Caveolae are flask or w-shaped cell membrane invaginations of cholesterol-rich cell surface microdomains that have been implicated in assembling many signaling molecules and facilitating and integrating their functions Caveolae may also play an important role in sequestering inactive signaling molecules and down-regulating receptor activities  Additionally  caveolae may provide an environment for the regulated activation of these molecules and explain the cross-talk between different signaling pathways