Differentiation of HL-60 cells is associated with an increase in the 35-kDa protein lipocortin I

✍ Scribed by Felicia William; Barbara Mroczkowski; Stanley Cohen; Andrew S. Kraft

• Publisher: John Wiley and Sons
• Year: 1988
• Tongue: English
• Weight: 912 KB
• Volume: 137
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1041370303

✦ Synopsis

Lipocortin I, a 35-kDa protein, has been detected in terminally differentiated monocytes and neutrophils. This calcium-phospholipid binding protein appears to be identical to a 35-kDa protein that can serve as a substrate for the ECF-receptor/tryosine kinase. We have used the human myelocytic cell line HL-60 to explore whether differentiation of hematopoietic cells i s associated with changes in the level of lipocortin I. We find that differentiation of HL-60 cells toward the macrophage lineage by the addition of phorbol esters or vitamin D3 or toward neutrophils with dibutyryl cyclic AMP or dimethyl sulfoxide is accompanied by an increase in the cellular content of Iipocortin I. In comparison, treatment of HL-60 cells with bryostatin 1, a compound that activates protein kinase C but does not differentiate HL-60 cells, did not effect the level of 35 kDa protein. We have developed a radioimmunoassay to quantitate this protein by using a polyclonal antibody to a synthetic amino terminal peptide of the 35-kDa protein. This antibody recognizes purified pig lung 35-kDa protein as well as a single 35-kDa protein in HL-60 and A-431 cells as determined by Western blotting and immune precipitation. Differentiated HL-60 cells contain 2.h-fold the amount of 35-kDa protein found in undifferentiated HL-60 cells. Our findings that the addition of phorbol esters to HL-60 cells results in an increase in the mRNA for the 35-kDa protein and in an increase in the incorporation of "S-methionine