Two Beclin 1-binding proteins, Atg14L and Rubicon, reciprocally regulate autophagy at different stages

Abstract

Beclin 1, a protein essential for autophagy, binds to hVps34/Class III phosphatidylinositol-3-kinase and UVRAG. Here, we have identified two Beclin 1 associated proteins, Atg14L and Rubicon. Atg14L and UVRAG bind to Beclin 1 in a mutually exclusive manner, whereas Rubicon binds only to a subpopulation of UVRAG complexes; thus, three different Beclin 1 complexes exist. GFP-Atg14L localized to the isolation membrane and autophagosome, as well as to the ER and unknown puncta. Knockout of Atg14L in mouse ES cells caused a defect in autophagosome formation. GFP-Rubicon was localized at the endosome/lysosome. Knockdown of Rubicon caused enhancement of autophagy, especially at the maturation step, as well as enhancement of endocytic trafficking. These data suggest that the Beclin 1-hVps34 complex functions in two different steps of autophagy by altering the subunit composition.

A current perspective of autophagosome biogenesis

“…Consistently, Atg14L, a subunit of the autophagyspecific PI3K, was shown to localize to the ER by fluorescence and immuno-electron microscopy [35]. Under resting conditions, Atg14L evenly localized to the ER, and during starvation, Atg14L formed punctate structures on the ER.…”

“…The discovery of autophagy-related (ATG) genes in the 1990's by yeast genetics provided powerful genetic and molecular tools to investigate autophagy [16]. To date, over 35 ATG genes have been identified in yeast. A total of 15 core ATG genes required for both starvationinduced and selective autophagy (ATG1-10, 12-14, 16, 18) are highly conserved in mammals [17].…”

“…In yeast, the autophagy-specific PI3K complex is composed of four proteins: Vps34 (catalytic unit), Vps15, Atg6/Vps30, and Atg14 [31]. In mammals, Beclin 1 [32,33] and Atg14L/Barkor [34][35][36][37] are identified as the orthologues of Atg6/Vps30 and Atg14, respectively. It is thought that the production of PI3P is initiated by the dot-like accumulation of the Atg14/Atg14L-containing PI3K complex at the PAS (in yeast) or on the endoplasmic reticulum (ER) (in mammals; discussed below).…”

New frontiers in promoting tumour cell death: targeting apoptosis, necroptosis and autophagy

“…Cells lacking atg5 and overexpressing p62 exhibited a significantly higher tumourigenic potential compared with atg5-deficient cells overexpressing the control vector in xenograft studies (Mathew et al, 2009). Additionally, the ability of autophagic proteins, Beclin 1, Ambra 1, UVRAG and Bif-1, to inhibit cell proliferation, promote non-apoptotic cell death and regulate endocytosis (Liang et al, 1999(Liang et al, , 2006Qu et al, 2003;Yu et al, 2004;Fimia et al, 2007;Koneri et al, 2007;Takahashi et al, 2007;Matsunaga et al, 2009) may also contribute to their tumour suppressive effects.…”

MHC presentation via autophagy and how viruses escape from it

“…In addition, it is used to recruit autophagic cargo [18][19][20] . In addition to its role in autophagosome formation, Atg6/Beclin-1 containing PI3 kinase complexes are then once more involved in macroautophagy at the stage of autophagosome fusion with the lysosome [21][22][23][24] . In addition to macroautophagy, chaperone-mediated autophagy also imports cytosolic proteins into lysosomes for degradation 25 .…”