title: Mistargeting of SH3TC2 away from the recycling endosome causes Charcot-Marie-Tooth disease type 4C.
abstract: Mutations in the functionally uncharacterized protein SH3TC2 are associated with the severe hereditary peripheral neuropathy, Charcot-Marie-Tooth disease type 4C (CMT4C). Similarly, to other proteins mutated in CMT, a role for SH3TC2 in endocytic membrane traffic has been previously proposed. However, recent descriptions of the intracellular localization of SH3TC2 are conflicting. Furthermore, no clear functional pathogenic mechanisms have so far been proposed to explain why both nonsense and missense mutations in SH3TC2 lead to similar clinical phenotypes. Here, we describe our intracellular localization studies, supported by biochemical and functional data, using wild-type and mutant SH3TC2. We show that wild-type SH3TC2 targets to the intracellular recycling endosome by associating with the small GTPase, Rab11, which is known to regulate the recycling of internalized membrane and receptors back to the plasma membrane. Furthermore, we demonstrate that SH3TC2 interacts preferentially with the GTP-bound form of Rab11, identifying SH3TC2 as a novel Rab11 effector. Of clinical pathological relevance, all SH3TC2 constructs harbouring disease-causing mutations are shown to be unable to associate with Rab11 with consequent loss of recycling endosome localization. Moreover, we show that wild-type SH3TC2, but not mutant SH3TC2, influences transferrin receptor dynamics, consistent with a functional role on the endocytic recycling pathway. Our data therefore implicate mistargeting of SH3TC2 away from the recycling endosome as the fundamental molecular defect that leads to CMT4C.
authors.affiliation: Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, UK. rcr20@cam.ac.uk
authors.forename: Rhys C
authors.initials: RC
authors.lastname: Roberts
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Peden
authors.forename: Folma
authors.initials: F
authors.lastname: Buss
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Bright
authors.forename: Morwena
authors.initials: M
authors.lastname: Latouche
authors.forename: Mary M
authors.initials: MM
authors.lastname: Reilly
authors.forename: John
authors.initials: J
authors.lastname: Kendrick-Jones
authors.forename: J Paul
authors.initials: JP
authors.lastname: Luzio
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002457:Cell Extracts; D002462:Cell Membrane / Q000378:metabolism; D002607:Charcot-Marie-Tooth Disease / Q000378:metabolism*; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism*; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D042541:Intracellular Space / Q000378:metabolism; D018613:Microscopy, Confocal; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D011990:Receptors, Transferrin / Q000378:metabolism
chemical_list: D002457:Cell Extracts; D047908:Intracellular Signaling Peptides and Proteins; D050505:Mutant Proteins; D011506:Proteins; D011990:Receptors, Transferrin; C488620:SH3TC2 protein, human; D049452:Green Fluorescent Proteins