Roles of p62/SQSTM1 and novel ATG8-binding proteins in selective autophagy and cell signalling

Macroautophagy, here referred to as autophagy (greek: eating oneself), is a protein degradation pathway that involves lysosomal degradation of cytoplasm and organelles. Autophagy plays an important role in degradation of damaged organelles and toxic prote in aggregates which cannot be degraded by the proteasomes. There is great interest in establishing the significance of autophagy in cancer and neurodegenerative diseases. Autophagy has been considered as a non-specific, bulk degradation pathway. However, we have identified p62 and NBR1 as the first selective autophagy substrates and as cargo receptors for degradation of ubiquitinated targets by autophagy. p62 also plays pivotal roles in several important cell signalling pathways. We now aim to determine t he relationships between their autophagic degradation and cell signalling. We will employ specific mutants to address the role of autophagic degradation of p62 in cell signalling using transgenic approaches with both mammalian cell lines and Drosophila a s models. We will express relevant mutants of p62 in murine embryo fibroblasts deficient for p62 in an inducible manner and study mutants of Drosophila p62, Ref(2)p, in transgenic flies deficient for endogneous Ref(2)p. Our discovery of the interaction o f p62 and NBR1 with the ATG8 family of proteins, involved in autophagy and vesicle transport, has enabled us to identify a number of novel interaction partners for ATG8 family proteins. Several of these proteins will be analysed in this project for their relevance to autophagy, vesicle transport and cellular signalling pathways. The LIR-ATG8 protein interaction lies at the heart of specific recognition required for selective autophagy and we are certain this type of interaction is important in other cellu lar processes too. This will be addressed in this project which will involve confocal, live cell, fluorescence- and electron microscopy imaging, proteomics, structural biology, cell- and animal models.