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Kohlbrenner T, Berger S, Laranjeira AC, Aegerter-Wilmsen T, Comi LF, deMello A, Hajnal A. Actomyosin-mediated apical constriction promotes physiological germ cell death in C. elegans. PLoS Biol 2024; 22:e3002775. [PMID: 39178318 PMCID: PMC11376560 DOI: 10.1371/journal.pbio.3002775] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Revised: 09/05/2024] [Accepted: 07/30/2024] [Indexed: 08/25/2024] Open
Abstract
Germ cell apoptosis in Caenorhabditis elegans hermaphrodites is a physiological process eliminating around 60% of all cells in meiotic prophase to maintain tissue homeostasis. In contrast to programmed cell death in the C. elegans soma, the selection of germ cells undergoing apoptosis is stochastic. By live-tracking individual germ cells at the pachytene stage, we found that germ cells smaller than their neighbors are selectively eliminated through apoptosis before differentiating into oocytes. Thus, cell size is a strong predictor of physiological germ cell death. The RAS/MAPK and ECT/RHO/ROCK pathways together regulate germ cell size by controlling actomyosin constriction at the apical rachis bridges, which are cellular openings connecting the syncytial germ cells to a shared cytoplasmic core. Enhancing apical constriction reduces germ cell size and increases the rate of cell death while inhibiting the actomyosin network in the germ cells prevents their death. We propose that actomyosin contractility at the rachis bridges of the syncytial germ cells amplifies intrinsic disparities in cell size. Through this mechanism, the animals can adjust the balance between physiological germ cell death and oocyte differentiation.
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Affiliation(s)
- Tea Kohlbrenner
- Institute of Molecular Life Sciences, University of Zürich, Zürich, Switzerland
- Molecular Life Science PhD Program, University of Zürich and ETH Zürich, Zürich, Switzerland
| | - Simon Berger
- Institute of Molecular Life Sciences, University of Zürich, Zürich, Switzerland
- Institute for Chemical and Bioengineering, ETH Zürich, Zürich, Switzerland
| | - Ana Cristina Laranjeira
- Institute of Molecular Life Sciences, University of Zürich, Zürich, Switzerland
- Molecular Life Science PhD Program, University of Zürich and ETH Zürich, Zürich, Switzerland
| | | | - Laura Filomena Comi
- Institute of Molecular Life Sciences, University of Zürich, Zürich, Switzerland
- Molecular Life Science PhD Program, University of Zürich and ETH Zürich, Zürich, Switzerland
| | - Andrew deMello
- Institute for Chemical and Bioengineering, ETH Zürich, Zürich, Switzerland
| | - Alex Hajnal
- Institute of Molecular Life Sciences, University of Zürich, Zürich, Switzerland
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Lyu H, Chamberlin HM. Functional distinction in oncogenic Ras variant activity in Caenorhabditis elegans. Dis Model Mech 2024; 17:dmm050577. [PMID: 38946472 PMCID: PMC11340813 DOI: 10.1242/dmm.050577] [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: 11/02/2023] [Accepted: 06/21/2024] [Indexed: 07/02/2024] Open
Abstract
Ras genes are important oncogenes that are frequently mutated in cancer. Human oncogenic variants exhibit functional distinctions in terms of their representation in different cancer types, impact on cellular targets and sensitivity to pharmacological treatments. However, how these distinct variants influence and respond to the cellular networks in which they are embedded is poorly understood. To identify novel participants in the complex interplay between Ras genotype and cell interaction networks in vivo, we have developed and tested an experimental framework using a simple vulva-development assay in the nematode C. elegans. Using this system, we evaluated a set of Ras oncogenic substitution changes at G12, G13 and Q61. We found that these variants fall into distinct groups based on phenotypic differences, sensitivity to gene dosage and inhibition of the downstream kinase MEK and their response to genetic modulators that influence Ras activity in a non-autonomous manner. Together, our results demonstrated that oncogenic C. elegans Ras variants exhibit clear distinctions in how they interface with the vulva-development network and showed that extracellular modulators yield variant-restricted effects in vivo.
