1,25-DIHYDROXYVITAMIN D-3 STIMULATES EXPRESSION AND TRANSLOCATION OF PROTEIN-KINASE C-ALPHA AND C-DELTA VIA A NONGENOMIC MECHANISM AND RAPIDLY INDUCES PHOSPHORYLATION OF A 33-KDA PROTEIN IN ACUTE PROMYELOCYTICNB4 CELLS

1,25-Dihydroxyvitamin D-3 (1,25-(OH)(2)D-3) primes NB4 cells for 12-O- tetradecanoylphorbol-13-acetate-induced monocytic differentiation in a dose- and sequence-dependent fashion, Experiments utilizing 1,25-(OH) (2)D-3 analogues and kinase/phosphatase inhibitors suggested that tyro sine kinase and serine/threonine phosphorylation cascades, rather than vitamin D-3 receptor-mediated signals, were involved in 1,25-(OH)(2)D -3 action. Here we show that NB4 cells express the alpha and delta (bu t not the beta, epsilon, and theta) isoforms of protein kinase C (PKC) . Both authentic 1,25-(OH)(2)D-3 and the nongenomic analogue 1 alpha,2 5-dihydroxyprevitamin D-3 (HF) increased expression of PKC alpha and P KC delta. PKC alpha and PKC delta were translocated to the nucleus of the cell in response to 1,25-(OH)(2)D-3 or HF. The effects of HF were attenuated by the nongenomic antagonist 1 beta,25-dihydroxyvitamin D-3 , suggesting that changes in PKC expression are mediated by a nongenom ic signaling pathway. Consistent with the involvement of serine, threo nine, and tyrosine phosphorylation cascades mediating 1,25-(OH)(2)D-3 action, enhanced phosphorylation of a variety of cellular proteins at serine and threonine residues and the specific enhanced phosphotyrosyl content of a 33-kDa protein (vdrp33) were observed immediately after 1,25-(OH)(2)D-3 addition. We propose that 1,25-(OH)(2)D-3 primes NB4 c ells for 12-O-tetradecanoylphorbol-13-acetate-induced monocytic differ entiation by increasing the expression of specific PRC isoforms and in ducing the specific phosphorylation of key protein signaling intermedi ates.