Interaction of Human Laminin Receptor with Sup35, the [PSI+] Prion-Forming Protein from S. cerevisiae: A Yeast Model for Studies of LamR Interactions with Amyloidogenic Proteins

The laminin receptor (LamR) is a cell surface receptor for extracellular matrix laminin, whereas the same protein within the cell interacts with ribosomes, nuclear proteins and cytoskeletal fibers. LamR has been shown to be a receptor for several bacteria and viruses. Furthermore, LamR interacts with both cellular and infectious forms of the prion protein, PrPC and PrPSc. Indeed, LamR is a receptor for PrPC. Whether LamR interacts with PrPSc exclusively in a capacity of the PrP receptor, or LamR specifically recognizes prion determinants of PrPSc, is unclear. In order to explore whether LamR has a propensity to interact with prions and amyloids, we examined LamR interaction with the yeast prion-forming protein, Sup35. Sup35 is a translation termination factor with no homology or functional relationship to PrP. Plasmids expressing LamR or LamR fused with the green fluorescent protein (GFP) were transformed into yeast strain variants differing by the presence or absence of the prion conformation of Sup35, respectively [PSI+] and [psi−]. Analyses by immunoprecipitation, centrifugal fractionation and fluorescent microscopy reveal interaction between LamR and Sup35 in [PSI+] strains. The presence of [PSI+] promotes LamR co-precipitation with Sup35 as well as LamR aggregation. In [PSI+] cells, LamR tagged with GFP or mCherry forms bright fluorescent aggregates that co-localize with visible [PSI+] foci. The yeast prion model will facilitate studying the interaction of LamR with amyloidogenic prions in a safe and easily manipulated system that may lead to a better understanding and treatment of amyloid diseases.