In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field

[Abstract unavailable

Autophagy is a fundamental function of eukaryotic cells and is well conserved from yeast to humans. The most remarkable feature of autophagy is the synthesis of double membrane-bound compartments that sequester materials to be degraded in lytic compartments, a process that seems to be mechanistically distinct from conventional membrane traffic. The discovery of autophagy in yeast and the genetic tractability of this organism have allowed us to identify genes that are responsible for this process, which has led to the explosive growth of this research field seen today. Analyses of autophagy-related (Atg) proteins have unveiled dynamic and diverse aspects of mechanisms that underlie membrane formation during autophagy.

Autophagy is a membrane trafficking to vacuole/lysosome induced by nutrient starvation. In Saccharomyces cerevisiae, Tor protein, a phosphatidylinositol kinase-related kinase, is involved in the repression of autophagy induction by a largely unknown mechanism. Here, we show that the protein kinase activity of Apg1 is enhanced by starvation or rapamycin treatment. In addition, we have also found that Apg13, which binds to and activates Apg1, is hyperphosphorylated in a Tor-dependent manner, reducing its affinity to Apg1. This Apg1–Apg13 association is required for autophagy, but not for the cytoplasm-to-vacuole targeting (Cvt) pathway, another vesicular transport mechanism in which factors essential for autophagy (Apg proteins) are also employed under vegetative growth conditions. Finally, other Apg1-associating proteins, such as Apg17 and Cvt9, are shown to function specifically in autophagy or the Cvt pathway, respectively, suggesting that the Apg1 complex plays an important role in switching between two distinct vesicular transport systems in a nutrient-dependent manner.

Macroautophagy is a bulk degradation process induced by starvation in eukaryotic cells. In yeast, 15 Apg proteins coordinate the formation of autophagosomes. Several key reactions performed by these proteins have been described, but a comprehensive understanding of the overall network is still lacking. Based on Apg protein localization, we have identified a novel structure that functions in autophagosome formation. This pre‐autophagosomal structure, containing at least five Apg proteins, i.e. Apg1p, Apg2p, Apg5p, Aut7p/Apg8p and Apg16p, is localized in the vicinity of the vacuole. Analysis of apg mutants revealed that the formation of both a phosphatidylethanolamine‐conjugated Aut7p and an Apg12p–Apg5p conjugate is essential for the localization of Aut7p to the pre‐autophagosomal structure. Vps30p/Apg6p and Apg14p, components of an autophagy‐ specific phosphatidylinositol 3‐kinase complex, Apg9p and Apg16p are all required for the localization of Apg5p and Aut7p to the structure. The Apg1p protein kinase complex functions in the late stage of autophagosome formation. Here, we present the classification of Apg proteins into three groups that reflect each step of autophagosome formation.