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Abstract
Fibroblast growth factor 23 (FGF23) is a phosphotropic hormone that belongs to a subfamily of endocrine FGFs with evolutionarily conserved functions in worms and fruit flies. FAM20C phosphorylates FGF23 post-translationally, targeting it to proteolysis through subtilisin-like proprotein convertase FURIN, resulting in secretion of FGF23 fragments. O-glycosylation of FGF23 through GALNT3 appears to prevent proteolysis, resulting in secretion of biologically active intact FGF23. In the circulation, FGF23 may undergo further processing by plasminogen activators. Crystal structures show that the ectodomain of the cognate FGF23 receptor FGFR1c binds with the ectodomain of the co-receptor alpha-KLOTHO. The KLOTHO-FGFR1c double heterodimer creates a high-affinity binding site for the FGF23 C-terminus. The topology of FGF23 deviates from that of paracrine FGFs, resulting in poor affinity for heparan sulphate, which may explain why FGF23 diffuses freely in the bone matrix to enter the bloodstream following its secretion by cells of osteoblastic lineage. Intact FGF23 signalling by this canonical pathway activates FRS2/RAS/RAF/MEK/ERK1/2. It reduces serum phosphate by inhibiting 1,25-dihydroxyvitamin D synthesis, suppressing intestinal phosphate absorption, and by downregulating the transporters NPT2a and NPT2c, suppressing phosphate reabsorption in the proximal tubules. The physiological role of FGF23 fragments, which may be inhibitory, remains unclear. Pharmacological and genetic activation of canonical FGF23 signalling causes hypophosphatemic disorders, while its inhibition results in hyperphosphatemic disorders. Non-canonical FGF23 signalling through binding and activation of FGFR3/FGFR4/calcineurin/NFAT in an alpha-KLOTHO-independent fashion mainly occurs at extremely elevated circulating FGF23 levels and may contribute to mortality due to cardiovascular disease and left ventricular hypertrophy in chronic kidney disease.
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Affiliation(s)
- Bryan B Ho
- Department of Internal Medicine, Section Endocrinology, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Clemens Bergwitz
- Department of Internal Medicine, Section Endocrinology, Yale University School of Medicine, New Haven, Connecticut, USA
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2
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Gaffney CJ, Pollard A, Barratt TF, Constantin-Teodosiu D, Greenhaff PL, Szewczyk NJ. Greater loss of mitochondrial function with ageing is associated with earlier onset of sarcopenia in C. elegans. Aging (Albany NY) 2019; 10:3382-3396. [PMID: 30455409 PMCID: PMC6286836 DOI: 10.18632/aging.101654] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Accepted: 11/15/2018] [Indexed: 12/29/2022]
Abstract
Sarcopenia, the age-related decline of muscle, is a significant and growing public health burden. C. elegans, a model organism for investigating the mechanisms of ageing, also displays sarcopenia, but the underlying mechanism(s) remain elusive. Here, we use C. elegans natural scaling of lifespan in response to temperature to examine the relationship between mitochondrial content, mitochondrial function, and sarcopenia. Mitochondrial content and maximal mitochondrial ATP production rates (MAPR) display an inverse relationship to lifespan, while onset of MAPR decline displays a direct relationship. Muscle mitochondrial structure, sarcomere structure, and movement decline also display a direct relationship with longevity. Notably, the decline in mitochondrial network structure occurs earlier than sarcomere decline, and correlates more strongly with loss of movement, and scales with lifespan. These results suggest that mitochondrial function is critical in the ageing process and more robustly explains the onset and progression of sarcopenia than loss of sarcomere structure.
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Affiliation(s)
- Christopher J Gaffney
- MRC/ARUK Centre for Musculoskeletal Ageing Research, NIHR Nottingham BRC, University of Nottingham, Nottingham, UK.,Lancaster University Medical School, Lancaster University, Lancaster, UK
| | - Amelia Pollard
- MRC/ARUK Centre for Musculoskeletal Ageing Research, NIHR Nottingham BRC, University of Nottingham, Nottingham, UK
| | - Thomas F Barratt
- MRC/ARUK Centre for Musculoskeletal Ageing Research, NIHR Nottingham BRC, University of Nottingham, Nottingham, UK
| | - Dumitru Constantin-Teodosiu
- MRC/ARUK Centre for Musculoskeletal Ageing Research, NIHR Nottingham BRC, University of Nottingham, Nottingham, UK
| | - Paul L Greenhaff
- MRC/ARUK Centre for Musculoskeletal Ageing Research, NIHR Nottingham BRC, University of Nottingham, Nottingham, UK
| | - Nathaniel J Szewczyk
- MRC/ARUK Centre for Musculoskeletal Ageing Research, NIHR Nottingham BRC, University of Nottingham, Nottingham, UK
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3
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A Receptor Tyrosine Kinase Network Regulates Neuromuscular Function in Response to Oxidative Stress in Caenorhabditis elegans. Genetics 2019; 211:1283-1295. [PMID: 30782598 DOI: 10.1534/genetics.119.302026] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Accepted: 02/14/2019] [Indexed: 11/18/2022] Open
Abstract
The transcription factor Nrf2 plays a critical role in the organism-wide regulation of the antioxidant stress response. The Nrf2 homolog SKN-1 functions in the intestinal cells nonautonomously to negatively regulate neuromuscular junction (NMJ) function in Caenorhabditis elegans To identify additional molecules that mediate SKN-1 signaling to the NMJ, we performed a candidate screen for suppressors of aldicarb resistance caused by acute treatment with the SKN-1 activator arsenite. We identified two receptor tyrosine kinases, EGL-15 (fibroblast growth factor receptor, FGFR) and DAF-2 (insulin-like peptide receptor), that are required for NMJ regulation in response to stress. Through double-mutant analysis, we found that EGL-15 functions downstream of, or parallel to, SKN-1 and SPHK-1 (sphingosine kinase), and that the EGL-15 ligand EGL-17 FGF and canonical EGL-15 effectors are required for oxidative stress-mediated regulation of NMJ function. DAF-2 also functions downstream of or parallel to SKN-1 to regulate NMJ function. Through tissue-specific rescue experiments, we found that FGFR signaling functions primarily in the hypodermis, whereas insulin-like peptide receptor signaling is required in multiple tissues. Our results support the idea that the regulation of NMJ function by SKN-1 occurs via a complex organism-wide signaling network involving receptor tyrosine kinase signaling in multiple tissues.
