PTH-mediated osteoblast retraction: possible participation of the calpain pathway.
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.
Murray
E J
EJ
Geriatric Research, Education and Clinical Center, Department of Veterans Affairs Medical Center, Sepulveda, Calif., USA.
Tram
K K
KK
Spencer
M J
MJ
Tidball
J G
JG
Murray
S S
SS
Lee
D B
DB
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*
D015853:Cysteine Proteinase Inhibitors; D009712:Nucleotides, Cyclic; D010281:Parathyroid Hormone; D002154:Calpain; D002118:Calcium