Regulatory system for the G1‐arrest during neuronal development in Drosophila

Neuronal network consists of many types of neuron and glial cells. This diversity is guaranteed by the constant cell proliferation of neuronal stem cells following stop cell cycle re‐entry, which leads to differentiation during development. Neuronal differentiation occurs mainly at the specific cell cycle phase, the G1 phase. Therefore, cell cycle exit at the G1 phase is quite an important issue in understanding the process of neuronal cell development. Recent studies have revealed that aberrant S phase re‐entry from the G1 phase often links cellular survival. In this review we discuss the different types of G1 arrest on the process of neuronal development in Drosophila. We also describe the issue that aberrant S phase entry often causes apoptosis, and the same mechanism might contribute to sensory organ defects, such as deafness.     

SNR1 is an essential subunit in a subset of Drosophila brm complexes,targeting specific functions during development

The snr1 gene of Drosophila melanogaster encodes a conserved component of the multiprotein Brahma (Brm) complex, a counterpart to the SWI/SNF complexes that participate in ATP-dependent chromatin remodeling. Loss-of-function and null mutations in the snr1 gene reveal its essential role in Drosophila development. We identified new mutant alleles and ectopically expressed deleted forms to dissect the specific functions of SNR1. Somatic and germ cell clone analyses confirmed its requirement in a continuous and widespread fashion for proper cell fate determination and oogenesis. Expression of SNR1 transgenes revealed unexpected roles in wing patterning, abdomen development, oogenesis, and sustained adult viability. A widespread distribution of SNR1 and BRM on the salivary gland polytene chromosomes showed that the Brm complex associated with many genes, but not always at transcribed loci, consistent with genetic data suggesting roles in both gene activation and repression. Despite essential Brm complex functions in leg development, genetic and protein localization studies revealed that snr1 was not required or expressed in all tissues dependent on Brm complex activities. Thus, SNR1 is essential for some, but not all Brm functions, and it likely serves as an optional subunit, directing Brm complex activity to specific gene loci or cellular processes.     

LAD-1, the Caenorhabditis elegans L1CAM homologue, participates in embryonic and gonadal morphogenesis and is a substrate for fibroblast growth factor receptor pathway-dependent phosphotyrosine-based signaling

This study shows that L1-like adhesion (LAD-1), the sole Caenorhabditis elegans homologue of the L1 family of neuronal adhesion molecules, is required for proper development of the germline and the early embryo and embryonic and gonadal morphogenesis. In addition, the ubiquitously expressed LAD-1, which binds to ankyrin-G, colocalizes with the C. elegans ankyrin, UNC-44, in multiple tissues at sites of cell-cell contact. Finally, we show that LAD-1 is phosphorylated in a fibroblast growth factor receptor (FGFR) pathway-dependent manner on a tyrosine residue in the highly conserved ankyrin-binding motif, FIGQY, which was shown previously to abolish the L1 family of cell adhesion molecule (L1CAM) binding to ankyrin in cultured cells. Immunofluorescence studies revealed that FIGQY-tyrosine-phosphorylated LAD-1 does not colocalize with nonphosphorylated LAD-1 or UNC-44 ankyrin but instead is localized to sites that undergo mechanical stress in polarized epithelia and axon-body wall muscle junctions. These findings suggest a novel ankyrin-independent role for LAD-1 related to FGFR signaling. Taken together, these results indicate that L1CAMs constitute a family of ubiquitous adhesion molecules, which participate in tissue morphogenesis and maintaining tissue integrity in metazoans.     

Two closely related human members of chitinase-like family, CHI3L1 and CHI3L2, activate ERK1/2 in 293 and U373 cells but have the different influence on cell proliferation

The activation of extracellular signal-regulated kinases (ERK1/2) has been associated with specific outcomes. Sustained activation of ERK1/2 by nerve growth factor (NGF) is associated with translocation of ERKs to the nucleus of PC12 cells and precedes their differentiation into sympathetic-like neurons whereas transient activation by epidermal growth factor (EGF) leads to cell proliferation. It was demonstrated that different growth factors initiating the same cellular signaling pathways may lead to the different cell destiny, either to proliferation or to the inhibition of mitogenesis and apoptosis. Thus, further investigation on kinetic differences in activation of certain signal cascades in different cell types by biologically different agents are necessary for understanding the mechanisms as to how cells make a choice between proliferation and differentiation.It was reported that chitinase 3-like 1 (CHI3L1) protein promotes the growth of human synovial cells as well as skin and fetal lung fibroblasts similarly to insulin-like growth factor 1 (IGF1). Both are involved in mediating the mitogenic response through the signal-regulated kinases ERK1/2. In addition, CHI3L1 which is highly expressed in different tumors including glioblastomas possesses oncogenic properties. As we found earlier, chitinase 3-like 2 (CHI3L2) most closely related to human CHI3L1 also showed increased expression in glial tumors at both the RNA and protein levels and stimulated the activation of the MAPK pathway through phosphorylation of ERK1/2 in 293 and U87 MG cells. The work described here demonstrates the influence of CHI3L2 and CHI3L1 on the duration of MAPK cellular signaling and phosphorylated ERK1/2 translocation to the nucleus. In contrast to the activation of ERK1/2 phosphorylation by CHI3L1 that leads to a proliferative signal (similar to the EGF effect in PC12 cells), activation of ERK1/2 phosphorylation by CHI3L2 (similar to NGF) inhibits cell mitogenesis and proliferation.     

