Autophagy Is Pro-Senescence When Seen in Close-Up, but Anti-Senescence in Long-Shot

Kwon, Yoojin,Kim, Ji Wook,Jeoung, Jo Ae,Kim, Mi-Sung,Kang, Chanhee Korean Society for Molecular and Cellular Biology 2017 Molecules and cells Vol.40 No.9

When mammalian cells and animals face a variety of internal or external stresses, they need to make homeostatic changes so as to cope with various stresses. To this end, mammalian cells are equipped with two critical stress responses, autophagy and cellular senescence. Autophagy and cellular senescence share a number of stimuli including telomere shortening, DNA damage, oncogenic stress and oxidative stress, suggesting their intimate relationship. Autophagy is originally thought to suppress cellular senescence by removing damaged macromolecules or organelles, yet recent studies also indicated that autophagy promotes cellular senescence by facilitating the synthesis of senescence-associated secretory proteins. These seemingly opposite roles of autophagy may reflect a complex picture of autophagic regulation on cellular senescence, including different types of autophagy or a unique spatiotemporal activation of autophagy. Thus, a better understanding of autophagy process will lead us to not only elucidate the conundrum how autophagy plays dual roles in the regulation of cellular senescence but also helps the development of new therapeutic strategies for many human diseases associated with cellular senescence. We address the pro-senescence and anti-senescence roles of autophagy while focusing on the potential mechanistic aspects of this complex relationship between autophagy and cellular senescence.

Enhancing Anti-Cancer Therapy with Selective Autophagy Inhibitors by Targeting Protective Autophagy

Lee Min Ju,Park Jae-Sung,Jo Seong Bin,Joe Young Ae 한국응용약물학회 2023 Biomolecules & Therapeutics(구 응용약물학회지) Vol.31 No.1

Autophagy is a process of eliminating damaged or unnecessary proteins and organelles, thereby maintaining intracellular homeostasis. Deregulation of autophagy is associated with several diseases including cancer. Contradictory dual roles of autophagy have been well established in cancer. Cytoprotective mechanism of autophagy has been extensively investigated for overcoming resistance to cancer therapies including radiotherapy, targeted therapy, immunotherapy, and chemotherapy. Selective autophagy inhibitors that directly target autophagic process have been developed for cancer treatment. Efficacies of autophagy inhibitors have been tested in various pre-clinical cancer animal models. Combination therapies of autophagy inhibitors with chemotherapeutics are being evaluated in clinal trials. In this review, we will focus on genetical and pharmacological perturbations of autophagy- related proteins in different steps of autophagic process and their therapeutic benefits. We will also summarize combination therapies of autophagy inhibitors with chemotherapies and their outcomes in pre-clinical and clinical studies. Understanding of current knowledge of development, progress, and application of cytoprotective autophagy inhibitors in combination therapies will open new possibilities for overcoming drug resistance and improving clinical outcomes.

A progressive reduction in autophagic capacity contributes to induction of replicative senescence in Hs68 cells

Han, Byeal-I,Hwang, Sung-Hee,Lee, Michael Elsevier 2017 The international journal of biochemistry & cell b Vol.92 No.-

