Antiapoptotic action of 1,25-dihydroxyvitamin D3 is associated with increased mitochondrial MCL-1 and RAF-1 proteins and reduced release of cytochrome c.
Release of mitochondrial cytochrome c has been recently linked to the activation of the "executioner" phase of the cellular programs for death by apoptosis. This release is known to be negatively regulated by Bcl-2 and Bcl-XL proteins. We show here that treatment of human leukemia cells HL60 with 1,25-dihydroxyvitamin D3 (1,25D3) results in progressive increases in the levels of cellular antiapoptotic protein Mcl-1, a transient increase in Al protein level, but no increases in Bcl-2 or Bcl-XL proteins. The increase in Mcl-1 protein levels correlates with a reduced extent of apoptotic cell death induced by etoposide or the calcium ionophore A23187. The Mcl-1 protein is primarily localized in the mitochondria, and etoposide- or A23187-induced cytochrome c release is reduced in cells in which the mitochondria contain the Mcl-1 protein demonstrable by immunoblots. Raf-1 protein can also be detected in the mitochondrial fractions that contain Mcl-1 protein but not in the Mcl-1-negative fractions. These findings suggest that in these promyelocytic leukemia cells Mcl-1 has a function analogous to that of Bcl-2 in other cells, i.e., to target Raf-1 to mitochondria and to reduce cell damage-induced release of mitochondrial cytochrome c. Our findings provide a potential mechanism for the antiapoptotic action of 1,25D3 and show that differentiation and apoptosis signaling pathways not only interact but involve a proliferation-associated gene, Raf-1.
Wang
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Department of Pathology and Laboratory Medicine, UMDNJ-New Jersey Medical School, 185 South Orange Avenue, Newark, New Jersey 07103, USA.
Studzinski
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D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D000001:Calcimycin / Q000494:pharmacology; D002117:Calcitriol / Q000494:pharmacology*; D053148:Caspase 3; D020169:Caspases; D002453:Cell Cycle / Q000187:drug effects; D003546:Cysteine Endopeptidases / Q000096:biosynthesis; D003574:Cytochrome c Group / Q000378:metabolism*; D053938:DNA Fragmentation; D004792:Enzyme Precursors / Q000096:biosynthesis; D005047:Etoposide / Q000633:toxicity; D019254:Genes, bcl-2; D018922:HL-60 Cells; D006801:Humans; D015151:Immunoblotting; D007700:Kinetics; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D005810:Multigene Family; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000096:biosynthesis*; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis*; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis / Q000096:biosynthesis; D019908:Proto-Oncogene Proteins c-raf; D051020:bcl-X Protein
C494811:BCL2L1 protein, human; D003574:Cytochrome c Group; D004792:Enzyme Precursors; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; D000001:Calcimycin; D005047:Etoposide; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D003546:Cysteine Endopeptidases; D002117:Calcitriol