Microtubule-dependent redistribution of a cytoplasmic cornified envelope precursor

Several cytoplasmic cornified envelope precursors have been described. Nevertheless, the mechanism whereby these proteins are positioned at the site of crosslink formation is not known. In this study, we examine the intracellular distribution of the cornified envelope precursor S100A11 (S100C) and the effects of the physiologic differentiating agent calcium on this distribution. S100A11 is localized in the cytoplasm of resting cultured human keratinocytes. Treatment with calcium causes S100A11 to relocate to the cell periphery. Immunoprecipitation studies reveal that S100A11 associates with microtubules, and inhibitor studies indicate that functional micro-tubules are required for S100A11 peripheral redistribution. Parallel studies indicate that S100A11 is not present in the Golgi or endoplasmic reticulum (ER), suggesting that S100A11 is not moved to the cell periphery via the classical Golgi/ER export pathway. Further evidence that the Golgi/ER is not involved is provided by the observation that the Golgi/ER disruptor brefeldin A does not alter movement. These results suggest that redistribution along microtubules is a mechanism whereby S100A11 is positioned at the cell periphery in preparation for transglutaminase-dependent crosslinking. Staining of epidermal tissue sections from uninvolved and psoriatic epidermis reveals strong staining at the cell periphery in the majority of suprabasal cells, confirming a peripheral distribution of S100A11 in vivo.