New isoform of the neuronal Ca2+ channel α1E subunit in islets of Langerhans and kidney -: Distribution of voltage-gated Ca2+ channel α1 subunits in cell lines and tissues

The expression of Ca2+ channel alpha 1E isoforms has been analyzed in different cell lines, embryoid bodies and tissues. The comparison of the different cloned alpha 1E cDNA sequences led to the prediction of alpha 1E splice variants. Transcripts of two cloned alpha 1E isoforms, which are discriminated by a carboxy terminal 129-bp sequence, have been detected in different cell lines and tissues. Transcripts of the shorter alpha 1E isoform have been assigned to the rat cerebrum and to neuron-like cells from in vitro. differentiated embryonic stem cells. The shorter isoform is the major transcript amplified from total RNA by reverse transcription (RT)-PCR and visualized on the protein level by Western blotting with common and isoform-specific antibodies. Transcripts of the longer alpha 1E isoform have been identified in mouse, rat and human cerebellum. in in vitro. differentiated embryoid bodies, in the insulinoma cell lines INS-1 (rat) and beta TC-3 (mouse). in the pituitary cell line AtT-20 (mouse) when grown in 5 mM glucose, and in islets of Langerhans (rat) and kidney (rat and human). The detection of different-isoforms of alpha 1E in cell lines and tissues shows that the wide expression of alpha 1E has to be specified by identifying the corresponding isoforms in each tissue. In islets of Langerhans and in kidney, a distinct isoform called alpha 1Ee has been determined by RT-PCR, while in cerebellum a set of different alpha 1E structures has been detected. which might reflect the functional heterogeneity of cerebellar neurons. The tissue-specific expression of different isoforms might be related to specific functions. which are not yet known, but the expression of the new isoform alpha 1Ee in islets of Langerhans and kidney leads to the suggestion that alpha 1E might be involved in the modulation of the Ca2+-mediated hormone secretion.