The entry includes Guanine nucleotide exchange factor C9orf72 protein, a component of the C9orf72-SMCR8 complex, which has guanine nucleotide exchange factor activity []and regulates autophagy [, ]. The C9orf72 protein is proposed to be a catalytic component for the exchange of GDP to GTP and promoting autophagosome maturation by converting inactive GDP-bound RAB8A and RAB39B into their active forms []. Defects in the C9orf72 gene are the cause of frontotemporal dementia and/or amyotrophic lateral sclerosis (FTDALS) which is an autosomal dominant neurodegenerative disorder. The disorder is caused by a large expansion of a GGGGCC hexanucleotide within the first C9orf72 intron located between the first and the second non-coding exons. The expansion leads to the loss of transcription of one of the two transcripts encoding isoform 1 and to the formation of nuclear RNA foci []. This family is found in eukaryotes.C9orf72 contains the DENN domain, which forms a heart-shaped structure (), with the N-terminal residues forming one lobe and the C-terminal residues forming the second one. The tripartite DENN (after differentially expressed in neoplastic versus normal cells) domain is found in several proteins that share common structural features and have been shown to be guanine nucleotide exchange factors (GEFs) for Rab GTPases, which are regulators of practically all membrane trafficking events in eukaryotes [, ].
