UC San Diego

The vertebrate nuclear pore complex is the sole gateway for nuclear-cytoplasmic transport. As it is composed of multiple copies of approximately 30 unique nucleoporin proteins, deciphering the role of each of these is a work in progress. The diverse roles of these proteins have been implicated in countless cellular processes, including the import and export of proteins, RNA export, mitotic regulation, and cytoskeletal re-arrangement. Here, I have set out to better characterize the role of the scaffold nucleoporin, Nup155. Nup155 is of interest because an R391H mutation has been implicated in atrial fibrillation and early sudden cardiac death in both humans and mice. My work began with an analysis of the localization of wild type and R391H mutant Nup155, as well as their functional domains. Nuclear rim localization was exhibited by WT Nup155 and less so for the α-solenoid and [beta]- propeller domains of WT Nup155. However, neither full length R391H Nup155 nor a R391H [beta]-propeller localized to the nuclear rim. When poly[A]⁺ mRNA export was assayed, it was found that overexpression of the R391H [beta]- propeller, R391H full length Nup155, and WT [beta]- propeller inhibited export. In contrast, protein import and export through the importin [beta]/exportin-1 pathways were not affected by overexpression of wild type or R391H Nup155. Nor was the actin cytoskeleton affected by overexpression of any of the Nup155 domains or mutants. To determine Nup155 binding partners, a LacI-CFP-Nup155 fusion protein was anchored to a LacO repeat array in the genome. Antibodies to various nucleoporins were used to probe this array. Co-localization of Nup53 and the integral membrane nucleoporin Pom121 revealed that these are likely Nup155 binding partners