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Structural diversity of the voltage‐dependent Ca 2+ channel α 1E ‐subunit
Author(s) -
Pereverzev A.,
Klöckner U.,
Henry M.,
Grabsch H.,
Vajna R.,
Olyschläger S.,
ViatchenkoKarpinski S.,
Schröder R.,
Hescheler J.,
Schneider T.
Publication year - 1998
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1046/j.1460-9568.1998.00099.x
Subject(s) - gene isoform , complementary dna , protein subunit , alternative splicing , biology , microbiology and biotechnology , rna splicing , hek 293 cells , peptide sequence , gene , amino acid , transfection , biochemistry , rna
Voltage‐operated Ca 2+ channels are heteromultimeric proteins. Their structural diversity is caused by several genes encoding homologous subunits and by alternative splicing of single transcripts. Isoforms of α 1 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 α 1E 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 α 1E transcripts have been analysed by reverse transcription–polymerase chain reaction and by sequencing of amplified fragments. For the II–III loop three different α 1E 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 α 1E cDNA fragments of the carboxy terminus are identified in vivo . Two different α 1E 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 α 1E subunit showed properties, typical for a high‐voltage activated Ca 2+ 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 α 1E isoforms changes during development. In human cerebellum the longer α 1E isoform is expressed predominantly. Although, it has not been possible to assign functional differences to the two α 1E constructs tested in vitro , the expression pattern of the structurally related isoforms may have functional importance in vivo .