Increase in β‐1,4‐Galactosyltransferase Activity During PC12 Cell Differentiation Induced by Forskolin and 2‐Chloroadenosine

Galactosyltransferase (GAL Tase) activity was measured in differentiating PC12 cells induced by either forskolin or 2‐chloroadenosine. The specific activity of GALTase in whole cells and isolated Golgi membranes increased as early as 3 h after initiating treatment with 2‐chloroadenosine, and maximal activity was reached at approximately 12 h. In two mutant PC12 cell lines deficient in protein kinase A, both forskolin and 2‐chtoroadenosine failed to increase GALTase activity. The adenosine A₂ receptor antagonist, xanthine amine congener, prevented 2‐chloroadenosine stimulation of GALTase, demonstrating that this adenosine derivative was mediating its effect via the A2 receptor. These data suggest that GALTase activity during PC12 cell differentiation is regulated by cyclic AMP (cAMP)‐ and protein kinase A‐dependent processes. In support of the role of cAMP in regulating GALTase activity were studies with murine F9 carcinoma cells demonstrating that the greatest stimulation of GALTase activity occurred with cells treated with both retinoic acid and dibutyryl cAMP.