Surveillance mechanisms regulating nuclear envelope architecture and homeostasis

The nuclear envelope (NE) is a major hub of eukaryotic cellular organization, influencing a myriad of processes, from gene regulation and repair to cell motility and fate. This central role of the NE depends on its elaborate structure, particularly on the organization of its inner nuclear membrane (INM). This peculiar membrane is continuous with the rest of the endoplasmic reticulum (ER) but faces the nucleoplasm and contains a distinctive set of proteins, which confer a unique identity to the INM. Importantly, mutations in several INM proteins result in a wide range of diseases, such as muscular dystrophies and premature aging syndromes, highlighting the key roles of the INM proteome in cell homeostasis. However, the mechanisms establishing and maintaining the INM proteome identity and integrity have remained mysterious. My lab recently identified a quality control system that, by targeting aberrant proteins for degradation, regulates INM identity and homeostasis. This proposal describes a framework to expand our findings and to provide a comprehensive and integrated understanding of the INM proteome. By combining my expertise in membrane protein analysis with newly developed proximity biotinylation and proteomics approaches, we will for the first time probe the complex INM environment of living mammalian cells. A systematic examination of the INM proteome, its turnover rates and changes in response to different physiological conditions will reveal functions of INM proteins and their regulatory pathways. Moreover, it will characterize INM surveillance mechanisms and evaluate their contributions to NE proteostasis. In sum, this proposal will provide a panoramic yet detailed view of the mechanisms underlying INM functions, identity and homeostasis, both in interphase and during NE reformation in mitosis. Given the clinical relevance of many INM proteins, our studies may illuminate current understanding of diseases such as laminopathies and cancer.