Premium
Parathyroid hormone (PTH) mediates shear‐induced actin organization and mechanosensitivity via Ras Homologous A (RhoA) GTPase in osteoblasts
Author(s) -
Madden Gregory Russell,
Kronbergs Andris,
Adams Elizabeth,
Golen Kenneth van,
Duncan Randall
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.1218.7
Subject(s) - rhoa , osteoblast , chemistry , actin , microbiology and biotechnology , actin cytoskeleton , cytoskeleton , rho associated protein kinase , small gtpase , parathyroid hormone , stress fiber , rac1 , biophysics , calcium , signal transduction , cell , in vitro , biology , biochemistry , organic chemistry
PTH enhances the mechanical loading‐induced increases in bone formation that we postulate results from PTH disruption of the actin cytoskeleton to increase the mechanosensitivity of the osteoblast. Since Ras homologous A (RhoA) GTPase activation promotes actin assembly, we examined the effects of these stimuli on RhoA activation, actin organization, and cellular stiffness. Fluid shear (12 dynes/cm 2 ) increases actin stress fiber formation (ASFF) within 15 min in MC3T3‐E1 osteoblasts that is blocked by pretreatment with 50nM PTH. Using a RhoA G‐LISA assay, we found that shear activated RhoA within 15 min of the onset of shear and that 15 min pretreatment with PTH significantly inhibited this activation. AFM quantification of the stress‐strain relationship of MC3T3‐E1 cells indicated that shear produced a 6fold increase in cellular stiffness that was blocked by PTH pretreatment. Inhibition of Rho‐dependent kinase (ROCK), an effector protein of RhoA with Y27632 blocked the shear‐induced ASFF as well as the increase in cellular stiffness. These changes in cell stiffness closely correlated with shear‐induced calcium signaling. These studies suggest that PTH inhibits shear‐induced actin organization through the RhoA‐ROCK pathway and that the resultant changes in cell stiffness play a role in the PTH‐mediated enhancement of osteoblast mechanosensitivity. Supported by HHMI and NIH/NIAMS AR043222