Constitutively activated Akt-1 is vital for the survival of human monocyte-differentiated macrophages. Role of Mcl-1, independent of nuclear factor (NF)-kappaB, Bad, or caspase activation.
Recent data from mice deficient for phosphatase and tensin homologue deleted from chromosome 10 or src homology 2 domain-containing 5' inositol phosphatase, phosphatases that negatively regulate the phosphatidylinositol 3-kinase (PI3K) pathway, revealed an increased number of macrophages in these animals, suggesting an essential role for the PI3K pathway for macro-phage survival. Here, we focused on the role of the PI3K-regulated serine/threonine kinase Akt-1 in modulating macrophage survival. Akt-1 was constitutively activated in human macrophages and addition of the PI3K inhibitor, LY294002, suppressed the activation of Akt-1 and induced cell death. Furthermore, suppression of Akt-1 by inhibition of PI3K or a dominant negative (DN) Akt-1 resulted in loss of mitochondrial transmembrane potential, activation of caspases-9 and -3, and DNA fragmentation. The effects of PI3K inhibition were reversed by the ectopic expression of constitutively activated Akt-1 or Bcl-x(L). Inhibition of PI3K/Akt-1 pathway either by LY294002 or DN Akt-1 had no effect on the constitutive or inducible activation of nuclear factor (NF)-kappaB in human macrophages. However, after inhibition of the PI3K/Akt-1 pathway, a marked decrease in the expression of the antiapoptotic molecule Mcl-1, but not other Bcl-2 family members was observed, and Mcl-1 rescued macrophages from LY294002-induced cell death. Further, inhibition of Mcl-1 by antisense oligonucleotides, also resulted in macrophage apoptosis. Thus, our findings demonstrate that the constitutive activation of Akt-1 regulates macrophage survival through Mcl-1, which is independent of caspases, NF-kappaB, or Bad.
Liu
H
H
Division of Rheumatology, Department of Medicine, Northwestern University Medical School, and the VA Chicago Health Care System, Lakeside Division, Chicago, IL 60611, USA.
Perlman
H
H
Pagliari
L J
LJ
Pope
R M
RM
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001483:Base Sequence; D002352:Carrier Proteins / Q000378:metabolism; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002454:Cell Differentiation; D002470:Cell Survival; D002867:Chromones / Q000494:pharmacology; D017931:DNA Primers / Q000235:genetics; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009025:Morpholines / Q000494:pharmacology; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D016328:NF-kappa B / Q000378:metabolism; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2; D051025:bcl-Associated Death Protein
D002352:Carrier Proteins; D061945:Caspase Inhibitors; D020169:Caspases; D002867:Chromones; D017931:DNA Primers; D004791:Enzyme Inhibitors; D009025:Morpholines; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D016328:NF-kappa B; D009363:Neoplasm Proteins; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2; D051025:bcl-Associated Death Protein; C494819:BAD protein, human; C494820:Bad protein, mouse; C579094:Mcl1 protein, mouse; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C494918:AKT1 protein, human