The enterocyte microvillus is a vesicle-generating organelle.

McConnell RE, Higginbotham JN, Shifrin DA, Tabb DL, Coffey RJ, Tyska MJ
J Cell Biol. 2009 185 (7): 1285-98

PMID: 19564407 · PMCID: PMC2712962 · DOI:10.1083/jcb.200902147

For decades, enterocyte brush border microvilli have been viewed as passive cytoskeletal scaffolds that serve to increase apical membrane surface area. However, recent studies revealed that in the in vitro context of isolated brush borders, myosin-1a (myo1a) powers the sliding of microvillar membrane along core actin bundles. This activity also leads to the shedding of small vesicles from microvillar tips, suggesting that microvilli may function as vesicle-generating organelles in vivo. In this study, we present data in support of this hypothesis, showing that enterocyte microvilli release unilamellar vesicles into the intestinal lumen; these vesicles retain the right side out orientation of microvillar membrane, contain catalytically active brush border enzymes, and are specifically enriched in intestinal alkaline phosphatase. Moreover, myo1a knockout mice demonstrate striking perturbations in vesicle production, clearly implicating this motor in the in vivo regulation of this novel activity. In combination, these data show that microvilli function as vesicle-generating organelles, which enable enterocytes to deploy catalytic activities into the intestinal lumen.

MeSH Terms (14)

Alkaline Phosphatase Animals Cell Membrane Cell Polarity Enterocytes Isoenzymes Mice Mice, Knockout Microvilli Myosin Heavy Chains Organelles Rats Rats, Sprague-Dawley Unilamellar Liposomes

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