Institute for Cell and Molecular Biosciences

Staff Profile

Dr Viktor Korolchuk

Reader in Molecular Cell Biology

Background

 

Introduction: 

My scientific interests lie in the area of intracellular protein trafficking and degradation pathways. The current focus of research in my laboratory is autophagy (literally self-eating) where portions of cytoplasm are recruited into intracellular vesicles called autophagosomes and transported for degradation by lysosomal hydrolases. Autophagy is now widely accepted to be beneficial for cellular and organismal health by removing damaged and harmful cellular entities while autophagy inhibition due to persistent nutrient signalling could have deleterious effects (see our recent feature in the Biochemist http://www.biochemist.org/bio/03402/0008/034020008.pdf). The questions being addressed in the lab include: 1) How autophagy is controlled by nutrient-sensing signalling pathways? 2) What are the endogenous autophagy substrates and what are the mechanisms of their recruitment to autophagic vesicles? 3) How autophagy affects other cellular processes and pathways? In addition to basic biological problems we investigate how perturbations of protein trafficking and degradation contribute to neurodegenerative diseases and ageing.

 

Background:

I obtained my PhD from the Institute of Biochemistry in Kiev, Ukraine. During the postdoctoral training at Bristol and Cambridge Universities, UK, I have been studying intracellular trafficking and signalling pathways using a range of biochemical, cell biological and genetic approaches. My contributions to the field include: isolation and characterisation of protein kinases associated with endocytic clathrin-coated vesicles (Traffic, 2002; J Biol Chem, 2005); studies of the topologically unusual protein tetherin, its trafficking and role in the development and maintenance of cell polarity (Traffic, 2003; J Cell Sci, 2007; J Cell Biol, 2009); the role of Drosophila trafficking proteins in the recycling of synaptic vesicles, in neuronal development and in regulation of signalling pathways (J Cell Biol, 2007; J Cell Sci, 2007); characterisation of several mechanisms of autophagy regulation including those by calcium, reactive oxygen species, reactive nitrogen species and in the context of a glycogen storage disease (Autophagy, 2009; Hum Mol Genet, 2010; Mol Cell, 2011); a mechanism of cross-talk between autophagy and the ubiquitin proteasome system (Mol Cell, 2009); a novel mechanism of coordinated control of both mTOR and autophagy by nutrients (Nat Cell Biol, 2011); identification of autophagy regulators that suppress the toxicity caused by mutant huntingtin.

 

Qualifications:

  • 1996    High Degree Diploma (MSc in Biology), Kiev State University, Ukraine
  • 2000    PhD Biochemistry, Institute of Biochemistry, Kiev, National Academy of Sciences, Ukraine

 

Membership of societies:

  • Biochemical Society
  • British Society for Cell Biology
  • British Society for Research on Ageing (Executive board member)


 

Funding:

  • BBSRC New Investigator Grant to study mechanisms of mTOR regulation.
  • DTA funding from BBSRC for a PhD project to study the role of autophagy in DNA damage repair.
  • DTA funding from BBSRC for a PhD project to study mitophagy.
  • PhD studentship in the Brain Research Centre to study the mechanisms of protein oligomerisation in ageing and age-related diseases.
  • British Skin Foundation grant to study mTOR signalling in melanoma.
  • Confidence in Concept MRC funding to develop reporters of mTOR pathway.

 

Keywords

  • Intracellular trafficking, autophagy, ubiquitin, protein degradation, nutrient signalling, mTOR, DNA damage, neurodegenerative diseases, ageing. 



Research

RESEARCH FOCUS: AUTOPHAGY IN HEALTH AND DISEASE

Macroautophagy, for simplicity frequently called autophagy, is a mechanism used by cells to survive periods of starvation by degrading cytoplasmic components and releasing much-needed metabolites and energy. Autophagy is a vesicular trafficking pathway in which double-membraned intracellular structures called autophagosomes are formed around portions of cytoplasm containing cellular components destined for degradation. Autophagosomes are transported along microtubules and their lives end when they fuse with lysosomes, where autophagic substrates are degraded. The process of autophagosome formation and maturation is under tight control and is orchestrated by dedicated machinery.

Both basal and induced autophagy is an important determinant of health and longevity. Indeed, perturbations in the autophagy pathway have been recognised as a causative factor in a number of human pathologies including cancer, heart diseases, diabetes and neurodegeneration. Moreover, the ageing itself, being the most important risk factor in the development of many human diseases, has been associated with insufficient clearance of misfolded, toxic and aggregate-prone proteins via the autophagosome- and lysosome-dependent degradation mechanisms. Most excitingly, many of the treatments prolonging lifespan in model organisms are doing so in an autophagy-dependent manner indicating that efficient protein degradation via autophagy may be the major determinant of lifespan extension.