Comparative analysis of antitumor activity of CD40L, RANKL, and 4-1BBL in vivo following intratumoral administration of viral vectors or transduced dendritic cells

The tumor necrosis factor (TNF) family comprises a group of ligands that regulate cell proliferation, differentiation, activation, maturation and apoptosis through interaction with the corresponding TNF receptor family members. In this study, we have evaluated whether adenovirus-mediated intratumoral gene transfer of CD40L, RANKL, or 4-1BBL elicits an immune response to established murine MC38 and TS/A tumors. Intratumoral administration of the recombinant adenoviral vectors expressing CD40L, RANKL or 4-1BBL 7 days post-tumor cell inoculation resulted in significant inhibition of MC38 tumor growth for all three ligands when compared with control groups treated with either saline or control adenovirus. However, intratumoral injection of Ad-4-1BBL or Ad-CD40L resulted in a significantly stronger inhibition of TS/A tumor progression than did Ad-RANKL treatment. We also demonstrated that intratumoral administration of dendritic cells (DC) transduced with adenoviral vectors encoding the TNF-related ligands resulted in a significant inhibition of MC38 tumor growth as compared with control groups treated with Ad-LacZ-transduced DC or saline-treated DC. In addition, DC overexpressing CD40L secreted considerably more IL-12 and expressed higher levels of the co-stimulatory molecules, CD80, CD86 and CD40, than did DC overexpressing LacZ, 4-1BBL or RANKL. We have also demonstrated that DC/CD40L, DC/4-1BBL, and DC/RANKL survived significantly longer than control DC or DC infected with the LacZ vector. Taken together, these results demonstrate that adenoviral gene transfer of CD40L, RANKL or 4-1BBL elicit a significant antitumor effect in two different tumor models, with CD40L gene transfer inducing the strongest antitumor effect.     

The candidate sour taste receptor, PKD2L1, is expressed by type III taste cells in the mouse

The transient receptor potential channel, PKD2L1, is reported to be a candidate receptor for sour taste based on molecular biological and functional studies. Here, we investigated the expression pattern of PKD2L1-immunoreactivity (IR) in taste buds of the mouse. PKD2L1-IR is present in a few elongate cells in each taste bud as reported previously. The PKD2L1-expressing cells are different from those expressing PLCbeta2, a marker of Type II cells. Likewise PKD2L1-immunoreactive taste cells do not express ecto-ATPase which marks Type I cells. The PKD2L1-positive cells are immunoreactive for neural cell adhesion molecule, serotonin, PGP-9.5 (ubiquitin carboxy-terminal transferase), and chromogranin A, all of which are present in Type III taste cells. At the ultrastructural level, PKD2L1-immunoreactive cells form synapses onto afferent nerve fibers, another feature of Type III taste cells. These results are consistent with the idea that different taste cells in each taste bud perform distinct functions. We suggest that Type III cells are necessary for transduction and/or transmission of information about "sour", but have little or no role in transmission of taste information of other taste qualities.     

Dwarf and deformed flower 1, encoding an F‐box protein,is critical for vegetative and floral development in rice (Oryza sativa L.)

Recent studies have shown that F‐box proteins constitute a large family in eukaryotes, and play pivotal roles in regulating various developmental processes in plants. However, their functions in monocots are still obscure. In this study, we characterized a recessive mutant dwarf and deformed flower 1‐1 (ddf1‐1) in Oryza sativa (rice). The mutant is abnormal in both vegetative and reproductive development, with significant size reduction in all organs except the spikelet. DDF1 controls organ size by regulating both cell division and cell expansion. In the ddf1‐1 spikelet, the specification of floral organs in whorls 2 and 3 is altered, with most lodicules and stamens being transformed into glume‐like organs and pistil‐like organs, respectively, but the specification of lemma/palea and pistil in whorls 1 and 4 is not affected. DDF1 encodes an F‐box protein anchored in the nucleolus, and is expressed in almost all vegetative and reproductive tissues. Consistent with the mutant floral phenotype, DDF1 positively regulates B‐class genes OsMADS4 and OsMADS16, and negatively regulates pistil specification gene DL. In addition, DDF1 also negatively regulates the Arabidopsis LFY ortholog APO2, implying a functional connection between DDF1 and APO2. Collectively, these results revealed that DDF1, as a newly identified F‐box gene, is a crucial genetic factor with pleiotropic functions for both vegetative growth and floral organ specification in rice. These findings provide additional insights into the molecular mechanism controlling monocot vegetative and reproductive development.     

