Increased mitogen-activated protein kinase activity and TNF-alpha production associated with Mycobacterium smegmatis- but not Mycobacterium avium-infected macrophages requires prolonged stimulation of the calmodulin/calmodulin kinase and cyclic AMP/protein kinase A pathways.
Previous studies have shown the mitogen-activated protein kinases (MAPKs) to be activated in macrophages upon infection with Mycobacterium, and that expression of TNF-alpha and inducible NO synthase by infected macrophages was dependent on MAPK activation. Additional analysis demonstrated a diminished activation of p38 and extracellular signal-regulated kinase (ERK)1/2 in macrophages infected with pathogenic strains of Mycobacterium avium compared with infections with the fast-growing, nonpathogenic Mycobacterium smegmatis and Mycobacterium phlei. However, the upstream signals required for MAPK activation and the mechanisms behind the differential activation of the MAPKs have not been defined. In this study, using bone marrow-derived macrophages from BALB/c mice, we determined that ERK1/2 activation was dependent on the calcium/calmodulin/calmodulin kinase II pathway in both M. smegmatis- and M. avium-infected macrophages. However, in macrophages infected with M. smegmatis but not M. avium, we observed a marked increase in cAMP production that remained elevated for 8 h postinfection. This M. smegmatis-induced cAMP production was also dependent on the calmodulin/calmodulin kinase pathway. Furthermore, stimulation of the cAMP/protein kinase A pathway in M. smegmatis-infected cells was required for the prolonged ERK1/2 activation and the increased TNF-alpha production observed in these infected macrophages. Our studies are the first to demonstrate an important role for the calmodulin/calmodulin kinase and cAMP/protein kinase A pathways in macrophage signaling upon mycobacterial infection and to show how cAMP production can facilitate macrophage activation and subsequent cytokine production.
Yadav
Mahesh
M
Department of Biological Sciences, Center for Tropical Disease Research and Training, University of Notre Dame, Notre Dame, IN 46556, USA.
Roach
Shannon K
SK
Schorey
Jeffrey S
JS
D000818:Animals; D002118:Calcium / Q000502:physiology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000502:physiology*; D002147:Calmodulin / Q000502:physiology; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000096:biosynthesis; D017868:Cyclic AMP-Dependent Protein Kinases / Q000276:immunology*; D004789:Enzyme Activation / Q000276:immunology; D008264:Macrophages / Q000201:enzymology / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology; D051379:Mice; D008807:Mice, Inbred BALB C; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009162:Mycobacterium avium / Q000276:immunology*; D020102:Mycobacterium smegmatis / Q000276:immunology*; D015398:Signal Transduction / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis*; D015854:Up-Regulation / Q000276:immunology; D048051:p38 Mitogen-Activated Protein Kinases
D002147:Calmodulin; D014409:Tumor Necrosis Factor-alpha; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D002118:Calcium