STRUCTURAL DIVERSITY OF THE VOLTAGE-DEPENDENT CA2-SUBUNIT( CHANNEL ALPHA(1E))

Citation
A. Pereverzev et al., STRUCTURAL DIVERSITY OF THE VOLTAGE-DEPENDENT CA2-SUBUNIT( CHANNEL ALPHA(1E)), European journal of neuroscience, 10(3), 1998, pp. 916-925
Citations number
50
Categorie Soggetti
Neurosciences
ISSN journal
0953816X
Volume
10
Issue
3
Year of publication
1998
Pages
916 - 925
Database
ISI
SICI code
0953-816X(1998)10:3<916:SDOTVC>2.0.ZU;2-P
Abstract
Voltage-operated Ca2+ channels are heteromultimeric proteins. Their st ructural diversity is caused by several genes encoding homologous subu nits and by alternative splicing of single transcripts. Isoforms of al subunits, which contain the ion conducting pore, have been deduced fr om each of the six cDNA sequences cloned so far from different species . The isoforms predicted for the alpha(1E) subunit are structurally re lated to the primary sequence of the amino terminus, the centre of the subunit (II-III loop), and the carboxy terminus. Mouse and human alph a(1E) transcripts have been analysed by reverse transcription-polymera se chain reaction and by sequencing of amplified fragments. For the II -III loop three different alpha(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 alpha(1E) cDNA fragments of the carboxy terminus are identified in vivo, Two different alpha(1E) constructs, referring to t he major structural difference in the carboxy terminus, were stably tr ansfected in HEK293 cells. The biophysical properties of these cells w ere compared in order to evaluate the importance in vitro of the carbo xy terminal insertion found in vivo. The wild-type alpha(1E) subunit s howed properties, typical for a high-voltage activated Ca2+ channel. T he deletion of 43 amino acid residues at the carboxy terminus does not cause significant differences in the current density and the basic bi ophysical properties. However, a functional difference is suggested, a s in embryonic stem cells, differentiated in vitro to neuronal cells, the pattern of transcripts indicative for different alpha(1E) isoforms changes during development. In human cerebellum the longer alpha(1E) isoform is expressed predominantly. Although, it has not been possible to assign functional differences to the two alpha(1E) constructs test ed in vitro, the expression pattern of the structurally related isofor ms may have functional importance in vivo.