An Amphipathic Alpha‐Helical Domain Identified in Nucleoporins Plays a Role at The Nuclear Pore Complex of Saccharomyces Cerevisiae

Abstract

All macromolecular transport between the nucleus and cytoplasm occurs via nuclear pore complexes (NPCs) embedded in the nuclear envelope. NPCs are composed of multiple copies of proteins, termed nucleoporin (Nups) which assemble sequentially into nascent nuclear pores generated following fusion of the inner and outer nuclear membranes. While much is known about NPC structure, the mechanisms governing NPC biogenesis remain largely undefined. Recently, an amphipathic α‐helix (ALPS for ArfGAP1 lipid packing sensor) motif, which mediates protein association with highly curved liposomes, has been defined. This ALPS motif was identified in protein components of two early associating S. Cerevisiae (sc) NPC subcomplexes; the scNup84 subcomplex (specifically Nup85 and Nup120) and the scNup170 subcomplex (specifically Nup170 and Nup188) and may help proteins associate with newly developing NPCs. Utilizing microscopy techniques and yeast genetics we have identified an important role for the ALPS domain in vivo and our evidence suggests that ALPS domains of different NUPs have redundant functions. Utilizing in vitro liposome binding assays we find that the ALPS domain is sufficient for liposome binding and that this binding is dependent on liposome size. Together, this data provides the first evidence for an in vivo function of the ALPS motif with an impact in the broad membrane biology field, and concomitantly expands our understanding of NPC assembly.Grant Funding Source: IRACDA & RO1