TBC1 domain family member 23 (TBC1D23) belongs to a family of TBC domain-containing Rab-specific GTPase-activating proteins, which plays a role in endosome-to-Golgi trafficking. It acts as a bridging factor in which the TBC domain binds to Golgi adaptor proteins golgin-97 and golgin-245 and its C-terminal to FAM21 subunit of the WASH complex, which regulates multiple endosomal trafficking routes. TBC1D23 is important for normal brain development, especially in axonal and dendritic growth. This entry represents the C-terminal domain that contains residues for specific FAM21 binding and for the cargo of endosome-derived carriers. It adopts a fold similar to the Pleckstrin homology (PH) domain. Mutations in this protein, and particularly in this domain, are linked with Pontocerebellar hypoplasia (PCH) [1-3], suggesting that the TBC1D23 C-terminal domain is required for neuronal growth and brain development.

1: Homozygous Mutations in TBC1D23 Lead to a Non-degenerative Form of Pontocerebellar Hypoplasia. Marin-Valencia I, Gerondopoulos A, Zaki MS, Ben-Omran T, Almureikhi M, Demir E, Guemez-Gamboa A, Gregor A, Issa MY, Appelhof B, Roosing S, Musaev D, Rosti B, Wirth S, Stanley V, Baas F, Barr FA, Gleeson JG; Am J Hum Genet. 2017;101:441-450. PMID:28823706

2: Structural and functional studies of TBC1D23 C-terminal domain provide a link between endosomal trafficking and PCH. Huang W, Liu Z, Yang F, Zhou H, Yong X, Yang X, Zhou Y, Xue L, Zhang Y, Liu D, Meng W, Zhang W, Zhang X, Shen X, Sun Q, Li L, Ma C, Wei Y, Billadeau DD, Mo X, Jia D; Proc Natl Acad Sci U S A. 2019;116:22598-22608. PMID:31624125

3: TBC1D23 is a bridging factor for endosomal vesicle capture by golgins at the trans-Golgi. Shin JJH, Gillingham AK, Begum F, Chadwick J, Munro S; Nat Cell Biol. 2017;19:1424-1432. PMID:29084197