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Notes: Voltage-operated Ca2+ channels are heteromultimeric proteins. Their structural diversity is caused by several genes encoding homologous subunits and by alternative splicing of single transcripts. Isoforms of α1 subunits, which contain the ion conducting pore, have been deduced from each of the six cDNA sequences cloned so far from different species. The isoforms predicted for the α1E subunit are structurally related to the primary sequence of the amino terminus, the centre of the subunit (II–III loop), and the carboxy terminus. Mouse and human α1E transcripts have been analysed by reverse transcription–polymerase chain reaction and by sequencing of amplified fragments. For the II–III loop three different α1E cDNA fragments are amplified from mouse and human brain, showing that isoforms originally predicted from sequence alignment of different species are expressed in a single one. Both predicted α1E cDNA fragments of the carboxy terminus are identified in vivo. Two different α1E constructs, referring to the major structural difference in the carboxy terminus, were stably transfected in HEK293 cells. The biophysical properties of these cells were compared in order to evaluate the importance in vitro of the carboxy terminal insertion found in vivo. The wild-type α1E subunit showed properties, typical for a high-voltage activated Ca2+ channel. The deletion of 43 amino acid residues at the carboxy terminus does not cause significant differences in the current density and the basic biophysical properties. However, a functional difference is suggested, as in embryonic stem cells, differentiated in vitro to neuronal cells, the pattern of transcripts indicative for different α1E isoforms changes during development. In human cerebellum the longer α1E isoform is expressed predominantly. Although, it has not been possible to assign functional differences to the two α1E constructs tested in vitro, the expression pattern of the structurally related isoforms may have functional importance in vivo.

Notes: Different patterns of β-catenin expression in gastric carcinomas: relationship with clinicopathological parameters and prognostic outcome Aims: The cadherin–catenin complex is known to play a critical role in maintenance of cell adhesion. Additionally β-catenin (β-ct) can also take part in signal transduction and nuclear β-ct expression could be correlated with poor prognosis in several malignancies. Since, in gastric cancer, this role of β-ct is still uncertain, we investigated the expression pattern of β-ct as well as the possible prognostic role. Methods and results: β-catenin expression was immunohistochemically investigated in a retrospective series of 401 R0-resected gastric carcinomas. Out of these cases, 54 tumours (13.5%) revealed a preserved membranous β-ct expression similar to that in normal gastric mucosa. In 80 tumours β-ct expression was moderately reduced and in 117 tumours highly reduced. In 150 tumours (37.4%), no or only a weak membranous β-ct expression was found. Additionally, in 53 tumours, a strong β-ct expression could be observed in the cytoplasm with a simultaneous nuclear β-ct immunoreactivity in 17 of these 53 tumours, while nine tumours only showed nuclear immunoreactivity without cytoplasmic staining. There were no significant correlations between the degree of membranous β-ct expression or the different staining pattern (membranous vs. cytoplasmic/nuclear) and the grade of tumour differentiation, the histological tumour type according to Lauren, as well as with the prognostic parameters pT, pN category and vascular invasion. No associations could be found with tumour cell proliferation and the expression of E-cadherin, irrespectively of the different β-ct staining pattern. Univariate analysis revealed no influence on survival, either for membranous or for cytoplasmic/nuclear β-ct expression. Conclusion: Our data on 401 tumours suggest that activation of the Wnt/β-catenin signalling does also occur in a subset of gastric carcinomas. However, in gastric cancer, neither the presence of cytoplasmic/nuclear β-ct expression nor the reduction or loss of membranous β-ct expression is correlated with a specific histological tumour type, tumour progression or prognosis.