The adaptor protein Shc contains a phosphotyrosine binding (PTB) domain and a Src homology 2 (SH2) domain, both of which are known to interact with phosphorylated tyrosines. We have shown previously that tyrosine 1148 of the activated epidermal growth factor (EGF) receptor is a major binding site for Shc while tyrosine 1173 is a secondary binding site in intact cells. In the present study, we investigated the interaction between the PTB and SH2 domains of Shc and the activated human EGF receptor. Mutant 52-kDa Shc with an arginine-to-lysine substitution at residue 175 in the PTB domain (Shc R175K) or 397 in the SH2 domain (Shc R397K) was coexpressed in Chinese hamster ovary cells overexpressing the wild-type or mutant EGF receptors that retained only one of the autophosphorylation sites at tyrosine 1148 (QM1148) or 1173 (QM1173). Shc R397K was coprecipitated with the QM1148 and QM1173 receptors, was tyrosine-phosphorylated, and associated with Grb2 and Sos. In contrast, coprecipitation of Shc R175K with the mutant receptors was barely detectable. In cells expressing the QM1173 receptor, Shc R175K was tyrosine-phosphorylated and associated with Grb2, while association of Sos was barely detectable. In cells expressing the QM1148 receptor, tyrosine phosphorylation of Shc R175K was markedly reduced. When both Shc R175K and 46-kDa Shc R397K were coexpressed with the mutant receptors, p46 Shc R397K was dominantly tyrosine-phosphorylated. In cells expressing the wild-type receptor, Shc R397K, but not Shc R175K, translocated to the membrane in an EGF-dependent manner. In addition, Ras activity stimulated by the immunoprecipitates of Shc R397K was significantly higher than that by the immunoprecipitates of Shc R175K. The present results indicate that tyrosine 1148 of the activated EGF receptor mainly interacts with the Shc PTB domain in intact cells. Tyrosine 1173 interacts with both the PTB and SH2 domains, although the interaction with the PTB domain is dominant. In addition, Shc bound to the activated EGF receptor via the PTB domain dominantly interacts with Grb2-Sos complex and plays a major role in the Ras-signaling pathway.

In order to clarify the genetic factors in alcohol-related chronic pancreatitis among Japanese, we determined the genotype of two major alcohol-metabolizing enzymes, alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH). The restriction fragment-length polymorphisms of the ADH2 and the ALDH2 genes were analyzed in 47 normal subjects and 31 patients with alcoholic pancreatitis. No significant difference between the patient and control groups was found in the ADH2 genotypes. A significant genetic difference between the two groups was found in the ALDH2 locus. The frequency of the ALDH2*1 allele was found to be 0.681 and that of the ALDH2*2 allele was 0.319 in the controls, while these values were 0.935 and 0.065 in the patients, respectively. Most of the patients (27 of 31) were ALDH2*1/2*1, only four were ALDH2*1/2*2, and none of the patients were ALDH2*2/2*2. These results indicate that genetic polymorphism of the ALDH2 gene influences the risk of developing alcoholic pancreatitis in Japanese.

Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene and the 5T genotype of the polythymidine tract at the exon 9 splice branch/acceptor site are shown to be associated with chronic pancreatitis in Caucasian patients. In contrast to Western countries, cystic fibrosis is extremely rare in Japan. In this study, we investigated the association of mutations or polymorphisms of the CFTR gene with chronic pancreatitis in Japanese patients. Forty-seven patients with chronic pancreatitis (alcohol-related in 31, idiopathic in 14, and familial in 2) were examined for the deltaF508 and R117H mutations and polymorphisms of intron 8. DNA was extracted from leukocytes. Mutations and polymorphisms were examined by the allele-specific polymerase chain reactions and confirmed by direct sequencing. None of the patients had deltaF508 or R117H mutations in the CFTR gene. All of 47 healthy Japanese showed the homozygous 7T/7T genotype, whereas the frequencies of 5T, 7T, and 9T alleles were 0.043, 0.894, and 0.064 in the patients, respectively. The difference in allele frequency is statistically significant. Therefore, the present study indicates the association of polymorphism of the polythymidine tract in intron 8 of the CFTR gene with chronic pancreatitis in Japanese patients.

Cholecystokinin (CCK), a known mitogen for the exocrine pancreas, is shown to activate 70-kDa S6 kinase in isolated pancreatic acini. In this study, we examined the kinetics and cellular mechanisms of CCK-induced p70 S6 kinase activation in vivo and in vitro. Fasted mice were intraperitoneally injected with 0.01-10 microg/kg CCK analoge cerulein. Cerulein caused a concentration-dependent activation of p70 S6 kinase, with the maximal effect at 1-10 microg/kg. After 1 microg/kg cerulein administration, the kinase activity was increased at 5 min, peaked at 10 min, and subsequently decreased. Cerulein also caused a rapid and transient activation of Src. Prior administration of the tyrosine kinase inhibitor herbimycin A compeletely inhibited cerulein-induced Src activation, while the inhibition of p70 S6 kinase activity was partial. Similar results were obtained with pancreatic acinar cell line AR42J cells. These results suggest that tyrosine kinases, including Src as a possible candidate, are partly implicated in the signaling pathway of CCK-induced p70 S6 kinase activation in the exocrine pancreas.