Cellular autophagy is an evolutionarily highly conserved degradation pathway for both stochastic and selective degradation of cytoplasmic cargo within the lysosomal compartment. As such, this process of self-eating secures cellular homeostasis and survival, while malfunction contributes to the initiation and development of many agerelated human diseases including diabetes, tumorigenesis, and neurodegeneration ( 1-4 ). Autophagy is constitutively active on a low basal level resulting in constant cytoplasmic turnover and the specifi c elimination of macromolecule aggregates and damaged organelles. Following a great variety of cellular insults such as nutrient starvation, autophagy is induced above basal level and produces monomers and energy for subsequent recycling processes.Autophagy is hallmarked by the formation of doublemembrane vesicles called autophagosomes that are generated from initial preautophagosomal membrane precursors or phagophores. Elongation of the phagophore and subsequent vesicle closure complete the formation of autophagosomes that sequester the cytoplasmic cargo and communicate with the lysosomal compartment to acquire acidic hydrolases for cargo breakdown ( 5-7 ).Abstract Autophagy is a lysosomal bulk degradation pathway for cytoplasmic cargo, such as long-lived proteins, lipids, and organelles. Induced upon nutrient starvation, autophagic degradation is accomplished by the concerted actions of autophagy-related (ATG) proteins. Here we demonstrate that two ATGs, human Atg2A and Atg14L, colocalize at cytoplasmic lipid droplets (LDs) and are functionally involved in controlling the number and size of LDs in human tumor cell lines. We show that Atg2A is targeted to cytoplasmic ADRP-positive LDs that migrate bidirectionally along microtubules. The LD localization of Atg2A was found to be independent of the autophagic status. Further, Atg2A colocalized with Atg14L under nutrient-rich conditions when autophagy was not induced. Upon nutrient starvation and dependent on phosphatidylinositol 3-phosphate [PtdIns(3)P] generation, both Atg2A and Atg14L were also specifically targeted to endoplasmic reticulum-associated early autophagosomal membranes, marked by the PtdIns(3)P effectors double-FYVE containing protein 1 (DFCP1) and WD-repeat protein interacting with phosphoinositides 1 (WIPI-1) , both of which function at the onset of autophagy. These data provide evidence for additional roles of Atg2A and Atg14L in the formation of early autophagosomal membranes and also in lipid metabolism. -Pfi sterer, S. G., D. Bakula, T. Frickey, A. Cezanne, D. Brigger, M. P. Tschan, H. Robenek, and T. ProikasCezanne. Lipid droplet and early autophagosomal membrane targeting of Atg2A and Atg14L in human tumor cells.