Autophagy in the light of sphingolipid metabolism

Maintenance of cellular homeostasis requires tight and coordinated control of numerous metabolic pathways, which are governed by interconnected networks of signaling pathways and energy-sensing regulators. Autophagy(definition), a lysosomal degradation pathway by which the cell self-digests its own components, has over the past decade been recognized as an essential part of metabolism. Autophagy not only rids the cell of excessive or damaged organelles, misfolded proteins, and invading microorganisms, it also provides nutrients to maintain crucial cellular functions. Besides serving as essential structural moieties of biomembranes, lipids including sphingolipids are increasingly being recognized as central regulators of a number of important cellular processes, including autophagy. In the present review we describe how sphingolipids, with special emphasis on ceramides and sphingosine-1-phosphate, can act as physiological regulators of autophagy in relation to cellular and organismal growth, survival, and aging.