A novel component of protein aggregates regulates fertility and ageing

Advances in modern medicine have led to a significant increase in human life expectancy. A consequence of this has been the increase of the frequency of ageing-related diseases and ageing-related reproductive dysfunction. Parents are becoming older and this trent is likely to be more frequent in the future. Thus, understanding the biology of ageing of the reproductive systems is an urgently required task in order to ensure a viable and sustainable future for our human community.

One of the hallmarks of ageing cells is the intracellular accumulation of protein aggregates. Recent studies have indicated that a breakdown of one of the major proteolytic cellular machineries in cells, namely autophagy, is involved in the development of ageing-related diseases. Autophagy is an essential catabolic process that involves the degradation of cellular material. Cells use autophagy to generate materials and energy when conditions become unfavourable. They also use this process to clear damaged cellular components.

We discovered that a protein called UbcD4 is selectively degraded by autophagy and accumulates in male reproductive system of autophagy mutants We also found that UbcD4 mutant males show reduced lifespan. Therefore, we hypothesize that UbcD4 maintains healthy lifespan through an autophagy-regulated mechanism.

We will use the fruit fly Drosophila melanogaster as a genetically modifiable model organism to understand at the molecular level how selective autophagy regulates ageing and reproduction. These mechanisms are very similar between fruit flies and humans, so the results will have direct relevance to human health.

This project will make a major contribution to our understanding of the fundamental mechanisms of autophagy during reproduction and ageing and could potentially be used in applied research aimed towards developing new strategies to fight age-related diseases and to promote healthy ageing.

Ageing is associated with the lifelong, gradual accumulation of molecular and cellular damage and this has been observed in species ranging from yeast to humans. One of the phenotypic hallmarks of ageing cells is the intracellular accumulation of protein aggregates. It is known that a breakdown of autophagy, the major proteolytic cellular machinery, is involved in the development of ageing-related diseases. Autophagy is an essential catabolic process that involves the degradation of cytoplasmic material through the lysosomal pathway. However, the links between protein aggregates, autophagy and ageing remain elusive.

We found that UbcD4, an E2 ubiquitin conjugating enzyme, is selectively degraded by autophagy. We also found that UbcD4 accumulates and forms aggregates in male reproductive system of autophagy mutants and that UbcD4 mutant males show reduced lifespan.

Our proposal aims to elucidate how selective autophagic degradation of UbcD4, a novel component of protein aggregates, regulates ageing and male fertility in the fruit fly Drosophila melanogaster.

The aims and objectives of our proposal are the following:

Aim 1: Elucidate the molecular mechanisms of selective autophagic degradation of UbcD4, using biochemical methods (GST pull downs) and mass spectrometry.

Aim 2: Examine whether UbcD4 controls the formation of protein aggregates in the brain and male reproductive system, using targeted gene expression and microscopy.

Aim 3: Elucidate why UbcD4 male mutant flies have reduce lifespan by performing behavioural and morphological analysis.

Aim 4: Examine if UbcD4 mutant flies have fertility defects, using a combination of mating/physiology experimental procedures and proteomics.

Using this approach we expect to identify novel links between autophagy, protein aggregation and ageing.