Cellular Mechanisms of Protection against Protein Misfolding in Neurodegenerative Disease

Projektförslag för kandidatarbete inom inst. Kemi och kemiteknik och Biologi och bioteknik
 
​Projektexamenskod: BBTX01-20-01

Avdelningen för Systembiologi
Institutionen för Biologi och Bioteknik, Chalmers tekniska högskola 


Bakgrund 
Proteins must be folded in order to perform their functions. Cells have evolved exquisite molecular machineries, for example molecular chaperones, that aid in protein folding and in maintaining proteins folded. Under stress conditions, however, proteins may unfold or fail to fold correctly.

Misfolding can lead to aggregate formation and protein configurations that gain toxic functions. Protein misfolding and aggregation are particular problems in the brain, being the underlying cause of several severe and incurable age-related disorders including Alzheimer’s and Parkinson’s disease as well as the motor neuron disorder ALS. The pathophysiology of ALS is also characterized by increased oxidative stress.

Recent studies have pointed to age-related protein aggregates engaging a different set of chaperones than the stress conditions typically used to study aggregates, e.g. heat shock. Notably, a peroxiredoxin was found to be absolutely required for other molecular chaperones to engage aggregates in aged and H2O2-stressed cells. Peroxiredoxins are anti-oxidant proteins, H2O2-receptors in signaling and H2O2-controlled chaperones that slow down aging and decrease the incidence of age-related disease in organisms ranging from yeast to mice.
The RNA-binding protein TDP-43 has been identified as a major component of the protein aggregates characterizing ALS. By expressing TDP-43 in baker’s yeast, an important eukaryotic model organism highly amenable to genetic analysis, several novel regulators of ALS have been identified in genome-wide screens, notably genes encoding ribosomal proteins and regulators of so called stress granules. These are a type of beneficial inclusions where mRNA and translational components are thought to be stored transiently under unfavorable conditions until translation can resume.

BBTX01-20-01_img1.pngNotably, mutants deficient in stress-granule formation strongly modify TDP-43 aggregation but in different ways. However, the exact relationship between such ‘beneficial aggregates’ and the pathophysiological TDP- 43 aggregates are still mostly unclear. Interestingly, yeast cells lacking the peroxiredoxin involved in age-
related protein quality control are more susceptible to TDP-43 toxicity. In addition, these cells have a  problem in compartmentalizing TDP-43 aggregates (see figure, ctrl vs prx-).

 

 
imageThe relevance of interesting insights from mechanistic studies in yeast will be evaluated in a cellular TDP-43 model and by in vitro protein studies.


Problembeskrivning 
Roles of beneficial and pathological aggregates in TDP-43 pathology – what is the role of a peroxiredoxin in redox-related TDP-43 aggregation?

In this project you will look for markers for and regulators of the different types of TDP-43 aggregates. By in detail studying the kinetics of formation of different types of aggregates in TDP-43 humanized yeast expressing TDP-43 tagged with green fluorescent protein (GFP) a better understanding of their relationship is possible. By studying TDP-43 toxicity and aggregation in humanized yeast cells deficient in different peroxiredoxin functions under conditions where peroxiredoxin-mediated protein quality control is active, you will enquire how this aging-relevant chaperone may affect ALS. In addition, you will further investigate reasons for increased oxidative stress in ALS. Depending of the extent of the project and the number of students, all or some of these issues may be addressed.
 
Genomförande /Viktiga moment/teknikinnehåll 
Yeast genetics, molecular biology, protein analysis including Western blot and biochemical techniques to extract insoluble protein aggregates, fluorescence microscopy, and live cell confocal microscopy imaging. Image analysis including cell tracking.

Speciella förkunskapskrav: Basic knowledge of microbiology techniques and image analysis including cell tracking is meritorious

Möjlig målgrupp Students with an interest in molecular genetics and microbiology.

Gruppstorlek: 4–6 studenter 

Förslagsställare/kontaktperson/huvudhandledare: Mikael Molin, SysBio, BIO, Chalmers, mikael.molin@chalmers.se
Övriga handledare:
Elin Esbjörner-Winters, ChemBio, BIO, Chalmers, eline@chalmers.se
Per Sunnerhagen, CMB, GU, per.sunnerhagen@cmb.gu.se

Publicerad: ti 29 okt 2019.