Sun-Kyung Lee and Joohong AhnnMol. Cells 2020; 43(8): 671-685 https://doi.org/10.14348/molcells.2020.0060
Abstract : The regulator of calcineurin (RCAN) was first reported as a novel gene called DSCR1, encoded in a region termed the Down syndrome critical region (DSCR) of human chromosome 21. Genome sequence comparisons across species using bioinformatics revealed three members of the RCAN gene family, RCAN1, RCAN2, and RCAN3, present in most jawed vertebrates, with one member observed in most invertebrates and fungi. RCAN is most highly expressed in brain and striated muscles, but expression has been reported in many other tissues, as well, including the heart and kidneys. Expression levels of RCAN homologs are responsive to external stressors such as reactive oxygen species, Ca2+, amyloid β, and hormonal changes and upregulated in pathological conditions, including Alzheimer’s disease, cardiac hypertrophy, diabetes, and degenerative neuropathy. RCAN binding to calcineurin, a Ca2+/calmodulin-dependent phosphatase, inhibits calcineurin activity, thereby regulating different physiological events via dephosphorylation of important substrates. Novel functions of RCANs have recently emerged, indicating involvement in mitochondria homeostasis, RNA binding, circadian rhythms, obesity, and thermogenesis, some of which are calcineurin-independent. These developments suggest that besides significant contributions to DS pathologies and calcineurin regulation, RCAN is an important participant across physiological systems, suggesting it as a favorable therapeutic target.
Abstract : Autophagy is an intracellular degradation system that breaks down damaged organelles or damaged proteins using intracellular lysosomes. Recent studies have also revealed that various forms of selective autophagy play specific physiological roles under different cellular conditions. Lipid droplets, which are mainly found in adipocytes and hepatocytes, are dynamic organelles that store triglycerides and are critical to health. Lipophagy is a type of selective autophagy that targets lipid droplets and is an essential mechanism for maintaining homeostasis of lipid droplets. However, while processes that regulate lipid droplets such as lipolysis and lipogenesis are relatively well known, the major factors that control lipophagy remain largely unknown. This review introduces the underlying mechanism by which lipophagy is induced and regulated, and the current findings on the major roles of lipophagy in physiological and pathological status. These studies will provide basic insights into the function of lipophagy and may be useful for the development of new therapies for lipophagy dysfunction-related diseases.
Soyeon Jeong , Jinsook Ahn , Ae-Ran Kwon , and Nam-Chul HaMol. Cells 2020; 43(8): 694-704 https://doi.org/10.14348/molcells.2020.0074
Abstract : HslUV is a bacterial heat shock protein complex consisting of the AAA+ ATPase component HslU and the protease component HslV. HslV is a threonine (Thr) protease employing the N-terminal Thr residue in the mature protein as the catalytic residue. To date, HslUV from Gram-negative bacteria has been extensively studied. However, the mechanisms of action and activation of HslUV from Gram-positive bacteria, which have an additional N-terminal sequence before the catalytic Thr residue, remain to be revealed. In this study, we determined the crystal structures of HslV from the Gram-positive bacterium Staphylococcus aureus with and without HslU in the crystallization conditions. The structural comparison suggested that a structural transition to the symmetric form of HslV was triggered by ATP-bound HslU. More importantly, the additional N-terminal sequence was cleaved in the presence of HslU and ATP, exposing the Thr9 residue at the N-terminus and activating the ATP-dependent protease activity. Further biochemical studies demonstrated that the exposed N-terminal Thr residue is critical for catalysis with binding to the symmetric HslU hexamer. Since eukaryotic proteasomes have a similar additional N-terminal sequence, our results will improve our understanding of the common molecular mechanisms for the activation of proteasomes.
Yoon-Gu Jang , Yujin Choi , Kyoungho Jun , and Jongkyeong ChungMol. Cells 2020; 43(8): 705-717 https://doi.org/10.14348/molcells.2020.0089
Abstract : While the growth factors like insulin initiate a signaling cascade to induce conformational changes in the mechanistic target of rapamycin complex 1 (mTORC1), amino acids cause the complex to localize to the site of activation, the lysosome. The precise mechanism of how mTORC1 moves in and out of the lysosome is yet to be elucidated in detail. Here we report that microtubules and the motor protein KIF11 are required for the proper dissociation of mTORC1 from the lysosome upon amino acid scarcity. When microtubules are disrupted or KIF11 is knocked down, we observe that mTORC1 localizes to the lysosome even in the amino acid-starved situation where it should be dispersed in the cytosol, causing an elevated mTORC1 activity. Moreover, in the mechanistic perspective, we discover that mTORC1 interacts with KIF11 on the motor domain of KIF11, enabling the complex to move out of the lysosome along microtubules. Our results suggest not only a novel way of the regulation regarding amino acid availability for mTORC1, but also a new role of KIF11 and microtubules in mTOR signaling.
