A genetic model for understanding the regulation of muscle protein degradation by muscle attachment

Lead Research Organisation: University of Nottingham
Department Name: Graduate Entry Medical School

Abstract

The muscle of the tiny worm I use in my studies (C. elegans) is a surprisingly good model for muscles in human beings. It can be studied more easily and in many experimental situations that are impossible in people. At the moment, we do not understand what causes muscle wasting in people, a problem that affects the elderly and those with spinal injuries among others. My previous worm studies may offer some clues, others are applying my results to studies in human beings.
Muscle wasting occurs in response to spaceflight and immobilization. I discovered that in worms, a special complex of proteins (known as ?dense bodies? and which attach worm muscle to skeleton) were decreased after spaceflight. My experiments on Earth show that reducing these proteins causes muscle tissue breakdown. Others at my University found that a protein in human focal adhesions is decreased following cast immobilization. Additionally, mutations in focal adhesions cause Limb Girdle Muscular Dystrophies. The same proteins are found in worm dense bodies and human focal adhesions. Thus, similar changes are observed in worm and human attachment complexes and these changes cause worm muscle wasting.
We currently have no idea what the controlling and mediating factor are, if these factors also regulate human muscle wasting, nor if they differ among various clinical populations displaying wasting (e.g. trauma patients, burn patients, bed ridden patients, the elderly). I want to answer these questions. I currently want to understand one mechanism regulating wasting in worms. The ultimate goal is understanding all of the mechanisms regulating wasting in human beings. I feel that once we do, we can understand the differences between patients and identify drug targets providing appropriate treatment(s) to each group of patients. It is my hope that by first gaining an understanding of the regulation and treatment of wasting in a simple organism, we can more rapidly and cost effectively demonstrate the existence and treatment of the same processes in people.
I will also continue my efforts of communicating results directly to the public. In the past this has included making results freely available on-line, giving free talks to the public, actively engaging school children in my research, and communicating my work via reporters and radio and television presenters from around the world (in the UK these include the BBC, the Discovery Channel, CNN, and all of the ?wire? services that provide stories to newspapers).

Technical Summary

Clinically, muscle atrophy occurs in a variety of conditions. Atrophy has significant morbidity and can be a proximal cause of death. Altered regulation of protein synthesis and/or degradation causes an intramuscular Nitrogen imbalance and consequent atrophy. Despite the health impact, we understand little of the intramuscular signalling systems tying more than a dozen extramuscular regulators of atrophy to the intramuscular protein synthesis machinery and/or multiple proteases. Nor do we comprehensively understand how these signalling systems interact with one another inside muscle. To address these issues we have developed C. elegans into the simplest genetic model for understanding the intramuscular signalling networks regulating muscle protein degradation in vivo. Thus far we have examined three extramuscular regulators and found that proteasome based muscle protein degradation occurs as the result of disruption of normal membrane depolarization (for example loss of Acetylcholine signalling or rectifying Potassium currents) and that lysosome based degradation occurs as the result of disruption of a balance between Fibroblast Growth Factor Receptor and Insulin Receptor signalling. These signals appear to work in similar or identical fashions in mammals. Recently we found decreased expression of parts of a conserved muscle attachment complex following spaceflight. We further found that mutation in or RNAi against the genes encoding these proteins results in muscle protein degradation independently from our previously studied signalling and proteolytic systems. Mutations in genes encoding members of the human attachment complex cause Limb Girdle Muscular Dystrophies. Additionally, one complex member, Focal Adhesion Kinase, may regulate both human muscle hypertrophy and atrophy. To understand how this novel, conserved, mechanism regulates degradation we propose to: 1) Identify all of the members of the complex needed to prevent degradation, 2) Determine if and how degradation observed in the cytosol is linked to myofiber disruption and loss of mobility, 3) Determine the protease responsible for cytosolic degradation and the mechanism by which it is activated in response to disruption of the muscle attachment complex. We will employ the standard genetic, reverse genetic, pharmacological, and biochemical methods that we have previously used to successfully understand other signalling systems in C. elegans. Upon completion of this work we should be able to propose rational diagnostics and, possibly, treatments for muscle degradation resulting from disruption of this attachment complex. Following or in parallel to this work we will look to extend our findings into mammalian systems with the ultimate goal of improving outcomes in clinical populations.

