Structural and functional characterisation of hereditary polyneuropathy-associated protein N-myc downstream regulated gene 1 (NDRG1)

NDRG1 (N-myc downstream regulated gene 1) is a protein which participates in many physiological functions in human and other animal cells. NDRG1 plays a role for example in myelination, vesicular trafficking, lipid metabolism, cell differentiation, genome stability and DNA repair and replication. In different cancer types, NDRG1 acts as either a tumour suppressor or promoter. Mutations in human NDRG1 gene are causative for Charcot-Marie-Tooth disease type 4D (CMT4D), a demyelinating neuropathy caused by Schwann cell dysfunction. A clinically similar polyneuropathy caused by mutations in NDRG1 is found in certain dog breeds.

Human NDRG1 belongs to the NDRG protein family from which the crystal structures of NDRG2 and NDRG3 are known. This thesis focused on studying the three-dimensional structure of NDRG1. The crystal structure of NDRG1’s middle part revealed a possible substrate-binding pocket, which suggests that NDRG1 might function as an active enzyme in cells. The solution structure of full-length NDRG1 indicated several conformations for the flexible N- and C-terminal regions. With different in vitro methods, NDRG1 was shown to bind to metal ions and cell membrane-mimicking lipid vesicles. In addition, this thesis investigated how phosphorylation of NDRG1, or a CMT4D-causative mutation could affect the metal and lipid vesicle binding of NDRG1. The most important finding of the latter studies was that the CMT4D-causative mutation decreased the binding of certain lipid vesicles to NDRG1 protein.