1 alpha,25-dihydroxyvitamin D3-induced upregulation of calcineurin during leukemic HL-60 cell differentiation.
Cyclosporin A and FK506, at concentrations that inhibited phosphatase activity of calcineurin in HL-60 cellular lysates, augmented the proliferation of leukemic HL-60 cells. These immunosuppressants did not affect 1 alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3]-induced monocytic differentiation of HL-60 cells, but did abrogate the 1,25(OH)2D3-induced inhibition of HL-60 cell growth. Treatment with 20 nmol/L 1,25(OH)2D3 led to a progressive increase in calcineurin phosphatase activity in subcellular fractions from HL-60 cell extracts, the increase in this activity appeared to parallel the phenotypic and functional changes of HL-60 cells during monocytic differentiation induced by 1,25(OH)2D3. Immunoblot analysis indicated that increase in calcineurin activity was concordant with the increased expressions of calcineurin catalytic subunit isozymes, calcineurin A alpha (CNA alpha), and calcineurin A beta(CNA beta), and a regulatory calcineurin B subunit (CNB) proteins, which were preceded by a coordinate increase in the levels of CNA alpha, CNA beta and CNB mRNAs. The expression of calmodulin remained unaltered throughout 1,25(OH)2D3-induced monocytic differentiation. These results suggest that calcineurin activation has a net negative effect on HL-60 cell proliferation, and that the increased expression of calcineurin may be involved in 1,25(OH)2D3-induced inhibition of HL-60 cell proliferation.
Omay
S B
SB
2nd Department of Internal Medicine, Mie University School of Medicine, Tsu, Mie, Japan.
Nakai
K
K
Kuno
T
T
Shiku
H
H
Nishikawa
M
M
D019703:Calcineurin; D002117:Calcitriol / Q000494:pharmacology*; D002148:Calmodulin-Binding Proteins / Q000096:biosynthesis*; D002454:Cell Differentiation / Q000187:drug effects; D018922:HL-60 Cells / Q000378:metabolism / Q000473:pathology; D006801:Humans; D010749:Phosphoprotein Phosphatases / Q000096:biosynthesis*; D015854:Up-Regulation / Q000187:drug effects
D002148:Calmodulin-Binding Proteins; D019703:Calcineurin; D010749:Phosphoprotein Phosphatases; D002117:Calcitriol