Identifying Atg1 substrates: four means to an end.

Autophagy is essential for normal development and the response to a variety of stress conditions, including nutrient deprivation. The Atg1 serine/threonine-specific protein kinase appears to be a key regulator of many forms of autophagy that occur in eukaryotic cells. Therefore, to fully understand the regulation of autophagy, it is essential that we identify the signaling pathways regulating Atg1 and the physiologically-relevant targets of Atg1 kinase activity. Although some progress has been made on the former question, no Atg1 substrates important for autophagy have yet been identified. In this review, we discuss four different experimental strategies that should facilitate the search for Atg1 substrates.