Publications

10 25 50
publication icon
Adenle AA (2009) Review of the results from the International C. elegans first experiment (ICE-FIRST). in Advances in space research : the official journal of the Committee on Space Research (COSPAR)

publication icon
Crossland H (2013) Focal adhesion kinase is required for IGF-I-mediated growth of skeletal muscle cells via a TSC2/mTOR/S6K1-associated pathway. in American journal of physiology. Endocrinology and metabolism

publication icon
Etheridge T (2011) Effects of hypoxia on muscle protein synthesis and anabolic signaling at rest and in response to acute resistance exercise. in American journal of physiology. Endocrinology and metabolism

publication icon
Etheridge T (2015) The integrin-adhesome is required to maintain muscle structure, mitochondrial ATP production, and movement forces in Caenorhabditis elegans. in FASEB journal : official publication of the Federation of American Societies for Experimental Biology

 
Description UK Space Agency review of participation in ELIPS
Geographic Reach Asia 
Policy Influence Type Participation in a national consultation
Impact The choice to join ELIPS has resulted in increased economic return to the UK. Industry has identified£1 billion in additional projects as a result.
 
Description APS International Early Career Travel Award/The American Physiological Society
Amount £500 (GBP)
Organisation The American Physiological Society (APS) 
Sector Charity/Non Profit
Country United States
Start 12/2010 
End 12/2010
 
Description Access to ground based facilities
Amount £602,301 (GBP)
Funding ID ESA-AO-13-BR-06, BBSRC-BB/P005004/1 
Organisation European Space Agency 
Sector Public
Country France
Start 03/2015 
End 06/2018
 
Description BBSRC DTG
Amount £40,000 (GBP)
Organisation University of Nottingham 
Sector Academic/University
Country United Kingdom
Start 09/2011 
End 10/2014
 
Description Confidence in Concept award
Amount £83,751 (GBP)
Funding ID CiC12019 
Organisation Medical Research Council (MRC) 
Sector Academic/University
Country United Kingdom
Start 02/2013 
End 11/2013
 
Description MRC DTP
Amount £45,000 (GBP)
Organisation University of Nottingham 
Sector Academic/University
Country United Kingdom
Start 09/2012 
End 10/2015
 
Description MRC/ARUK Centre for Musculoskeletal Aging research (Nottingham/Birmingham
Amount £2,454,050 (GBP)
Funding ID MRC- K00414X, ARUK- 19891 
Organisation Versus Arthritis 
Start 07/2012 
End 06/2017
 
Description Project Grant
Amount £502,923 (GBP)
Funding ID BB/K019104/1 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 09/2013 
End 08/2016
 
Description Travel award
Amount £6,000 (GBP)
Organisation Japan Society for the Promotion of Science (JSPS) 
Sector Learned Society
Country Japan
Start 06/2011 
End 09/2011
 
Description University of Nottingham, School of Graduate Entry Medicine, Research Investment Fund
Amount £35,000 (GBP)
Funding ID G2 
Organisation University of Nottingham 
Sector Academic/University
Country United Kingdom
Start 09/2009 
End 08/2010
 
Title Adhesome dataset 
Description We have collected new data on 150 genes known to influence muscle development and physiology. 
Type Of Material Biological samples 
Year Produced 2012 
Provided To Others? Yes  
Impact We have identified a novel mechanism underlying muscle protein degradation. 
 
Title C. elegans LGMD models 
Description We have demonstrated the validity of C. elegans as an in vivo model for the LGMDs. 
Type Of Material Model of mechanisms or symptoms - non-mammalian in vivo 
Provided To Others? No  
Impact This development of this model is specifically in line with the 3Rs as it is an innvert. genetic model for a set of human diseases. 
 
