Agonist stimulation of smooth muscle contractility involves integration of many signal-transducing events from the plasma membrane to myofilaments in the cytoplasm. Recent evidence suggests an important role for membranous invaginations termed caveolae, and their integral protein components caveolins, in the coordination of extracellular contractile stimuli and intracellular effectors in smooth muscle.
Taggart, M. J. (2001). Smooth muscle excitation-contraction coupling: A role for Caveolae and Caveolins? News in Physiological Sciences, 16(2), 61–65. https://doi.org/10.1152/physiologyonline.2001.16.2.61