The enterocyte microvillus is a vesicle-generating organelle.
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.
McConnell
Russell E
RE
Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
Higginbotham
James N
JN
Shifrin
David A
DA
Tabb
David L
DL
Coffey
Robert J
RJ
Tyska
Matthew J
MJ
D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D016764:Cell Polarity; D020895:Enterocytes / Q000166:cytology / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008871:Microvilli / Q000378:metabolism / Q000648:ultrastructure; D018995:Myosin Heavy Chains / Q000235:genetics / Q000378:metabolism; D015388:Organelles / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D053835:Unilamellar Liposomes / Q000378:metabolism*
D007527:Isoenzymes; C491827:Myo1a protein, mouse; D053835:Unilamellar Liposomes; D000469:Alkaline Phosphatase; D018995:Myosin Heavy Chains