S63845 (MCL-1i) enhanced sensitivity in a cell-specific manner. In addition, we demonstrate that both G2/M cell cycle arrest and DNA damage induction put a similar stress on DLBCL cells, thereby enhancing anti-apoptotic dependency. Therefore, genotoxic or cell cycle disrupting agents combined with specific anti-apoptotic inhibitors may be very effective in genomic unstable cancers such as DLBCL and therefore warrants further clinical evaluation.
Collapse
Affiliation(s)
- Mathilde Rikje Willemijn de Jong
- Department of Hematology, University Medical Center Groningen, University of Groningen, 9713 GZ Groningen, the Netherlands (M.L.); (B.R.); (P.H.); (M.N.); (G.H.); (E.A.)
- Department of Pathology and Medical Biology, University Medical Center Groningen, University of Groningen, 9713 GZ Groningen, the Netherlands; (A.v.d.B.); (L.V.)
| | - Myra Langendonk
- Department of Hematology, University Medical Center Groningen, University of Groningen, 9713 GZ Groningen, the Netherlands (M.L.); (B.R.); (P.H.); (M.N.); (G.H.); (E.A.)
- Department of Pathology and Medical Biology, University Medical Center Groningen, University of Groningen, 9713 GZ Groningen, the Netherlands; (A.v.d.B.); (L.V.)
| | - Bart Reitsma
- Department of Hematology, University Medical Center Groningen, University of Groningen, 9713 GZ Groningen, the Netherlands (M.L.); (B.R.); (P.H.); (M.N.); (G.H.); (E.A.)
| | - Pien Herbers
- Department of Hematology, University Medical Center Groningen, University of Groningen, 9713 GZ Groningen, the Netherlands (M.L.); (B.R.); (P.H.); (M.N.); (G.H.); (E.A.)
| | - Marcel Nijland
- Department of Hematology, University Medical Center Groningen, University of Groningen, 9713 GZ Groningen, the Netherlands (M.L.); (B.R.); (P.H.); (M.N.); (G.H.); (E.A.)
| | - Gerwin Huls
- Department of Hematology, University Medical Center Groningen, University of Groningen, 9713 GZ Groningen, the Netherlands (M.L.); (B.R.); (P.H.); (M.N.); (G.H.); (E.A.)
| | - Anke van den Berg
- Department of Pathology and Medical Biology, University Medical Center Groningen, University of Groningen, 9713 GZ Groningen, the Netherlands; (A.v.d.B.); (L.V.)
| | - Emanuele Ammatuna
- Department of Hematology, University Medical Center Groningen, University of Groningen, 9713 GZ Groningen, the Netherlands (M.L.); (B.R.); (P.H.); (M.N.); (G.H.); (E.A.)
| | - Lydia Visser
- Department of Pathology and Medical Biology, University Medical Center Groningen, University of Groningen, 9713 GZ Groningen, the Netherlands; (A.v.d.B.); (L.V.)
| | - Tom van Meerten
- Department of Hematology, University Medical Center Groningen, University of Groningen, 9713 GZ Groningen, the Netherlands (M.L.); (B.R.); (P.H.); (M.N.); (G.H.); (E.A.)
- Correspondence: ; Tel.: +31-503-611-761
| |
Collapse
|
9
|
Zhu LY, Zhu YR, Dai DJ, Wang X, Jin HC. Epigenetic regulation of alternative splicing. Am J Cancer Res 2018; 8:2346-2358. [PMID: 30662796 PMCID: PMC6325479] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Accepted: 11/21/2018] [Indexed: 06/09/2023] Open
Abstract
Alternative splicing (AS) serves as an additional regulatory process for gene expression after transcription, and it generates distinct mRNA species, and even noncoding RNAs (ncRNAs), from one primary transcript. Generally, AS can be coupled with transcription and subjected to epigenetic regulation, such as DNA methylation and histone modifications. In addition, ncRNAs, especially long noncoding RNAs (lncRNAs), can be generated from AS and function as splicing factors ("interactors" or "hijackers") in AS. Recently, RNA modifications, such as the RNA N6-methyladenosine (m6A) modification, have been found to regulate AS. In this review, we summarize recent achievements related to the epigenetic regulation of AS.
