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Kolli S, Kline CJ, Rad KM, Wehman AM. Phagolysosomes break down the membrane of a non-apoptotic corpse independent of macroautophagy. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.19.599770. [PMID: 38948720 PMCID: PMC11212964 DOI: 10.1101/2024.06.19.599770] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/02/2024]
Abstract
Cell corpses must be cleared in an efficient manner to maintain tissue homeostasis and regulate immune responses. Ubiquitin-like Atg8/LC3 family proteins promote the degradation of membranes and internal cargo during both macroautophagy and corpse clearance, raising the question how macroautophagy contributes to corpse clearance. Studying the clearance of non-apoptotic dying polar bodies in Caenorhabditis elegans embryos, we show that the LC3 ortholog LGG-2 is enriched in the polar body phagolysosome independent of membrane association or autophagosome formation. We demonstrate that ATG-16.1 and ATG-16.2, which promote membrane association of lipidated Atg8/LC3 proteins, redundantly promote polar body membrane breakdown in phagolysosomes independent of their role in macroautophagy. We also show that the lipid scramblase ATG-9 is needed for autophagosome formation in early embryos but is dispensable for timely polar body membrane breakdown or protein cargo degradation. These findings demonstrate that macroautophagy is not required to promote polar body degradation, in contrast to recent findings with apoptotic corpse clearance in C. elegans embryos. Determining how membrane association of Atg8/LC3 promotes the breakdown of different types of cell corpses in distinct cell types or metabolic states is likely to give insights into the mechanisms of immunoregulation during normal development, physiology, and disease.
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Affiliation(s)
- Shruti Kolli
- Department of Biological Sciences, University of Denver, Denver, CO, USA
| | - Cassidy J. Kline
- Department of Biological Sciences, University of Denver, Denver, CO, USA
| | - Kimya M. Rad
- Department of Biological Sciences, University of Denver, Denver, CO, USA
| | - Ann M. Wehman
- Department of Biological Sciences, University of Denver, Denver, CO, USA
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Kuo YH, Lai TC, Chang CH, Hsieh HC, Yang FM, Hu MC. 5,6-Dichloro-1-β-D-ribofuranosylbenzimidazole (DRB) induces apoptosis in breast cancer cells through inhibiting of Mcl-1 expression. Sci Rep 2023; 13:12621. [PMID: 37537243 PMCID: PMC10400577 DOI: 10.1038/s41598-023-39340-x] [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: 10/12/2022] [Accepted: 07/24/2023] [Indexed: 08/05/2023] Open
Abstract
The effective treatment of breast cancer remains a profound clinical challenge, especially due to drug resistance and metastasis which unfortunately arise in many patients. The transcription inhibitor 5,6-dichloro-1-beta-D-ribofuranosyl-benzimidazole (DRB), as a selective inhibitor of cyclin-dependent kinase 9, was shown to be effective in inducing apoptosis in various hematopoietic malignancies. However, the anticancer efficacy of DRB against breast cancer is still unclear. Herein, we demonstrated that administration of DRB to the breast cancer cell line led to the inhibition of cellular proliferation and induction of the typical signs of apoptotic cells, including the increases in Annexin V-positive cells, DNA fragmentation, and activation of caspase-7, caspase-9, and poly (ADP ribose) polymerase (PARP). Treatment of DRB resulted in a rapid decline in the myeloid cell leukemia 1 (Mcl-1) protein, whereas levels of other antiapoptotic proteins did not change. Overexpression of Mcl-1 decreased the DRB-induced PARP cleavage, whereas knockdown of Mcl-1 enhanced the effects of DRB on PARP activation, indicating that loss of Mcl-1 accounts for the DRB-mediated apoptosis in MCF-7 cells, but not in T-47D. Furthermore, we found that co-treatment of MCF-7 cells with an inhibitor of AKT (LY294002) or an inhibitor of the proteasome (MG-132) significantly augmented the DRB-induced apoptosis. These data suggested that DRB in combination with LY294002 or MG-132 may have a greater therapeutic potency against breast cancer cells.
