Role of the cAMP‐dependent protein kinase and protein kinase C in regulating the morphological differentiation of PC12 cells

Abstract

The cell line A126‐1B2 is a PC12‐derived mutant that is resistance to the toxic effects of dibutyryladenosine 3′:5′‐cyclic monophosphate (dbcAMP) and is deficient in adenosine 3′:5′‐cyclic monophosphate (cAMP)‐dependent protein kinase II (PKAII). This mutant formed neurites in response to nerve growth factor (NGF), but not in response to dbcAMP; and dbcAMP did not increase the rate of NGF‐dependent neurite formation. Thus, while PKAII is essential for process formation in response to agentsw that act through the cAMP‐dependent pathway, activation of PKAII is not essential for NGF‐dependent neurite formation. Unexpectedaly, NGF and phorbol 12‐myristate 13‐acetate (PMA; 10–1,000 nm) synergistically stimulated the formation of shortprocesses that were apparent within 30 min of NGF addition in 85% of these mutant dells. These processes were similar, but not identical, in appearance to the NGF‐dependent neurites that formed only after a period of 24–48 hr. This effect is dependent on the activation of protein kinase C (PKC) because an inactive phorbol ester was without effect. In contrast, therewas only a small effect of NGF and/or PMA on process formation in wiod type cells within the first few hours. The effect of PMA is not augmented by dbcAMP in the A126‐1B2 mutant cells. After several hours, PMA caused a concentration‐dependent decrease in cell adhesion; and higher concetrations of PMA resulted in a transient detachment of the cells and a loss of neurites. These experiments suggest a role for PKC in the regulation of process formation.