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Affiliation(s)
- Haimeng Lyu
- Department of Molecular Genetics, Ohio State University, 484 West 12th Avenue, Columbus, OH 43210, USA
| | - Helen M. Chamberlin
- Department of Molecular Genetics, Ohio State University, 484 West 12th Avenue, Columbus, OH 43210, USA
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3
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Rahmani A, Chew YL. Investigating the molecular mechanisms of learning and memory using Caenorhabditis elegans. J Neurochem 2021; 159:417-451. [PMID: 34528252 DOI: 10.1111/jnc.15510] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 08/15/2021] [Accepted: 09/08/2021] [Indexed: 11/30/2022]
Abstract
Learning is an essential biological process for survival since it facilitates behavioural plasticity in response to environmental changes. This process is mediated by a wide variety of genes, mostly expressed in the nervous system. Many studies have extensively explored the molecular and cellular mechanisms underlying learning and memory. This review will focus on the advances gained through the study of the nematode Caenorhabditis elegans. C. elegans provides an excellent system to study learning because of its genetic tractability, in addition to its invariant, compact nervous system (~300 neurons) that is well-characterised at the structural level. Importantly, despite its compact nature, the nematode nervous system possesses a high level of conservation with mammalian systems. These features allow the study of genes within specific sensory-, inter- and motor neurons, facilitating the interrogation of signalling pathways that mediate learning via defined neural circuits. This review will detail how learning and memory can be studied in C. elegans through behavioural paradigms that target distinct sensory modalities. We will also summarise recent studies describing mechanisms through which key molecular and cellular pathways are proposed to affect associative and non-associative forms of learning.
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Affiliation(s)
- Aelon Rahmani
- Flinders Health and Medical Research Institute, Flinders University, Adelaide, South Australia, Australia
| | - Yee Lian Chew
- Flinders Health and Medical Research Institute, Flinders University, Adelaide, South Australia, Australia
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Rasmussen NR, Dickinson DJ, Reiner DJ. Ras-Dependent Cell Fate Decisions Are Reinforced by the RAP-1 Small GTPase in Caenorhabditiselegans. Genetics 2018; 210:1339-1354. [PMID: 30257933 PMCID: PMC6283165 DOI: 10.1534/genetics.118.301601] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Accepted: 09/15/2018] [Indexed: 12/15/2022] Open
Abstract
The notoriety of the small GTPase Ras as the most mutated oncoprotein has led to a well-characterized signaling network largely conserved across metazoans. Yet the role of its close relative Rap1 (Ras Proximal), which shares 100% identity between their core effector binding sequences, remains unclear. A long-standing controversy in the field is whether Rap1 also functions to activate the canonical Ras effector, the S/T kinase Raf. We used the developmentally simpler Caenorhabditis elegans, which lacks the extensive paralog redundancy of vertebrates, to examine the role of RAP-1 in two distinct LET-60/Ras-dependent cell fate patterning events: induction of 1° vulval precursor cell (VPC) fate and of the excretory duct cell. Fluorescence-tagged endogenous RAP-1 is localized to plasma membranes and is expressed ubiquitously, with even expression levels across the VPCs. RAP-1 and its activating GEF PXF-1 function cell autonomously and are necessary for maximal induction of 1° VPCs. Critically, mutationally activated endogenous RAP-1 is sufficient both to induce ectopic 1°s and duplicate excretory duct cells. Like endogenous RAP-1, before induction GFP expression from the pxf-1 promoter is uniform across VPCs. However, unlike endogenous RAP-1, after induction GFP expression is increased in presumptive 1°s and decreased in presumptive 2°s. We conclude that RAP-1 is a positive regulator that promotes Ras-dependent inductive fate decisions. We hypothesize that PXF-1 activation of RAP-1 serves as a minor parallel input into the major LET-60/Ras signal through LIN-45/Raf.
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Affiliation(s)
- Neal R Rasmussen
- Institute of Biosciences and Technology, College of Medicine, Texas A&M University, Houston, Texas 77030
| | - Daniel J Dickinson
- Department of Molecular Biosciences, University of Texas, Austin, Texas 78705
| | - David J Reiner
- Institute of Biosciences and Technology, College of Medicine, Texas A&M University, Houston, Texas 77030
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Sherwood DR, Plastino J. Invading, Leading and Navigating Cells in Caenorhabditis elegans: Insights into Cell Movement in Vivo. Genetics 2018; 208:53-78. [PMID: 29301948 PMCID: PMC5753875 DOI: 10.1534/genetics.117.300082] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2017] [Accepted: 10/26/2017] [Indexed: 12/30/2022] Open
Abstract
Highly regulated cell migration events are crucial during animal tissue formation and the trafficking of cells to sites of infection and injury. Misregulation of cell movement underlies numerous human diseases, including cancer. Although originally studied primarily in two-dimensional in vitro assays, most cell migrations in vivo occur in complex three-dimensional tissue environments that are difficult to recapitulate in cell culture or ex vivo Further, it is now known that cells can mobilize a diverse repertoire of migration modes and subcellular structures to move through and around tissues. This review provides an overview of three distinct cellular movement events in Caenorhabditis elegans-cell invasion through basement membrane, leader cell migration during organ formation, and individual cell migration around tissues-which together illustrate powerful experimental models of diverse modes of movement in vivo We discuss new insights into migration that are emerging from these in vivo studies and important future directions toward understanding the remarkable and assorted ways that cells move in animals.