Collapse
Affiliation(s)
- Li-Yuan Zhu
- Laboratory of Cancer Biology, Key Lab of Biotherapy in Zhejiang, Sir Run Run Shaw Hospital, Medical School of Zhejiang UniversityHangzhou, China
| | - Yi-Ran Zhu
- Laboratory of Cancer Biology, Key Lab of Biotherapy in Zhejiang, Sir Run Run Shaw Hospital, Medical School of Zhejiang UniversityHangzhou, China
| | - Dong-Jun Dai
- Department of Medical Oncology, Sir Run Run Shaw Hospital, Medical School of Zhejiang UniversityHangzhou, China
| | - Xian Wang
- Department of Medical Oncology, Sir Run Run Shaw Hospital, Medical School of Zhejiang UniversityHangzhou, China
| | - Hong-Chuan Jin
- Laboratory of Cancer Biology, Key Lab of Biotherapy in Zhejiang, Sir Run Run Shaw Hospital, Medical School of Zhejiang UniversityHangzhou, China
| |
Collapse
|
10
|
Chen X, Wang L, Roozbahani GM, Zhang Y, Xiang J, Guan X. Nanopore label-free detection of single-nucleotide deletion in Baxα/BaxΔ2. Electrophoresis 2018; 39:2410-2416. [PMID: 29998460 PMCID: PMC6168411 DOI: 10.1002/elps.201800193] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Revised: 06/14/2018] [Accepted: 07/01/2018] [Indexed: 12/13/2022]
Abstract
Baxα, a key tumor suppressor gene, will not be expressed correctly as a result of single nucleotide mutation in its microsatellite region; Instead, BaxΔ2, an isoform of Baxα, is often produced. In addition, lack of the exon 2 due to an alternative splicing, BaxΔ2 has the same sequence as Baxα except single base deletion from eight continuous guanines (G8) to G7. Most of the currently available methods for Bax∆2 detection are inefficient and time-consuming, and/or require the use of labels or dyes. In this work, we reported a label-free nanopore sensing strategy to differentiate between Baxα and BaxΔ2 with a DNA polymer as a molecular probe based on alternative spliced sequences. Two DNA molecules were designed to selectively detect Baxα and BaxΔ2, respectively. The method was rapid, accurate, and highly sensitive: picomolar concentrations of target nucleic acids could be detected in minutes. Our developed simple and fast nanopore-based detection strategy is not only useful for distinguishing between Baxα and Bax∆2, but also provides a useful tool for detection of other single-base mutations in genetic diagnosis.
Collapse
Affiliation(s)
- Xiaohan Chen
- Department of Chemistry, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Liang Wang
- Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, PR China
| | - Golbarg M Roozbahani
- Department of Chemistry, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Youwen Zhang
- Department of Chemistry, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Jialing Xiang
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Xiyun Guan
- Department of Chemistry, Illinois Institute of Technology, Chicago, IL 60616, USA
| |
Collapse
|
11
|
Mañas A, Davis A, Lamerand S, Xiang J. Detection of pro-apoptotic Bax∆2 proteins in the human cerebellum. Histochem Cell Biol 2018; 150:77-82. [PMID: 29663074 DOI: 10.1007/s00418-018-1669-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/10/2018] [Indexed: 12/17/2022]
Abstract
Bax∆2 is a pro-apoptotic protein originally discovered in colon cancer patients with high microsatellite instability. Unlike most pro-apoptotic Bax family members, Bax∆2 mediates cell death through a non-mitochondrial caspase 8-dependent pathway. In the scope of analyzing the distribution of Bax∆2 expression in human tissues, we examined a panel of human brain samples. Here, we report four cerebellar cases in which the subjects had no neurological disorder or disease documented. We found Bax∆2 positive cells scattered in all areas of the cerebellum, but most strikingly concentrated in Purkinje cell bodies and dendrites. Two out the four subjects tested had strong Bax∆2-positive staining in nearly all Purkinje cells; one was mainly negative; and one had various levels of positive staining within the same sample. Further genetic analysis of the Purkinje cell layer, collected by microdissection from two subjects, showed that the samples contained G7 and G9 Bax microsatellite mutations. Both subjects were young and had no diseases reported at the time of death. As the distribution of Bax∆2 is consistent with that known for Baxα, but in a less ubiquitous manner, these results may imply a potential function of Bax∆2 in Purkinje cells.
