The endoplasmic reticulum (ER) is the cellular organelle that serves as the entry site into the secretory pathway. Although the ER has a single continuous membrane, it is functionally divided into subdomains (SDs). These specialized regions allow the ER to carry out a multitude of functions such as folding, maturation, quality control and export, of all secreted and most membrane bound proteins; lipid biosynthesis; ion homeostasis; and communication with all other organelles. The ER is therefore not only the largest single copy organelle in most eukaryotic cells, but, thanks to the presence of SDs, also one of the more functionally diverse and structurally complex.
Changes in ER functions have been shown to contribute to the progression of many diseases such as heart disease, neurodegeneration and diabetes. Moreover, a robustly functioning ER is required for development of dedicated secretory cells such as antibody producing plasma cells and insulin secreting pancreatic cells. The past years have brought about a revolution in our understanding of basic ER functions and the homeostatic responses coordinating them. However, despite their obvious importance for robust activity of the ER, we still know very little about SD biogenesis and function. Therefore, the time is now ripe to extend our understanding by facing the next challenges in the field.
Specifically, it is now of major importance to understand how cells ensure accurate SD biogenesis and function. This proposal tackles this question by three independent but complementary screens each aimed at revealing one aspect of SDs: their structure/function, biogenesis or dynamics. The merging of all three aspects of information will give us a holistic picture of this process – one that could not have been attained by the pixilated view of any single piece of data. We propose to explore these facets in both yeast and mammals utilizing systematic tools such as high content microscopic screens followed up by the creation of genetic interaction maps and follow-up hypothesis based biochemical and genetic experiments. By combining several approaches and different organisms we hope to enable a more efficient reconstruction of this complex process.
When completed this proposal will have shed light on a little explored but central question in cellular biology. More broadly, the mechanisms that arise as guiding SD biogenesis may help us in understanding how membrane domains form in general. Due to the novelty of our approach and the cutting-edge tools used to tackle this fundamental problem in cell biology, this work will provide a paradigm for addressing complex biological questions in eukaryotic cells. It may very well be that it is this aspect of the proposal that may ultimately most broadly impact the biological community.