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Lehmann S, Bass JJ, Barratt TF, Ali MZ, Szewczyk NJ. Functional phosphatome requirement for protein homeostasis, networked mitochondria, and sarcomere structure in C. elegans muscle. J Cachexia Sarcopenia Muscle 2017; 8:660-672. [PMID: 28508547 PMCID: PMC5566650 DOI: 10.1002/jcsm.12196] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Revised: 12/08/2016] [Accepted: 01/26/2017] [Indexed: 01/04/2023] Open
Abstract
BACKGROUND Skeletal muscle is central to locomotion and metabolic homeostasis. The laboratory worm Caenorhabditis elegans has been developed into a genomic model for assessing the genes and signals that regulate muscle development and protein degradation. Past work has identified a receptor tyrosine kinase signalling network that combinatorially controls autophagy, nerve signal to muscle to oppose proteasome-based degradation, and extracellular matrix-based signals that control calpain and caspase activation. The last two discoveries were enabled by following up results from a functional genomic screen of known regulators of muscle. Recently, a screen of the kinome requirement for muscle homeostasis identified roughly 40% of kinases as required for C. elegans muscle health; 80 have identified human orthologues and 53 are known to be expressed in skeletal muscle. To complement this kinome screen, here, we screen most of the phosphatases in C. elegans. METHODS RNA interference was used to knockdown phosphatase-encoding genes. Knockdown was first conducted during development with positive results also knocked down only in fully developed adult muscle. Protein homeostasis, mitochondrial structure, and sarcomere structure were assessed using transgenic reporter proteins. Genes identified as being required to prevent protein degradation were also knocked down in conditions that blocked proteasome or autophagic degradation. Genes identified as being required to prevent autophagic degradation were also assessed for autophagic vesicle accumulation using another transgenic reporter. Lastly, bioinformatics were used to look for overlap between kinases and phosphatases required for muscle homeostasis, and the prediction that one phosphatase was required to prevent mitogen-activated protein kinase activation was assessed by western blot. RESULTS A little over half of all phosphatases are each required to prevent abnormal development or maintenance of muscle. Eighty-six of these phosphatases have known human orthologues, 57 of which are known to be expressed in human skeletal muscle. Of the phosphatases required to prevent abnormal muscle protein degradation, roughly half are required to prevent increased autophagy. CONCLUSIONS A significant portion of both the kinome and phosphatome are required for establishing and maintaining C. elegans muscle health. Autophagy appears to be the most commonly triggered form of protein degradation in response to disruption of phosphorylation-based signalling. The results from these screens provide measurable phenotypes for analysing the combined contribution of kinases and phosphatases in a multi-cellular organism and suggest new potential regulators of human skeletal muscle for further analysis.
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Affiliation(s)
- Susann Lehmann
- MRC/Arthritis Research UK Centre for Musculoskeletal Ageing Research, Medical School, University of Nottingham, Royal Derby Hospital, Derby, DE22 3DT, UK
| | - Joseph J Bass
- MRC/Arthritis Research UK Centre for Musculoskeletal Ageing Research, Medical School, University of Nottingham, Royal Derby Hospital, Derby, DE22 3DT, UK
| | - Thomas F Barratt
- MRC/Arthritis Research UK Centre for Musculoskeletal Ageing Research, Medical School, University of Nottingham, Royal Derby Hospital, Derby, DE22 3DT, UK
| | - Mohammed Z Ali
- MRC/Arthritis Research UK Centre for Musculoskeletal Ageing Research, Medical School, University of Nottingham, Royal Derby Hospital, Derby, DE22 3DT, UK
| | - Nathaniel J Szewczyk
- MRC/Arthritis Research UK Centre for Musculoskeletal Ageing Research, Medical School, University of Nottingham, Royal Derby Hospital, Derby, DE22 3DT, UK
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5
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Anti-Differentiation Effect of Oncogenic Met Receptor in Terminally-Differentiated Myotubes. Biomedicines 2015; 3:124-137. [PMID: 28536403 PMCID: PMC5344230 DOI: 10.3390/biomedicines3010124] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Accepted: 02/04/2015] [Indexed: 01/12/2023] Open
Abstract
Activation of the hepatocyte growth factor/Met receptor is involved in muscle regeneration, through promotion of proliferation and inhibition of differentiation in myogenic stem cells (MSCs). We previously described that the specific expression of an oncogenic version of the Met receptor (Tpr-Met) in terminally-differentiated skeletal muscle causes muscle wasting in vivo. Here, we induced Tpr-Met in differentiated myotube cultures derived from the transgenic mouse. These cultures showed a reduced protein level of myosin heavy chain (MyHC), increased phosphorylation of Erk1,2 MAPK, the formation of giant sacs of myonuclei and the collapse of elongated myotubes. Treatment of the cultures with an inhibitor of the MAPK kinase pathway or with an inhibitor of the proteasome increased the expression levels of MyHC. In addition, the inhibition of the MAPK kinase pathway prevented the formation of myosacs and myotube collapse. Finally, we showed that induction of Tpr-Met in primary myotubes was unable to produce endoreplication in their nuclei. In conclusion, our data indicate that multinucleated, fused myotubes may be forced to disassemble their contractile apparatus by the Tpr-Met oncogenic factor, but they resist the stimulus toward the reactivation of the cell cycle.
