Fig. 5.

Effect of postreceptor stimulants, PKC inhibition, or Ca²⁺ depletion on pS474 p21-activated kinase (PAK)4 phosphorylation by cholecystokinin (CCK)-8 and 12-O-tetradecanoylphobol-13-acetate (TPA). A: effect of the calcium ionophore, A23187 (1 μM), TPA (1 μM), thapsigargin (TG; 1 μM), or CCK-8 (1 nM) on PAK4 phosphorylation (all for 5 min, except CCK-8 for 3 min, in calcium containing media). Top: results of a representative blot of six independent experiments. Bottom: means ± SE of six independent experiments. Results are expressed as % of basal stimulation of the control group. *P < 0.05 compared with th0e control group. B: effect of PKC inhibition or Ca²⁺ depletion on pS474 PAK4 CCK-8- and TPA-induced phosphorylation. Isolated acini were preincubated for 2 h, alone or in the additional presence of GF109203X (GFX; 5 μM, 1 h), TG (1 μM, 1 h), or both (in a media with or without 5 mM calcium), and then incubated with or without 1 nM CCK-8 or 1 μM TPA for 3 or 5 min, respectively. Top: results of a representative blot of six independent experiments. Bottom: means ± SE of six independent experiments. Results are expressed as % of basal stimulation of the control group. *P < 0.05 compared with its control; ^>P < 0.05 vs. compared with similar stimulants with no additions (i.e., Ca²⁺ media).