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Affiliation(s)
- Yi-Hsuan Kuo
- Graduate Institute of Physiology, National Taiwan University College of Medicine, Taipei, 100, Taiwan
| | - Tsai-Chun Lai
- Graduate Institute of Physiology, National Taiwan University College of Medicine, Taipei, 100, Taiwan
- Department of Life Sciences, College of Life Sciences, National Chung Hsing University, Taichung, 402, Taiwan
| | - Chia-Hsin Chang
- Graduate Institute of Physiology, National Taiwan University College of Medicine, Taipei, 100, Taiwan
| | - Han-Ching Hsieh
- Graduate Institute of Physiology, National Taiwan University College of Medicine, Taipei, 100, Taiwan
| | - Feng-Ming Yang
- School of Respiratory Therapy, College of Medicine, Taipei Medical University, Taipei, 110, Taiwan.
| | - Meng-Chun Hu
- Graduate Institute of Physiology, National Taiwan University College of Medicine, Taipei, 100, Taiwan.
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Regulation of TLR4 signaling through the TRAF6/sNASP axis by reversible phosphorylation mediated by CK2 and PP4. Proc Natl Acad Sci U S A 2021; 118:2107044118. [PMID: 34789577 DOI: 10.1073/pnas.2107044118] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/06/2021] [Indexed: 02/06/2023] Open
Abstract
Recognition of invading pathogens by Toll-like receptors (TLRs) activates innate immunity through signaling pathways that involved multiple protein kinases and phosphatases. We previously demonstrated that somatic nuclear autoantigenic sperm protein (sNASP) binds to TNF receptor-associated factor 6 (TRAF6) in the resting state. Upon TLR4 activation, a signaling complex consisting of TRAF6, sNASP, interleukin (IL)-1 receptor-associated kinase 4, and casein kinase 2 (CK2) is formed. CK2 then phosphorylates sNASP to release phospho-sNASP (p-sNASP) from TRAF6, initiating downstream signaling pathways. Here, we showed that protein phosphatase 4 (PP4) is the specific sNASP phosphatase that negatively regulates TLR4-induced TRAF6 activation and its downstream signaling pathway. Mechanistically, PP4 is directly recruited by phosphorylated sNASP to dephosphorylate p-sNASP to terminate TRAF6 activation. Ectopic expression of PP4 specifically inhibited sNASP-dependent proinflammatory cytokine production and downstream signaling following bacterial lipopolysaccharide (LPS) treatment, whereas silencing PP4 had the opposite effect. Primary macrophages and mice infected with recombinant adenovirus carrying a gene encoding PP4 (Ad-PP4) showed significant reduction in IL-6 and TNF-α production. Survival of Ad-PP4-infected mice was markedly increased due to a better ability to clear bacteria in a sepsis model. These results indicate that the serine/threonine phosphatase PP4 functions as a negative regulator of innate immunity by regulating the binding of sNASP to TRAF6.
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Regulation of liver receptor homologue-1 by DDB2 E3 ligase activity is critical for hepatic glucose metabolism. Sci Rep 2019; 9:5304. [PMID: 30923324 PMCID: PMC6438966 DOI: 10.1038/s41598-019-41411-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 02/07/2019] [Indexed: 02/07/2023] Open
Abstract
Liver receptor homologue-1 (LRH-1) plays a critical role in hepatic metabolism and disease. Here we show that LRH-1 protein stability is regulated by the cullin 4 (CUL4) E3 ubiquitin ligase complex. We found that DNA damage-binding protein 2 (DDB2) directly interacts with LRH-1 and functions as a substrate recognition component of CUL4-DDB1 to promote LRH-1 ubiquitination and proteasomal degradation. In human hepatoma (HepG2) cells, we observed that protein levels of endogenous LRH-1 are increased by insulin without a change in mRNA levels of LRH-1. However, overexpression of DDB2 impaired the insulin-stimulated increase in LRH-1 levels. In addition, DDB2 overexpression decreased LRH-1 transcriptional activation and expression of target genes, such as glucokinase, whereas knockdown of DDB2 increased the expression of glucokinase. Finally, we demonstrated that DDB2 knockdown increases glucose uptake and intracellular levels of glucose-6-phosphate in HepG2 cells. Our study reveals a novel regulatory mechanism of LRH-1 activity and suggests a role for DDB2 in hepatic glucose metabolism.