Description CERISE 
Organisation Tohoku University
Country Japan 
Sector Academic/University 
PI Contribution We have prepared an independent experiment to be conducted onboard the International Space Station. We have disseminated our project to the public (worldwide) via interviews with English and Russian speaking media outlets.
Collaborator Contribution They have provided us with access to the Japanese research facilities onboard the International Space Station.
Impact The importance of conducting research aimed at understanding the molecular basis of muscle atrophy has been disseminated to the UK public via BBC (World Service, Radio 1, 4 & 5), The Times, The Telegraph and various other print outlets. The fact that scientific research can also be fun has been comunicated. The first publication from this collaboration has now come out, two more are in the works and a fellowship application for time in Japan has been generated, funded, and completed.
Start Year 2008
 
Description Extension of results into humans 
Organisation Umea University
Department Institute for Anatomy
Country Sweden 
Sector Academic/University 
PI Contribution We are providing antibodies to our collaborator to determine if the molecular mechanisms we have demonstrated in worms also exist in humans.
Collaborator Contribution This institute has agreed to provide pilot data for extending our C. elegans muscle repair work into human beings and may form the basis for future grant/fellowship applications.
Impact None to date.
Start Year 2010
 
Description Further attempt at extension of results into humans 
Organisation University of Nottingham
Department School of Graduate Entry Medicine & Health Nottingham
Country United Kingdom 
Sector Academic/University 
PI Contribution We are attempting to extend our findings in C. elegans into mammalian muscle. We have partnered with two investigators within our own School. We bring data on the full adhesome to the partnership.
Collaborator Contribution Our collaborators bring data on a handful of adhesome members (in man) to the partnership as well as experience conducting human studies.
Impact One paper is drafted, an MRC Centre has been funded, a BBSRC PhD student has been funded, and a BBSRC application to support this collaboration has been submitted and funded. An additional MRC application has been submitted.
Start Year 2011
 
Description JSPS 
Organisation Tohoku University
Department Life Sciences Tohoku
Country Japan 
Sector Academic/University 
PI Contribution We have provided samples for proteomic analysis and our post-doc has learned how to do proteomics.
Collaborator Contribution We anticipate at least one paper from this travel scheme.
Impact This should result in a publication in the next year or two and potentially a funding application. The collaboration bridges genetics and proteomics.
Start Year 2011
 
Description Interview with BBC Scotland 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Radio interview with BBC Scotland (evening drive time).

Unknown.
Year(s) Of Engagement Activity 2009
 
Description Interview with Chris Evans 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Radio interview with Chris Evans (BBC Radio national eve. drive time).

Increased local (Nottingham & Derby) interest in biomedical research as evidenced by additional requests for local interviews with these outlets.
Year(s) Of Engagement Activity 2009
 
Description Interview with Radio 4 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Policymakers/politicians
Results and Impact Radio interview for morning news coverage.

Unkown. However, the UK did subsequently subscribe to the microgravity programme of ESA which was underdebate at the time of this interview.
Year(s) Of Engagement Activity 2009
 
Description Interview with Radio 5 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Policymakers/politicians
Results and Impact Radio interview for the morning news roundup.

Unknown. However, the UK did subsequently subscribe to the European Microgravity research programme which was under debate at the time of this activity.
Year(s) Of Engagement Activity 2009
 
Description Interview with Russia blog 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Provided an interview for a russian blog that tracks spaceflight experiments.

Unknown, it is hoped that we can strengthen relations with the Russian Space Agency and/or the Chinese Space Agency.
Year(s) Of Engagement Activity 2009
 
Description Interview with a Free lance journalist 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Provided an interview for a free lance journalist with the intention of broadly informing the UK public about our research activities.

This interview was successful as it resulted in a story run by the Times. Consequently stories were run by most UK media outlets and several follow up interviews were given. Additionally 2 undergraduate medical students were hosted for research experiences and a talk was given at UCL.
Year(s) Of Engagement Activity 2009
 
Description Interviews with BBC worldservice 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Interviews were given to the BBC worldservice for use in print and radio distribution.

Largely unknown, however media coverage was extended to Spanish and Portuguese speaking outlets.
Year(s) Of Engagement Activity 2009
 
Description Press Release 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Type Of Presentation Paper Presentation
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact The University of Nottingham issued a press release regarding our upcoming spaceflight activities and after publication of our first paper.

The press release was successful as it resulted in contact with a free lance journalist and several UK media outlets. All three releases resulted in stories run by the national papers and several online outlets.
Year(s) Of Engagement Activity 2009,2011,2012
 
Description Radio interview (Material World) 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact This was a radio interview on a science programme intended to increase the public awareness of science.

Has lead to my appointment on a government advisory panel.
Year(s) Of Engagement Activity 2011