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Fisher K, Gee F, Wang S, Xue F, Knapp S, Philpott M, Wells C, Rodriguez M, Snoek LB, Kammenga J, Poulin GB. Maintenance of muscle myosin levels in adult C. elegans requires both the double bromodomain protein BET-1 and sumoylation. Biol Open 2013; 2:1354-63. [PMID: 24285704 PMCID: PMC3863420 DOI: 10.1242/bio.20136007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Attenuation of RAS-mediated signalling is a conserved process essential to control cell proliferation, differentiation, and apoptosis. Cooperative interactions between histone modifications such as acetylation, methylation and sumoylation are crucial for proper attenuation in C. elegans, implying that the proteins recognising these histone modifications could also play an important role in attenuation of RAS-mediated signalling. We sought to systematically identify these proteins and found BET-1. BET-1 is a conserved double bromodomain protein that recognises acetyl-lysines on histone tails and maintains the stable fate of various lineages. Unexpectedly, adults lacking both BET-1 and SUMO-1 are depleted of muscle myosin, an essential component of myofibrils. We also show that this muscle myosin depletion does not occur in all animals at a specific time, but rather that the penetrance of the phenotype increases with age. To gain mechanistic insights into this process, we sought to delay the occurrence of the muscle myosin depletion phenotype and found that it requires caspase activity and MEK-dependent signalling. We also performed transcription profiling on these mutants and found an up-regulation of the FGF receptor, egl-15, a tyrosine kinase receptor acting upstream of MEK. Consistent with a MEK requirement, we could delay the muscle phenotype by systemic or hypodermal knock down of egl-15. Thus, this work uncovered a caspase- and MEK-dependent mechanism that acts specifically on ageing adults to maintain the appropriate net level of muscle myosin.
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Affiliation(s)
- Kate Fisher
- Faculty of Life Sciences, Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT, UK
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Lehmann S, Bass JJ, Szewczyk NJ. Knockdown of the C. elegans kinome identifies kinases required for normal protein homeostasis, mitochondrial network structure, and sarcomere structure in muscle. Cell Commun Signal 2013; 11:71. [PMID: 24060339 PMCID: PMC3849176 DOI: 10.1186/1478-811x-11-71] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Accepted: 09/15/2013] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND Kinases are important signalling molecules for modulating cellular processes and major targets of drug discovery programs. However, functional information for roughly half the human kinome is lacking. We conducted three kinome wide, >90%, RNAi screens and epistasis testing of some identified kinases against known intramuscular signalling systems to increase the functional annotation of the C. elegans kinome and expand our understanding of kinome influence upon muscle protein degradation. RESULTS 96 kinases were identified as required for normal protein homeostasis, 74 for normal mitochondrial networks and 50 for normal sarcomere structure. Knockdown of kinases required only for normal protein homeostasis and/or mitochondrial structure was significantly less likely to produce a developmental or behavioural phenotype than knockdown of kinases required for normal sarcomere structure and/or other sub-cellular processes. Lastly, assessment of kinases for which knockdown produced muscle protein degradation against the known regulatory pathways in C. elegans muscle revealed that close to half of kinase knockdowns activated autophagy in a MAPK dependent fashion. CONCLUSIONS Roughly 40% of kinases studied, 159 of 397, are important in establishing or maintaining muscle cell health, with most required for both. For kinases where decreased expression triggers protein degradation, autophagy is most commonly activated. These results increase the annotation of the C. elegans kinome to roughly 75% and enable future kinome research. As 33% of kinases identified have orthologues expressed in human muscle, our results also enable testing of whether identified kinases function similarly in maintaining human muscle homeostasis.
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Affiliation(s)
- Susann Lehmann
- Medical Research Council/Arthritis Research UK Centre for Musculoskeletal Ageing Research, University of Nottingham, Royal Derby Hospital, Derby DE22 3DT, England
| | - Joseph J Bass
- Medical Research Council/Arthritis Research UK Centre for Musculoskeletal Ageing Research, University of Nottingham, Royal Derby Hospital, Derby DE22 3DT, England
| | - Nathaniel J Szewczyk
- Medical Research Council/Arthritis Research UK Centre for Musculoskeletal Ageing Research, University of Nottingham, Royal Derby Hospital, Derby DE22 3DT, England
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Masoudi N, Fancsalszky L, Pourkarimi E, Vellai T, Alexa A, Reményi A, Gartner A, Mehta A, Takács-Vellai K. The NM23-H1/H2 homolog NDK-1 is required for full activation of Ras signaling in C. elegans. Development 2013; 140:3486-95. [PMID: 23900546 PMCID: PMC3737725 DOI: 10.1242/dev.094011] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/17/2013] [Indexed: 11/21/2022]
Abstract
The group I members of the Nm23 (non-metastatic) gene family encode nucleoside diphosphate kinases (NDPKs) that have been implicated in the regulation of cell migration, proliferation and differentiation. Despite their developmental and medical significance, the molecular functions of these NDPKs remain ill defined. To minimize confounding effects of functional compensation between closely related Nm23 family members, we studied ndk-1, the sole Caenorhabditis elegans ortholog of group I NDPKs, and focused on its role in Ras/mitogen-activated protein kinase (MAPK)-mediated signaling events during development. ndk-1 inactivation leads to a protruding vulva phenotype and affects vulval cell fate specification through the Ras/MAPK cascade. ndk-1 mutant worms show severe reduction of activated, diphosphorylated MAPK in somatic tissues, indicative of compromised Ras/MAPK signaling. A genetic epistasis analysis using the vulval induction system revealed that NDK-1 acts downstream of LIN-45/Raf, but upstream of MPK-1/MAPK, at the level of the kinase suppressors of ras (KSR-1/2). KSR proteins act as scaffolds facilitating Ras signaling events by tethering signaling components, and we suggest that NDK-1 modulates KSR activity through direct physical interaction. Our study reveals that C. elegans NDK-1/Nm23 influences differentiation by enhancing the level of Ras/MAPK signaling. These results might help to better understand how dysregulated Nm23 in humans contributes to tumorigenesis.
