Western blotting analysis of heat shock proteins of Rickettsiales and other eubacteria

Promyelocytic leukemia HL-60 cells promoted by PMA to differentiate along the monocyte pathway adhere to tissue culture plates. To explore the regulation of adhesion molecules in cells promoted to differentiate, the expression and secretion of osteopontin (OPN) and expression of associated cell surface receptors, CD44 and integrin subunits alpha(v), beta3, beta1, were examined. Results were as follows: 1) PMA induced OPN mRNA and OPN secretion into media; 2) untreated cells expressed beta1 and CD44 mRNA, and PMA induced alpha(v), and beta3 mRNA and increased beta1 and CD44 mRNA expression; 3) PMA increased levels of alpha(v), beta3, beta1 and CD44 protein on the cell surface; and 4) retinoic acid, which promotes granulocytic differentiation of HL-60 cells, did not affect OPN, alpha(v), beta3, beta1, or CD44 mRNA or protein expression. These data suggest that induction of OPN and associated receptors may play a role during monocytic differentiation of HL-60 cells.