title: Fluid shear stress remodels expression and function of junctional proteins in cultured bone cells.
abstract: We tested the hypothesis that fluid shear stress (tau) modifies the expression, function, and distribution of junctional proteins [connexin (Cx)43, Cx45, and zona occludens (ZO)-1] in cultured bone cells. Cell lines with osteoblastic (MC3T3-E1 cells) and osteocytic (MLO-Y4 cells) phenotypes were exposed to tau-values of 5 or 20 dyn/cm(2) for 1-3 h. Immunostaining indicated that at 5 dyn/cm(2), the distribution of Cx43, Cx45, and ZO-1 was moderately disrupted at cell membranes; at 20 dyn/cm(2), disruption was more severe. Intercellular coupling was significantly decreased at both shear stress levels. Western blots showed the downregulation of membrane-bound Cx43 and ZO-1 and the upregulation of cytosolic Cx43 and Cx45 at different levels of shear stress. Similarly, Northern blots revealed that expression of Cx43, Cx45, and ZO-1 was selectively up- and downregulated in response to different shear stress levels. These results indicate that in cultured bone cells, fluid shear stress disrupts junctional communication, rearranges junctional proteins, and determines de novo synthesis of specific connexins to an extent that depends on the magnitude of the shear stress. Such disconnection from the bone cell network may provide part of the signal whereby the disconnected cells or the remaining network initiate focal bone remodeling.
authors.affiliation: New York Center for Biomedical Engineering, City College of the City University of New York, New York, 10031, USA.
authors.forename: Mia M
authors.initials: MM
authors.lastname: Thi
authors.forename: Takashi
authors.initials: T
authors.lastname: Kojima
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Cowin
authors.forename: Sheldon
authors.initials: S
authors.lastname: Weinbaum
authors.forename: David C
authors.initials: DC
authors.lastname: Spray
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001826:Body Fluids / Q000378:metabolism; D016723:Bone Remodeling / Q000502:physiology*; D001842:Bone and Bones / Q000166:cytology / Q000378:metabolism*; D002450:Cell Communication / Q000502:physiology; D048429:Cell Size / Q000502:physiology; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism; D017630:Connexins / Q000235:genetics / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure; D005455:Fluorescent Antibody Technique; D017629:Gap Junctions / Q000378:metabolism / Q000648:ultrastructure; D007365:Intercellular Junctions / Q000378:metabolism* / Q000648:ultrastructure; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism*; D015675:Osteocalcin / Q000378:metabolism; D010011:Osteocytes / Q000166:cytology / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D033081:Shear Strength; D013314:Stress, Mechanical; D062826:Zonula Occludens-1 Protein
chemical_list: D018031:Connexin 43; D017630:Connexins; D008565:Membrane Proteins; D010750:Phosphoproteins; D062826:Zonula Occludens-1 Protein; C082920:connexin 45; D015675:Osteocalcin; D000469:Alkaline Phosphatase