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Affiliation(s)
- Neda Masoudi
- Department of Genetics, Eötvös Loránd University, Pázmány Péter stny. 1/C, H-1117 Budapest, Hungary
- Wellcome Trust Centre for Gene Regulation and Expression, University of Dundee, Dow Street, Dundee DD1 5EH, UK
| | - Luca Fancsalszky
- Department of Genetics, Eötvös Loránd University, Pázmány Péter stny. 1/C, H-1117 Budapest, Hungary
| | - Ehsan Pourkarimi
- Department of Genetics, Eötvös Loránd University, Pázmány Péter stny. 1/C, H-1117 Budapest, Hungary
- Wellcome Trust Centre for Gene Regulation and Expression, University of Dundee, Dow Street, Dundee DD1 5EH, UK
| | - Tibor Vellai
- Department of Genetics, Eötvös Loránd University, Pázmány Péter stny. 1/C, H-1117 Budapest, Hungary
| | - Anita Alexa
- Department of Biochemistry, Eötvös Loránd University, Pázmány Péter stny. 1/C, H-1117 Budapest, Hungary
- Institute of Molecular Pharmacology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Pusztaszeri út 59-67, H-1025 Budapest, Hungary
| | - Attila Reményi
- Department of Biochemistry, Eötvös Loránd University, Pázmány Péter stny. 1/C, H-1117 Budapest, Hungary
- Institute of Molecular Pharmacology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Pusztaszeri út 59-67, H-1025 Budapest, Hungary
| | - Anton Gartner
- Wellcome Trust Centre for Gene Regulation and Expression, University of Dundee, Dow Street, Dundee DD1 5EH, UK
| | - Anil Mehta
- Division of Medical Sciences, Centre for CVS and Lung Biology, Ninewells Hospital Medical School, Dundee DD1 9SY, UK
| | - Krisztina Takács-Vellai
- Department of Genetics, Eötvös Loránd University, Pázmány Péter stny. 1/C, H-1117 Budapest, Hungary
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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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10
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Using Multiple Phenotype Assays and Epistasis Testing to Enhance the Reliability of RNAi Screening and Identify Regulators of Muscle Protein Degradation. Genes (Basel) 2012; 3:686-701. [PMID: 23152949 PMCID: PMC3495584 DOI: 10.3390/genes3040686] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
RNAi is a convenient, widely used tool for screening for genes of interest. We have recently used this technology to screen roughly 750 candidate genes, in C. elegans, for potential roles in regulating muscle protein degradation in vivo. To maximize confidence and assess reproducibility, we have only used previously validated RNAi constructs and have included time courses and replicates. To maximize mechanistic understanding, we have examined multiple sub-cellular phenotypes in multiple compartments in muscle. We have also tested knockdowns of putative regulators of degradation in the context of mutations or drugs that were previously shown to inhibit protein degradation by diverse mechanisms. Here we discuss how assaying multiple phenotypes, multiplexing RNAi screens with use of mutations and drugs, and use of bioinformatics can provide more data on rates of potential false positives and negatives as well as more mechanistic insight than simple RNAi screening.
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Lehmann S, Shephard F, Jacobson LA, Szewczyk NJ. Integrated control of protein degradation in C. elegans muscle. WORM 2012; 1:141-50. [PMID: 23457662 PMCID: PMC3583358 DOI: 10.4161/worm.20465] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Revised: 04/14/2012] [Accepted: 04/23/2012] [Indexed: 12/26/2022]
Abstract
Protein degradation is a fundamental cellular process, the genomic control of which is incompletely understood. The advent of transgene-coded reporter proteins has enabled the development of C. elegans into a model for studying this problem. The regulation of muscle protein degradation is surprisingly complex, integrating multiple signals from hypodermis, intestine, neurons and muscle itself. Within the muscle, degradation is executed by separately regulated autophagy-lysosomal, ubiquitin-proteasome and calpain-mediated systems. The signal-transduction mechanisms, in some instances, involve modules previously identified for their roles in developmental processes, repurposed in terminally differentiated muscle to regulate the activities of pre-formed proteins. Here we review the genes, and mechanisms, which appear to coordinately control protein degradation within C. elegans muscle. We also consider these mechanisms in the context of development, physiology, pathophysiology and disease models.
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Affiliation(s)
- Susann Lehmann
- Medical Research Council/Arthritis Research UK Centre for Musculoskeletal Ageing Research; University of Nottingham; Royal Derby Hospital; Derby, UK
| | - Freya Shephard
- Medical Research Council/Arthritis Research UK Centre for Musculoskeletal Ageing Research; University of Nottingham; Royal Derby Hospital; Derby, UK
| | - Lewis A. Jacobson
- Department of Biological Sciences; University of Pittsburgh; Pittsburgh, PA USA
| | - Nathaniel J. Szewczyk
- Medical Research Council/Arthritis Research UK Centre for Musculoskeletal Ageing Research; University of Nottingham; Royal Derby Hospital; Derby, UK
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12
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Etheridge T, Oczypok EA, Lehmann S, Fields BD, Shephard F, Jacobson LA, Szewczyk NJ. Calpains mediate integrin attachment complex maintenance of adult muscle in Caenorhabditis elegans. PLoS Genet 2012; 8:e1002471. [PMID: 22253611 PMCID: PMC3257289 DOI: 10.1371/journal.pgen.1002471] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Accepted: 11/23/2011] [Indexed: 11/23/2022] Open
Abstract
Two components of integrin containing attachment complexes, UNC-97/PINCH and UNC-112/MIG-2/Kindlin-2, were recently identified as negative regulators of muscle protein degradation and as having decreased mRNA levels in response to spaceflight. Integrin complexes transmit force between the inside and outside of muscle cells and signal changes in muscle size in response to force and, perhaps, disuse. We therefore investigated the effects of acute decreases in expression of the genes encoding these multi-protein complexes. We find that in fully developed adult Caenorhabditis elegans muscle, RNAi against genes encoding core, and peripheral, members of these complexes induces protein degradation, myofibrillar and mitochondrial dystrophies, and a movement defect. Genetic disruption of Z-line– or M-line–specific complex members is sufficient to induce these defects. We confirmed that defects occur in temperature-sensitive mutants for two of the genes: unc-52, which encodes the extra-cellular ligand Perlecan, and unc-112, which encodes the intracellular component Kindlin-2. These results demonstrate that integrin containing attachment complexes, as a whole, are required for proper maintenance of adult muscle. These defects, and collapse of arrayed attachment complexes into ball like structures, are blocked when DIM-1 levels are reduced. Degradation is also blocked by RNAi or drugs targeting calpains, implying that disruption of integrin containing complexes results in calpain activation. In wild-type animals, either during development or in adults, RNAi against calpain genes results in integrin muscle attachment disruptions and consequent sub-cellular defects. These results demonstrate that calpains are required for proper assembly and maintenance of integrin attachment complexes. Taken together our data provide in vivo evidence that a calpain-based molecular repair mechanism exists for dealing with attachment complex disruption in adult muscle. Since C. elegans lacks satellite cells, this mechanism is intrinsic to the muscles and raises the question if such a mechanism also exists in higher metazoans. Muscle is a dynamic tissue that grows in response to use and nutrition and shrinks in response to lack of use, poor nutrition, or disease. Loss of muscle mass is an important public health problem, but we understand little of the genes that regulate muscle shrinkage. We have found that, in adult worm muscle, attachment to the basement membrane is continuously required to prevent catastrophic sub-cellular defects that result in impaired ability of muscle to function. We have also identified a group of proteases that are activated when the attachment fails to be properly maintained. Conversely, when these proteases are lacking in adult muscle, the muscles fail to maintain attachment to the basement membrane. Thus, we have discovered a group of proteases that appear to act to maintain attachment to the basement membrane and therefore to maintain muscle itself. Because these worms lack satellite cells, this maintenance system is intrinsic to muscle, thus raising the question whether a similar or identical system also works in humans.