<P><B>Abstract</B></P> <P>Autophagy has been implicated in delayed aging and extended longevity. Here, we aimed to study the possible effects of autophagy during the progression of replicative senescence, which is one of the major features of aging. Human foreskin fibroblasts, Hs68 cells, at an initial passage of 15 were serially cultured for several months until they reached cellular senescence. A decrease in cell proliferation was observed during the progression of senescence. Induction of replicative senescence in aged cells (at passage 40) was confirmed by senescence-associated β-galactosidase (SA-β-gal) activity that represents a sensitive and reliable marker for quantifying senescent cells. We detected a significantly increased percentage (%) of SA-β-gal-positive cells at passage 40 (63%) when compared with the younger SA-β-gal-positive cells at passage 15 (0.5%). Notably, the gradual decrease in basal autophagy coincided with replicative senescence induction. However, despite decreased basal autophagic activity in senescent cells, autophagy inducers could induce autophagy in senescent cells. RT-PCR analysis of 11 autophagy-related genes revealed that the decreased basal autophagy in senescent cells might be due to the downregulation of autophagy-regulatory proteins, but not autophagy machinery components. Moreover, the senescence phenotype was not induced in the cells in which rapamycin was added to the culture to continuously induce autophagy from passage 29 until passage 40. Together, our findings suggest that reduced basal autophagy levels due to downregulation of autophagy-regulatory proteins may be the mechanism underlying replicative senescence in Hs68 cells.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Gradual decrease in basal autophagy coincides with replicative senescence induction. </LI> <LI> Autophagy is inducible by rapamycin in senescent cells. </LI> <LI> Senescent cells show decreased expression of autophagy-related genes. </LI> <LI> Rapamycin-induced autophagy suppresses replicative senescence. </LI> </UL> </P>

Silkworm Storage Protein 1 Inhibits Autophagy-Mediated Apoptosis

Kang, Su Jin,Rhee, Won Jong MDPI 2019 INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES Vol.20 No.2

<P>Autophagy is a natural physiological process, and it induces the lysosomal degradation of intracellular components in response to environmental stresses, including nutrient starvation. Although an adequate autophagy level helps in cell survival, excessive autophagy triggered by stress such as starvation leads to autophagy-mediated apoptosis. Chinese hamster ovary (CHO) cells are widely used for producing biopharmaceuticals, including monoclonal antibodies. However, apoptosis induced by high stress levels, including nutrient deficiency, is a major problem in cell cultures grown in bioreactors, which should be overcome. Therefore, it is necessary to develop a method for suppressing excessive autophagy and for maintaining an appropriate autophagy level in cells. Therefore, we investigated the effect of silkworm storage protein 1 (SP1), an antiapoptotic protein, on autophagy-mediated apoptosis. SP1-expressing CHO cells were generated to assess the effect and molecular mechanism of SP1 in suppressing autophagy. These cells were cultured under starvation conditions by treatment with Earle’s balanced salt solution (EBSS) to induce autophagy. We observed that SP1 significantly inhibited autophagy-mediated apoptosis by suppressing caspase-3 activation and reactive oxygen species generation. In addition, SP1 suppressed EBSS-induced conversion of LC3-I to LC3-II and the expression of autophagy-related protein 7. Notably, basal Beclin-1 level was significantly low in the SP1-expressing cells, indicating that SP1 regulated upstream events in the autophagy pathway. Together, these findings suggest that SP1 offers a new strategy for overcoming severe autophagy-mediated apoptosis in mammalian cells, and it can be used widely in biopharmaceutical production.</P>

