Figure 5. Autophagy in kidney aging. In both podocytes and proximal tubular cells, autophagy maintains cellular and organelles homeostasis under both basal and stress conditions. Normal aging process or a deletion of Atg5 gene alters autophagy in podocytes and proximal tubular cells, leading to kidney aging. Calorie restriction prevents the progression of kidney aging in a part through SIRT1-dependent autophagy.