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Affiliation(s)
- Timothy Etheridge
- School of Graduate Entry Medicine and Health, University of Nottingham, Royal Derby Hospital, Derby, United Kingdom
| | - Elizabeth A. Oczypok
- School of Graduate Entry Medicine and Health, University of Nottingham, Royal Derby Hospital, Derby, United Kingdom
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Susann Lehmann
- School of Graduate Entry Medicine and Health, University of Nottingham, Royal Derby Hospital, Derby, United Kingdom
| | - Brandon D. Fields
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Freya Shephard
- School of Graduate Entry Medicine and Health, University of Nottingham, Royal Derby Hospital, Derby, United Kingdom
| | - Lewis A. Jacobson
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Nathaniel J. Szewczyk
- School of Graduate Entry Medicine and Health, University of Nottingham, Royal Derby Hospital, Derby, United Kingdom
- * E-mail:
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13
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Shephard F, Adenle AA, Jacobson LA, Szewczyk NJ. Identification and functional clustering of genes regulating muscle protein degradation from amongst the known C. elegans muscle mutants. PLoS One 2011; 6:e24686. [PMID: 21980350 PMCID: PMC3181249 DOI: 10.1371/journal.pone.0024686] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Accepted: 08/15/2011] [Indexed: 01/08/2023] Open
Abstract
Loss of muscle mass via protein degradation is an important clinical problem but we know little of how muscle protein degradation is regulated genetically. To gain insight our labs developed C. elegans into a model for understanding the regulation of muscle protein degradation. Past studies uncovered novel functional roles for genes affecting muscle and/or involved in signalling in other cells or tissues. Here we examine most of the genes previously identified as the sites of mutations affecting muscle for novel roles in regulating degradation. We evaluate genomic (RNAi knockdown) approaches and combine them with our established genetic (mutant) and pharmacologic (drugs) approaches to examine these 159 genes. We find that RNAi usually recapitulates both organismal and sub-cellular mutant phenotypes but RNAi, unlike mutants, can frequently be used acutely to study gene function solely in differentiated muscle. In the majority of cases where RNAi does not produce organismal level phenotypes, sub-cellular defects can be detected; disrupted proteostasis is most commonly observed. We identify 48 genes in which mutation or RNAi knockdown causes excessive protein degradation; myofibrillar and/or mitochondrial morphologies are also disrupted in 19 of these 48 cases. These 48 genes appear to act via at least three sub-networks to control bulk degradation of protein in muscle cytosol. Attachment to the extracellular matrix regulates degradation via unidentified proteases and affects myofibrillar and mitochondrial morphology. Growth factor imbalance and calcium overload promote lysosome based degradation whereas calcium deficit promotes proteasome based degradation, in both cases myofibrillar and mitochondrial morphologies are largely unaffected. Our results provide a framework for effectively using RNAi to identify and functionally cluster novel regulators of degradation. This clustering allows prioritization of candidate genes/pathways for future mechanistic studies.
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Affiliation(s)
- Freya Shephard
- School of Graduate Entry Medicine and Health, University of Nottingham, Royal Derby Hospital, Derby, United Kingdom
| | - Ademola A. Adenle
- School of Graduate Entry Medicine and Health, University of Nottingham, Royal Derby Hospital, Derby, United Kingdom
| | - Lewis A. Jacobson
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Nathaniel J. Szewczyk
- School of Graduate Entry Medicine and Health, University of Nottingham, Royal Derby Hospital, Derby, United Kingdom
- * E-mail:
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Klotho interferes with a novel FGF-signalling pathway and insulin/Igf-like signalling to improve longevity and stress resistance in Caenorhabditis elegans. Aging (Albany NY) 2011; 2:567-81. [PMID: 20844315 PMCID: PMC2984606 DOI: 10.18632/aging.100195] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Klotho exerts anti-aging properties in mammals in two different ways. While membrane-bound Klotho, which is primarily expressed in the kidney, acts as an obligate co-receptor of FGF23 to regulate phosphate homeostasis, secreted Klotho, resulting from the shedding of the KL1-KL2 ectodomain into the bloodstream, inhibits Insulin/IGF1 signalling. However, the underlying molecular mechanisms are not fully understood. Here, we investigated the biological role of Klotho inCaenorhabditis elegans. Two redundant homologues of the klotho gene exist in C. elegans and encode predicted proteins homologous to the β glucosidase-like KL1 domain of mammalian Klotho. We have used a genetic approach to investigate the functional activity of Klotho in C. elegans. Here, we report that whereas Klotho requires EGL-15 (FGFR) and EGL-17 to promote longevity and oxidative stress resistance, it is not involved in the regulation of fluid homeostasis, controlled by LET-756. Besides revealing a new post-developmental role for EGL-17, our data suggest that the KL1 form of Klotho is involved in FGF23-independent FGF signalling. We also report a genetic interaction between Klotho and the DAF-2 (Ins/IGF1R)/DAF-16 (FOXO) pathway. While the regulation of longevity requires functional DAF-2/DAF-16 signalling, the control of oxidative stress resistance involves a DAF-2- independent, DAF-16-dependent pathway, suggesting that Klotho may target either DAF-2 or DAF-16, depending of environmental conditions. Thus, the predictive KL1 form of Klotho appears to crosstalk with both FGF and Insulin/IGF1/FOXO pathways to exert anti-aging properties in C. elegans.
