Mechanisms of cholecystokinin-induced calcium mobilization in gastric antral interstitial cells of Cajal

Figure 5 Sulfated cholecystokinin-8 stimulation of interstitial cells of Cajal resulted in the protein kinase C-dependent phosphorylation of type III inositol 1,4,5-triphosphate receptor. A: Western blots of proteins were immunoprecipitated with type III inositol 1,4,5-triphosphate receptor (InsP₃R3)-specific antibody. The immunoprecipitated proteins were probed with antibody specific for phosphorylated Ser/Thr protein kinase C (PKC) substrate sequences. The sulfated cholecystokinin-8 (CCK-8S)-induced phosphorylation of InsP₃R3 was apparently inhibited by pretreatment with chelerythine. Pretreatment with lorglumide (5 μmol/L) could significantly reduce the CCK-8S intensified phosphorylation of InsP₃R3. In the positive control group, treatment of cells with phorbol-12-myristate-13-acetate (PMA) also resulted in an enhanced phosphorylation of InsP₃R3; B: The nitrocellulose membrane in A was stripped and reprobed with InsP₃R3 (1:1000) to determine the levels of InsP₃R3 immunoprecipitated. Each cell sample contained nearly equal amounts of InsP₃R3.