Autophagy and Oral Cancer

Seung Hwa Son(손승화),Eun-Jung Kim(김은정) 한국생명과학회 2017 생명과학회지 Vol.27 No.8

Autophagy는 세포 내에서 세포의 재활용과 다양한 스트레스에 세포 homeostasis와 survival에 중요한 역할을 한다. 최근 연구에서는 autophagy 활성이 oncogenes과 tumor suppressor genes의 발현이 조절됨으로써 암이 발달되거나 억제됨이 보고되고 있다. Autophagy의 유도는 정상세포에서는 암 발생을 예방하는데 관여하며, 손상된 세포사멸 기능을 가진 암세포에서는 특정세포사멸기전을 유발하는데 중요한 역할을 한다. 또한 autophagy 억제는 항암약물과 치료법에 저항을 나타내는 암세포를 민감하게 만들어 치료효능을 증가시킨다고 증명되고 있다. 그러나 cancer 치료에서의 autophagy의 역할은 아직까지 완전히 이해되지 않았다. Oral squamous cell carcinoma (OSCC)는 구강암의 90% 이상을 차지하고 있으며, 전세계적으로 6th 가장 흔한 암중의 하나로, 최근 2배 이상 증가하고 있으며 높은 mortality rate를 보이고 있다. 구강암에서의 autophagy의 역할은 다른 암들과 마찬가지로 종양형성의 초기 단계 동안 종양억제성을 보이나, 종양진행 동안은 종양세포 생존에 관여하는 두 가지의 기능을 나타내는 것으로 보고되고 있다. 본 리뷰에서는, 암에서의 autophagy의 조절에 대한 다양한 역할을 요약하고, 이를 바탕으로 효과적인 암 치료를 위한 유망한 target으로 autophagy의 가능성을 제시하고자 한다. Autophagy plays an important role in cellular homeostasis and survival for cell recycling and various stresses within the cell. Recent studies have shown that autophagy activity modulates the expression of oncogene and tumor suppressor genes, leading to the development or suppression of cancer. Induction of autophagy is involved in preventing cancer development in normal cells and plays an important role in prompting a specific cell death mechanism in cancer cells with damaged cell death function. It is also known that autophagy inhibition increases the therapeutic efficacy by sensitizing cancer cells that are resistant to chemotherapy. However, the role of autophagy has not yet been fully understood in cancer treatment. Oral squamous cell carcinoma accounts for more than 90% of oral cancer and is the sixth most common cancer in the world. The incidence of oral cancer has increased by 50% over the last 20 years and the mortality rate is over 40% within 5 years after the onset. In oral cancers, the role of autophagy are described to look for tumor inhibitory in the early stages of tumor formation, like other cancers, indicating the dual functions involved in tumor cell survival include tumor progression stages. This review summarizes the various roles of autophagy in cancer cells and suggests the possibility of autophagy as a promising target for effective oral cancer therapy.

Overview of the Minireviews on Autophagy

이명식 한국분자세포생물학회 2018 Molecules and cells Vol.41 No.1

After coining the term ‘autophagy’ by Dr. Christian De Duve in 1967 during a study using glucagon-perfused liver (Deter and de Duve, 1967), researches on autophagy was slow. The discovery of autophagy genes using a yeast model revolutionized the field and ushered into the era of molecular autophagy (Noda et al., 1995). In recognition of this discovery, Yoshinori Ohsumi was awarded the Nobel Prize in Physiology or Medicine 2016. Because of extensive effort and contribution by other investigators, we now know that autophagy is indeed critical for the maintenance or rejuvenation of cellular organelles and for energy homeostasis from yeast to human. Thus, many aspects of physiological or pathological phenomena are influenced by autophagy and its dysregulation. Dysregulated autophagy appears to participate in the development of multitudes of diseases such as neurodegeneration, cancer, metabolic diseases, cardiovascular diseases, inflammatory disorders, and aging. Considering enormous implication of autophagy in cellu-lar physiology and in the pathogenesis of diverse diseases at the organismal level, the current minireview series was organized. Nakamura and Yoshimori (2018) summarized the role of autophagy in longevity and aging. Aging could be considered either as a physiological or pathological process, and would be affected by autophagy regardless of grouping. Shimizu (2018) reviewed the topic of non-canonical autophagy. In addition to classical Atg5/Atg7-dependent macroautophagy, several other types of autophagy have emerged, including unconventional autophagy that does not involve certain classical Atg genes. Fukuda and Kanki focused on mitophagy in yeast system, while Yoo and Jung (2018) summarized recent findings regarding mitophagy in mammalian system. Mitophagy is an example of selective autophagy that has implications in several important diseases such as Parkinson’s disease. Cho et al. (2018) reviewed another type of selective autophagy – pexophagy, autophagy of peroxisome which is critical in very-long chain fatty acids oxidation. While the role of lysosome in autophagy execution is well known, fate of lysosome after execution of autophagy is not well recognized. Chen and Yu (2018) addressed this point and discussed the molecular mechanism of autophagic lysosome reformation (Yu et al., 2010). Kim et al. (2018) reviewed the role of autophagy in the development of diabetes associated with obesity and also of human-type diabetes. Human diabetes is different from murine diabetes in that islet amyloid is found in > 90% of patients with human diabetes. Since amyloid-prone protein is a well-recognized substrate of autophagy, efficient autophagy could be important for normal islet function and viability. Namkoong et al. (2018) discussed about autophagy in obesity, and particularly focused on the reciprocal interaction between obesity and autophagy. Autophagy has a crucial role in the clearance of microbes through a specific phenomenon named xenophagy. Kwon and Song (2018) reviewed interaction between autophagy machinery and bacterial products from the structural perspective. These minireviews illustrate recent progress in understanding of the molecular mechanism of autophagy, and also potential application of this knowledge to the development of autophagy modulators that can be employed for treatment of the aforementioned diseases. Since many investigators and pharmaceutical or biotech companies are making great efforts to develop such autophagy enhancers or blockers, depending on the target diseases or processes, novel therapeutic agents that modulate autophagy will become a reality in the near future.

