Structural basis for the ARF GAP activity and specificity of the C9orf72 complex.

ABSTRACT: Mutation of C9ORF72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontal temporal degeneration (FTD), which is attributed to both a gain and loss of function. C9orf72 forms a complex with SMCR8 and WDR41, which was reported to have GTPase activating protein activity toward ARF proteins, RAB8A, and RAB11A. We determined the cryo-EM structure of ARF1-GDP-BeF₃^- bound to C9orf72:SMCR8:WDR41. The SMCR8^longin and C9orf72^longin domains form the binding pocket for ARF1. One face of the C9orf72^longin domain holds ARF1 in place, while the SMCR8^longin positions the catalytic finger Arg147 in the ARF1 active site. Mutations in interfacial residues of ARF1 and C9orf72 reduced or eliminated GAP activity. RAB8A GAP required ~10-fold higher concentrations of the C9orf72 complex than for ARF1. These data support a specific function for the C9orf72 complex as an ARF GAP. The structure also provides a model for the active forms of the longin domain GAPs of FLCN and NPRL2 that regulate the Rag GTPases of the mTORC1 pathway.

SUBMITTER: Su MY 

PROVIDER: S-EPMC8213707 | biostudies-literature | 2021 Jun

REPOSITORIES: biostudies-literature