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Caenorhabditis elegans fibroblast growth factor receptor signaling can occur independently of the multi-substrate adaptor FRS2. Genetics 2010; 185:537-47. [PMID: 20308281 DOI: 10.1534/genetics.109.113373] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The components of receptor tyrosine kinase signaling complexes help to define the specificity of the effects of their activation. The Caenorhabditis elegans fibroblast growth factor receptor (FGFR), EGL-15, regulates a number of processes, including sex myoblast (SM) migration guidance and fluid homeostasis, both of which require a Grb2/Sos/Ras cassette of signaling components. Here we show that SEM-5/Grb2 can bind directly to EGL-15 to mediate SM chemoattraction. A yeast two-hybrid screen identified SEM-5 as able to interact with the carboxy-terminal domain (CTD) of EGL-15, a domain that is specifically required for SM chemoattraction. This interaction requires the SEM-5 SH2-binding motifs present in the CTD (Y(1009) and Y(1087)), and these sites are required for the CTD role of EGL-15 in SM chemoattraction. SEM-5, but not the SEM-5 binding sites located in the CTD, is required for the fluid homeostasis function of EGL-15, indicating that SEM-5 can link to EGL-15 through an alternative mechanism. The multi-substrate adaptor protein FRS2 serves to link vertebrate FGFRs to Grb2. In C. elegans, an FRS2-like gene, rog-1, functions upstream of a Ras/MAPK pathway for oocyte maturation but is not required for EGL-15 function. Thus, unlike the vertebrate FGFRs, which require the multi-substrate adaptor FRS2 to recruit Grb2, EGL-15 can recruit SEM-5/Grb2 directly.
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16
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Banduseela VC, Ochala J, Chen YW, Göransson H, Norman H, Radell P, Eriksson LI, Hoffman EP, Larsson L. Gene expression and muscle fiber function in a porcine ICU model. Physiol Genomics 2009; 39:141-59. [DOI: 10.1152/physiolgenomics.00026.2009] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Skeletal muscle wasting and impaired muscle function in response to mechanical ventilation and immobilization in intensive care unit (ICU) patients are clinically challenging partly due to 1) the poorly understood intricate cellular and molecular networks and 2) the unavailability of an animal model mimicking this condition. By employing a unique porcine model mimicking the conditions in the ICU with long-term mechanical ventilation and immobilization, we have analyzed the expression profile of skeletal muscle biopsies taken at three time points during a 5-day period. Among the differentially regulated transcripts, extracellular matrix, energy metabolism, sarcomeric and LIM protein mRNA levels were downregulated, while ubiquitin proteasome system, cathepsins, oxidative stress responsive genes and heat shock proteins (HSP) mRNAs were upregulated. Despite 5 days of immobilization and mechanical ventilation single muscle fiber cross-sectional areas as well as the maximum force generating capacity at the single muscle fiber level were preserved. It is proposed that HSP induction in skeletal muscle is an inherent, primary, but temporary protective mechanism against protein degradation. To our knowledge, this is the first study that isolates the effect of immobilization and mechanical ventilation in an ICU condition from various other cofactors.
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Affiliation(s)
- Varuna C. Banduseela
- Department of Clinical Neurophysiology, Uppsala University Hospital, Uppsala, Sweden
| | - Julien Ochala
- Department of Clinical Neurophysiology, Uppsala University Hospital, Uppsala, Sweden
| | - Yi-Wen Chen
- Research Center for Genetic Medicine, Children National Medical Center
- Department of Pediatrics, The George Washington University Medical Center, Washington, District of Columbia
| | - Hanna Göransson
- Department of Medical Sciences, Uppsala University Hospital, Uppsala, Sweden
| | - Holly Norman
- Department of Clinical Neurophysiology, Uppsala University Hospital, Uppsala, Sweden
- Department of Physiology, University of Wisconsin, Madison, Wisconsin; and
| | - Peter Radell
- Department of Anesthesiology, Karolinska Institute, Stockholm, Sweden
| | - Lars I. Eriksson
- Department of Anesthesiology, Karolinska Institute, Stockholm, Sweden
| | - Eric P. Hoffman
- Research Center for Genetic Medicine, Children National Medical Center
- Department of Pediatrics, The George Washington University Medical Center, Washington, District of Columbia
| | - Lars Larsson
- Department of Clinical Neurophysiology, Uppsala University Hospital, Uppsala, Sweden
- Department of Biobehavioral Health, Pennsylvania State University, University Park, Pennsylvania
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17
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Szewczyk NJ, Peterson BK, Barmada SJ, Parkinson LP, Jacobson LA. Opposed growth factor signals control protein degradation in muscles of Caenorhabditis elegans. EMBO J 2007; 26:935-43. [PMID: 17290229 PMCID: PMC1852841 DOI: 10.1038/sj.emboj.7601540] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2006] [Accepted: 12/10/2006] [Indexed: 02/06/2023] Open
Abstract
In addition to contractile function, muscle provides a metabolic buffer by degrading protein in times of organismal need. Protein is also degraded during adaptive muscle remodeling upon exercise, but extreme degradation in diverse clinical conditions can compromise function(s) and threaten life. Here, we show how two independent signals interact to control protein degradation. In striated muscles of Caenorhabditis elegans, reduction of insulin-like signaling via DAF-2 insulin/IGF receptor or its intramuscular effector PtdIns-3-kinase (PI3K) causes unexpected activation of MAP kinase (MAPK), consequent activation of pre-existing systems for protein degradation, and progressive impairment of mobility. Degradation is prevented by mutations that increase signal downstream of PI3K or by disruption of autocrine signal from fibroblast growth factor (FGF) via the FGF receptor and its effectors in the Ras-MAPK pathway. Thus, the activity of constitutive protein degradation systems in normal muscle is minimized by a balance between directly interacting signaling pathways, implying that physiological, pathological, or therapeutic alteration of this balance may contribute to muscle remodeling or wasting.