Verification of autophagy in porcine oocytes and investigation of its roles

Seunghoon Lee,Seokho Kim,Hyeon Yang,Hayeon Wi,Yongjin Jo,Haeyun Jeong,Ji-Youn Kim,Sun Keun Jung,Sung June Byun 한국실험동물학회 2021 한국실험동물학회 학술발표대회 논문집 Vol.2021 No.7

Autophagy is well-conserved cellular recycling process. However, autophagy in in-vitro porcine oocyte maturation have not been discovered yet. In this study, we confirmed autophagosome in-vitro culturing porcine oocytes by detection of LC3 which is promised marker protein of autophagosome. Then, we also examine the relationship between autophagy and oocyte maturation by treatment of autophagic inhibitors or nuclear maturation inhibitors. Autophagy activation was regarded to amount of autophagosome in this study. To autophagosome detection in porcine oocytes, Immunochemistry and westernblotting using LC3 antibody was conducted by culturing time of 0 h, 14 h, 28 h, and 42 h. Then, we measured LC3-II levels using western blotting after inhibiting nuclear maturation of oocytes via cAMP treatment in an in vitro culture, to clarify whether nuclear maturation affects autophagy. To clarify whether autophagy affects nuclear maturation, we also counted mature oocytes after inhibiting autophagy by treating with wortmannin or a mixture of E64d and pepstatin A. Both groups of cAMP, which were applied for different treatment times, showed the same levels of LC3-II, while their maturation rate was approximately four times higher in 22h treatment than that of the cAMP 42h treatment group. This indicated that neither cAMP nor nuclear status affected autophagy. Autophagy inhibition during in vitro maturation with wortmannin treatment decreased oocyte maturation rates by approximately half, but autophagy inhibition in the E64d/pepstatin A mixture treatment did not significantly affect the oocyte maturation rate. Thus, wortmannin itself, or the autophagy induction step, but not the degradation step, is involved in the oocyte maturation of porcine oocytes. Overall, we confirmed autophagic dynamic during porcine in-vitro maturation. Moreover, we suggest that oocyte maturation does not exist upstream of autophagy, but autophagy may exist upstream of oocyte maturation.

Autophagy Is Pro-Senescence When Seen in Close-Up, but Anti-Senescence in Long-Shot

권유진,김지욱,정조애,김미성,강찬희 한국분자세포생물학회 2017 Molecules and cells Vol.40 No.9

When mammalian cells and animals face a variety of internal or external stresses, they need to make homeostatic changes so as to cope with various stresses. To this end, mammalian cells are equipped with two critical stress responses, autophagy and cellular senescence. Autophagy and cellular senescence share a number of stimuli including telomere shortening, DNA damage, oncogenic stress and oxidative stress, suggesting their intimate relationship. Autophagy is originally thought to suppress cellular senescence by removing damaged macromolecules or organelles, yet recent studies also indicated that autophagy promotes cellular senescence by facilitating the synthesis of senescence-associated secretory proteins. These seemingly opposite roles of autophagy may reflect a complex picture of autophagic regulation on cellular senescence, including different types of autophagy or a unique spatiotemporal activation of autophagy. Thus, a better understanding of autophagy process will lead us to not only elucidate the conundrum how autophagy plays dual roles in the regulation of cellular senescence but also helps the devel-opment of new therapeutic strategies for many human diseases associated with cellular senescence. We address the pro-senescence and anti-senescence roles of autophagy while focusing on the potential mechanistic aspects of this complex relationship between autophagy and cellular senescence.

