I-plastin, a central element for brush border integrity and proper apical transport

Abstract

1-plastin, one of three mammalian plastin isoforms, is an actinbundling protein of the brush border (BB) of the small intestine, colon and kidney. To investigate the contribution of 1-plastin to the microvillar architecture we have generated a KO mouse strain. Although at the whole animal level KO mice do not show any overt phenotype, ultrastructural studies revealed important morphological alterations. In particular the rootlet that extends the microvillar core actin bundle into the. terminal web (TW) is missing, microvilli are shorter and the organelle free zone occupied by the TW is thinner. Inununohistochemistry studies revealed a depletion of important TW components like myosin 11, spectrin and tropomyosin and an altered localization of cytokeratins. These alterations result in increased fragility of the BB, altered targeting of apical components and decreased transepithelial resistance. 1-plastin emerges as a central regulator of the morphological structure and stability of the intestinal BB.