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Protein kinase C (PKC) family members are multifunctional kinases that have been implicated in many cell biological and physiological tasks including acid, pepsinogen, and mucous production. Through the use of small-molecule PKC modulators, PKC has been found to be involved in gene expression, the control of cytoskeleton, membrane and secretagogue-dependent signal transduction for secretion of acid. Gastric carcinoma and adenocarcinoma cells often show dysregulated PKC-dependent cell signal transduction compared to normal gastric cells. Moreover, PKC was the first known target of tumor promoting phorbol esters. These findings support PKC as a potential chemotherapy target in gastric cancer. Various approaches have been launched in directly targeting PKC for chemotherapy of gastric cancer. The macrocyclic lactone bryostatin-1 is a promising agent that acts as a modulator of PKC activity, and enhances the effect of chemotherapeutic agents such as paclitaxel. This article provides an overview of the findings to date regarding the physiological role of PKC in the gastric cell system by various pharmacological approaches and examines PKC as a target in gastric (adeno-)carcinoma chemotherapy.

A peripheral member of the Ca 2ϩ /calmodulin-dependent protein kinase II (CaMkinase II) group has been purified from hog gastric mucosa with the use of a novel affinity-chromatographic step. For the well known neural isotypes of CaMkinase II, it is proposed that the subunits form holoenzymes through a specific domain at the C-terminus called the 'association domain'. We immobilized a bacterially expressed association domain from CaMkinase II-δ-2 and used it as an affinity column. This matrix was used as the last step in a sequential enzyme purification procedure from hog gastric mucosa and yielded a homogeneous CaMkinase II which showed the typical physical and enzymatic properties of CaMkinase II. The enzyme activity showed a dependence on Ca 2ϩ and calmodulin (apparent K 0.5 ϭ 2.7 µM and K 0.5 ϭ 0.02 µM, respectively). We found a subunit molecular mass of 61 kDa. An apparent native molecular mass of 310 kDa was calculated. The Stokes radius and the sedimentation coefficient were 6.7 nm and 11.2 S, respectively. Moreover, the isolated CaMkinase II was very well inhibited by the CaMkinase-IIspecific inhibitors KN-62 (K i ϭ 0.52 nM) and KT5926 (K i ϭ 0.79 nM). The phosphorylation of several substrates revealed its multifunctionality. The purified CaMkinase II had an apparent K m for Mg-ATP of 24.0 µM and for autocamtide-II of 0.62 µM. CaMkinase II is considered as a strong candidate for regulating vesicle released quanta such as acid, neurotransmitters or insulin.Keywords : calmodulin; Ca 2ϩ /calmodulin-dependent protein kinase II ; protein kinase ; purification; affinity chromatography.In gastric parietal cells, at least three major cellular pathways bachol, histamine and forskolin on acid secretion in isolated rabbit gastric parietal cells with K i values of 0.15, 0.3 and 1 µM, mediate an agonist-induced acid secretion [1, 2]. Stimulation of the histaminic receptor H 2 causes the activation of the cAMP respectively. The main effect seemed to be unspecific on the pH gradient formation level [17]. pathway, followed by an unknown acid-secretion mechanism [3]. Another way of acid secretion is muscarinic M 3 receptorThe Ca 2ϩ /calmodulin-dependent protein kinases II are coded for by four genes. The isoforms are named A, β, γ and δ, all mediated [4Ϫ10], which activates phospholipase C, resulting in cleavage of phosphatidylinositol 4,5-bisphosphate into inositol established first in neural tissues [20Ϫ25]. The best characterized isoforms are mammalian CaMkinase II-A (50Ϫ54 kDa) 1,4,5-trisphosphate and diacylglycerol. Gastrin also elevates the intracellular calcium concentration [11]. A subsequent rise in and -β (58Ϫ60 kDa), which are rarely found in non-neural tissues. Both isotypes form holoenzymes of 10 and 8 subunits, cytosolic Ca 2ϩ activates Ca 2ϩ -dependent processes. A major target for Ca 2ϩ binding is the ubiquitous calmodulin [12Ϫ14]. respectively, which are likely homomeric [26]. The CaMkinase II isoforms γ and δ have only been characterized at the cDNA We recently found γ and δ subunits of Ca 2ϩ /calmodulin...