De novo design of a novel AIE fluorescent probe tailored to autophagy visualization via pH manipulation

Huang Xueyan,Chen Fei,Ma Yeshuo,Zheng Fan,Fang Yanpeng,Feng Bin,Huang Shuai,Zeng Hongliang,Zeng Wenbin 한국생체재료학회 2023 생체재료학회지 Vol.27 No.00

Macroautophagy is an essential cellular self-protection mechanism, and defective autophagy has been considered to contribute to a variety of diseases. During the process, cytoplasmic components are transported via autophagosomes to acidic lysosomes for metabolism and recycling, which represents application niches for lysosome-targeted fluorescent probes. Additionally, in view of the complexity of the autophagy pathway, it entails more stringent requirements for probes suitable for monitoring autophagy. Meanwhile, aggregation-induced emission (AIE) fluorescent probes have been impressively demonstrated in the biomedical field, which bring fascinating possibilities to the autophagy visualization.We reported a generalizable de novo design of a novel pH-sensitive AIE probe ASMP-AP tailored to lysosome targeting for the interpretation of autophagy. Firstly, the theoretical calculation was carried out followed by the investigation of optical properties. Then, the performance of ASMP-AP in visualizing autophagy was corroborated by starvation or drugs treatments. Furthermore, the capability of ASMP-AP to monitor autophagy was demonstrated in ex vivo liver tissue and zebrafish in vivo.ASMP-AP displays a large stokes shift, great cell permeability and good biocompatibility. More importantly, ASMP-AP enables a good linear response to pH, which derives from the fact that its aggregation state can be manipulated by the acidity. It was successfully applied for imaging autophagy in living cells and was proved capable of monitoring mitophagy. Moreover, this novel molecular tool was validated by ex vivo visualization of activated autophagy in drug-induced liver injury model. Interestingly, it provided a meaningful pharmacological insight that the melanin inhibitor 1-phenyl-2-thiourea (PTU)-induced autophagy was clearly presented in wild-type zebrafish.ASMP-AP offers a simple yet effective tool for studying lysosome and autophagy. This is the first instance to visualize autophagy in zebrafish using a small-molecule probe with AIE characters, accurate lysosome targeting and simultaneous pH sensitivity. Ultimately, this novel fluorescent system has great potential for in vivo translation to fuel autophagy research.

Neuronal Autophagy: Characteristic Features and Roles in Neuronal Pathophysiology

( McNeil Valencia ),( Sung Rae Kim ),( Yeseul Jang ),( Sung Hoon Lee ) 한국응용약물학회 2021 Biomolecules & Therapeutics(구 응용약물학회지) Vol.29 No.6

Autophagy is an important degradative pathway that eliminates misfolded proteins and damaged organelles from cells. Autophagy is crucial for neuronal homeostasis and function. A lack of or deficiency in autophagy leads to the accumulation of protein aggregates, which are associated with several neurodegenerative diseases. Compared with non-neuronal cells, neurons exhibit rapid autophagic flux because damaged organelles or protein aggregates cannot be diluted in post-mitotic cells; because of this, these cells exhibit characteristic features of autophagy, such as compartment-specific autophagy, which depends on polarized structures and rapid autophagy flux. In addition, neurons exhibit compartment-specific autophagy, which depends on polarized structures. Neuronal autophagy may have additional physiological roles other than amino acid recycling. In this review, we focus on the characteristics and regulatory factors of neuronal autophagy. We also describe intracellular selective autophagy in neurons and its association with neurodegenerative diseases.