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Affiliation(s)
- Nathaniel J Szewczyk
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Brant K Peterson
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Sami J Barmada
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Leah P Parkinson
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
| | - Lewis A Jacobson
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA. Tel.: +1 412 624 4647; Fax: +1 412 624 4759; E-mail:
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18
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Higashibata A, Szewczyk NJ, Conley CA, Imamizo-Sato M, Higashitani A, Ishioka N. Decreased expression of myogenic transcription factors and myosin heavy chains in Caenorhabditis elegans muscles developed during spaceflight. J Exp Biol 2006; 209:3209-18. [PMID: 16888068 DOI: 10.1242/jeb.02365] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
SUMMARY
The molecular mechanisms underlying muscle atrophy during spaceflight are not well understood. We have analyzed the effects of a 10-day spaceflight on Caenorhabditis elegans muscle development. DNA microarray, real-time quantitative PCR, and quantitative western blot analyses revealed that the amount of MHC in both body-wall and pharyngeal muscle decrease in response to spaceflight. Decreased transcription of the body-wall myogenic transcription factor HLH-1 (CeMyoD) and of the three pharyngeal myogenic transcription factors, PEB-1, CEH-22 and PHA-4 were also observed. Upon return to Earth animals displayed reduced rates of movement, indicating a functional defect. These results demonstrate that C. elegans muscle development is altered in response to spaceflight. This altered development occurs at the level of gene transcription and was observed in the presence of innervation,not simply in isolated cells. This important finding coupled with past observations of decreased levels of the same myogenic transcription factions in vertebrates after spaceflight raises the possibility that altered muscle development is a contributing factor to spaceflight-induced muscle atrophy in vertebrates.
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Affiliation(s)
- Akira Higashibata
- Japan Aerospace Exploration Agency, 2-1-1, Sengen, Tsukuba, Ibaraki 305-8505, Japan.
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Pak SC, Tsu C, Luke CJ, Askew YS, Silverman GA. The Caenorhabditis elegans muscle specific serpin, SRP-3, neutralizes chymotrypsin-like serine peptidases. Biochemistry 2006; 45:4474-80. [PMID: 16584183 PMCID: PMC2654365 DOI: 10.1021/bi052626d] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Members of the intracellular serpin family may help regulate apoptosis, tumor progression, and metastasis. However, their in vivo functions in the context of a whole organism have not been easily defined. To better understand the biology of these serpins, we initiated a comparative genomics study using Caenorhabditis elegans as a model organism. Previous in silico analysis suggested that the C. elegans genome harbors nine serpin-like sequences bearing significant similarities to the human clade B intracellular serpins. However, only five genes appear to encode full-length serpins with intact reactive site loops. To determine if this was the case, we have cloned and expressed a putative inhibitory-type C. elegans serpin, srp-3. Analysis of SRP-3 inhibitory activity indicated that SRP-3 was a potent inhibitor of the serine peptidases, chymotrypsin and cathepsin G. Spatial and temporal expression studies using GFP and LacZ promoter fusions indicated that SRP-3 was expressed primarily in the anterior body wall muscles, suggesting that it may play a role in muscle cell homeostasis. Combined with previous studies showing that SRP-2 is an inhibitor of the serine peptidase, granzyme B, and lysosomal cysteine peptidases, these data suggested that C. elegans expressed at least two inhibitory-type serpins with nonoverlapping expression and inhibitory profiles. Moreover, the profiles of these clade L serpins in C. elegans share significant similarities with the profiles of clade B intracellular serpin members in higher vertebrates. This degree of conservation suggests that C. elegans should prove to be a valuable resource in the study of metazoan intracellular serpin function.
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Affiliation(s)
- Stephen C Pak
- UPMC Newborn Medicine Program, Department of Pediatrics, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh, and Magee-Womens Research Institute, Pittsburgh, Pennsylvania 15213, USA
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20
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Birnbaum D, Popovici C, Roubin R. A pair as a minimum: the two fibroblast growth factors of the nematode Caenorhabditis elegans. Dev Dyn 2005; 232:247-55. [PMID: 15614779 DOI: 10.1002/dvdy.20219] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Fibroblast growth factors (FGFs) regulate many important developmental and homeostatic physiological events. The FGF superfamily contains several families. In this review, we present recent findings on the two FGFs of the nematode Caenorhabditis elegans from both functional and phylogenic points of view. C. elegans has a single FGFR (EGL-15) with two functionally exclusive isoforms, and two FGFs (LET-756 and EGL-17), which play distinct roles: an essential function for the former, and guidance of the migrating sex myoblasts for the latter. Regulation of homeostasis by control of the fluid balance could be the basis for the essential function of LET-756. Phylogenetic and functional studies suggest that LET-756, like vertebrate FGF9, -16, and -20, belongs to the FGF9 family, whereas EGL-17, like vertebrate FGF8, -17, and -18, could be included in the FGF8 family.
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Affiliation(s)
- Daniel Birnbaum
- Molecular Oncology Laboratory, UMR599 INSERM, 27 Bd. Lei Roure, 13009 Marseille, France.
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Gottschalk A, Almedom RB, Schedletzky T, Anderson SD, Yates JR, Schafer WR. Identification and characterization of novel nicotinic receptor-associated proteins in Caenorhabditis elegans. EMBO J 2005; 24:2566-78. [PMID: 15990870 PMCID: PMC1176467 DOI: 10.1038/sj.emboj.7600741] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2004] [Accepted: 06/13/2005] [Indexed: 11/09/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) mediate fast excitatory neurotransmission in neurons and muscles. To identify nAChR accessory proteins, which may regulate their expression or function, we performed tandem affinity purification of the levamisole-sensitive nAChR from Caenorhabditis elegans, mass spectrometry of associated components, and RNAi-based screening for effects on in vivo nicotine sensitivity. Among the proteins identified was the calcineurin A subunit TAX-6, which appeared to function as a negative regulator of nAChR activity. We also identified five proteins not previously linked to nAChR function, whose inactivation conferred nicotine resistance, implicating them as positive regulators of nAChR activity. Of these, the copine NRA-1 colocalized with the levamisole receptor at neuronal and muscle plasma membranes, and, when mutated, caused reduced synaptic nAChR expression. Loss of SOC-1, which acts in receptor tyrosine kinase (RTK) signaling, also reduced synaptic levamisole receptor levels, as did mutations in the fibroblast growth factor receptor EGL-15, and another RTK, CAM-1. Thus, tandem affinity purification is a viable approach to identify novel proteins regulating neurotransmitter receptor activity or expression in model systems like C. elegans.
