Identification and Functional Clustering of Genes Regulating Muscle Protein Degradation from amongst the Known C. elegans Muscle Mutants

Shephard, Freya; Adenle, Ademola A.; Jacobson, Lewis A.; Szewczyk, Nathaniel J.

doi:10.1371/journal.pone.0024686

Cited by 31 publications

(80 citation statements)

References 42 publications

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“…The genomic screen that identified unc-97 and unc-112 RNAi treatment as inducing protein degradation in adult C. elegans muscle demonstrated that in both cases, degradation could not be blocked by treatment with the proteasome inhibitor MG132 and occurred in mutants that block pro-autophagy signalling in C. elegans [29]. We confirmed and extended these results.…”

Section: Resultssupporting

confidence: 76%

Calpains Mediate Integrin Attachment Complex Maintenance of Adult Muscle in Caenorhabditis elegans

et al. 2012

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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.

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Section: Resultssupporting

confidence: 76%

Calpains Mediate Integrin Attachment Complex Maintenance of Adult Muscle in Caenorhabditis elegans

et al. 2012

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“…Although these studies could not rule out the possibility that Se induces damage to sub-cellular muscle compartments (e.g. mitochondria), a recent study examining mutations in genes affecting movement behavior suggested that these types of behavioral effects were least likely to result from sub-cellular muscle defects (Shephard et al, 2011). …”

Section: Discussionmentioning

confidence: 99%

Selenium induces cholinergic motor neuron degeneration in Caenorhabditis elegans

et al. 2012

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Selenium is an essential micronutrient required for cellular antioxidant systems, yet at higher doses it induces oxidative stress. Additionally, in vertebrates environmental exposures to toxic levels of selenium can cause paralysis and death. Here we show that selenium-induced oxidative stress leads to decreased cholinergic signaling and degeneration of cholinergic neurons required for movement and egg-laying in Caenorhabditis elegans. Exposure to high levels of selenium leads to proteolysis of a soluble muscle protein through mechanisms suppressible by two pharmacological agents, levamisole and aldicarb which enhance cholinergic signaling in muscle. In addition, animals with reduction-of-function mutations in genes encoding post-synaptic levamisole-sensitive acetylcholine receptor subunits or the vesicular acetylcholine transporter developed impaired forward movement faster during selenium-exposure than normal animals, again confirming that selenium reduces cholinergic signaling. Finally, the antioxidant reduced glutathione, inhibits selenium-induced reductions in egg-laying through a cellular protective mechanism dependent on the C. elegans glutaredoxin, GLRX-21. These studies provide evidence that the environmental toxicant selenium induces neurodegeneration of cholinergic neurons through depletion of glutathione, a mechanism linked to the neuropathology of Alzheimer’s disease, amyotrophic lateral sclerosis, and Parkinson’s disease.

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“…Acute RNAi experiments with these mutants were performed as described [12]. Degradation was scored as in acute RNAi treatments in two independent experiments; in case of discrepancy a third experiment was run.…”

Section: Methodsmentioning

confidence: 99%

Knockdown of the C. elegans Kinome identifies Kinases required for normal protein Homeostasis, Mitochondrial network structure, and Sarcomere structure in muscle

2013

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BackgroundKinases 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.Results96 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.ConclusionsRoughly 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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Identification and Functional Clustering of Genes Regulating Muscle Protein Degradation from amongst the Known C. elegans Muscle Mutants

Cited by 31 publications

References 42 publications

Calpains Mediate Integrin Attachment Complex Maintenance of Adult Muscle in Caenorhabditis elegans

Calpains Mediate Integrin Attachment Complex Maintenance of Adult Muscle in Caenorhabditis elegans

Selenium induces cholinergic motor neuron degeneration in Caenorhabditis elegans

Knockdown of the C. elegans Kinome identifies Kinases required for normal protein Homeostasis, Mitochondrial network structure, and Sarcomere structure in muscle

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