The discrete segregation of nuclear and cytosolic contents is a hallmark feature of all eukaryotic cells. It is achieved by the impermeability of the nuclear envelope membranes and the size-selective and active transport properties of nuclear pore complexes (NPCs), massive transport channels that span the nuclear envelope. Interestingly, it is becoming clear that there is a deleterious intermixing of cytosolic and nuclear contents in several human disease cell models where either NPC function or the integrity of the nuclear membranes is perturbed. Examples include the targeting of the nuclear transport machinery by the transcription and translation of hexanucleotide repeat expansions that are causative of neurodegenerative diseases, and nuclear rupture events observed in cancer cells. Through our work and others, we are discovering surveillance mechanisms that protect the nuclear compartment from aberrant NPCs and/or nuclear membrane ruptures. Indeed, we have discovered that even the ?normal? remodeling of the nuclear envelope membranes during NPC assembly can, if not monitored, lead to a loss of nuclear-cytosolic compartmentalization. Here, we will use budding yeast as a model to determine the molecular mechanisms that govern the surveillance of de novo NPC assembly, which depends on the recruitment of the membrane bending and scission endosomal sorting required for transport (ESCRT) machinery to nascent NPC assembly sites. Our work is consistent with a model in which integral inner nuclear membrane proteins of the Lap2, emerin, MAN1 (LEM) domain family serve as adaptors to link defective NPC assembly intermediates to the ESCRTs, which seal off defective NPCs under a double membrane. In this proposal, we will pinpoint what step(s) in NPC assembly are under surveillance while defining the mechanism by which cells differentiate between functional and non-functional NPCs. The long term goal is to fully define and ultimately reconstitute the NPC assembly surveillance mechanism to illuminate fundamental mechanisms of quality control and membrane remodeling while providing a new conceptual framework to understand human disease mechanisms that present with disruptions in the nuclear envelope barrier.

Public Health Relevance

Disruptions to the integrity of the nuclear envelope barrier leads to the intermixing of cytosolic and nuclear contents ? a common feature of the cellular pathology of cancers and neurodegenerative diseases. Here, we identify and experimentally assess surveillance mechanisms that serve to protect cells from nuclear envelope barrier malfunction.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Nuclear and Cytoplasmic Structure/Function and Dynamics Study Section (NCSD)
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Flicker, Paula F
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Yale University
Anatomy/Cell Biology
Schools of Medicine
New Haven
United States
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Thaller, David J; Patrick Lusk, C (2018) Fantastic nuclear envelope herniations and where to find them. Biochem Soc Trans 46:877-889
Fisher, Patrick D Ellis; Shen, Qi; Akpinar, Bernice et al. (2018) A Programmable DNA Origami Platform for Organizing Intrinsically Disordered Nucleoporins within Nanopore Confinement. ACS Nano 12:1508-1518
Lusk, C Patrick; King, Megan C (2017) The nucleus: keeping it together by keeping it apart. Curr Opin Cell Biol 44:44-50
Lusk, C Patrick (2016) Baby Nuclear Pores Grow Up Faster All the Time. Cell 166:534-535
King, Megan C; Lusk, C Patrick (2016) A model for coordinating nuclear mechanics and membrane remodeling to support nuclear integrity. Curr Opin Cell Biol 41:9-17
Webster, Brant M; Lusk, C Patrick (2016) Border Safety: Quality Control at the Nuclear Envelope. Trends Cell Biol 26:29-39
Webster, Brant M; Thaller, David J; J├Ąger, Jens et al. (2016) Chm7 and Heh1 collaborate to link nuclear pore complex quality control with nuclear envelope sealing. EMBO J 35:2447-2467
Huang, Fang; Sirinakis, George; Allgeyer, Edward S et al. (2016) Ultra-High Resolution 3D Imaging of Whole Cells. Cell 166:1028-1040
Webster, Brant M; Lusk, C Patrick (2015) ESCRTs breach the nuclear border. Nucleus 6:197-202
Lusk, C Patrick; Colombi, Paolo (2014) Toward a consensus on the mechanism of nuclear pore complex inheritance. Nucleus 5:97-102

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