Weimin Wang , Feifei Wu , Ping Ma , Silin Gan , Xue Li , Li Chen , Ling Sun , Hui Sun , Zhongxing Jiang , and Feng GuoMol. Cells 2020; 43(8): 718-727 https://doi.org/10.14348/molcells.2020.0065
Abstract : The imbalance between the proliferation and apoptosis of B-cell precursors is an important contributor to the pathogenesis of B-cell precursor acute lymphoblastic leukemia (BCP-ALL), while its specific regulatory mechanism remains perplexing. This study aimed to expound the underlying mechanism of the proliferation and apoptosis of BCP-ALL cells from the perspective of non-coding RNA. In this study, long non-coding RNA colorectal neoplasia differentially expressed (LncRNA CRNDE) was upregulated in the bone marrow of BCP-ALL patients and BCP-ALL cell lines (NALM-6 and RS4;11). Functionally, LncRNA CRNDE knockdown restrained cell proliferation and boosted cell apoptosis in NALM-6 and RS4;11 cells. The subsequent investigation confirmed that LncRNA CRNDE bound to miR-345-5p and negatively regulated miR-345-5p expression. The overexpression of miR-345-5p suppressed cell proliferation and boosted cell apoptosis in NALM-6 and RS4;11 cells. Further experiments revealed that miR-345-5p downregulated cyclic AMP response element-binding protein (CREB) expression by targeting its mRNA directly. CREB overexpression reversed the effect of miR-345-5p mimic on cell proliferation and apoptosis in NALM-6 and RS4;11 cells. Finally, in vivo experiments showed that LncRNA CRNDE knockdown prolonged the survival of mice xenotransplanted with NALM-6 cells. In conclusion, LncRNA CRNDE upregulated CREB expression by suppressing miR-345-5p, thus promoting cell proliferation and reducing cell apoptosis in BCP-ALL.
Jongin Lee , Nayoung Park , Daehwan Lee , and Jaebum KimMol. Cells 2020; 43(8): 728-738 https://doi.org/10.14348/molcells.2020.0040
Abstract : Time and cost-effective production of next-generation sequencing data has enabled the performance of population-scale comparative and evolutionary studies for various species, which are essential for obtaining the comprehensive insight into molecular mechanisms underlying species- or breed-specific traits. In this study, the evolutionary and functional analysis of Korean native pig (KNP) was performed using single nucleotide polymorphism (SNP) data by comparative and population genomic approaches with six different mammalian species and five pig breeds. We examined the evolutionary history of KNP SNPs, and the specific genes of KNP based on the uniqueness of non-synonymous SNPs among the used species and pig breeds. We discovered the evolutionary trajectory of KNP SNPs within the used mammalian species as well as pig breeds. We also found olfaction-associated functions that have been characterized and diversified during evolution, and quantitative trait loci associated with the unique traits of KNP. Our study provides new insight into the evolution of KNP and serves as a good example for a better understanding of domestic animals in terms of evolution and domestication using the combined approaches of comparative and population genomics.
Dong-Seol Lee , Song Yi Roh , Hojae Choi , and Joo-Cheol ParkMol. Cells 2020; 43(8): 739-748 https://doi.org/10.14348/molcells.2020.2272
Abstract : Stringent regulation of the chondrocyte cell cycle is required for endochondral bone formation. During the longitudinal growth of long bones, mesenchymal stem cells condense and differentiate into chondrocytes. Epiphyseal chondrocytes sequentially differentiate to form growth- plate cartilage, which is subsequently replaced with bone. Although the importance of nuclear factor 1C (Nfic) in hard tissue formation has been extensively studied, knowledge regarding its biological roles and molecular mechanisms in this process remains insufficient. Herein, we demonstrated that Nfic deficiency affects femoral growth-plate formation. Chondrocyte proliferation was downregulated and the number of apoptotic cell was increased in the growth plates of Nfic-/- mice. Further, the expression of the cell cycle inhibitor p21 was upregulated in the primary chondrocytes of Nfic-/- mice, whereas that of cyclin D1 was downregulated. Our findings suggest that Nfic may contribute to postnatal chondrocyte proliferation by inhibiting p21 expression and by increasing the stability of cyclin D1 protein.
JiSheng Hu , ShangJing Pi , MingRui Xiong , ZhongYing Liu , Xia Huang , Ran An , TongCun Zhang , and BaiYin YuanMol. Cells 2020; 43(8): 749-762 https://doi.org/10.14348/molcells.2020.0085
Abstract : The migration, dedifferentiation, and proliferation of vascular smooth muscle cells (VSMCs) are responsible for intimal hyperplasia, but the mechanism of this process has not been elucidated. WD repeat domain 1 (WDR1) promotes actin-depolymerizing factor (ADF)/cofilin-mediated depolymerization of actin filaments (F-actin). The role of WDR1 in neointima formation and progression is still unknown. A model of intimal thickening was constructed by ligating the left common carotid artery in Wdr1 deletion mice, and H&E staining showed that Wdr1 deficiency significantly inhibits neointima formation. We also report that STAT3 promotes the proliferation and migration of VSMCs by directly promoting WDR1 transcription. Mechanistically, we clarified that WDR1 promotes the proliferation and migration of VSMCs and neointima formation is regulated by the activation of the JAK2/STAT3/WDR1 axis.