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Affiliation(s)
- Alexander Gottschalk
- Institute for Biochemistry, Goethe-University, Frankfurt, Germany
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA, USA
- Institute for Biochemistry, Goethe-University, Biocenter N210, Marie-Curie-Str. 9, 60439 Frankfurt, Germany. Tel.: +49 69 798 29261; Fax: +49 69 798 29495; E-mail:
| | - Ruta B Almedom
- Institute for Biochemistry, Goethe-University, Frankfurt, Germany
| | | | - Scott D Anderson
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - John R Yates
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - William R Schafer
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA, USA
- Division of Biological Sciences, University of California, San Diego, 9500 Gilman Dr, La Jolla, CA 92093-0643, USA. Tel.: +1 858 822 0508; Fax: +1 858 822 2003; E-mail:
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Huang P, Stern MJ. FGF signaling in flies and worms: more and more relevant to vertebrate biology. Cytokine Growth Factor Rev 2005; 16:151-8. [PMID: 15863031 DOI: 10.1016/j.cytogfr.2005.03.002] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
FGF signaling in the invertebrate model systems Drosophila melanogaster and Caenorhabditis elegans was initially most obviously involved in cell motility events. More recently, however, FGFs and FGF signaling in these systems have been shown to affect many additional cellular processes. This recent work has shown that the pleiotropies of these FGF receptors resemble those of their vertebrate counterparts, and, in many cases, serve as excellent models for understanding the fundamental molecular mechanisms controlling these events.
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Affiliation(s)
- Peng Huang
- Yale University School of Medicine, Department of Genetics, I-354 SHM, P.O. Box 208005, New Haven, CT 06520-8005, USA
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23
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Szewczyk NJ, Jacobson LA. Signal-transduction networks and the regulation of muscle protein degradation. Int J Biochem Cell Biol 2005; 37:1997-2011. [PMID: 16125109 DOI: 10.1016/j.biocel.2005.02.020] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2004] [Revised: 01/18/2005] [Accepted: 02/22/2005] [Indexed: 02/05/2023]
Abstract
Protein degradation in muscle functions in maintaining normal physiological homeostasis and adapting to new homeostatic states, and is required for muscle wasting or atrophy in various pathological states. The interplay between protein synthesis and degradation to maintain homeostasis is complex and responds to a variety of autocrine and intercellular signals from neuronal inputs, hormones, cytokines, growth factors and other regulatory molecules. The intracellular events that connect extracellular signals to the molecular control of protein degradation are incompletely understood, but likely involve interacting signal-transduction networks rather than isolated pathways. We review some examples of signal-transduction systems that regulate protein degradation, including effectors of proteolysis inducing factor (PIF), insulin and insulin-like growth factor (IGF) and their receptors, and fibroblast growth factor (FGF) and its receptors.
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Affiliation(s)
- Nathaniel J Szewczyk
- Department of Biological Sciences, University of Pittsburgh, 304 Langley Hall, Pittsburgh, PA 15260, USA
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Dinkova TD, Keiper BD, Korneeva NL, Aamodt EJ, Rhoads RE. Translation of a small subset of Caenorhabditis elegans mRNAs is dependent on a specific eukaryotic translation initiation factor 4E isoform. Mol Cell Biol 2005; 25:100-13. [PMID: 15601834 PMCID: PMC538781 DOI: 10.1128/mcb.25.1.100-113.2005] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2004] [Revised: 08/19/2004] [Accepted: 09/20/2004] [Indexed: 11/20/2022] Open
Abstract
The mRNA cap-binding protein eukaryotic translation initiation factor 4E (eIF4E) participates in protein synthesis initiation, translational repression of specific mRNAs, and nucleocytoplasmic shuttling. Multiple isoforms of eIF4E are expressed in a variety of organisms, but their specific roles are poorly understood. We investigated one Caenorhabditis elegans isoform, IFE-4, which has homologues in plants and mammals. IFE-4::green fluorescent protein (GFP) was expressed in pharyngeal and tail neurons, body wall muscle, spermatheca, and vulva. Knockout of ife-4 by RNA interference (RNAi) or a null mutation produced a pleiotropic phenotype that included egg-laying defects. Sedimentation analysis demonstrated that IFE-4, but not IFE-1, was present in 48S initiation complexes, indicating that it participates in protein synthesis initiation. mRNAs affected by ife-4 knockout were determined by DNA microarray analysis of polysomal distribution. Polysome shifts, in the absence of total mRNA changes, were observed for only 33 of the 18,967 C. elegans mRNAs tested, of which a disproportionate number were related to egg laying and were expressed in neurons and/or muscle. Translational regulation was confirmed by reduced levels of DAF-12, EGL-15, and KIN-29. The functions of these proteins can explain some phenotypes observed in ife-4 knockout mutants. These results indicate that translation of a limited subset of mRNAs is dependent on a specific isoform of eIF4E.
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Affiliation(s)
- Tzvetanka D Dinkova
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, LA 71130-3932, USA
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Sasson IE, Stern MJ. FGF and PI3 kinase signaling pathways antagonistically modulate sex muscle differentiation in C. elegans. Development 2004; 131:5381-92. [PMID: 15469970 DOI: 10.1242/dev.01423] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Myogenesis in vertebrate myocytes is promoted by activation of the phosphatidyl-inositol 3'-kinase (PI3 kinase) pathway and inhibited by fibroblast growth factor (FGF) signaling. We show that hyperactivation of the Caenorhabditis elegans FGF receptor, EGL-15, similarly inhibits the differentiation of the hermaphrodite sex muscles. Activation of the PI3 kinase signaling pathway can partially suppress this differentiation defect, mimicking the antagonistic relationship between these two pathways known to influence vertebrate myogenesis. When ectopically expressed in body wall muscle precursor cells, hyperactivated EGL-15 can also interfere with the proper development of the body wall musculature. Hyperactivation of EGL-15 has also revealed additional effects on a number of fundamental processes within the postembryonic muscle lineage, such as cell division polarity. These studies provide important in vivo insights into the contribution of FGF signaling events to myogenesis.
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Affiliation(s)
- Isaac E Sasson
- Yale University School of Medicine, Department of Genetics, I-354 SHM, PO Box 208005, New Haven, CT 06520-8005, USA
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