Rab11 is associated with epidermal lamellar granules

Epidermal lamellar granules (LGs) are specialized organelles that transport and secrete various molecules, including lipids, proteases, protease inhibitors, and structural proteins, thereby providing a protective barrier against the environment. Abnormalities in LG-related molecules result in severe skin diseases, but their transport mechanisms are poorly understood. We studied the distribution of Rab-11, a common GTPase in recycling enclosomes, in normal human epidermis. Confocal laser scanning microscopy detected Rabll immunoreactivity in differentiated epidermal keratinocytes. Staining was strong at the apical side of each cell, a pattern commonly seen in LG-associated molecules. Around the nuclei, Rabll was colocalized with TGN46, a trans-Golgi network marker. Rabll was also colocalized with known LG-molecules, namely lymphoepithelial Kazal -type- related inhibitor, corneodesmosine, cathepsin D, and gl ucosylceram ides. Immunoelectron microscopy revealed that Rabll was widely distributed along TGN and tubular-vesicular structures containing different LG molecules. The present results suggest that Rabll plays a role in the intracellular trafficking of various types of LG-molecule from the TGN to the cell surface.