Collapse
Affiliation(s)
- Adriana Mañas
- Department of Biology, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL, 60616, USA
| | - Aislinn Davis
- Department of Biology, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL, 60616, USA
| | - Sydney Lamerand
- Department of Biology, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL, 60616, USA
| | - Jialing Xiang
- Department of Biology, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL, 60616, USA.
| |
Collapse
|
12
|
Alternative Splicing as a Target for Cancer Treatment. Int J Mol Sci 2018; 19:ijms19020545. [PMID: 29439487 PMCID: PMC5855767 DOI: 10.3390/ijms19020545] [Citation(s) in RCA: 74] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2017] [Revised: 01/29/2018] [Accepted: 01/29/2018] [Indexed: 02/06/2023] Open
Abstract
Alternative splicing is a key mechanism determinant for gene expression in metazoan. During alternative splicing, non-coding sequences are removed to generate different mature messenger RNAs due to a combination of sequence elements and cellular factors that contribute to splicing regulation. A different combination of splicing sites, exonic or intronic sequences, mutually exclusive exons or retained introns could be selected during alternative splicing to generate different mature mRNAs that could in turn produce distinct protein products. Alternative splicing is the main source of protein diversity responsible for 90% of human gene expression, and it has recently become a hallmark for cancer with a full potential as a prognostic and therapeutic tool. Currently, more than 15,000 alternative splicing events have been associated to different aspects of cancer biology, including cell proliferation and invasion, apoptosis resistance and susceptibility to different chemotherapeutic drugs. Here, we present well established and newly discovered splicing events that occur in different cancer-related genes, their modification by several approaches and the current status of key tools developed to target alternative splicing with diagnostic and therapeutic purposes.
Collapse
|
13
|
Mañas A, Chen W, Nelson A, Yao Q, Xiang J. BaxΔ2 sensitizes colorectal cancer cells to proteasome inhibitor-induced cell death. Biochem Biophys Res Commun 2018; 496:18-24. [PMID: 29291406 PMCID: PMC6022363 DOI: 10.1016/j.bbrc.2017.12.156] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Accepted: 12/26/2017] [Indexed: 12/23/2022]
Abstract
Proteasome inhibitors, such as bortezomib and carfilzomib, are FDA approved for the treatment of hemopoietic cancers, but recent studies have shown their great potential for treatment of solid tumors. BaxΔ2, a unique proapoptotic Bax isoform, promotes non-mitochondrial cell death and sensitizes cancer cells to chemotherapy. However, endogenous BaxΔ2 proteins are unstable and susceptible to proteasomal degradation. Here, we screened a panel of proteasome inhibitors in colorectal cancer cells with different Bax statuses. We found that all proteasome inhibitors tested were able to block BaxΔ2 degradation without affecting the level of Baxα or Bcl-2 proteins. Among the inhibitors tested, only bortezomib and carfilzomib were able to induce differential cell death corresponding to the distinct Bax statuses. BaxΔ2-positive cells had a significantly higher level of cell death at low nanomolar concentrations than Baxα-positive or Bax-negative cells. Furthermore, bortezomib-induced cell death in BaxΔ2-positive cells was predominantly dependent on the caspase 8/3 pathway, consistent with our previous studies. These results imply that BaxΔ2 can selectively sensitize cancer cells to proteasome inhibitors, enhancing their potential to treat colon cancer and other solid tumors.
Collapse
Affiliation(s)
- Adriana Mañas
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Wenjing Chen
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Adam Nelson
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Qi Yao
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Jialing Xiang
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA.
| |
Collapse
|
14
|
Mañas A, Wang S, Nelson A, Li J, Zhao Y, Zhang H, Davis A, Xie B, Maltsev N, Xiang J. The functional domains for Bax∆2 aggregate-mediated caspase 8-dependent cell death. Exp Cell Res 2017; 359:342-355. [PMID: 28807790 PMCID: PMC5718386 DOI: 10.1016/j.yexcr.2017.08.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Revised: 08/07/2017] [Accepted: 08/08/2017] [Indexed: 01/09/2023]
Abstract
Bax∆2 is a functional pro-apoptotic Bax isoform having alterations in its N-terminus, but sharing the rest of its sequence with Baxα. Bax∆2 is unable to target mitochondria due to the loss of helix α1. Instead, it forms cytosolic aggregates and activates caspase 8. However, the functional domain(s) responsible for BaxΔ2 behavior have remained elusive. Here we show that disruption of helix α1 makes Baxα mimic the behavior of Bax∆2. However, the other alterations in the Bax∆2 N-terminus have no significant impact on aggregation or cell death. We found that the hallmark BH3 domain is necessary but not sufficient for aggregation-mediated cell death. We also noted that the core region shared by Baxα and Bax∆2 is required for the formation of large aggregates, which is essential for BaxΔ2 cytotoxicity. However, aggregation by itself is unable to trigger cell death without the C-terminus. Interestingly, the C-terminal helical conformation, not its primary sequence, appears to be critical for caspase 8 recruitment and activation. As Bax∆2 shares core and C-terminal sequences with most Bax isoforms, our results not only reveal a structural basis for Bax∆2-induced cell death, but also imply an intrinsic potential for aggregate-mediated caspase 8-dependent cell death in other Bax family members.
