Lipid Rafts and Caveolae in the Terminal Differentiation of Epidermal Keratinocytes

Abstract

Lipid rafts are cholesterol and sphingolipid-enriched plasma membrane domains, Caveolae represent a subclass of lipid rafts and the chief structural proteins are caveolins (caveolin-1, -2 and –3). Caveolae formation plays a major role in epidermal barrier permeability, regulating lamellar body secretion and terminal differentiation. Disruption of the epidermal barrier leads to protease-activated receptor-2 activation and an increased intracellular calcium resulting in lamellar body secretion. Caveolin-1 is transported via the lamellar bodies to the plasma membrane, inserted into lipid rafts and initiates caveolae formation. The insertion of caveolin-1 serves as a “brake” in lamellar body secretion and signals terminal differentiation in order to restore an efficient epidermal barrier.