Structural and energetic basis of ALS-causing mutations in the atypical proline-tyrosine nuclear localization signal of the Fused in Sarcoma protein (FUS).

ABSTRACT: Mutations in the proline/tyrosine-nuclear localization signal (PY-NLS) of the Fused in Sarcoma protein (FUS) cause amyotrophic lateral sclerosis (ALS). Here we report the crystal structure of the FUS PY-NLS bound to its nuclear import receptor Karyopherin?2 (Kap?2; also known as Transportin). The FUS PY-NLS occupies the structurally invariant C-terminal arch of Kap?2, tracing a path similar to that of other characterized PY-NLSs. Unlike other PY-NLSs, which generally bind Kap?2 in fully extended conformations, the FUS peptide is atypical as its central portion forms a 2.5-turn ?-helix. The Kap?2-binding epitopes of the FUS PY-NLS consist of an N-terminal PGKM hydrophobic motif, a central arginine-rich ?-helix, and a C-terminal PY motif. ALS mutations are found almost exclusively within these epitopes. Each ALS mutation site makes multiple contacts with Kap?2 and mutations of these residues decrease binding affinities for Kap?2 (K(D) for wild-type FUS PY-NLS is 9.5 nM) up to ninefold. Thermodynamic analyses of ALS mutations in the FUS PY-NLS show that the weakening of FUS-Kap?2 binding affinity, the degree of cytoplasmic mislocalization, and ALS disease severity are correlated.

SUBMITTER: Zhang ZC 

PROVIDER: S-EPMC3409756 | biostudies-literature | 2012 Jul

REPOSITORIES: biostudies-literature