Collapse
Affiliation(s)
- Adriana Mañas
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Sheng Wang
- Human Genetics Department, Computation Institute, University of Chicago, Chicago, IL 60637, USA
| | - Adam Nelson
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Jiajun Li
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Yu Zhao
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Huaiyuan Zhang
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Aislinn Davis
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Bingqing Xie
- Department of Computer Science, Illinois Institute of Technology, Chicago, IL 60616, USA
| | - Natalia Maltsev
- Human Genetics Department, Computation Institute, University of Chicago, Chicago, IL 60637, USA
| | - Jialing Xiang
- Department of Biology, Illinois Institute of Technology, Chicago, IL 60616, USA.
| |
Collapse
|
15
|
Identification and expression analysis of alternatively spliced new transcript isoform of Bax gene in mouse. Gene 2017; 621:21-31. [DOI: 10.1016/j.gene.2017.04.020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2016] [Revised: 04/07/2017] [Accepted: 04/12/2017] [Indexed: 12/29/2022]
|
16
|
Lin JC, Tsao MF, Lin YJ. Differential Impacts of Alternative Splicing Networks on Apoptosis. Int J Mol Sci 2016; 17:ijms17122097. [PMID: 27983653 PMCID: PMC5187897 DOI: 10.3390/ijms17122097] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Revised: 11/26/2016] [Accepted: 12/02/2016] [Indexed: 12/16/2022] Open
Abstract
Apoptosis functions as a common mechanism to eliminate unnecessary or damaged cells during cell renewal and tissue development in multicellular organisms. More than 200 proteins constitute complex networks involved in apoptotic regulation. Imbalanced expressions of apoptosis-related factors frequently lead to malignant diseases. The biological functions of several apoptotic factors are manipulated through alternative splicing mechanisms which expand gene diversity by generating discrete variants from one messenger RNA precursor. It is widely observed that alternatively-spliced variants encoded from apoptosis-related genes exhibit differential effects on apoptotic regulation. Alternative splicing events are meticulously regulated by the interplay between trans-splicing factors and cis-responsive elements surrounding the regulated exons. The major focus of this review is to highlight recent studies that illustrate the influences of alternative splicing networks on apoptotic regulation which participates in diverse cellular processes and diseases.
Collapse
Affiliation(s)
- Jung-Chun Lin
- School of Medical Laboratory Science and Biotechnology, College of Medical Science and Technology, Taipei Medical University, Taipei 11031, Taiwan.
| | - Mei-Fen Tsao
- Department of Laboratory Medicine, Taipei Medical University Hospital, Taipei 11031, Taiwan.
| | - Ying-Ju Lin
- School of Chinese Medicine, China Medical University, Taichung 404, Taiwan.
| |
Collapse
|
17
|
Alternative splicing and cell survival: from tissue homeostasis to disease. Cell Death Differ 2016; 23:1919-1929. [PMID: 27689872 DOI: 10.1038/cdd.2016.91] [Citation(s) in RCA: 125] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 05/26/2016] [Accepted: 07/15/2016] [Indexed: 12/17/2022] Open
Abstract
Most human genes encode multiple mRNA variants and protein products through alternative splicing of exons and introns during pre-mRNA processing. In this way, alternative splicing amplifies enormously the coding potential of the human genome and represents a powerful evolutionary resource. Nonetheless, the plasticity of its regulation is prone to errors and defective splicing underlies a large number of inherited and sporadic diseases, including cancer. One key cellular process affected by alternative splicing is the programmed cell death or apoptosis. Many apoptotic genes encode for splice variants having opposite roles in cell survival. This regulation modulates cell and tissue homeostasis and is implicated in both developmental and pathological processes. Furthermore, recent evidence has also unveiled splicing-mediated regulation of genes involved in autophagy, another essential process for tissue homeostasis. In this review, we highlight some of the best-known examples of alternative splicing events involved in cell survival. Emphasis is given to the role of this regulation in human cancer and in the response to chemotherapy, providing examples of how alternative splicing of apoptotic genes can be exploited therapeutically.
