Activation of protein kinase C-zeta and phosphatidylinositol 3'-kinase and promotion of macrophage differentiation by insulin-like growth factor-I.
Phosphoinositides that are phosphorylated at the D3 position have been reported to activate an atypical, Ca2-independent protein kinase C (PKC) isoform designated PKC-zeta, and overexpression of this enzyme leads to monocytic differentiation. In this study, we cultured human HL-60 promyeloid cells with vitamin D3 and insulin-like growth factor-I (IGF-I), a 70-amino-acid peptide that activates phosphatidylinositol 3'-kinase (PI 3-kinase) in murine promyeloid cells. Two days later, the proportion of cells differentiating into macrophages in serum-free medium, as assessed by expression of the alpha-subunit of the beta2 integrin CD11b, increased from 5 +/- 1% to 25 +/- 3%. Addition of IGF-I increased the proportion of cells differentiating into CD11b-positive macrophages to 78 +/- 5%. In the absence of vitamin D3, IGF-I did not induce expression of CD11b (6 +/- 1%). The IGF-I-promoted macrophage differentiation was blocked specifically by preincubation of HL-60 cells with a mAb (alphaIR3) directed against the IGF type I receptor. Similarly, pretreatment of cells with either alphaIR3 or an IGF-binding protein, IGFBP-3, led to a 75% inhibition of CD11b expression when cells were cultured with vitamin D3 in serum-containing medium. IGF-I, but not vitamin D3, caused a sevenfold increase in the enzymatic activity of both PI 3-kinase and atypical PKC-zeta. Inhibition of IGF-I-inducible PI 3-kinase with either wortmannin or LY294002 abrogated the IGF-I-induced activation of PKC-zeta and totally blocked the enhancement in macrophage differentiation caused by IGF-I. These data establish that PKC-zeta is a putative downstream target of PI 3-kinase that is activated during IGF-I-promoted macrophage differentiation.
Liu
Q
Q
Department of Animal Sciences, University of Illinois, Urbana 61801, USA.
Ning
W
W
Dantzer
R
R
Freund
G G
GG
Kelley
K W
KW
D019138:Antibodies, Blocking / Q000494:pharmacology; D002452:Cell Count / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects / Q000276:immunology; D002470:Cell Survival / Q000187:drug effects / Q000276:immunology; D002762:Cholecalciferol / Q000494:pharmacology; D004789:Enzyme Activation / Q000276:immunology; D005312:Fetal Blood / Q000502:physiology; D018922:HL-60 Cells; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000037:antagonists & inhibitors / Q000502:physiology*; D007527:Isoenzymes / Q000378:metabolism*; D016177:Macrophage-1 Antigen / Q000096:biosynthesis; D008264:Macrophages / Q000166:cytology* / Q000201:enzymology / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D019000:Phosphotyrosine / Q000276:immunology; D011233:Precipitin Tests; D011493:Protein Kinase C / Q000378:metabolism*; D017526:Receptor, IGF Type 1 / Q000276:immunology; D000099221:Protein Kinase C zeta
D019138:Antibodies, Blocking; D002762:Cholecalciferol; D007334:Insulin-Like Growth Factor I; D007527:Isoenzymes; D016177:Macrophage-1 Antigen; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D019000:Phosphotyrosine; D011493:Protein Kinase C; D017526:Receptor, IGF Type 1; D000099221:Protein Kinase C zeta