 

CURRENT RESEARCH PROJECTS IN THE LABORATORY

1) Investigation of mechanisms controlling cellular nutrient responses

The majority of treatments prolonging healthy lifespan of laboratory animals suppress nutrient sensing pathways such as mTOR (mammalian Target Of Rapamycin) and stimulate autophagy. The elaborate network of mTOR signalling events integrates upstream signals such as binding of growth factors to plasma membrane receptors, presence of nutrients such as amino acids, glucose and various metabolites in the extracellular medium as well as the intracellular ATP/ADP ratio signifying cellular energy levels (detected by AMP-dependent kinase, AMPK). We have recently described yet another layer of mTOR control which is mediated by nutrient-imposed changes in intracellular pH. This potentially allows regulation of mTOR activity independently of nutrients and, therefore, offers an opportunity to mimic the effect of dietary restriction on lifespan/ageing through pharmaceutical means. Studying processes regulating cellular nutrient responses and extending the knowledge of their fine molecular detail will increase our chances to fight age-related diseases and ultimately to extend human lifespan.

We are currently addressing the following questions:

What receptors/transporters are involved in implementation of nutrient-dependent changes in intracellular pH?

What is the contribution of this regulatory mechanism to the overall control of mTOR by growth factors, amino acids and energy levels?

What is the potential physiological relevance of this mechanism?

 

2) Physiologic functions of autophagy

The prominent role of autophagy in cellular and organismal health is commonly explained by the homeostatic function. Indeed, having the capacity to dispose of the large intracellular entities, including protein aggregates and entire organelles such as defective mitochondria, autophagy is a major quality control mechanism clearing damaged and dysfunctional cellular components and thus preventing further cellular damage. However, autophagy is also perfectly positioned to serve regulatory roles. Thus, it can be hypothesised that changes in autophagic flux, induced by upstream signalling events, may lead to changes in the activity of downstream pathways by selective degradation of their regulatory components. This selective recruitment of substrates to autophagosomes can be mediated by adapter molecules such as sequestosome-1/p62, which recruits ubiquitylated proteins for selective autophagosomal degradation. We are interested in characterisation of autophagy-dependent regulatory degradative events as this could result in a conceptually novel model of the control over cellular physiology.

Among the questions that we ask here are the following:

What are the endogenous protein substrates of selective autophagy?

How are endogenous autophagy substrates targeted and recruited to autophagosomes?

How do different substrates define physiological roles of autophagy?

 

3) Role of autophagy in DNA damage response

One potential mechanism by which autophagy can control the rate of aging is by regulating the DNA damage response (DDR) which contributes to the cellular senescence phenotype.  This is supported by the evidence that DDR proteins such as p53 and p38MAPK are shown to affect autophagic activity while autophagy may in turn regulate DDR and cellular senescence. Despite the evidence the molecular details that would explain involvement of autophagy in DDR, senescence and ageing are still largely missing.

In collaboration with Dr. Joao Passos we are using a systematic approach to study the molecular mechanisms underlying the function of autophagy in DDR and senescence. We use systems-based and experimental approaches to identify molecular links between autophagic and DDR machinery. We are testing if DDR proteins interacting with autophagosomal machinery may be targeted to autophagosome-lysosome pathway for degradation. This is achieved by the analysis of the formation and degradation of relevant DDR complexes induced by stressors such as gamma-irradiation in normal or autophagy-impaired cells. We are aiming to evaluate the relative contribution of both autophagy and the proteasome, two major cellular degradative system, to the regulation of DDR complexes. As DDR and autophagy take place in different cellular compartments (nucleus and cytoplasm, respectively), delivery of DDR machinery to cytoplasm, co-localisation with autophagosomes and subsequent degradation is being investigated by biochemical techniques as well as imaging methods such as high-resolution confocal microscopy of fixed and live specimens and by immuno-electron microscopy. Possible feedback mechanisms, whereby DDR proteins are in turn affecting autophagic activity, are also being investigated.


 

LABORATORY TECHNIQUES

Biochemistry:                Subcellular fractionation, purification of proteins from complex biological samples; chromatographic and electrophoresis techniques; immunoblotting.

Molecular biology:        Cloning, site-directed mutagenesis, qPCR, production and purification of recombinant proteins using variety of expression systems.

Cell biology:                  Fluorescent and confocal microscopy, immunocytochemistry; flow cytometry; electron microscopy.

In vivo approaches:      Drosophila genetics, imaging techniques.

 

THE RESEARCH TEAM

Dr. Bernadette Carroll, postdoctoral Research Associate

Dr. Yoana Rabanal, postdoctoral Research Associate

Ms. Gisela Otten, PhD student

Mr. Alvaro Martinez Guimera, PhD student

Ms. Lucia Sedlackova, PhD student

 

OPEN VACANCIES

No postdoctoral vacancies are currently available but we always welcome an interest from enthusiastic students and postdocs who are interested in applying for funding. Applicants should have a strong background in molecular cell biology or genetics and a record of successful research in the areas of molecular biology, cell biology, biochemistry, or genetics.

To discuss available options forward your curriculum vitae, bibliography, and the names and addresses of referees to: Dr. Viktor Korolchuk, Ageing Research Laboratories, Institute for Ageing and Health, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne, NE4 5PL or by e-mail addressed to viktor.korolchuk@ncl.ac.uk.

Teaching

Biology of Ageing, undergraduate course for biomedical students (Deputy Module Leader)

MBBS Life Cycle Unit 3: Ageing, undergraduate course for medical students (Module Leader)


Publications