Collapse
|
18
|
Zhang H, Tassone C, Lin N, Mañas A, Zhao Y, Xiang J. Detection of Bax Microsatellite Mutations and BaxΔ2 Isoform in Human Buccal Cells. ACTA ACUST UNITED AC 2015; 6. [PMID: 29302381 PMCID: PMC5749267 DOI: 10.4172/2157-7013.s8-002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Loss of the pro-apoptotic Bcl-2 family protein Bax occurs in ~50%
of hereditary nonpolyposis colorectal cancer (HNPCC) due to microsatellite
instability (MSI). Recently, we found that some of the
“Bax-negative” MSI tumor cells contain a functional Bax isoform,
BaxΔ2, which sensitizes cells to selective chemotherapeutics. Here we
show the detection of Bax microsatellite mutations and expression of
BaxΔ2 proteins in human buccal cells. Our study provides a sensitive and
non-invasive approach and a potential clinical application in diagnosis and
treatment of MSI colon cancer patients.
Collapse
Affiliation(s)
- Honghong Zhang
- Department of Biology, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL 60616
| | - Cecilie Tassone
- Department of Biology, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL 60616
| | - Nora Lin
- Department of Biology, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL 60616
| | - Adriana Mañas
- Department of Biology, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL 60616
| | - Yu Zhao
- Department of Biology, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL 60616
| | - Jialing Xiang
- Department of Biology, Illinois Institute of Technology, 3101 South Dearborn Street, Chicago, IL 60616
| |
Collapse
|
19
|
Yamamoto H, Imai K. Microsatellite instability: an update. Arch Toxicol 2015; 89:899-921. [PMID: 25701956 DOI: 10.1007/s00204-015-1474-0] [Citation(s) in RCA: 150] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Accepted: 02/09/2015] [Indexed: 02/08/2023]
Abstract
Deficient DNA mismatch repair (MMR) results in a strong mutator phenotype known as microsatellite instability (MSI), which is a hallmark of Lynch syndrome-associated cancers. MSI is characterized by length alterations within simple repeated sequences that are called microsatellites. Lynch syndrome is primarily caused by mutations in the MMR genes, mainly MLH1 and MSH2, and less frequently in MSH6, and rarely PMS2, and large genomic rearrangements account for 5-20 % of all mutations. Germ line hemiallelic methylations of MLH1 or MSH2 are termed as epimutations and have been identified as causative of Lynch syndrome. Moreover, germ line 3' deletions of EPCAM gene is involved in MSH2 methylation. MSI is also observed in about 15 % of sporadic colorectal cancer (CRC), gastric cancer (GC), and endometrial cancer (EC), and at lower frequencies in other cancers, often in association with hypermethylation of the MLH1 gene. Trimethylation of histone H3 on Lys36 (H3K36 me3) is an epigenetic histone mark that was required for DNA MMR in vivo. Thus, mutations in the H3K36 trimethyltransferase SETD2 have been reported as a potential cause of MSI. Genetic, epigenetic, and transcriptomic differences have been identified between cancers with and without MSI. Recent comprehensive molecular characterizations of CRC, EC, and GC by The Cancer Genome Atlas indicate that MSI+ cancers are distinct biological entities. The BRAF V600E mutation is specifically associated with sporadic MSI+ CRCs with methylated MLH1, but is not associated with Lynch syndrome-related CRCs. Accumulating evidence indicates a role of interactions between MSI and microRNA (miRNA) in the pathogenesis of MSI-positive (MSI+) cancer. As another new mechanism underlying MSI, overexpression of miR-155 or miR-21 has been shown to downregulate the expression of the MMR genes. Gene targets of frameshift mutations caused by MSI are involved in various cellular functions, including DNA repair (MSH3 and MSH6), cell signaling (TGFBR2 and ACVR2A), apoptosis (BAX), epigenetic regulation (HDAC2 and ARID1A), and miRNA processing (TARBP2 and XPO5), and a subset of MSI+ CRCs reportedly shows the mutated miRNA machinery phenotype. Moreover, microsatellite repeats in miRNA genes, such as hsa-miR-1273c, may be novel MSI targets for CRC, and mutations in noncoding regulatory regions of MRE11, BAX (BaxΔ2), and HSP110 (HSP110ΔE9) may affect the efficiency of chemotherapy. Thus, analyses of MSI and its related molecular alterations in cancers are increasingly relevant in clinical settings, and MSI is a useful screening marker for identifying patients with Lynch syndrome and a prognostic factor for chemotherapeutic interventions. In this review, we summarize recent advances in the pathogenesis of MSI and focus on genome-wide analyses that indicate the potential use of MSI and related alterations as biomarkers and novel therapeutic targets.