The miR‐3127‐5p/p‐STAT3 axis up‐regulates PD‐L1 inducing chemoresistance in non‐small‐cell lung cancer

It is less known about miRNA3127‐5p induced up‐regulation of PD‐L1, immune escape and drug resistance caused by increased PD‐L1 in lung cancer. In this study, lentivirus was transduced into lung cancer cells, and quantitative PCR and Western blot were used to detect the expression of PD‐L1. Then immunofluorescence assay was applied to detect autophagy, finally we explored the relationship between PD‐L1 expressions and chemoresistance in patients. As a result, we found that microRNA‐3127‐5p promotes pSTAT3 to induce the expression of PD‐L1; microRNA‐3127‐5p promotes STAT3 phosphorylation through suppressing autophagy, and autophagy could retaine pSTAT3 into the nucleus in miRNA‐3127‐5p knocked cells, and immune escape induced by elevated level of PD‐L1 results in chemoresistance of lung cancer. In conclusion, microRNA‐3127‐5p induces PD‐L1 elevation through regulating pSTAT3 expression. We also demonstrate that immune escape induced by PD‐L1 can be dismissed by corresponding monoclonal antibody.     

Inhibition of NF‐κB is required for oleanolic acid to downregulate PD‐L1 by promoting DNA demethylation in gastric cancer cells

Gastric cancer is one of the most common causes of cancer‐related death worldwide. Immunotherapy via programmed cell death protein 1 (PD‐1)/programmed cell death‐ligand 1 (PD‐L1) blockade has shown benefits for gastric cancer. Epigenetic DNA methylation critically regulates cancer immune checkpoints. We investigated how the natural compound oleanolic acid (OA) affected PD‐L1 expression in gastric cancer cells. Interleukin‐1β (IL‐1β) at 20 ng/mL was used to stimulate human gastric cancer MKN‐45 cells. IL‐1β significantly increased PD‐L1 expression, which was abolished by OA. Next, OA‐treated MKN‐45 cells were co‐cultured with activated and PD‐1‐overexpressing Jurkat T cells. OA restored IL‐2 levels in the co‐culture system and increased T cell killing toward MKN‐45 cells. Overexpression of PD‐L1 eliminated OA‐enhanced T cell killing capacity; however, PD‐1 blocking antibody abrogated the cytotoxicity of T cells. Moreover, OA abolished IL‐1β‐increased DNA demethylase activity in MKN‐45 cells. DNA methyltransferase inhibitor 5‐azacytidine rescued OA‐reduced PD‐L1 expression; whereas DNA demethylation inhibitor gemcitabine inhibited PD‐L1 expression, and, in combination with OA, provided more potent inhibitory effects. Furthermore, OA selectively reduced the expression of DNA demethylase TET3 in IL‐1β‐treated MKN‐45 cells, and overexpression of TET3 restored OA‐reduced PD‐L1 expression. Finally, OA disrupted nuclear factor κB (NF‐κB) signaling IL‐1β‐treated MKN‐45 cells, and overexpression of NF‐κB restored OA downregulation of TET3 and PD‐L1. The cytotoxicity of T cells toward MKN‐45 cells was also weakened by NF‐κB overexpression. Altogether, OA blocked the IL‐1β/NF‐κB/TET3 axis in gastric cancer cells, leading to DNA hypomethylation and downregulation of PD‐L1. Our discoveries suggested OA as an epigenetic modulator for immunotherapy or an adjuvant therapy against gastric cancer.     

The classic receptor for 1alpha,25-dihydroxy vitamin D3 is required for non-genomic actions of 1alpha,25-dihydroxy vitamin D3 in osteosarcoma cells

1alpha,25-dihydroxy vitamin D3 has a major role in the regulation of the bone metabolism as it promotes the expression of key bone-related proteins in osteoblastic cells. In recent years it has become increasingly evident that in addition to its well-established genomic actions, 1alpha,25-dihydroxy vitamin D3 induces non-genomic responses by acting through a specific plasma membrane-associated receptor. Results from several groups suggest that the classical nuclear 1alpha,25-dihydroxy vitamin D3 receptor (VDR) is also responsible for these non-genomic actions of 1alpha,25-dihydroxy vitamin D3. Here, we have used siRNA to suppress the expression of VDR in osteoblastic cells and assessed the role of VDR in the non-genomic response to 1alpha,25-dihydroxy vitamin D3. We report that expression of the classic VDR in osteoblasts is required to generate a rapid 1alpha,25-dihydroxy vitamin D3-mediated increase in the intracellular Ca(2+) concentration, a hallmark of the non-genomic actions of 1alpha,25-dihydroxy vitamin D3 in these cells.     