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Yang FM, Zuo Y, Zhou W, Xia C, Hahm B, Sullivan M, Cheng J, Chang HM, Yeh ET. sNASP inhibits TLR signaling to regulate immune response in sepsis. J Clin Invest 2018; 128:2459-2472. [PMID: 29733298 PMCID: PMC5983344 DOI: 10.1172/jci95720] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 03/16/2018] [Indexed: 01/10/2023] Open
Abstract
Many Toll-like receptors (TLRs) signal through TNF receptor-associated factor 6 (TRAF6) to activate innate immune responses. Here, we show that somatic nuclear autoantigenic sperm protein (sNASP) binds to TRAF6 to prevent TRAF6 autoubiquitination in unstimulated macrophages. Following LPS stimulation, a complex consisting of sNASP, TRAF6, IRAK4, and casein kinase 2 (CK2) is formed. CK2 phosphorylates sNASP at serine 158, allowing sNASP to dissociate from TRAF6. Free TRAF6 is then autoubiquitinated, followed by activation of downstream signaling pathways. In sNasp S158A knockin (S158A-KI) mice, LPS-treated macrophages could not phosphorylate sNASP, which remained bound to TRAF6. S158A-KI mice were more susceptible to sepsis due to a marked reduction in IL-1β, TNF-α, and IFN-γ production accompanied by an inability to clear bacteria and recruit leukocytes. Furthermore, phosphorylation-regulated release of sNASP from TRAF6 is observed following activation of TLR-1, -2, -4, -5, and -6. Thus, sNASP is a negative regulator of TLR signaling to modulate the innate immune response.
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Affiliation(s)
- Feng-Ming Yang
- Center for Precision Medicine, Department of Medicine, University of Missouri, Columbia, Missouri, USA
| | - Yong Zuo
- Department of Biochemistry and Molecular Cell Biology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- State Key Laboratory of Oncogenes & Related Genes, Shanghai Cancer Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Wei Zhou
- Department of Biochemistry and Molecular Cell Biology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- State Key Laboratory of Oncogenes & Related Genes, Shanghai Cancer Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Chuan Xia
- Departments of Surgery and Molecular Microbiology and Immunology, University of Missouri, Columbia, Missouri, USA
| | - Bumsuk Hahm
- Departments of Surgery and Molecular Microbiology and Immunology, University of Missouri, Columbia, Missouri, USA
| | - Mark Sullivan
- Department of Microbiology and Immunology, University of Rochester, School of Medicine and Dentistry, Rochester, New York, USA
| | - Jinke Cheng
- Department of Biochemistry and Molecular Cell Biology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- State Key Laboratory of Oncogenes & Related Genes, Shanghai Cancer Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Hui-Ming Chang
- Center for Precision Medicine, Department of Medicine, University of Missouri, Columbia, Missouri, USA
| | - Edward T.H. Yeh
- Center for Precision Medicine, Department of Medicine, University of Missouri, Columbia, Missouri, USA
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Tecalco-Cruz AC. Molecular pathways involved in the transport of nuclear receptors from the nucleus to cytoplasm. J Steroid Biochem Mol Biol 2018; 178:36-44. [PMID: 29107180 DOI: 10.1016/j.jsbmb.2017.10.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 10/18/2017] [Accepted: 10/25/2017] [Indexed: 12/30/2022]
Abstract
Nuclear receptors (NRs) are transcription regulators that direct the expression of many genes linked to cellular processes, such as proliferation, differentiation, and apoptosis. Additionally, some cellular events are also modulated by signaling pathways induced by NRs outside of the nucleus. Hence, the subcellular transport of NRs is dynamic and is modulated by several signals, protein-protein interactions, and posttranslational modifications. Particularly, the exit of NRs from the nucleus to cytoplasm and/or other compartments is transcendental, as it is this export event, which determines their abundance in the cells' compartments, the activation or attenuation of nuclear or extranuclear pathways, and the magnitude and duration of their effects inside or outside of the nucleus. Consequently, an adequate control of the distribution of NRs is critical for homeostasis, because a deregulation in the nucleo-cytoplasmic transport of NRs could be involved in diseases including cancer as well as metabolic and vascular alterations. In this review, we investigated the pathways and molecular and biological aspects that have been described for the nuclear export of NRs so far and their functional relevance in some diseases. This information suggests that the transport of NRs out of the nucleus is a key mechanism for the identification of new therapeutic targets for alterations associated with the deregulation of the function of NRs.