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Affiliation(s)
- David R Sherwood
- Department of Biology, Regeneration Next, Duke University, Durham, North Carolina 27705
| | - Julie Plastino
- Institut Curie, PSL Research University, CNRS, UMR 168, F-75005 Paris, France
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, UMR 168, F-75005 Paris, France
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Yuan J, Zhang X, Liu C, Duan H, Li F, Xiang J. Convergent Evolution of the Osmoregulation System in Decapod Shrimps. MARINE BIOTECHNOLOGY (NEW YORK, N.Y.) 2017; 19:76-88. [PMID: 28204969 DOI: 10.1007/s10126-017-9729-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Accepted: 01/09/2017] [Indexed: 06/06/2023]
Abstract
In adaptating to different aquatic environments, seawater (SW) and freshwater (FW) shrimps have exploited different adaptation strategies, which should generate clusters of genes with different adaptive features. However, little is known about the genetic basis of these physiological adaptations. Thus, in this study, we performed comparative transcriptomics and adaptive evolution analyses on SW and FW shrimps and found that convergent evolution may have happened on osmoregulation system of shrimps. We identified 275 and 234 positively selected genes in SW and FW shrimps, respectively, which enriched in the functions of ion-binding and membrane-bounded organelles. Among them, five (CaCC, BEST2, GPDH, NKA, and Integrin) and four (RasGAP, RhoGDI, CNK3, and ODC) osmoregulation-related genes were detected in SW and FW shrimps, respectively. All five genes in SW shrimps have been reported to have positive effects on ion transportation, whereas RasGAP and RhoGDI in FW shrimps are associated with negative control of ion transportation, and CNK3 and ODC play central roles in cation homeostasis. Besides, the phylogenetic tree reconstructed from the positively selected sites separated the SW and FW shrimps into two groups. Distinct subsets of parallel substitutions also have been found in these osmoregulation-related genes in SW and FW shrimps. Therefore, our results suggest that distinct convergent evolution may have occurred in the osmoregulation systems of SW and FW shrimps. Furthermore, positive selection of osmoregulation-related genes may be beneficial for the regulation of water and salt balance in decapod shrimps.
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Affiliation(s)
- Jianbo Yuan
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, 7, Nanhai Road, Qingdao, 266071, China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266071, China
| | - Xiaojun Zhang
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, 7, Nanhai Road, Qingdao, 266071, China.
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266071, China.
| | - Chengzhang Liu
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, 7, Nanhai Road, Qingdao, 266071, China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266071, China
| | - Hu Duan
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, 7, Nanhai Road, Qingdao, 266071, China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266071, China
| | - Fuhua Li
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, 7, Nanhai Road, Qingdao, 266071, China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266071, China
| | - Jianhai Xiang
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, 7, Nanhai Road, Qingdao, 266071, China.
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266071, China.
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Gyurkó MD, Csermely P, Sőti C, Steták A. Distinct roles of the RasGAP family proteins in C. elegans associative learning and memory. Sci Rep 2015; 5:15084. [PMID: 26469632 PMCID: PMC4606830 DOI: 10.1038/srep15084] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Accepted: 09/09/2015] [Indexed: 12/14/2022] Open
Abstract
The Ras GTPase activating proteins (RasGAPs) are regulators of the conserved Ras/MAPK pathway. Various roles of some of the RasGAPs in learning and memory have been reported in different model systems, yet, there is no comprehensive study to characterize all gap genes in any organism. Here, using reverse genetics and neurobehavioural tests, we studied the role of all known genes of the rasgap family in C. elegans in associative learning and memory. We demonstrated that their proteins are implicated in different parts of the learning and memory processes. We show that gap-1 contribute redundantly with gap-3 to the chemosensation of volatile compounds, gap-1 plays a major role in associative learning, while gap-2 and gap-3 are predominantly required for short- and long-term associative memory. Our results also suggest that the C. elegans Ras orthologue let-60 is involved in multiple processes during learning and memory. Thus, we show that the different classes of RasGAP proteins are all involved in cognitive function and their complex interplay ensures the proper formation and storage of novel information in C. elegans.