The ABCs of flower development: mutational analysis of AP1/FUL‐like genes in rice provides evidence for a homeotic (A)‐function in grasses

The well‐known ABC model describes the combinatorial interaction of homeotic genes in specifying floral organ identities. While the B‐ and C‐functions are highly conserved throughout flowering plants and even in gymnosperms, the A‐function, which specifies the identity of perianth organs (sepals and petals in eudicots), remains controversial. One reason for this is that in most plants that have been investigated thus far, with Arabidopsis being a remarkable exception, one does not find recessive mutants in which the identity of both types of perianth organs is affected. Here we report a comprehensive mutational analysis of all four members of the AP1/FUL‐like subfamily of MADS‐box genes in rice (Oryza sativa). We demonstrate that OsMADS14 and OsMADS15, in addition to their function of specifying meristem identity, are also required to specify palea and lodicule identities. Because these two grass‐specific organs are very likely homologous to sepals and petals of eudicots, respectively, we conclude that there is a floral homeotic (A)‐function in rice as defined previously. Together with other recent findings, our data suggest that AP1/FUL‐like genes were independently recruited to fulfil the (A)‐function in grasses and some eudicots, even though other scenarios cannot be excluded and are discussed.     

Caveolin-1 mutants P132L and Y14F are dominant negative regulators of invasion, migration and aggregation in H1299 lung cancer cells

Caveolin-1 is an essential protein constituent of caveolae. Accumulating evidence indicates that caveolin-1 may act as a positive regulator of cancer progression. In this study, we investigated the function of caveolin-1 in human lung cancer cells. Caveolin-1 knockdown inhibited cell proliferation and reduced focal adhesion kinase (Fak) phosphorylation. Matrix invasion and cell migration as well as expression and activity of matrix metalloproteases were attenuated following caveolin-1 RNAi-mediated knockdown or overexpression of Y14F and P132L mutants, demonstrating dominant-negative activity of these mutants. Time-lapse fluorescence microscopy revealed that caveolin-1 and its mutants P132L and Y14F are localized to the trailing edge of migrating cells during both random and directed cell movement, implying an active role of caveolin-1 in the migration process. Suppression of caveolin-1 function greatly elevated the percentage of H1299 cells exhibiting focal adhesions. In addition, cell aggregation was increased by wild type caveolin-1 and attenuated by both P132L and Y14F mutants. Overexpression of wild type caveolin-1 increased caveolae density, however, P132L and Y14F mutants did not affect caveolae formation, suggesting that in this respect that the mutants do not act in a dominant negative manner, and that effects of caveolin-1 on caveolae and cell invasion, migration, focal adhesion and aggregation, are separable. Our data provide novel mechanistic insights into the role of caveolin-1 in cell motility, invasiveness and aggregation, therefore, expanding our understanding of the tumor-promoting activities of caveolin-1 in advanced-stage cancer.     

The Arabidopsis Spontaneous Cell Death1 gene, encoding a ζ-carotene desaturase essential for carotenoid biosynthesis, is involved in chloroplast development,photoprotection and retrograde signalling

Carotenoids, a class of natural pigments found in all photosynthetic organisms, are involved in a variety of physiological processes, including coloration, photoprotection, biosynthesis of abscisic acid （ABA） and chloroplast biogenesis. Although carotenoid biosynthesis has been well studied biochemically, the genetic basis of the pathway is not well understood. Here, we report the characterization of two allelic Arabidopsis mutants, spontaneous cell death1-1 （spcl-1） and spc1-2. The weak allele spc1-1 mutant showed characteristics of bleached leaves, accumulation of superoxide and mosaic cell death. The strong mutant allele spc1-2 caused a complete arrest of plant growth and development shortly after germination, leading to a seedling-lethal phenotype. Genetic and molecular analyses indicated that SPC1 encodes a putative ζ-carotene desaturase （ZDS） in the carotenoid biosynthesis pathway. Analysis of carotenoids revealed that several major carotenoid compounds downstream of SPC 1/ZDS were substantially reduced in spc1-1, suggesting that SPC 1 is a functional ZDS. Consistent with the downregulated expression of CAO and PORB, the chlorophyll content was decreased in spc1-1 plants. In addition, expression of Lhcb1. 1, Lhcbl. 4 and RbcS was absent in spc1-2, suggesting the possible involvement of carotenoids in the plastid-to-nucleus retrograde signaling. The spc1-1 mutant also displays an ABA-deficient phenotype that can be partially rescued by the externally supplied phytohormone. These results suggest that SPC1/ZDS is essential for biosynthesis of carotenoids and plays a crucial role in plant growth and development.