title: TipC and the chorea-acanthocytosis protein VPS13A regulate autophagy in Dictyostelium and human HeLa cells.
abstract: Deficient autophagy causes a distinct phenotype in Dictyostelium discoideum, characterized by the formation of multitips at the mound stage. This led us to analyze autophagy in a number of multitipped mutants described previously (tipA(-), tipB(-), tipC(-), and tipD(-)). We found a clear autophagic dysfunction in tipC(-) and tipD(-) while the others showed no defects. tipD codes for a homolog of Atg16, which confirms the role of this protein in Dictyostelium autophagy and validates our approach. The tipC-encoded protein is highly similar to human VPS13A (also known as chorein), whose mutations cause the chorea-acanthocytosis syndrome. No member of the VPS13 protein family has been previously related to autophagy despite the presence of a region of similarity to Atg2 at the C terminus. This region also contains the conserved domain of unknown function DUF1162. Of interest, the expression of the TipC C-terminal coding sequence containing these 2 motifs largely complemented the mutant phenotype. Dictyostelium cells lacking TipC displayed a reduced number of autophagosomes visualized with the markers GFP-Atg18 and GFP-Atg8 and an impaired autophagic degradation as determined by a proteolytic cleavage assay. Downregulation of human VPS13A in HeLa cells by RNA interference confirmed the participation of the human protein in autophagy. VPS13A-depleted cells showed accumulation of autophagic markers and impaired autophagic flux.
authors.affiliation: a Instituto de Investigaciones Biomedicas Alberto Sols; Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid ; Madrid , Spain.
authors.forename: Sandra
authors.initials: S
authors.lastname: Muñoz-Braceras
authors.forename: Rosa
authors.initials: R
authors.lastname: Calvo
authors.forename: Ricardo
authors.initials: R
authors.lastname: Escalante
mesh_terms: D001343:Autophagy / Q000235:genetics / Q000502:physiology*; D004023:Dictyostelium / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D054546:Neuroacanthocytosis; D010641:Phenotype; D015800:Protozoan Proteins / Q000235:genetics* / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D015800:Protozoan Proteins; C429654:VPS13A protein, human; D033921:Vesicular Transport Proteins
keywords: ATG, autophagy related; AX4, axenic strain 4; DUF, domain of unknown function; Dictyostelium; GFP, green fluorescent protein; HeLa cells; LC3, microtubule-associated protein 1 light chain 3; PtdIns3K, phosphatidylinositol 3-kinase; PtdIns3P, phosphatidylinositol 3-phosphate; TipC; VPS13; VPS13, vacuolar protein sorting 13 homolog (S. cerevisiae); VPS13A; WIPI, WD repeat domain, phosphoinoside interacting; autophagy; chorea-acanthocytosis; chorein