Examination of changes in protein phosphorylation following the acquisition of nickel resistance in BALB/C-3T3 cells

Because nickel-resistant cells acquired an elongated morphology which was similar to the response seen in cells acutely treated with dibutyryl cAMP (db-cAMP), we investigated whether the nickel-resistant cells had changes in the cAMP dependent phosphorylation system. Treatment of wild type Balb/c-3T3 cells with nickel chloride or db-cAMP resulted in extensive elongation of the cells. In nickel-resistant cells, treatment with db-cAMP but not nickel compounds induced a similar elongation. Nickel-resistant cells had half the total activity of cAMP dependent protein kinase compared to wild type cells. Both cAMP and NiCl2 enhanced specific protein phosphorylation in intact wild type cells as judged by 32P autoradiography of phosphoproteins separated on two-dimensional gels. However, the increased phosphorylation of specific proteins seen following NiCl2 treatment of wild type cells was not observed when resistant cells were treated with similar levels of NiCl2. Dibutyryl-cAMP stimulated protein phosphorylation was similar in wild type and resistant cells. These preliminary results suggest that, in addition to other changes during nickel resistance, there may also be alterations in protein phosphorylation. The precise nature of this change is unknown at the present time but is currently being studied in our laboratory