Figure 7. Models of how photoswitchable ceramides may enable optical control over sphingolipid biosynthesis and signaling.

(a) UV-A or blue light trigger alterations in the curvature of the carbon chains of azobenzene-containing ceramides (caCers), which reversibly enhance or reduce their affinity for ceramide metabolic enzymes and signaling proteins. (b) Blue light triggers self-assembly of photoswitchable ceramides (caCers) into tightly packed clusters driven by intermolecular stacking of the flat trans-azobenzene groups. In contrast, UV-A light causes caCers to disperse in the plane of the membrane as the bent cis-azobenzene groups disrupt intermolecular stacking. These light-induced changes in lateral packing of caCers reversibly enhance or reduce their availability for metabolic conversion or stimulating ceramide signaling proteins.