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Affiliation(s)
- M Dávid Gyurkó
- Semmelweis University, Department of Medical Chemistry, Budapest, Üllői út 26 1085, Hungary
| | - Péter Csermely
- Semmelweis University, Department of Medical Chemistry, Budapest, Üllői út 26 1085, Hungary
| | - Csaba Sőti
- Semmelweis University, Department of Medical Chemistry, Budapest, Üllői út 26 1085, Hungary
| | - Attila Steták
- University of Basel, Transfaculty Research Platform Molecular and Cognitive Neurosciences, Birmannsgasse 8, 4055 Basel, Switzerland.,University of Basel, University Psychiatric Clinics, Wilhelm Klein-Strasse 27, 4055 Basel, Switzerland
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8
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Schmid T, Snoek LB, Fröhli E, van der Bent ML, Kammenga J, Hajnal A. Systemic Regulation of RAS/MAPK Signaling by the Serotonin Metabolite 5-HIAA. PLoS Genet 2015; 11:e1005236. [PMID: 25978500 PMCID: PMC4433219 DOI: 10.1371/journal.pgen.1005236] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Accepted: 04/23/2015] [Indexed: 11/18/2022] Open
Abstract
Human cancer is caused by the interplay of mutations in oncogenes and tumor suppressor genes and inherited variations in cancer susceptibility genes. While many of the tumor initiating mutations are well characterized, the effect of genetic background variation on disease onset and progression is less understood. We have used C. elegans genetics to identify genetic modifiers of the oncogenic RAS/MAPK signaling pathway. Quantitative trait locus analysis of two highly diverged C. elegans isolates combined with allele swapping experiments identified the polymorphic monoamine oxidase A (MAOA) gene amx-2 as a negative regulator of RAS/MAPK signaling. We further show that the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA), which is a product of MAOA catalysis, systemically inhibits RAS/MAPK signaling in different organs of C. elegans. Thus, MAOA activity sets a global threshold for MAPK activation by controlling 5-HIAA levels. To our knowledge, 5-HIAA is the first endogenous small molecule that acts as a systemic inhibitor of RAS/MAPK signaling.
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Affiliation(s)
- Tobias Schmid
- University of Zurich, Institute of Molecular Life Sciences, Zurich, Switzerland
- PhD Program in Molecular Life Sciences, University and ETH Zurich, Zurich, Switzerland
| | - L. Basten Snoek
- Laboratory of Nematology, Wageningen University, Wageningen, The Netherlands
| | - Erika Fröhli
- University of Zurich, Institute of Molecular Life Sciences, Zurich, Switzerland
| | | | - Jan Kammenga
- Laboratory of Nematology, Wageningen University, Wageningen, The Netherlands
| | - Alex Hajnal
- University of Zurich, Institute of Molecular Life Sciences, Zurich, Switzerland
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9
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Abstract
Receptor Tyrosine Kinase (RTK)-Ras-Extracellular signal-regulated kinase (ERK) signaling pathways control many aspects of C. elegans development and behavior. Studies in C. elegans helped elucidate the basic framework of the RTK-Ras-ERK pathway and continue to provide insights into its complex regulation, its biological roles, how it elicits cell-type appropriate responses, and how it interacts with other signaling pathways to do so. C. elegans studies have also revealed biological contexts in which alternative RTK- or Ras-dependent pathways are used instead of the canonical pathway.
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Affiliation(s)
- Meera V Sundaram
- Dept. of Genetics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6145, USA.
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Vaid S, Ariz M, Chaturbedi A, Kumar GA, Subramaniam K. PUF-8 negatively regulates RAS/MAPK signalling to promote differentiation of C. elegans germ cells. Development 2013; 140:1645-54. [PMID: 23487310 PMCID: PMC3621483 DOI: 10.1242/dev.088013] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/29/2013] [Indexed: 12/30/2022]
Abstract
Signals that promote germ cell self-renewal by preventing premature meiotic entry are well understood. However, signals that control mitotic proliferation to promote meiotic differentiation have not been well characterized. In Caenorhabditis elegans, GLP-1 Notch signalling promotes the proliferative fate by preventing premature meiotic entry. The germline niche cell, which is the source of the ligand for GLP-1, spatially restricts GLP-1 signalling and thus enables the germ cells that have moved away from the niche to enter meiosis. Here, we show that the suppression of RAS/MAP kinase signalling in the mitotic and meiotic-entry regions is essential for the regulation of the mitosis-meiosis switch by niche signalling. We provide evidence that the conserved PUF family RNA-binding protein PUF-8 and the RAS GAP protein GAP-3 function redundantly to suppress the LET-60 RAS in the mitotic and meiotic entry regions. Germ cells missing both PUF-8 and GAP-3 proliferate in an uncontrolled fashion and fail to undergo meiotic development. MPK-1, the MAP kinase downstream of the LET-60 RAS, is prematurely activated in these cells; downregulation of MPK-1 activation eliminates tumours and restores differentiation. Our results further reveal that PUF-8 negatively regulates LET-60 expression at a post-transcriptional step. LET-60 is misexpressed in the puf-8(-) mutant germlines and PUF-8 physically interacts with the let-60 3' UTR. Furthermore, PUF-8 suppresses let-60 3' UTR-mediated expression in the germ cells that are transitioning from the mitotic to meiotic fate. These results reveal that PUF-8-mediated inhibition of the RAS/MAPK pathway is essential for mitotic-to-meiotic fate transition.