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Affiliation(s)
- Angeles C Tecalco-Cruz
- Programa de Investigación de Cáncer de Mama, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Apdo Postal, D.F. 04510, Mexico.
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Lai TC, Li HF, Li YS, Hung PY, Shyu MK, Hu MC. Proximal GATA-binding sites are essential for human HSD3B1 gene transcription in the placenta. Sci Rep 2017; 7:4271. [PMID: 28655875 PMCID: PMC5487343 DOI: 10.1038/s41598-017-04133-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Accepted: 05/10/2017] [Indexed: 11/09/2022] Open
Abstract
The enzyme 3β-hydroxysteroid dehydrogenase/isomerase (3β-HSD) is involved in the synthesis of active steroid hormones. Two human 3β-HSD isoforms are expressed in a tissue-specific pattern. HSD3B1 (type I) expression is essential to produce progesterone for pregnancy maintenance. To understand the mechanisms of human HSD3B1 activation in the placenta, 2.2 kb of 5'-flanking sequence and 5'-deletions were fused to the luciferase reporter gene and transfected into human JEG-3 cells. The proximal -238/+337 sequence had the highest promoter activity. Two GATA elements were identified at -106/-99 and -52/-45. Mutations of either sites greatly reduced promoter activity in JEG-3 cells, demonstrating the importance of GATA sites. EMSA revealed the specific binding of GATA2 and GATA3 to the GATA sequences at -106/-99 and -52/-45. ChIP assays demonstrated the association of GATA2 but not GATA3 with the GATA-binding regions of the HSD3B1 promoter in JEG-3 cells. GATA2 knockdown significantly reduced HSD3B1 expression in JEG-3 cells; however, GATA3 knockdown increased HSD3B1 expression. Western blot analysis revealed high levels of GATA2 but not GATA3 in human placental tissues. This study identified GATA motifs as essential control elements for HSD3B1 transcription and GATA2 as a novel transcriptional regulator of HSD3B1 expression in the human placenta.
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Affiliation(s)
- Tsai-Chun Lai
- Graduate Institute of Physiology, National Taiwan University College of Medicine, Taipei, 100, Taiwan
| | - Hsiao-Fang Li
- Graduate Institute of Physiology, National Taiwan University College of Medicine, Taipei, 100, Taiwan
| | - Yu-Shian Li
- Graduate Institute of Physiology, National Taiwan University College of Medicine, Taipei, 100, Taiwan
| | - Pei-Yu Hung
- Graduate Institute of Physiology, National Taiwan University College of Medicine, Taipei, 100, Taiwan
| | - Ming-Kwang Shyu
- Department of Obstetrics and Gynecology, National Taiwan University Hospital, Taipei, 100, Taiwan
| | - Meng-Chun Hu
- Graduate Institute of Physiology, National Taiwan University College of Medicine, Taipei, 100, Taiwan.
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Nucleo-cytoplasmic transport of estrogen receptor alpha in breast cancer cells. Cell Signal 2017; 34:121-132. [PMID: 28341599 DOI: 10.1016/j.cellsig.2017.03.011] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2016] [Revised: 03/19/2017] [Accepted: 03/21/2017] [Indexed: 02/07/2023]
Abstract
Approximately 70% cases of breast cancers exhibit high expression and activity levels of estrogen receptor alpha (ERα), a transcription regulator that induces the expression of genes associated with cellular proliferation and survival. These nuclear functions of the receptor are associated with the development of breast cancer. However, ERα localization is not static, but rather, dynamic with continuous shuttling between the nucleus and the cytoplasm. Interestingly, both the nuclear import and export of ERα are modulated by several stimuli that include estradiol, antiestrogens, and growth factors. As ERα nuclear accumulation is critical to the regulation of gene expression, nuclear export of this receptor modulates the intensity and duration of its transcriptional activity. Thus, the subcellular spatial distribution of ERα ensures tight modulation of its concentration in cellular compartments, as well as of its nuclear and extranuclear functions. In this review, we will discuss current findings regarding the biological importance of molecular mechanisms of, and proteins responsible for, the nuclear import and export of ERα in breast cancer cells.
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