Regulation of osteoclastic acid secretion by cGMP-dependent protein kinase

• Published in: Biochemical and biophysical research communications Vol. 204; no. 2; p. 565
• Main Authors: Van Epps-Fung, C, Williams, J P, Cornwell, T L, Lincoln, T M, McDonald, J M, Radding, W, Blair, H C
• Format: Journal Article
• Language: English
• Published: United States 28-10-1994
• Subjects: Animals; Biological Transport; Blotting, Western; Cell Membrane - metabolism; Cells, Cultured; Chickens; Cyclic GMP - metabolism; Cyclic GMP-Dependent Protein Kinases - physiology; Hydrochloric Acid - metabolism; Microscopy, Fluorescence; Osteoclasts - enzymology; Osteoclasts - metabolism
• ISSN: 0006-291X
• DOI: 10.1006/bbrc.1994.2496

Nitric oxide (NO) down-regulates osteoclastic activity. The mechanism is unknown, although, in some cells NO acts by stimulating guanylate cyclase which activates cGMP-dependent proteins. We demonstrated cGMP-dependent protein kinase in osteoclasts by immunofluorescence microscopy. Specificity was confirmed by Western blot analysis showing a single 78 kDa band, the size of the Type I isoform, in isolated avian osteoclasts. Osteoclast function centers on HCl secretion at a specialized membrane organelle. We found that purified cGMP-dependent protein kinase inhibits ATP-dependent acid transport in reconstituted osteoclast membrane vesicles >90%, while cAMP-dependent kinase catalytic subunit, calmodulin kinase II, or cGMP alone were ineffective. This novel, direct modulation of acid transport by cGMP-dependent kinase and the occurrence of the enzyme in osteoclasts suggest that a mechanism of NO-regulation of bone turnover is via cGMP and cGMP-dependent protein kinase inhibition of HCl transport.