title: PTH-mediated osteoblast retraction: possible participation of the calpain pathway.
abstract: Parathyroid hormone (PTH)-induced osteoblast retraction may play a pivotal role a role in bone resorption by providing osteoclasts direct access to mineralized bone surface. We have been working on the hypothesis that the calpains participate in this retractile response through a calcium-dependent process. We have first demonstrated the presence of calpain activities in MC3T3-E1 osteoblastic cells and that these activities can be stimulated by PTH. Second, we have demonstrated that the PTH-induced osteoblast retraction is dramatically attenuated by two different cysteine protease inhibitors. Finally, initial immunofluorescent cytochemical studies suggest that this PTH-induced osteoblastic retraction is mediated through a calpain-dependent, proteolytic modification of the cytoskeletal organization.
authors.affiliation: Geriatric Research, Education and Clinical Center, Department of Veterans Affairs Medical Center, Sepulveda, Calif., USA.
authors.forename: E J
authors.initials: EJ
authors.lastname: Murray
authors.forename: K K
authors.initials: KK
authors.lastname: Tram
authors.forename: M J
authors.initials: MJ
authors.lastname: Spencer
authors.forename: J G
authors.initials: JG
authors.lastname: Tidball
authors.forename: S S
authors.initials: SS
authors.lastname: Murray
authors.forename: D B
authors.initials: DB
authors.lastname: Lee
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001862:Bone Resorption / Q000139:chemically induced*; D002118:Calcium / Q000378:metabolism; D002154:Calpain / Q000502:physiology*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D051379:Mice; D008969:Molecular Sequence Data; D009712:Nucleotides, Cyclic / Q000378:metabolism; D010006:Osteoblasts / Q000187:drug effects*; D010281:Parathyroid Hormone / Q000494:pharmacology*
chemical_list: D015853:Cysteine Proteinase Inhibitors; D009712:Nucleotides, Cyclic; D010281:Parathyroid Hormone; D002154:Calpain; D002118:Calcium