Identification and characterization of a truncated variant of the 5-hydroxytryptamine(2A) receptor produced by alternative splicing

We have identified an alternatively spliced 5-hydroxytryptamine 2A receptor (5-HT2A-R) transcript by PCR of human brain cDNA using degenerate oligonuc leotide primers to transmembrane (TM) domains 3 and 7 of the 5-HT2-R subfam ily. The variant contains a 118-bp insertion at the exon II/III boundary of the 5-HT2A-R, which produces a frame shift in the coding sequence and a pr emature stop codon. PCR analysis showed that the truncated receptor (5-HT2A -tr) and native 5-HT2A-R were co-expressed in most brain tissues, with the highest levels being found in hippocampus, corpus collosum, amygdala and ca udate nucleus. Western blot analysis of HEK-293 cells transfected transient ly with a 5-HT2A-tr construct showed that a 30-kDa protein was expressed on cell membranes. Co-transfection studies showed no effect of the 5-HT2A-tr variant on H-3-ketanserin binding to the native 5-HT2A-R or on functional c oupling of the 5-HT2A-R to 5-HT-stimulated Ca2+ mobilization. The functiona l significance of the 5-HT2A-tr variant and other truncated receptors remai ns to be established. (C) 2000 Elsevier Science B.V. All rights reserved.