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Affiliation(s)
- Samir Vaid
- Department of Biological Sciences and Bioengineering, Indian Institute of Technology, Kanpur 208016, India
| | - Mohd Ariz
- Department of Biological Sciences and Bioengineering, Indian Institute of Technology, Kanpur 208016, India
| | - Amaresh Chaturbedi
- Department of Biological Sciences and Bioengineering, Indian Institute of Technology, Kanpur 208016, India
| | - Ganga Anil Kumar
- Department of Biological Sciences and Bioengineering, Indian Institute of Technology, Kanpur 208016, India
| | - Kuppuswamy Subramaniam
- Department of Biological Sciences and Bioengineering, Indian Institute of Technology, Kanpur 208016, India
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Abstract
PURPOSE OF REVIEW It has been known for decades that in order to grow, tumors need to activate quiescent endothelial cells to form a functional vascular network, a process termed 'angiogenesis'. However, the molecular determinants that reverse this endothelial quiescence to facilitate pathological angiogenesis are not yet completely understood. This review examines a critical regulatory switch at the level of Ras that activates this angiogenic switch process and the role that microRNAs play in this process. RECENT FINDINGS In the last few years, microRNAs, a new class of small RNA molecules, have emerged as key regulators of several cellular processes, including angiogenesis. MicroRNAs such as miR-126, miR-296, and miR-92a have been shown to play important roles in angiogenesis. We recently described how miR-132, an angiogenic growth factor inducible microRNA in the endothelium, facilitates pathological angiogenesis by downregulating p120RasGAP, a molecular brake for Ras. Importantly, targeting miR-132 with a complementary, synthetic antimicroRNA restored the brake and decreased angiogenesis and tumor burden in multiple tumor models. Taken together, emerging evidence suggests a central role for microRNAs downstream of multiple growth factors in regulating endothelial proliferation, migration, and vascular patterning. SUMMARY Further research into miR-132-p120RasGAP biology and more broadly, microRNA regulation of Ras pathways in the endothelium will not only advance our understanding of angiogenesis but also provide opportunities for therapeutic intervention.
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Yang Y, Han SM, Miller MA. MSP hormonal control of the oocyte MAP kinase cascade and reactive oxygen species signaling. Dev Biol 2010; 342:96-107. [PMID: 20380830 DOI: 10.1016/j.ydbio.2010.03.026] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2009] [Revised: 03/12/2010] [Accepted: 03/31/2010] [Indexed: 11/28/2022]
Abstract
The MSP domain is a conserved immunoglobulin-like structure that is important for C. elegans reproduction and human motor neuron survival. C. elegans MSPs are the most abundant proteins in sperm, where they function as intracellular cytoskeletal proteins and secreted hormones. Secreted MSPs bind to multiple receptors on oocyte and ovarian sheath cell surfaces to induce oocyte maturation and sheath contraction. MSP binding stimulates oocyte MPK-1 ERK MAP Kinase (MAPK) phosphorylation, but the function and mechanism are not well understood. Here we show that the Shp class protein-tyrosine phosphatase PTP-2 acts in oocytes downstream of sheath/oocyte gap junctions to promote MSP-induced MPK-1 phosphorylation. PTP-2 functions in the oocyte cytoplasm, not at the cell surface to inhibit multiple RasGAPs, resulting in sustained Ras activation. We also provide evidence that MSP promotes production of reactive oxygen species (ROS), which act as second messengers to augment MPK-1 phosphorylation. The Cu/Zn superoxide dismutase SOD-1, an enzyme that catalyzes ROS breakdown in the cytoplasm, inhibits MPK-1 phosphorylation downstream of or in parallel to ptp-2. Our results support the model that MSP triggers PTP-2/Ras activation and ROS production to stimulate MPK-1 activity essential for oocyte maturation. We propose that secreted MSP domains and Cu/Zn superoxide dismutases function antagonistically to control ROS and MAPK signaling.
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Affiliation(s)
- Youfeng Yang
- Department of Cell Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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