title: A role for myosin IXb, a motor-RhoGAP chimera, in epithelial wound healing and tight junction regulation.
abstract: Polymorphisms in the gene encoding the heavy chain of myosin IXb (Myo9b) have been linked to several forms of inflammatory bowel disease (IBD). Given that Myo9b contains a RhoGTPase-activating protein domain within its tail, it may play key roles in Rho-mediated actin cytoskeletal modifications critical to intestinal barrier function. In wounded monolayers of the intestinal epithelial cell line Caco2(BBe) (BBe), Myo9b localizes to the extreme leading edge of lamellipodia of migrating cells. BBe cells exhibiting loss of Myo9b expression with RNA interference or Myo9b C-terminal dominant-negative (DN) tail-tip expression lack lamellipodia, fail to migrate into the wound, and form stress fiber-like arrays of actin at the free edges of cells facing the wound. These cells also exhibit disruption of tight junction (TJ) protein localization, including ZO-1, occludin, and claudin-1. Torsional motility and junctional permeability to dextran are greatly increased in cells expressing DN-tail-tip. Of interest, this effect is propagated to neighboring cells. Consistent with a role for Myo9b in regulating levels of active Rho, localization of both RhoGTP and myosin light chain phosphorylation corresponds to Myo9b-knockdown regions of BBe monolayers. These data reveal critical roles for Myo9b during epithelial wound healing and maintenance of TJ integrity-key functions that may be altered in patients with Myo9b-linked IBD.
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520, USA. surjit.chandhoke@yale.edu
authors.forename: Surjit K
authors.initials: SK
authors.lastname: Chandhoke
authors.forename: Mark S
authors.initials: MS
authors.lastname: Mooseker
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000205:Actomyosin / Q000378:metabolism; D002460:Cell Line; D002465:Cell Movement; D057167:Claudins / Q000378:metabolism; D004847:Epithelial Cells / Q000201:enzymology* / Q000378:metabolism / Q000502:physiology; D055785:Gene Knockdown Techniques; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000201:enzymology / Q000473:pathology; D008565:Membrane Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D009218:Myosins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D010750:Phosphoproteins / Q000378:metabolism; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D015398:Signal Transduction; D019108:Tight Junctions / Q000201:enzymology / Q000378:metabolism*; D014945:Wound Healing; D062826:Zonula Occludens-1 Protein; D020741:rho GTP-Binding Proteins / Q000378:metabolism
chemical_list: D057167:Claudins; D008565:Membrane Proteins; D010750:Phosphoproteins; C569042:TJP1 protein, human; D062826:Zonula Occludens-1 Protein; C113469:myosin IXB; D000205:Actomyosin; D009218:Myosins; D020741:rho GTP-Binding Proteins