Collapse
Affiliation(s)
- Hiroyuki Yamamoto
- Division of Gastroenterology and Hepatology, Department of Internal Medicine, St. Marianna University School of Medicine, Kawasaki, 216-8511, Japan,
| | | |
Collapse
|
20
|
Zhang H, Lin Y, Mañas A, Zhao Y, Denning MF, Ma L, Xiang J. BaxΔ2 Promotes Apoptosis through Caspase-8 Activation in Microsatellite-Unstable Colon Cancer. Mol Cancer Res 2014; 12:1225-32. [DOI: 10.1158/1541-7786.mcr-14-0162] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
21
|
Haferkamp B, Zhang H, Kissinger S, Wang X, Lin Y, Schultz M, Xiang J. BaxΔ2 Family Alternative Splicing Salvages Bax Microsatellite-Frameshift Mutations. Genes Cancer 2014; 4:501-12. [PMID: 24386510 DOI: 10.1177/1947601913515906] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Accepted: 11/14/2013] [Indexed: 12/15/2022] Open
Abstract
Mutation or aberrant splicing can interrupt gene expression. Tumor suppressor Bax is one of the susceptible genes prone to microsatellite frameshifting mutations in coding regions. As a result, tumors exhibiting microsatellite instability (MSI) often present a "Bax-negative" phenotype. We previously reported that some Bax-negative cells in fact contain a functional Bax isoform (BaxΔ2), generated when unique alternative splicing "salvages" the shifted reading frame introduced by a microsatellite mutation. Here we compared Bax alternative splicing profiles in a range of cell lines and primary tumors with and without Bax microsatellite mutations. We found that MSI tumors exhibit a high Bax alternative splicing frequency, especially in exon 2, and produce a family of alternatively spliced isoforms that retain many important Bax functional domains. Surprisingly, these BaxΔ2 family isoforms can rescue Bax from all common microsatellite frameshift mutations. Production of BaxΔ2 requires specific cis mutations, while trans components are not cell-type specific. Furthermore, all BaxΔ2 family isoforms are more potent cell death inducers than the parental Bax without directly targeting mitochondria. These results indicate that the BaxΔ2 family can potentially salvage Bax tumor suppressor expression otherwise lost to mutation.
Collapse
Affiliation(s)
- Bonnie Haferkamp
- Department of Biological and Chemical Sciences, Illinois Institute of Technology, Chicago, IL, USA
| | - Honghong Zhang
- Department of Biological and Chemical Sciences, Illinois Institute of Technology, Chicago, IL, USA
| | - Samuel Kissinger
- Department of Biological and Chemical Sciences, Illinois Institute of Technology, Chicago, IL, USA
| | - Xin Wang
- Department of Biological and Chemical Sciences, Illinois Institute of Technology, Chicago, IL, USA
| | - Yuting Lin
- Department of Biological and Chemical Sciences, Illinois Institute of Technology, Chicago, IL, USA
| | - Megan Schultz
- Department of Biological and Chemical Sciences, Illinois Institute of Technology, Chicago, IL, USA
| | - Jialing Xiang
- Department of Biological and Chemical Sciences, Illinois Institute of Technology, Chicago, IL, USA
| |
Collapse
|
22
|
Silva AG, Lisboa BCG, Achatz MIW, Carraro DM, da Cunha IW, Pearson PL, Krepischi ACV, Rosenberg C. Germline BAX deletion in a patient with melanoma and gastrointestinal stromal tumor. Am J Gastroenterol 2013; 108:1372-5. [PMID: 23912413 DOI: 10.1038/ajg.2013.176] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
|