Restoration of cytoskeletal and membrane tethering defects but not defects in membrane trafficking in the intestinal brush border of mice lacking both myosin Ia and myosin VI.
Myosin Ia (Myo1a), the most prominent plus-end directed motor and myosin VI (Myo6) the sole minus-end directed motor, together exert opposing tension between the microvillar (MV) actin core and the apical brush border (BB) membrane of the intestinal epithelial cell (IEC). Mice lacking Myo1a or Myo6 each exhibit a variety of defects in the tethering of the BB membrane to the actin cytoskeleton. Double mutant (DM) mice lacking both myosins revealed that all the defects observed in either the Myo1a KO or Snell's waltzer (sv/sv) Myo6 mutant mouse are absent. In isolated DM BBs, Myo1a crosslinks between MV membrane and MV actin core are absent but the gap (which is lost in Myo1a KO) between the MV core and membrane is maintained. Several myosins including Myo1c, d, and e and Myo5a are ectopically recruited to the BB. Consistent with the restoration of membrane tethering defects by one or more of these myosins, upward ATP-driven shedding of the BB membrane, which is blocked in the Myo1a KO, is restored in the DM BB. However, Myo1a or Myo6 dependent defects in expression of membrane proteins that traffic between the BB membrane and endosome (NaPi2b, NHE3, CFTR) are not restored. Compared to controls, Myo1a KO, sv/sv mice exhibit moderate and DM high levels of hypersensitivity to dextran sulfate sodium-induced colitis. Consistent with Myo1a and Myo6 playing critical roles in maintaining IEC integrity and response to injury, DM IECs exhibit increased numbers of apoptotic nuclei, above that reported for Myo1a KO.
Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut.
Peter S
PS
Hegan
Department of Pediatrics/Gastroenterology and Hepatology, Yale School of Medicine, New Haven, Connecticut.
Dmitri V
DV
Kravtsov
Department of Respiratory Medicine, Yale School of Medicine, New Haven, Connecticut.
Christina
C
Caputo
Department of Respiratory Medicine, Yale School of Medicine, New Haven, Connecticut.|Department of Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut.
Marie E
ME
Egan
Department of Pediatrics/Gastroenterology and Hepatology, Yale School of Medicine, New Haven, Connecticut.|Department of Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut.
Nadia A
NA
Ameen
Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut.|Department of Cell Biology, Yale School of Medicine, New Haven, Connecticut.|Department of Pathology, Yale School of Medicine, New Haven, Connecticut.
Mark S
MS
Mooseker
D000255:Adenosine Triphosphate / Q000737:chemistry; D000818:Animals; D017209:Apoptosis; D002462:Cell Membrane / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D003092:Colitis / Q000378:metabolism / Q000503:physiopathology; D003433:Crosses, Genetic; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics; D003599:Cytoskeleton / Q000378:metabolism*; D018450:Disease Progression; D004386:Duodenum / Q000378:metabolism / Q000503:physiopathology; D011992:Endosomes / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism; D005838:Genotype; D020287:In Situ Nick-End Labeling; D007413:Intestinal Mucosa / Q000378:metabolism* / Q000503:physiopathology; D007422:Intestines / Q000503:physiopathology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D008871:Microvilli / Q000378:metabolism*; D009154:Mutation; D018995:Myosin Heavy Chains / Q000235:genetics*; D024461:Myosin Type I / Q000235:genetics*; D010710:Phosphates / Q000737:chemistry
D010710:Phosphates; C089785:myosin VI; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D000255:Adenosine Triphosphate; D024461:Myosin Type I; D018995:Myosin Heavy Chains
CFTR; DSS; NaPi2b; Snell's waltzer; minus end-directed motors; plus end-