Abstract
Cathepsin K (Cat K) is the major cysteine protease expressed in osteoclast and is thought to play a key role in matrix degradation during bone resorption. It is shown that the intracellular maturation of Cat K was prevented by the cAMP antagonist, Rp-cAMP, and the protein kinase A (PKA) inhibitors of KT5720 and H89. In contrast, forskolin, an adenylate cyclase agonist, rather induced Cat K processing and maturation in osteoclast. Furthermore, to determine whether Cat K processing and maturation signaling involves protein kinase C (PKC), mouse total bone cells were treated with calphostin C, a specific inhibitor of PKC, however, no effect was observed, indicating that PKC calphostin C did not affect to osteoclast-mediated Cat K processing and maturation in osteoclast. Thus, it is indicated that the cAMP-PKA signaling pathway regulate Cat K maturation in osteoclast. Since secreted proenzymes have the potential to reenter the cell via M6P receptor, to prevent this possibility, we tested cAMP antagonist Rp-cAMP and the PKA inhibitors KT5720 and H89 in the absence or presence of M6P. Inhibition of Cat K processing by Rp-cAMP, KT5720 or H89 was observed in a dose-dependent manner. Furthermore, the addition of M6P resulted in enhanced potency of Rp-cAMP, KT5720 and H89, which dose-dependently inhibited in vitro bone resorption with potency similar to that observed for inhibition of Cat K processing.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Antibodies / immunology
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Bone Resorption / metabolism
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Bone Resorption / physiopathology
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Carbazoles / pharmacology
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Cathepsin K
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Cathepsins / immunology
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Cathepsins / metabolism*
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Cells, Cultured
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Chloroquine / pharmacology
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Colforsin / pharmacology
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Cyclic AMP / analogs & derivatives
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Cyclic AMP / antagonists & inhibitors
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Cyclic AMP / physiology*
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Cyclic AMP-Dependent Protein Kinases / antagonists & inhibitors
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Cyclic AMP-Dependent Protein Kinases / physiology*
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Indoles / pharmacology
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Isoquinolines / pharmacology
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Lysosomes / drug effects
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Lysosomes / metabolism
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Mannose / analogs & derivatives
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Mannose / pharmacology
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Mice
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Monensin / pharmacology
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Naphthalenes / pharmacology
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Osteoclasts / cytology
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Osteoclasts / drug effects
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Osteoclasts / metabolism*
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Protein Kinase Inhibitors / pharmacology
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Protein Processing, Post-Translational
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Pyrroles / pharmacology
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Receptor, IGF Type 2 / antagonists & inhibitors
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Signal Transduction / drug effects
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Signal Transduction / physiology*
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Sulfonamides / pharmacology
Substances
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Antibodies
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Carbazoles
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Indoles
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Isoquinolines
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Naphthalenes
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Protein Kinase Inhibitors
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Pyrroles
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Receptor, IGF Type 2
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Sulfonamides
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Colforsin
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KT 5720
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Chloroquine
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Monensin
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mannose 6-sulfate
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Cyclic AMP
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Cyclic AMP-Dependent Protein Kinases
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Cathepsins
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Cathepsin K
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Ctsk protein, mouse
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calphostin C
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N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide
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Mannose