A new role for the architecture of microvillar actin bundles in apical retention of membrane proteins

Céline Revenu, Florent Ubelmann, Ilse Hurbain, Fatima El-Marjou, Florent Dingli, Damarys Loew, Delphine Delacour, Jules Gilet, Edith Brot-Laroche, Francisco Rivero, Daniel Louvard, Sylvie Robine (+1 others)
2012 Molecular Biology of the Cell  
Actin-bundling proteins are identified as key players in the morphogenesis of thin membrane protrusions. Until now, functional redundancy among the actin-bundling proteins villin, espin, and plastin-1 has prevented definitive conclusions regarding their role in intestinal microvilli. We report that triple knockout mice lacking these microvillar actin-bundling proteins suffer from growth delay but surprisingly still develop microvilli. However, the microvillar actin filaments are sparse and lack
more » ... the characteristic organization of bundles. This correlates with a highly inefficient apical retention of enzymes and transporters that accumulate in subapical endocytic compartments. Myosin-1a, a motor involved in the anchorage of membrane proteins in microvilli, is also mislocalized. These findings illustrate, in vivo, a precise role for local actin filament architecture in the stabilization of apical cargoes into microvilli. Hence, the function of actin-bundling proteins is not to enable microvillar protrusion, as has been assumed, but to confer the appropriate actin organization for the apical retention of proteins essential for normal intestinal physiology.
doi:10.1091/mbc.e11-09-0765 pmid:22114352 pmcid:PMC3258176 fatcat:ekh6xyjd4jftzhgn2ywomyn5xm